WO2007013257A1 - Nitride semiconductor device - Google Patents
Nitride semiconductor device Download PDFInfo
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- WO2007013257A1 WO2007013257A1 PCT/JP2006/313107 JP2006313107W WO2007013257A1 WO 2007013257 A1 WO2007013257 A1 WO 2007013257A1 JP 2006313107 W JP2006313107 W JP 2006313107W WO 2007013257 A1 WO2007013257 A1 WO 2007013257A1
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- WIPO (PCT)
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- layer
- nitride
- type
- carbon
- semiconductor layer
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- 239000004065 semiconductor Substances 0.000 title claims abstract description 171
- 150000004767 nitrides Chemical class 0.000 title claims abstract description 113
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 157
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 150
- 239000012535 impurity Substances 0.000 claims abstract description 45
- 239000000758 substrate Substances 0.000 claims abstract description 32
- 238000005253 cladding Methods 0.000 claims description 132
- 229910002601 GaN Inorganic materials 0.000 claims description 69
- 239000011777 magnesium Substances 0.000 claims description 60
- 239000000463 material Substances 0.000 claims description 14
- 229910052749 magnesium Inorganic materials 0.000 claims description 9
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 claims description 8
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 6
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical group [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 3
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 3
- 239000011787 zinc oxide Substances 0.000 claims description 3
- RNQKDQAVIXDKAG-UHFFFAOYSA-N aluminum gallium Chemical compound [Al].[Ga] RNQKDQAVIXDKAG-UHFFFAOYSA-N 0.000 claims description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 2
- 229910052732 germanium Inorganic materials 0.000 claims description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 2
- 229910052738 indium Inorganic materials 0.000 claims description 2
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 2
- 239000001301 oxygen Substances 0.000 claims description 2
- 229910052760 oxygen Inorganic materials 0.000 claims description 2
- 229910002704 AlGaN Inorganic materials 0.000 description 44
- 239000013078 crystal Substances 0.000 description 35
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- 238000009792 diffusion process Methods 0.000 description 17
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- 229910052739 hydrogen Inorganic materials 0.000 description 9
- 229910052757 nitrogen Inorganic materials 0.000 description 8
- JLTRXTDYQLMHGR-UHFFFAOYSA-N trimethylaluminium Chemical compound C[Al](C)C JLTRXTDYQLMHGR-UHFFFAOYSA-N 0.000 description 8
- 239000012159 carrier gas Substances 0.000 description 7
- 239000001257 hydrogen Substances 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
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- 230000007547 defect Effects 0.000 description 6
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- IBEFSUTVZWZJEL-UHFFFAOYSA-N trimethylindium Chemical compound C[In](C)C IBEFSUTVZWZJEL-UHFFFAOYSA-N 0.000 description 3
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 2
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- JGHYBJVUQGTEEB-UHFFFAOYSA-M dimethylalumanylium;chloride Chemical compound C[Al](C)Cl JGHYBJVUQGTEEB-UHFFFAOYSA-M 0.000 description 2
- 230000005669 field effect Effects 0.000 description 2
- 229910021480 group 4 element Inorganic materials 0.000 description 2
- 229910021478 group 5 element Inorganic materials 0.000 description 2
- 238000002248 hydride vapour-phase epitaxy Methods 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 230000010365 information processing Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
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- HJUGFYREWKUQJT-UHFFFAOYSA-N tetrabromomethane Chemical compound BrC(Br)(Br)Br HJUGFYREWKUQJT-UHFFFAOYSA-N 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- VOITXYVAKOUIBA-UHFFFAOYSA-N triethylaluminium Chemical compound CC[Al](CC)CC VOITXYVAKOUIBA-UHFFFAOYSA-N 0.000 description 2
- RGGPNXQUMRMPRA-UHFFFAOYSA-N triethylgallium Chemical compound CC[Ga](CC)CC RGGPNXQUMRMPRA-UHFFFAOYSA-N 0.000 description 2
- OTRPZROOJRIMKW-UHFFFAOYSA-N triethylindigane Chemical compound CC[In](CC)CC OTRPZROOJRIMKW-UHFFFAOYSA-N 0.000 description 2
- RHUYHJGZWVXEHW-UHFFFAOYSA-N 1,1-Dimethyhydrazine Chemical compound CN(C)N RHUYHJGZWVXEHW-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 1
- 101000983944 Homo sapiens CDK2-associated and cullin domain-containing protein 1 Proteins 0.000 description 1
- GPXJNWSHGFTCBW-UHFFFAOYSA-N Indium phosphide Chemical compound [In]#P GPXJNWSHGFTCBW-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
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- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- RQNWIZPPADIBDY-UHFFFAOYSA-N arsenic atom Chemical compound [As] RQNWIZPPADIBDY-UHFFFAOYSA-N 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- ATBAMAFKBVZNFJ-UHFFFAOYSA-N beryllium atom Chemical compound [Be] ATBAMAFKBVZNFJ-UHFFFAOYSA-N 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 229910052793 cadmium Inorganic materials 0.000 description 1
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- XOYLJNJLGBYDTH-UHFFFAOYSA-M chlorogallium Chemical compound [Ga]Cl XOYLJNJLGBYDTH-UHFFFAOYSA-M 0.000 description 1
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- UPWPDUACHOATKO-UHFFFAOYSA-K gallium trichloride Chemical compound Cl[Ga](Cl)Cl UPWPDUACHOATKO-UHFFFAOYSA-K 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000004020 luminiscence type Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- JOTBHEPHROWQDJ-UHFFFAOYSA-N methylgallium Chemical compound [Ga]C JOTBHEPHROWQDJ-UHFFFAOYSA-N 0.000 description 1
- 238000001451 molecular beam epitaxy Methods 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
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- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- VLCQZHSMCYCDJL-UHFFFAOYSA-N tribenuron methyl Chemical compound COC(=O)C1=CC=CC=C1S(=O)(=O)NC(=O)N(C)C1=NC(C)=NC(OC)=N1 VLCQZHSMCYCDJL-UHFFFAOYSA-N 0.000 description 1
- 238000000927 vapour-phase epitaxy Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
- H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
- H01S5/32308—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm
- H01S5/32341—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm blue laser based on GaN or GaP
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
- H10H20/80—Constructional details
- H10H20/81—Bodies
- H10H20/8215—Bodies characterised by crystalline imperfections, e.g. dislocations; characterised by the distribution of dopants, e.g. delta-doping
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/305—Structure or shape of the active region; Materials used for the active region characterised by the doping materials used in the laser structure
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
- H10H20/80—Constructional details
- H10H20/81—Bodies
- H10H20/822—Materials of the light-emitting regions
- H10H20/824—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP
- H10H20/825—Materials of the light-emitting regions comprising only Group III-V materials, e.g. GaP containing nitrogen, e.g. GaN
Definitions
- the present invention relates to a nitride-based semiconductor device.
- the nitride semiconductor device according to the present invention is a nitride such as a semiconductor laser, which is expected to be applied to the field of optoelectronic information processing, a light emitting diode, an ultraviolet detector, etc.
- Nitride-based semiconductors containing nitrogen (N) as a group V element are regarded as promising materials for short-wavelength light-emitting devices because of their large band gap.
- compound semiconductors nitride-based semiconductors: AlGalnN
- gallium nitride have been actively studied, and blue light-emitting diodes and green light-emitting diodes have already been put into practical use.
- semiconductor lasers having an oscillation wavelength in the 400 nm band have been eagerly desired, and semiconductor lasers made of nitride semiconductors have attracted attention and are now reaching a practical level.
- Nitride-based semiconductors have the characteristics that the band gap is large and the dielectric breakdown electric field is high and the saturation saturation speed of the electron is high. Therefore, high-temperature operation is possible and high power can flow. . For this reason, it is considered that it can be used for a field effect transistor realizing high-speed switching characteristics and a high electron mobility transistor.
- the performance of such a transistor using a nitride-based semiconductor is expected to exceed the characteristics of silicon (Si), gallium arsenide (GaAs), and indium phosphide (InP), which have been put into practical use. ing.
- Patent Documents 1 to 8 Conventional structures such as a semiconductor laser device manufactured using a nitride-based semiconductor are disclosed in, for example, Patent Documents 1 to 8 and Non-Patent Documents 1 to 3.
- Patent Document 1 Japanese Patent Laid-Open No. 10-126006
- Patent Document 2 JP-A-9 63962
- Patent Document 3 Japanese Patent Laid-Open No. 2003-264345
- Patent Document 4 Japanese Patent Laid-Open No. 2002-100837
- Patent Document 5 Japanese Unexamined Patent Publication No. 2003-69156
- Patent Document 6 Japanese Patent Laid-Open No. 11-4044
- Patent Document 7 Patent No. 3505442
- Patent Document 8 JP 2001-144378 A
- Non-Patent Document 1 Japanese Journal of Applied Physics, Vol. 38, L226 -L229 (1 999)
- Non-Patent Document 2 physica status solidi (A) 194, No. 2, 407-413 (2002)
- Non-Patent Document 3 IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM E
- Nitride-based semiconductor laser devices are currently required to achieve a high-power operation of, for example, more than 120 mW.
- the problem with achieving such a high-power operation is that the acceptor
- the activation rate of Mg doped as an impurity is low.
- a p-type GaN layer doped with Mg may activate only about 10% of doped Mg. Therefore, in order to form a p-type cladding layer having the same carrier concentration as that of the n-type cladding layer, it is necessary to dope 10 times or more of Mg.
- the effective mass of holes is 5 to 10 times heavier than the effective mass of electrons, and as a result, the resistivity is increased by about 20 to 50 times. Therefore, the p-type nitride semiconductor layer The resistivity of the semiconductor device tends to be high, and this high resistivity causes a problem that the operating voltage of the semiconductor element increases and heat is easily generated during operation.
- a mixed crystal layer containing In (for example, an active layer) is generally grown at a lower growth temperature than a GaN layer or an AlGaN mixed crystal layer in order to suppress decomposition of In from the crystal. It is done.
- nitride-based optical devices ranging from the visible light to the near-ultraviolet region
- the active layer deteriorates due to heat, causing problems such as disorder of the quantum well structure, segregation of In, contamination due to impurity diffusion, and increased lattice distortion due to impurity contamination.
- Mg which is a p-type acceptor impurity, also diffuses from the p-type cladding layer to the active layer, which also causes deterioration of the active layer (impurity contamination and introduction of lattice strain due to it).
- the luminous efficiency decreases.
- solving these problems is an indispensable condition for realizing a high-power and high-reliability nitride-based semiconductor laser.
- the increase in operating voltage and heat generation in the p-type cladding layer, and the thermal degradation of the active layer during the temperature rising process during the preparation of the p-type cladding layer adversely affect the reliability of the nitride-based semiconductor element. It is difficult to manufacture highly reliable nitride-based semiconductor elements with high reproducibility.
- Patent Document 2 p-type conversion is realized at a high activation rate by carbon doping to the p-type AlGaN cladding layer. It is disclosed that impurity diffusion to the side can be suppressed. Instead of Mg, which is usually used as a p-type dopant, a low-resistance p-type crystal is realized by doping only carbon. However, Patent Document 2 does not disclose an optimal carbon concentration range that can realize good electrical characteristics for the light-emitting element.
- Patent Document 8 describes the effect of carbon doping on an n-type AlGaN cladding layer with Si doping and a p-type AlGaN cladding layer with Mg doping.
- the optimum carbon concentration range that can realize good electrical characteristics for the device is not disclosed.
- the present invention has been made to solve the above problems, and a main object thereof is to provide a nitride semiconductor device having high reliability.
- a nitride-based semiconductor element wherein the stacked structure includes an n-type nitride-based semiconductor layer, a p-type nitride-based semiconductor layer, the n-type nitride-based semiconductor layer, and the p-type nitride-based device
- a nitride-based semiconductor layer positioned between the semiconductor layer, the p-type nitride-based semiconductor layer being doped with a p-type impurity other than carbon and carbon, and the p-type nitride Carbon concentration of semiconductor layer The degree is higher than the carbon concentration of the n-type nitride semiconductor layer, which is lower than the concentration of the p-type impurity other than the carbon.
- the p-type impurity other than carbon doped in the p-type nitride-based semiconductor layer is magnesium.
- the carbon concentration of the p-type nitride-based semiconductor layer is 8 ⁇ 10 16 cm ⁇ 3 or more and 1 ⁇ 10 18 cm ⁇ 3 or less.
- the carbon concentration of the p-type nitride semiconductor layer is 0.8 relative to the concentration of p-type impurities other than carbon doped in the p-type nitride semiconductor layer.
- the substrate includes gallium nitride, aluminum gallium nitride (
- the average value of threading dislocation density in the substrate is 3 ⁇ 10 6 cm or less.
- the nitride-based semiconductor layer located between the p-type nitride-based semiconductor layer and the n-type nitride-based semiconductor layer functions as an active layer that emits light, and the n-type
- Each of the nitride-based semiconductor layer and the p-type nitride-based semiconductor layer functions as a cladding layer for the active layer.
- the p-type nitride-based semiconductor layer and the n-type nitride-based semiconductor layer contain at least a part of aluminum, and the p-type nitride-based semiconductor layer and the n-type nitride-based layer are included.
- the nitride-based semiconductor layer located between the semiconductor layer contains indium at least partially.
- the n-type nitride semiconductor layer is doped with at least one element selected from the group consisting of silicon, germanium, and oxygen.
- the p-type nitride-based semiconductor layer is doped with p-type impurities (acceptor impurities) other than carbon (C) and carbon. Its carbon concentration The degree is adjusted to be lower than the concentration of P-type impurities other than carbon.
- carbon doped in the nitride-based semiconductor layer is a group IV element, it functions as a donor impurity if it is replaced with a group III element (for example, Ga) in the crystal. If replaced with some N, it functions as an acceptor impurity.
- group III element for example, Ga
- acceptor impurity for example, Ga
- by doping a p-type impurity other than carbon most of the carbon is replaced with N of the group V element. In other words, since carbon acts as an acceptor impurity at the N site, it has the effect of compensating for residual donors.
- nitride-based semiconductors have many N vacancies (point defects) that serve as donor sources, but in the present invention, doped C occupies N sites in the crystal, so In order to suppress the generation of, it is possible to greatly reduce the electrical resistivity of the p-type nitride semiconductor layer.
- FIG. 1 is a cross-sectional view showing a first embodiment (semiconductor laser element) of a nitride-based semiconductor element according to the present invention.
- FIG. 2 is a graph showing a SIMS profile in the semiconductor laser device shown in FIG.
- FIG. 3 is a graph showing the relationship between the resistivity of the n-GaN layer and the Si concentration.
- FIG. 4 is a graph showing the relationship between the resistivity of the p-GaN layer and the Mg concentration.
- FIG. 5 (a) is a graph showing IL and IV characteristics for a semiconductor laser device having a p-type cladding layer doped with Mg and C, and (b) is a graph showing only Mg doped.
- p This is a diagram showing IL and IV characteristics of a semiconductor laser device having a type cladding layer.
- FIG. 6 is a graph showing the relationship between Mg concentration in the light guide layer (p side) / active layer and threading dislocation density in the substrate.
- P _GaN layer (growth temperature: 900 ° C) is a graph showing the relationship between the resistivity and Mg concentration.
- FIG. 8 This is a graph showing the relationship between internal quantum efficiency and internal loss and carbon concentration in a nitride semiconductor laser device having a p-type cladding layer doped with carbon.
- FIG. 9 A sectional view showing a third embodiment (semiconductor laser element) of a nitride-based semiconductor element according to the present invention.
- FIG. 1 shows a cross-sectional structure of the nitride-based semiconductor laser device of this embodiment.
- the semiconductor laser device of this embodiment includes an n-GaN substrate 101 and a semiconductor multilayer structure formed on the n_GaN substrate 101.
- the stacked semiconductor structure consists of the ⁇ —GaN layer 102, n_Al Ga N cladding layer 103, n_GaN light guide layer 1 from the side close to the n_GaN substrate 101.
- Optical guide layer 106 Non-doped GaN second optical guide layer 107, Non-doped Al Ga N Third optical guide layer 108, p_Al Ga N first cladding layer 109, p_Al Ga N second cladding layer 11
- a mesa stripe having a width of approximately 1.4 to 1.8 zm is formed on the upper surface of the semiconductor multilayer structure, and a region other than the upper surface of the mesa stripe is covered with an insulating layer (Si layer) 114. It has been broken.
- N electrode 113 is formed.
- Gain occurs at 5, and laser oscillation occurs at a wavelength of 410 nm.
- the most characteristic feature of the semiconductor laser of the present embodiment is that the p-AlGaN first cladding layer 1
- the p-type nitride semiconductor layer from 09 to the p-GaN contact layer 111 is doped with carbon (C) together with Mg, which is an acceptor impurity.
- the above semiconductor stacked structure can be suitably formed by metal organic vapor phase epitaxy (MOVPE), but other methods such as hydride vapor phase epitaxy (HVPE) and molecular beam epitaxy (MBE).
- MOVPE metal organic vapor phase epitaxy
- HVPE hydride vapor phase epitaxy
- MBE molecular beam epitaxy
- the compound semiconductor crystal growth method can be used.
- the MOVPE method is used for crystal growth, but the atmosphere during crystal growth may be a reduced pressure or a pressure higher than atmospheric pressure. The pressure may be switched to an optimum pressure depending on the composition of the semiconductor layer to be grown. Also, to supply the growth layer material to the substrate As the carrier gas, a gas containing an inert gas such as nitrogen (N) or hydrogen (H) is used.
- N nitrogen
- H hydrogen
- an n-GaN substrate 101 is prepared, and the surface of the n-GaN substrate 101 is cleaned with an organic solvent or acid. After that, the n_GaN substrate 101 is placed on the susceptor in the growth chamber of the MOVPE apparatus, and the atmosphere gas in the growth chamber is sufficiently replaced with N. N substitution finished
- the n-GaN substrate 101 is heated in an N atmosphere, and the temperature rise rate is 10 ° C / 10 seconds.
- n-GaN layer 102 is grown. Subsequently, trimethylaluminum (TMA) is removed and 1. A thick n_AlGaN cladding layer 103 is grown.
- TMA trimethylaluminum
- the supply of TMA is stopped, and the n-GaN optical guide layer 104 is grown to a thickness of 0.1 ⁇ m.
- the carrier gas is switched to H force N, NH
- a In N well layer thickness is 5 nm
- Ga In N barrier layer thickness is 6 nm
- the number of well layers is 2
- the active layer 105 is not intentionally doped with impurities.
- a non-doped Ga In N first optical guide layer 106 having a thickness of 25 nm and a thickness of 50 nm
- Cp Mg biscyclopentagenenyl magnesium
- Methane (CH 3) was added as a p-AlGaN first cladding layer 109 by lOnm growth.
- the The p—Al Ga N first cladding layer 109 is composed of Ga In N / Ga In N—quantum well actives.
- Laminate. Mg and C are doped under the same conditions as those for the p-AlGaN first cladding layer 109.
- the ⁇ -GaN substrate 101 on which the laminated structure is formed is taken out of the MOVPE apparatus, and a microfabrication process using photolithography and etching techniques is performed. Specifically, P-A1 Ga N first cladding layer 109, p_Al Ga N first
- Cladding layer 110 and p-GaN contact layer 111 are processed into stripes as shown in FIG. 1 to form mesa stripes.
- the upper surface of the mesa stripe that is, the upper surface of the p-GaN contact layer 111 processed into the stripe shape is exposed at a portion (opening portion of the SiO layer 114) covered with the SiO layer 114.
- the stripe width is about 1 ⁇ 4 ⁇ :! ⁇ 8 / im.
- the upper surface of the N contact layer 111 is in contact with the upper surface of the Si layer 114.
- the N contact layer 111 in order to reduce the contact resistance with the p electrode 112, the concentration 1 X 10 2 ° cm- 3 from 2 X 10 2 ° cm- 3 of Mg is doped.
- the n-GaN substrate 101 is polished on the back side to reduce the thickness of the n-GaN substrate 101 to about 90 ⁇ m, and then an n-electrode 113 is formed on the back surface of the n-GaN substrate 101. To do.
- the supply of TMG is temporarily stopped, and N and NH are The temperature is quickly raised in the supplied state, and the carrier gas is changed to a mixed gas of N and H on the way.
- TMG and TMA can be supplied and the temperature can be raised while the A1 GaN third light guide layer 108 is crystal-grown. If the method does not generate defects that cause non-radiative recombination centers in the crystal, Such a temperature raising method may be adopted.
- FIG. 2 is a graph showing a SIMS profile for the semiconductor laser of the present embodiment.
- the “carbon concentration” in 07 is 8 ⁇ 10 16 cm ⁇ 3 to l ⁇ 10 17 cm ⁇ 3 . Since these semiconductor layers 1 05 to 107 are not intentionally doped with carbon, their carbon concentration is extremely low.
- n_AlGaN cladding layer 103 containing A1 is shown in FIG. 2, n_AlGaN cladding layer 103 containing A1, and
- the carbon concentration in the Al Ga N third light guide layer 108 is 1 to 3 ⁇ 10 17 cm ⁇ 3 .
- These semiconductor layers 103 and 808 contain a trace amount of C even though they are not intentionally carbon-doped because C is auto-doped from the raw material TMA.
- the carbon concentration also depends on the growth rate of the nitride-based semiconductor layer, and that the carbon concentration further decreases when the growth rate is decreased. Compared to the example in Fig. 2, when the growth rate is reduced to about 70%, the carbon concentration in these nitride-based semiconductor layers decreases to 7 x 10 16 cm 3 or less.
- the carbon concentration in the N second cladding layer 110 and the p-GaN contact layer 111 was in the range of about 7 ⁇ 10 17 to 1 ⁇ 10 18 cm 3 . In the case of these nitride semiconductor layers as well, the carbon concentration decreases from 8 ⁇ 10 16 cm 3 to 8 ⁇ 10 17 cm ⁇ 3 when the growth rate is reduced to about 70%.
- the magnitude relationship among the carbon concentrations of the n-type cladding layer, the active layer, and the p-type cladding layer was such that the active layer was n-type cladding layer ⁇ p-type cladding layer.
- a semiconductor layer having a thickness of 1 ⁇ m was grown and carbon doping was performed.
- Carbon concentration 3 Several samples were prepared in the range of X 10 17 cm— 3 to 5 X 10 18 cm— 3 , and the electrical characteristics of each sample were evaluated.
- the resistivity immediately after fabrication is IX 10 7 ⁇ cm or higher, regardless of n-type or p-type, and it exhibits very high resistance and n-type conductivity. I understand.
- the concentration of Si remaining in the crystal of the obtained GaN layer is about 1 to 2 X 10 16 cm 3 .
- the resistivity of the GaN layer was about 10 ⁇ cm.
- n-type cladding layer cannot be obtained even if only carbon doping is performed on the cladding layer, and a p-type cladding layer can also be obtained. You can see that you can't.
- C is a group IV element, so if C substitutes Ga in the GaN crystal, it functions as a donor impurity, and substitutes N Then, it functions as an acceptor impurity.
- C when only carbon doping was performed under the growth conditions in this embodiment, a GaN layer showing n-type conductivity having a very high resistance was obtained compared to a GaN layer without doping. Based on this, it is considered that most of the added C is replaced with N in the GaN crystal and acts as an acceptor impurity to compensate the residual donor.
- the GaN crystal has many N vacancies (point defects) that serve as donor sources. It is doped, but occupying N in the GaN crystal suppresses the generation of N vacancies. Conceivable.
- FIG. 3 is a graph showing the change in resistivity of the n-GaN layer, where the vertical axis represents the resistivity and the horizontal axis represents the Si concentration.
- “ ⁇ ” indicates data with a carbon concentration of 1 ⁇ 10 17 cm ⁇ 3
- “ ⁇ ” indicates data with a carbon concentration of 8 ⁇ 10 17 cm ⁇ 3
- Fig. 4 is a graph showing the change in resistivity of the ⁇ -GaN layer, where the vertical axis represents the resistivity and the horizontal axis represents the Mg concentration.
- “ki” is carbon. Data with a concentration of 1 X 10 17 cm- 3 are shown, and “ ⁇ ” indicates data with a carbon concentration of 8 X 10 17 cm 3 .
- the growth conditions are as described in the above embodiment.
- the carbon concentration of 1 X 10 17 cm 3 corresponds to the data without intentional C doping.
- the resistivity is about 50 when the carbon concentration is 8 X 10 17 cm 3 compared to 1 X 10 17 cm- 3. It was getting high. This is because most of the doped C replaces N in the GaN crystal and acts as an acceptor impurity, thus compensating for the Si donor.
- the p_GaN layer doped with Mg as the p-type impurity has a resistivity of about 10 by performing carbon doping. Decreased about / o. This is because doped C replaced N in the GaN crystal, resulting in compensation of residual donors and reduction of N vacancies.
- This force is a force that can reduce the resistivity by co-doping carbon and magnesium into the p-type nitride semiconductor layer. Simultaneous carbon and silicon doping into the n-type nitride semiconductor layer It was clear that the resistivity increased at one bing. Therefore, it is desirable to keep the carbon concentration of the n-type nitride semiconductor layer as low as possible.
- the carbon concentration is preferably adjusted to a range of 0.8% to 10% of the Mg concentration.
- Mg is replaced with Ga. Since it acts as an acceptor impurity, C can effectively replace N and act as an acceptor impurity. By substituting N for C instead of Ga, the residual donor can be compensated, and crystal defects caused by N vacancies can be reduced.
- N p-type impurities
- carbon has not been doped at a concentration sufficiently lower than that of other p-type impurities (Mg), and it is known that the resistivity of p-type nitride semiconductors can be effectively reduced. It was not done.
- Fig. 5 (a) is a graph showing the IL and IV characteristics obtained for a semiconductor laser (this embodiment) having a carbon-doped p-type cladding layer.
- Fig. 5 (b) 4 is a graph showing IL characteristics and IV characteristics obtained for a semiconductor laser (comparative example) having a p-type cladding layer without carbon doping.
- the resistivity of the p_AlGaN second cladding layer 110 is reduced, and the series resistance component in the IV characteristics is reduced.
- the efficiency of hole injection into the active layer is increased, and the threshold current is reduced. Specifically, it was reduced to about 37 mA by performing threshold current force doping that exceeded 50 mA in the absence of C doping.
- the carrier gas at the time of doping contains not only H but N It is preferable. This is because the presence of N gas in the atmosphere makes it easier for C to be taken into N sites in nitride-based semiconductor crystals. In order to increase the efficiency of C incorporation into the N site, it is effective to increase the growth pressure higher than the conventional conditions and lower the ⁇ ratio within a range that does not affect the electrical characteristics of the semiconductor laser. It is.
- the ⁇ ratio is 3000 or less, the residual donor concentration increases due to the decrease in crystallinity, and as a result, it becomes difficult to realize a low-resistance ⁇ -type cladding layer. Desirably 0 or more.
- the ⁇ -type Mg doped in the p-type semiconductor layer or the p-type semiconductor layer positioned thereon diffuses to the light guide layer (p side) and the active layer during the crystal growth process.
- the diffusion of Mg causes light absorption loss near the active layer / light guide layer (P side) and adversely affects the reliability of the laser.
- Mg diffusion is achieved from Ga In N / Ga In N—quantum well active layer 105 to non-doped G
- Mg diffusion can also occur in various situations, such as the subsequent heat treatment step or current application during laser operation. Such Mg diffusion occurs as a diffusion path by dislocations penetrating the semiconductor multilayer structure (threading dislocations) and N vacancies generated in the semiconductor multilayer structure.
- FIG. 6 is a graph showing the relationship between the threading dislocation density in the substrate and the Mg concentration present in the light guide layer (p side) / active layer.
- the data in this graph is based on the evaluation results performed on the wafer immediately after crystal growth before the heat treatment step and the like.
- the carbon concentration of the p-type cladding layer is at three levels. Mg and carbon concentrations were measured by SIMS analysis.
- the threading dislocation density in the light guide layer (p side) / active layer is Is almost equal to the threading dislocation density in. This is also confirmed from a comparison of dark spot density (spots correspond to threading dislocations) by active sword luminescence between the active layer and the substrate. Since the Mg concentration in the light guide layer (p-side) / active layer that is not doped with Mg during crystal growth is due to Mg diffusion, the extent of Mg diffusion is evaluated by the Mg concentration. be able to.
- Mg diffusion can be suppressed by carbon doping the p-type cladding layer.
- N vacancies functioning as Mg diffusion paths are filled with C, so that N vacancies can be formed even at high temperatures during crystal growth. Mg diffusion as a path This is because it becomes difficult.
- instrument threading dislocation density is to use a substrate of threading dislocation density is 3 X 10 6 cm- 2 or less is 1 X 10 6cm- 2 below substrate More preferably, is used.
- carbon doping is performed only on the p-type cladding layer. However, if the magnitude relationship of the carbon concentration is within the range satisfying the relationship of active layer ⁇ n-type cladding layer ⁇ p-type cladding layer. Also, carbon doping may be applied to the active layer and the n-type layer. However, since carbon doping in the active layer may cause an increase in light absorption loss, it is preferable not to perform carbon doping in the active layer.
- carbon doping into the n-type cladding layer may cause an increase in resistivity, so even when carbon doping into the n-type cladding layer is performed, the carbon concentration is 3 ⁇ 10 17 cm ⁇ 3 or less, More preferably, it is preferably adjusted to 0 ⁇ 7 ⁇ 10 17 cm ⁇ 3 or less.
- AlGaN is used for both the n-type cladding layer and the p-type cladding layer, but AlGaN / GaN superlattice is provided in at least one of the n-type cladding layer and the p-type cladding layer.
- a structural layer may be used.
- the cladding layer has a structure that can effectively confine light and carriers even if it contains In, boron (B), arsenic (As), phosphorus (P), and / or antimony (Sb). Any other configuration may be used.
- a Ga In N / Ga In N—quantum well active layer having two well layers is used as the active layer.
- the number of well layers may be 3 or more.
- a combination of a GalnN well layer and a GaN barrier layer, or a combination of a GalnN well layer and an AlGalnN barrier layer may be used, and any configuration capable of realizing high luminous efficiency with low power consumption can be used. These are also true for other embodiments described later.
- the semiconductor laser of this embodiment has the same configuration as the semiconductor laser shown in FIG.
- Clad layer 109 0.01 0.99 0.20 0.80 Clad layer 109, p-Al Ga N second clad layer 110, p-GaN contact layer 111 growth
- the growth temperature of these layers is 1000 ° C. In this embodiment, it is 900 ° C.
- FIG. 7 is a graph showing the relationship between the resistivity of the p-GaN layer (growth temperature: 900 ° C.) and the Mg concentration.
- the resistivity of the carbon-doped p_GaN layer increased by about 6% due to the lower growth temperature.
- the resistivity of the p_GaN layer is thought to increase.
- the resistivity of the p_GaN layer obtained in this embodiment is almost the same as that produced at a growth temperature of 1000 ° C. and without carbon doping. That is, according to the present embodiment, the effect of carbon doping can be obtained even when the growth temperature is lowered.
- FIG. 8 is a graph showing the relationship between the internal quantum efficiency (77) and internal loss ( ⁇ .) And the carbon concentration obtained for the semiconductor laser of this embodiment and the semiconductor laser of Embodiment 1.
- ⁇ and ⁇ indicate the internal quantum efficiency (77.) and internal loss ( ⁇ ), respectively, in the semiconductor laser of Embodiment 1, and “ ⁇ ” and “ ⁇ ” indicate the actual values, respectively.
- the internal quantum efficiency (77) and internal loss ( ⁇ ) in the semiconductor laser of the embodiment are shown.
- the hole injection efficiency into the active layer is increased, and the internal quantum efficiency is improved.
- the growth temperature of the ⁇ -type cladding layer to 900 ° C, it is possible to suppress thermal degradation of the active layer that is likely to occur during the crystal growth process of the p-type cladding layer, thereby further improving the internal quantum efficiency.
- the carbon concentration exceeds 2 X 10 18 cm 3 , the surface flatness of the growth layer deteriorates and a mirror surface cannot be obtained, so even if carbon doping is applied, the internal quantum efficiency is rather lowered. For this reason, it is preferable to control the carbon concentration to 2 ⁇ 10 18 cm ⁇ 3 or less.
- the main cause of internal loss in the semiconductor laser of the present embodiment is non-doped Al Ga This is the optical absorption loss due to the N third optical guide layer 108 and the p-AlGaN first cladding layer 109.
- the growth temperature of the p-type cladding layer is 1000 ° C (corresponding to Embodiment 1)
- the crystal characteristics deteriorate unless carbon doping is performed, so that the light absorption loss increases.
- the internal loss increases about twice as high as the growth temperature of 1000 ° C.
- the electrical characteristics of the p-AlGaN first cladding layer 109 are improved as described above, and the result is Since crystal characteristics are also improved, light absorption loss is reduced and internal loss is also improved.
- the internal loss at a growth temperature of 900 ° C is about 20 times that at a growth temperature of 1000 ° C. This difference is almost insignificant compared to the effect of improving internal quantum efficiency. That is, when the carbon concentration force is in the range of 3 ⁇ 4 X 10 17 cm— 3 to 8 X 10 17 cm— 3 , the growth temperature of the p-type cladding layer is lowered to about 900 ° C., and the threshold current and operating voltage are reduced. Reduction can be achieved.
- the growth temperature of the p-type cladding layer is reduced by 100 ° C. from the conventional value, but it is also possible to reduce the growth temperature by more than 100 ° C.
- carbon doping makes it possible to increase the internal quantum efficiency by lowering the growth temperature of the p-clad layer while realizing a low resistivity of the p-type cladding layer. If the growth temperature of the p-type cladding layer is lower than the growth temperature of the active layer, the residual donor concentration increases significantly, and the resistance of the p-type cladding layer increases. For this reason, it is preferable to set the growth temperature of the p-type cladding layer in a range between the active layer growth temperature and the n-type cladding layer growth temperature.
- the semiconductor laser of this embodiment has substantially the same configuration as that of the semiconductor laser of Embodiment 1, and the first difference is that the p_AlGaN second cladding layer 110 as shown in FIG. P
- carbon doping is also applied to the n-AlGaN cladding layer 103.
- the second cladding layer 1210 has a lower [C supply / Group III material supply] ratio than carbon doping.
- Ga N first cladding layer 109 and p-Al Ga N / p_GaN_ SLS second cladding layer 12
- the growth temperatures for all 10 are set to 1000 ° C.
- the carbon concentration is higher in the N layer and the AlGaN layer.
- the carbon concentration is the steady carbon concentration of the GaN layer (or AlGaN layer).
- the average Al composition of the Al Ga N / GaN— SLS layer is 5%
- the carbon concentration in the Al Ga N layer is the same [C supply / Group III raw material supply] ratio.
- the [C supply amount / III in the n-AlGaN cladding layer 103 is determined.
- Carbon doping is carried out at a low ratio of the amount of group raw material supplied]. However, if the relationship between the active layer, the n-type cladding layer, and the p-type cladding layer can be achieved, the ratio of [C supply amount / Group III material supply amount] may be increased.
- the carbon concentration in the n-Al Ga N clad layer 103 is 3 X 10 17 cm 3 or less
- the drag rate only increases by about 10% compared to when carbon doping was not performed, and there was no problem in practical use.
- the carbon concentration in the n_AlGaN cladding layer 103 is 3 X
- the resistivity of the / p—GaN—SLS second cladding layer 1210 can be reduced. As a result, the series resistance component in the IV characteristics is reduced, and low voltage driving becomes possible.
- the amount of heat generated in the high current injection state can be suppressed, and a 150 mW optical output can be realized under continuous oscillation conditions at room temperature.
- the growth temperature of the p-type cladding layer is made equal to the growth temperature of the n-type cladding layer (1000 ° C.). However, as described in the embodiment 2, the growth of the p-type cladding layer is performed.
- the temperature may be 900 ° C or less, and may be in the range of 900 ° C to 1000 ° C.
- the semiconductor laser according to the present embodiment has substantially the same configuration as that of the semiconductor laser according to the second embodiment. The difference is that the n-AlGaN cladding layer 103 is also carbon-doped.
- Group II raw material supply ratio is determined by the p-AlGaN first cladding layer 109 and p-AlGaN first
- the growth temperature of the n-Al Ga N cladding layer 103 is 1000 ° C, and the first cladding layer of p-Al Ga N
- the growth temperature of the cladding layer 109 and the p-AlGaN second cladding layer 110 is 920 ° C. Crystal
- the growth rate is higher than the Al Ga N layer with a growth temperature of 1000 ° C.
- the directional carbon concentration of the AlGaN layer at 920 ° C is increased.
- the carbon concentration in the n-Al Ga N clad layer 103 is 3 ⁇ 10 17 cm 3 or less
- the resistivity is increased only to the extent that there is no practical problem, and the device characteristics are not greatly affected.
- the C supply amount was controlled so that the carbon concentration in the n-AlGaN cladding layer 103 was 3 ⁇ 10 17 cm ⁇ , the p-AlGaN first cladding layer 109 and the p-AlGaN first layer
- the carbon concentration in the two cladding layers 110 was 8 ⁇ 10 17 cm 3 , and a P-type cladding layer having a lower resistance than that without carbon doping could be formed.
- the concentration of hydrogen necessary to activate the Mg acceptor can be reduced as compared with the case where carbon doping is not performed.
- heat treatment, electron beam irradiation treatment, plasma irradiation, etc. are required, but in the case of p-type cladding layer with carbon doping, Mg and It is possible to activate with a lower hydrogen bond energy than usual. This effect becomes significant by applying carbon doping to the n-type cladding layer.
- the resistivity of the p-AlGaN first cladding layer 109 and the p-AlGaN second cladding layer 110 can be reduced, and the series resistance component in the IV characteristics is reduced. To do.
- laser operation with low power consumption is possible.
- the amount of heat generated in the high current injection state can also be suppressed, so that an optical output of 150 mW was achieved under room temperature continuous oscillation conditions.
- the growth temperature of the p-type cladding layer is set to 920 ° C.
- the growth temperature of the p-type cladding layer may be 900 ° C. or less, or may be in the range of 900 ° C. to 1000 ° C.
- the carbon concentration of the p-type cladding layer is adjusted to 3 ⁇ 10 17 cm 3 or more. Adjusting force In that case, the growth rate of the p-type cladding layer was about 10 nm / min. According to the experiments of the present inventors, when this growth rate is reduced to about 6 to 7 nm / min, the preferable range of the carbon concentration in the p-cladding layer is 8 ⁇ 10 16 cm ⁇ 3 or more and 1 ⁇ 10 18 cm ⁇ 3 In the following, it was found that the more preferable range was 1 ⁇ 10 17 cm 3 or more and 1 ⁇ 10 18 cm ⁇ 3 or less. However, the concentration of p-type impurities such as Mg is maintained at the value in the above-described embodiment. Therefore, the carbon concentration of the p-type cladding layer is preferably in the range of 0.8% to 10% with respect to the concentration of p-type impurities other than carbon, and preferably in the range of 1% to 10%. Is more preferable.
- a GaN substrate is used.
- the substrate may be formed of a nitride-based semiconductor such as AlGaN, InGaN, or AlGalnN, which does not need to be formed.
- a substrate in which a nitride semiconductor layer such as GaN is formed on a substrate (sapphire substrate, SiC substrate, ZnO substrate, Si substrate, GaAs substrate, etc.) formed from a material other than a nitride semiconductor is used. May be.
- the n electrode is formed on the back surface of the substrate.
- a substrate having low conductivity or an insulating substrate is used. Moyore.
- a part of the semiconductor multilayer structure formed on the substrate surface is etched to the n-GaN layer, and an n-electrode is formed on the etched surface.
- a conductive substrate for example, an n-GaN substrate
- both the n electrode and the p electrode may be formed on the semiconductor stacked structure.
- TMG is used as the Ga material
- TMA is used as the A1 material
- TMI is used as the In material
- Cp Mg is used as the Mg material
- NH is used as the N material
- CH is used as the C material.
- Force Other raw materials may be used.
- triethylaluminum (TEA) as raw materials for A1
- N-dimethylaluminum hydride DMAH
- dimethylaluminum chloride DMAC1
- trimethylaminealane TMAA
- triethylindium TEI
- EtCp Mg bisethylcyclopentadienylmagnesium
- MeCp Mg Bismethylcyclopentadienylmagnesium
- NH hydrazine
- CBr Cylhydrazine
- DMH Dimethylhydrazine
- the p-type acceptor impurity that can be used in the present invention is not limited to Mg, and other p-type impurities such as zinc (Zn), beryllium (Be), and cadmium (Cd) may be used.
- the nitride-based semiconductor element of the present invention is not limited to a semiconductor laser element, but is applied to all nitride-based semiconductor elements having a P-type nitride-based semiconductor layer such as a light-emitting diode element and a light-receiving element.
- Nitride semiconductors widely include BAlGalnN mixed crystal semiconductors and AlGalnNAsPSb mixed crystal compound semiconductors containing As, P, and Sb.
- the present invention is suitably used for semiconductor laser elements for optical disk devices, light emitting diodes for illumination, bipolar electronic elements for communication / information processing, and the like.
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Abstract
Description
明 細 書 Specification
窒化物系半導体素子 Nitride semiconductor device
技術分野 Technical field
[0001] 本発明は窒化物系半導体素子に関する。本発明に係る窒化物系半導体素子は、 光電子情報処理分野などへの応用が期待されている半導体レーザ、全固体照明分 野への応用が期待されている発光ダイオード、紫外線検知器などの窒化物系半導 体受発光素子を含むとともに、高周波高出力通信分野への応用が期待されている電 界効果トランジスタや高電子移動度トランジスタなどの電子素子を広く含む。 [0001] The present invention relates to a nitride-based semiconductor device. The nitride semiconductor device according to the present invention is a nitride such as a semiconductor laser, which is expected to be applied to the field of optoelectronic information processing, a light emitting diode, an ultraviolet detector, etc. This includes a wide range of electronic devices such as field effect transistors and high electron mobility transistors, which are expected to be applied to the field of high-frequency and high-power communication, as well as semiconductor light-emitting / receiving devices.
背景技術 Background art
[0002] V族元素として窒素(N)を含有する窒化物系半導体は、そのバンドギャップの大き さから、短波長発光素子の材料として有望視されている。中でも窒化ガリウムを中心と した化合物半導体(窒化物系半導体: AlGalnN)は研究が盛んに行われ、青色発光 ダイオード、緑色発光ダイオードが既に実用化されている。また、光ディスク装置の大 容量化のために、 400nm帯に発振波長を有する半導体レーザが熱望されており、 窒化物系半導体を材料とする半導体レーザが注目され現在では実用レベルに達し つつある。 [0002] Nitride-based semiconductors containing nitrogen (N) as a group V element are regarded as promising materials for short-wavelength light-emitting devices because of their large band gap. In particular, compound semiconductors (nitride-based semiconductors: AlGalnN) centered on gallium nitride have been actively studied, and blue light-emitting diodes and green light-emitting diodes have already been put into practical use. In addition, in order to increase the capacity of optical disk devices, semiconductor lasers having an oscillation wavelength in the 400 nm band have been eagerly desired, and semiconductor lasers made of nitride semiconductors have attracted attention and are now reaching a practical level.
[0003] 窒化物系半導体は、そのバンドギャップが大きいとともに絶縁破壊電界が高ぐ電 子の飽和ドリフト速度が高いという性質を有しているため、高温動作が可能であり、大 電力を流し得る。このため、高速スイッチング特性を実現する電界効果トランジスタや 、高電子移動度トランジスタに用いることも可能であるとされ、その研究が進められて いる。このような窒化物系半導体を用いたトランジスタの性能は、従来、実用化されて きたシリコン(Si)系、砒化ガリウム(GaAs)系、リン化インジウム(InP)系を上回る特性 を有すると期待されている。 [0003] Nitride-based semiconductors have the characteristics that the band gap is large and the dielectric breakdown electric field is high and the saturation saturation speed of the electron is high. Therefore, high-temperature operation is possible and high power can flow. . For this reason, it is considered that it can be used for a field effect transistor realizing high-speed switching characteristics and a high electron mobility transistor. The performance of such a transistor using a nitride-based semiconductor is expected to exceed the characteristics of silicon (Si), gallium arsenide (GaAs), and indium phosphide (InP), which have been put into practical use. ing.
[0004] 窒化物系半導体を用いて作製された半導体レーザ素子などの従来構造は、例え ば特許文献 1〜8および非特許文献 1〜3に開示されている。 [0004] Conventional structures such as a semiconductor laser device manufactured using a nitride-based semiconductor are disclosed in, for example, Patent Documents 1 to 8 and Non-Patent Documents 1 to 3.
特許文献 1:特開平 10— 126006号公報 Patent Document 1: Japanese Patent Laid-Open No. 10-126006
特許文献 2:特開平 9 63962号公報 特許文献 3:特開 2003— 264345号公報 Patent Document 2: JP-A-9 63962 Patent Document 3: Japanese Patent Laid-Open No. 2003-264345
特許文献 4 :特開 2002— 100837号公報 Patent Document 4: Japanese Patent Laid-Open No. 2002-100837
特許文献 5 :特開 2003— 69156号公報 Patent Document 5: Japanese Unexamined Patent Publication No. 2003-69156
特許文献 6:特開平 11—4044号公報 Patent Document 6: Japanese Patent Laid-Open No. 11-4044
特許文献 7:特許第 3505442号明細書 Patent Document 7: Patent No. 3505442
特許文献 8:特開 2001— 144378号公報 Patent Document 8: JP 2001-144378 A
非特許文献 1 Japanese Journal of Applied Physics, Vol. 38, L226 -L229 (1 999) Non-Patent Document 1 Japanese Journal of Applied Physics, Vol. 38, L226 -L229 (1 999)
非特許文献 2 : physica status solidi (A) 194, No. 2, 407 - 413 (2002) 非特許文献 3: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM E Non-Patent Document 2: physica status solidi (A) 194, No. 2, 407-413 (2002) Non-Patent Document 3: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM E
LECTRONICS, VOL. 9, NO. 5, 1252- 1259 (2003) LECTRONICS, VOL. 9, NO. 5, 1252-1259 (2003)
発明の開示 Disclosure of the invention
発明が解決しょうとする課題 Problems to be solved by the invention
[0005] 窒化物系半導体レーザ素子では、現在、例えば 120mW超の高出力動作を実現 することが求められている力 そのような高出力動作を達成する上で問題となってい るのは、ァクセプタ不純物としてドープされる Mgの活性化率が低いことにある。例え ば、 Mgをドープした p型 GaN層では、ドープした Mgの 10%程度しか活性化しない 場合がある。このため、 n型クラッド層のキャリア濃度と同レベルのキャリア濃度を有す る p型クラッド層を形成するには、 10倍以上の Mgをドーピングする必要がある。 [0005] Nitride-based semiconductor laser devices are currently required to achieve a high-power operation of, for example, more than 120 mW. The problem with achieving such a high-power operation is that the acceptor The activation rate of Mg doped as an impurity is low. For example, a p-type GaN layer doped with Mg may activate only about 10% of doped Mg. Therefore, in order to form a p-type cladding layer having the same carrier concentration as that of the n-type cladding layer, it is necessary to dope 10 times or more of Mg.
[0006] 更に、正孔の有効質量は電子の有効質量に比べて 5倍から 10倍も重ぐ結果的に 抵抗率が約 20倍から 50倍も大きくなるため、 p型窒化物系半導体層の抵抗率が高く なる傾向があり、この高い抵抗率のために、半導体素子の動作電圧が上昇するととも に、動作時に発熱しやすいという問題も発生する。 [0006] Furthermore, the effective mass of holes is 5 to 10 times heavier than the effective mass of electrons, and as a result, the resistivity is increased by about 20 to 50 times. Therefore, the p-type nitride semiconductor layer The resistivity of the semiconductor device tends to be high, and this high resistivity causes a problem that the operating voltage of the semiconductor element increases and heat is easily generated during operation.
[0007] なお、 Inを含有する混晶層(例えば活性層)は、結晶からの Inの分解を抑制するた めに、一般に GaN層や AlGaN混晶層と比較して低い成長温度で成長させられる。 特に可視光から近紫外領域にわたる窒化物系光素子を作製する場合は、成長温度 を 80°Cから 400°Cも低温化する必要があり、 Inを含有する混晶層からなる活性層を 作製した後、 p型クラッド層を作製するためには 80°C以上の昇温をする必要がある。 このような昇温過程で活性層の熱による劣化が発生し、量子井戸構造の乱れ、 Inの 偏析、不純物の拡散による混入、不純物の混入による格子歪みの増大などの問題が 引き起こされる。このとき、 p型クラッド層から活性層に向けて、 p型ァクセプタ不純物 である Mgの拡散も起こるため、これによつても活性層の劣化(不純物の混入、それに よる格子歪みの導入)が生じてしまい、発光効率が低下する。現在、これらの問題を 解決することが高出力高信頼性窒化物系半導体レーザを実現するための必須条件 となっている。 [0007] Note that a mixed crystal layer containing In (for example, an active layer) is generally grown at a lower growth temperature than a GaN layer or an AlGaN mixed crystal layer in order to suppress decomposition of In from the crystal. It is done. In particular, when fabricating nitride-based optical devices ranging from the visible light to the near-ultraviolet region, it is necessary to lower the growth temperature by 80 ° C to 400 ° C, and an active layer consisting of a mixed crystal layer containing In is produced. After that, it is necessary to raise the temperature to 80 ° C or higher in order to produce the p-type cladding layer. In this temperature rising process, the active layer deteriorates due to heat, causing problems such as disorder of the quantum well structure, segregation of In, contamination due to impurity diffusion, and increased lattice distortion due to impurity contamination. At this time, Mg, which is a p-type acceptor impurity, also diffuses from the p-type cladding layer to the active layer, which also causes deterioration of the active layer (impurity contamination and introduction of lattice strain due to it). As a result, the luminous efficiency decreases. At present, solving these problems is an indispensable condition for realizing a high-power and high-reliability nitride-based semiconductor laser.
[0008] このように、 p型クラッド層における動作電圧の上昇や発熱、 p型クラッド層作製時の 昇温過程における活性層の熱劣化は、窒化物系半導体素子の信頼性に悪影響を 及ぼし、高い信頼性を有する窒化物系半導体素子を再現性良く製造することを困難 にしている。 As described above, the increase in operating voltage and heat generation in the p-type cladding layer, and the thermal degradation of the active layer during the temperature rising process during the preparation of the p-type cladding layer adversely affect the reliability of the nitride-based semiconductor element. It is difficult to manufacture highly reliable nitride-based semiconductor elements with high reproducibility.
[0009] 上記の特許文献のうち、特許文献 2では、 p型 AlGaNクラッド層への炭素ドーピン グにより、高い活性化率で p型化が実現されること、また、 p型クラッド層から活性層側 への不純物拡散が抑制できることが開示されている。通常は p型ドーパントとして使用 される Mgの代わりに、炭素のみをドーピングすることにより、低抵抗な p型結晶を実現 してレ、る。し力しながら、特許文献 2は、発光素子にとって良好な電気特性を実現し 得る最適な炭素濃度の範囲は開示されていない。 [0009] Among the above-mentioned patent documents, in Patent Document 2, p-type conversion is realized at a high activation rate by carbon doping to the p-type AlGaN cladding layer. It is disclosed that impurity diffusion to the side can be suppressed. Instead of Mg, which is usually used as a p-type dopant, a low-resistance p-type crystal is realized by doping only carbon. However, Patent Document 2 does not disclose an optimal carbon concentration range that can realize good electrical characteristics for the light-emitting element.
[0010] また、特許文献 8では、 Siドーピングが施された n型 AlGaNクラッド層、および、 Mg ドーピングが施された p型 AlGaNクラッド層への炭素ドーピングによる効果が説明さ れているが、発光素子にとって良好な電気特性を実現し得る最適な炭素濃度の範囲 は開示されていない。 [0010] Also, Patent Document 8 describes the effect of carbon doping on an n-type AlGaN cladding layer with Si doping and a p-type AlGaN cladding layer with Mg doping. The optimum carbon concentration range that can realize good electrical characteristics for the device is not disclosed.
[0011] 本発明は上記問題を解決するためになされたものであり、その主たる目的は、信頼 性の高い窒化物系半導体素子を提供することにある。 [0011] The present invention has been made to solve the above problems, and a main object thereof is to provide a nitride semiconductor device having high reliability.
課題を解決するための手段 Means for solving the problem
[0012] 窒化物系半導体素子であって、前記積層構造は、 n型窒化物系半導体層と、 p型 窒化物系半導体層と、前記 n型窒化物系半導体層と前記 p型窒化物系半導体層との 間に位置する窒化物系半導体層とを有し、前記 p型窒化物系半導体層には、炭素以 外の p型不純物と炭素とがドープされており、前記 p型窒化物系半導体層の炭素濃 度は、前記炭素以外の p型不純物の濃度よりも低ぐ前記 n型窒化物系半導体層の 炭素濃度よりも高い。 [0012] A nitride-based semiconductor element, wherein the stacked structure includes an n-type nitride-based semiconductor layer, a p-type nitride-based semiconductor layer, the n-type nitride-based semiconductor layer, and the p-type nitride-based device A nitride-based semiconductor layer positioned between the semiconductor layer, the p-type nitride-based semiconductor layer being doped with a p-type impurity other than carbon and carbon, and the p-type nitride Carbon concentration of semiconductor layer The degree is higher than the carbon concentration of the n-type nitride semiconductor layer, which is lower than the concentration of the p-type impurity other than the carbon.
[0013] 好ましい実施形態において、前記 p型窒化物系半導体層にドープされている炭素 以外の p型不純物はマグネシウムである。 In a preferred embodiment, the p-type impurity other than carbon doped in the p-type nitride-based semiconductor layer is magnesium.
[0014] 好ましい実施形態において、前記 p型窒化物系半導体層の炭素濃度は 8 X 1016c m— 3以上 1 X 1018cm— 3以下である。 In a preferred embodiment, the carbon concentration of the p-type nitride-based semiconductor layer is 8 × 10 16 cm− 3 or more and 1 × 10 18 cm− 3 or less.
[0015] 好ましい実施形態において、前記 p型窒化物系半導体層の炭素濃度は、前記 p型 窒化物系半導体層にドープされている炭素以外の p型不純物の濃度に対して 0. 8In a preferred embodiment, the carbon concentration of the p-type nitride semiconductor layer is 0.8 relative to the concentration of p-type impurities other than carbon doped in the p-type nitride semiconductor layer.
%以上 10%以下の範囲にある。 It is in the range of 10% to 10%.
[0016] 好ましい実施形態において、前記基板は、窒化ガリウム、窒化アルミニウムガリウム(In a preferred embodiment, the substrate includes gallium nitride, aluminum gallium nitride (
Al Ga Ν (0 < χ≤1) )、サファイア、炭化珪素、および酸化亜鉛からなる群から選択 1 Selected from the group consisting of Al Ga Ν (0 <χ≤1)), sapphire, silicon carbide, and zinc oxide 1
された材料から形成されてレ、る。 It is formed from the finished material.
[0017] 好ましい実施形態において、前記基板における貫通転位密度の平均値は 3 X 106c m 以下 ある。 In a preferred embodiment, the average value of threading dislocation density in the substrate is 3 × 10 6 cm or less.
[0018] 好ましい実施形態において、前記 p型窒化物系半導体層と n型窒化物系半導体層 との間に位置する前記窒化物系半導体層は、光を発する活性層として機能し、前記 n型窒化物系半導体層および前記 p型窒化物系半導体層は、それぞれ、前記活性 層に対するクラッド層として機能する。 In a preferred embodiment, the nitride-based semiconductor layer located between the p-type nitride-based semiconductor layer and the n-type nitride-based semiconductor layer functions as an active layer that emits light, and the n-type Each of the nitride-based semiconductor layer and the p-type nitride-based semiconductor layer functions as a cladding layer for the active layer.
[0019] 好ましい実施形態において、前記 p型窒化物系半導体層および n型窒化物系半導 体層は少なくとも一部にアルミニウムを含有し、前記 p型窒化物系半導体層と n型窒 化物系半導体層との間に位置する窒化物系半導体層は少なくとも一部にインジウム を含有する。 In a preferred embodiment, the p-type nitride-based semiconductor layer and the n-type nitride-based semiconductor layer contain at least a part of aluminum, and the p-type nitride-based semiconductor layer and the n-type nitride-based layer are included. The nitride-based semiconductor layer located between the semiconductor layer contains indium at least partially.
[0020] 好ましい実施形態において、前記 n型窒化物系半導体層には、シリコン、ゲルマ二 ゥム、および酸素からなる群から選択された少なくとも 1種類の元素がドープされてい る。 [0020] In a preferred embodiment, the n-type nitride semiconductor layer is doped with at least one element selected from the group consisting of silicon, germanium, and oxygen.
発明の効果 The invention's effect
[0021] 本発明の窒化物系半導体素子では、 p型窒化物系半導体層に対して、炭素(C)以 外の p型不純物(ァクセプタ不純物)と炭素とがドープされており、し力も、その炭素濃 度が炭素以外の P型不純物の濃度よりも低く調節されている。 In the nitride-based semiconductor element of the present invention, the p-type nitride-based semiconductor layer is doped with p-type impurities (acceptor impurities) other than carbon (C) and carbon. Its carbon concentration The degree is adjusted to be lower than the concentration of P-type impurities other than carbon.
[0022] 窒化物系半導体層にドープされた炭素は、 IV族元素であるため、結晶中の III族元 素(例えば Ga)と置換すれば、ドナー性不純物として機能するが、 V族元素である N と置換すれば、ァクセプタ不純物として機能する。本発明では、炭素以外の p型不純 物をドープすることにより、炭素の大部分を V族元素の Nと置換している。すなわち、 炭素は Nサイトでァクセプタ不純物として作用するため、残留ドナーを補償する効果 を発揮する。一般に、窒化物系半導体には、ドナー源となる多くの N空孔 (点欠陥)が 存在するが、本発明では、ドープされた Cが結晶中の Nサイトを占有することにより、 N空孔の生成を抑制するため、 p型窒化物系半導体層の電気抵抗率を大きく低下さ せること力 Sできる。 [0022] Since carbon doped in the nitride-based semiconductor layer is a group IV element, it functions as a donor impurity if it is replaced with a group III element (for example, Ga) in the crystal. If replaced with some N, it functions as an acceptor impurity. In the present invention, by doping a p-type impurity other than carbon, most of the carbon is replaced with N of the group V element. In other words, since carbon acts as an acceptor impurity at the N site, it has the effect of compensating for residual donors. In general, nitride-based semiconductors have many N vacancies (point defects) that serve as donor sources, but in the present invention, doped C occupies N sites in the crystal, so In order to suppress the generation of, it is possible to greatly reduce the electrical resistivity of the p-type nitride semiconductor layer.
[0023] このように炭素以外の p型不純物と炭素の両方をドープすることにより低抵抗化され た p型窒化物系半導体層を p型クラッド層として備える半導体レーザを作製すれば、 電流電圧特性 (IV特性)における直列抵抗成分が低下するため、しきい値電流およ び動作電圧を低減することが可能となり、信頼性や寿命が改善される。 [0023] If a semiconductor laser having a p-type nitride semiconductor layer having a low resistance by doping both p-type impurities other than carbon and carbon as a p-type cladding layer is produced, current-voltage characteristics Since the series resistance component in (IV characteristics) decreases, the threshold current and operating voltage can be reduced, improving reliability and life.
[0024] なお、従来、種々の炭素ドーピング技術が報告されている力 p型クラッド層に対し て、炭素以外の p型不純物とともに、その p型不純物よりも低濃度に炭素のドーピング を行うことは報告されていない。従来技術における炭素ドーピングは、炭素を p型不 純物(ァクセプタ不純物)として機能させることを目的として高濃度に行われているが 、半導体素子の通電動作時における p型クラッド層での動作電圧上昇や発熱を充分 に抑制することはできない。 [0024] It should be noted that conventionally, various carbon doping techniques have been reported for doping p-type cladding layers with p-type impurities other than carbon at a lower concentration than the p-type impurities. Not reported. Carbon doping in the prior art is performed at a high concentration for the purpose of functioning carbon as a p-type impurity (acceptor impurity), but the operating voltage rises in the p-type cladding layer during energization of the semiconductor element. And heat generation cannot be sufficiently suppressed.
図面の簡単な説明 Brief Description of Drawings
[0025] [図 1]本発明による窒化物系半導体素子の第 1の実施形態(半導体レーザ素子)を示 す断面図である。 FIG. 1 is a cross-sectional view showing a first embodiment (semiconductor laser element) of a nitride-based semiconductor element according to the present invention.
[図 2]図 1に示す半導体レーザ素子における SIMSプロファイルを示すグラフである。 2 is a graph showing a SIMS profile in the semiconductor laser device shown in FIG.
[図 3]n— GaN層の抵抗率と Si濃度との関係を示すグラフである。 FIG. 3 is a graph showing the relationship between the resistivity of the n-GaN layer and the Si concentration.
[図 4]p— GaN層の抵抗率と Mg濃度との関係を示すグラフである。 FIG. 4 is a graph showing the relationship between the resistivity of the p-GaN layer and the Mg concentration.
[図 5] (a)は、 Mgおよび Cがドープされた p型クラッド層を有する半導体レーザ素子に ついての IL特性および IV特性を示すグラフであり、(b)は、 Mgのみがドープされた p 型クラッド層を有する半導体レーザ素子についての IL特性および IV特性を示すダラ フである。 [Fig. 5] (a) is a graph showing IL and IV characteristics for a semiconductor laser device having a p-type cladding layer doped with Mg and C, and (b) is a graph showing only Mg doped. p This is a diagram showing IL and IV characteristics of a semiconductor laser device having a type cladding layer.
[図 6]光ガイド層(p側) /活性層における Mg濃度と基板における貫通転位密度との 関係を示すグラフである。 FIG. 6 is a graph showing the relationship between Mg concentration in the light guide layer (p side) / active layer and threading dislocation density in the substrate.
園 7]本発明による半導体レーザの第 2の実施形態に関する図面であり、 P_GaN層 (成長温度: 900°C)の抵抗率と Mg濃度との関係を示すグラフである。 A drawing relating to a second embodiment of a semiconductor laser according Garden 7] the present invention, P _GaN layer (growth temperature: 900 ° C) is a graph showing the relationship between the resistivity and Mg concentration.
園 8]炭素ドーピングが行われた p型クラッド層を有する窒化物系半導体レーザ素子 における内部量子効率および内部損失と炭素濃度との関係を示すグラフである。 園 9]本発明による窒化物系半導体素子の第 3の実施形態(半導体レーザ素子)を示 す断面図である。 8] This is a graph showing the relationship between internal quantum efficiency and internal loss and carbon concentration in a nitride semiconductor laser device having a p-type cladding layer doped with carbon. FIG. 9] A sectional view showing a third embodiment (semiconductor laser element) of a nitride-based semiconductor element according to the present invention.
符号の説明 Explanation of symbols
[0026] 101 n— GaN基板 [0026] 101 n— GaN substrate
102 n— GaN層 102 n— GaN layer
103 n-Al Ga Nクラッド層 103 n-Al Ga N cladding layer
104 n— GaN光ガイド層 104 n— GaN optical guide layer
105 Ga In N/Ga In N量子井戸活性層 105 Ga In N / Ga In N quantum well active layer
106 Ga In N第 1光ガイド層 106 Ga In N 1st light guide layer
107 GaN第 2光ガイド層 107 GaN second light guide layer
108 Al Ga N第 3光ガイド層 108 Al Ga N 3rd light guide layer
109 p-Al Ga N第 1クラッド層 109 p-Al Ga N 1st cladding layer
110 p-Al Ga N第 2クラッド層 110 p-Al Ga N second cladding layer
111 p— GaNコンタクト層 111 p— GaN contact layer
112 p電極 112 p electrode
113 n電極 113 n electrode
114 SiO 114 SiO
1210 p-Al Ga N/p— GaN— SLS第 2クラッド層 1210 p-Al Ga N / p— GaN— SLS second cladding layer
発明を実施するための最良の形態 BEST MODE FOR CARRYING OUT THE INVENTION
[0027] (実施形態 1) 以下、図面を参照しながら、本発明による窒化物系半導体素子の第 1の実施形態 を説明する。図 1は、本実施形態の窒化物系半導体レーザ素子の断面構造を示して いる。 [Embodiment 1] Hereinafter, a first embodiment of a nitride semiconductor device according to the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional structure of the nitride-based semiconductor laser device of this embodiment.
[0028] 本実施形態の半導体レーザ素子は、 n— GaN基板 101と、 n_GaN基板 101上に 形成した半導体積層構造とを備えている。半導体積層構造は、 n_GaN基板 101に 近い側から、 η— GaN層 102、 n_Al Ga Nクラッド層 103、 n_GaN光ガイド層 1 The semiconductor laser device of this embodiment includes an n-GaN substrate 101 and a semiconductor multilayer structure formed on the n_GaN substrate 101. The stacked semiconductor structure consists of the η—GaN layer 102, n_Al Ga N cladding layer 103, n_GaN light guide layer 1 from the side close to the n_GaN substrate 101.
04、 Ga In N/Ga In N—量子井戸活性層 105、ノンドープ Ga In N第04, Ga In N / Ga In N—Quantum well active layer 105, Non-doped Ga In N
1光ガイド層 106、ノンドープ GaN第 2光ガイド層 107、ノンドープ Al Ga N第 3光 ガイド層 108、p_Al Ga N第 1クラッド層 109、 p_Al Ga N第 2クラッド層 111 Optical guide layer 106, Non-doped GaN second optical guide layer 107, Non-doped Al Ga N Third optical guide layer 108, p_Al Ga N first cladding layer 109, p_Al Ga N second cladding layer 11
0、および ρ— GaNコンタクト層 111を有している。 0, and ρ-GaN contact layer 111.
[0029] 半導体積層構造の上面には、幅 1. 4〜: 1. 8 z m程度のメサストライプが形成されて おり、このメサストライプの上面以外の領域が絶縁層(Si〇層) 114で覆われている。[0029] A mesa stripe having a width of approximately 1.4 to 1.8 zm is formed on the upper surface of the semiconductor multilayer structure, and a region other than the upper surface of the mesa stripe is covered with an insulating layer (Si layer) 114. It has been broken.
SiO層 114によって覆われていない部分(SiO層 114の開口部)では、 p電極 112 力 — GaNコンタクト層 111の上面と接触している。 n— GaN基板 101の裏面側にはThe p electrode 112 force—the upper surface of the GaN contact layer 111 is in contact with the portion not covered by the SiO layer 114 (the opening of the SiO layer 114). n— On the back side of GaN substrate 101
、 n電極 113が形成されている。 N electrode 113 is formed.
[0030] n電極 113と p電極 112との間に電圧を印カ卩すると、量子井戸活性層 105に向かつ て p電極 112からは正孔力 n電極 113からは電子が注入され、量子井戸活性層 10[0030] When a voltage is applied between the n-electrode 113 and the p-electrode 112, the hole force is directed from the p-electrode 112 toward the quantum well active layer 105. Active layer 10
5で利得を生じ、 410nmの波長でレーザ発振が生じる。 Gain occurs at 5, and laser oscillation occurs at a wavelength of 410 nm.
[0031] 本実施形態の半導体レーザで最も特徴的な点は、 p— Al Ga N第 1クラッド層 1[0031] The most characteristic feature of the semiconductor laser of the present embodiment is that the p-AlGaN first cladding layer 1
09から p— GaNコンタクト層 111にわたる p型窒化物系半導体層に、ァクセプタ不純 物である Mgとともに炭素(C)がドーピングされていることにある。 The p-type nitride semiconductor layer from 09 to the p-GaN contact layer 111 is doped with carbon (C) together with Mg, which is an acceptor impurity.
[0032] 上記の半導体積層構造は、有機金属気相成長法 (MOVPE法)によって好適に形 成され得るが、ハイドライド気相成長法 (HVPE法)や分子線エピタキシー法 (MBE 法)などの他の化合物半導体結晶の成長方法を用いても形成され得る。 [0032] The above semiconductor stacked structure can be suitably formed by metal organic vapor phase epitaxy (MOVPE), but other methods such as hydride vapor phase epitaxy (HVPE) and molecular beam epitaxy (MBE). The compound semiconductor crystal growth method can be used.
[0033] 以下、図 1を参照しながら、本実施形態における半導体レーザ素子の製造方法を 説明する。本実施形態では、結晶成長に MOVPE法を用いるが、結晶成長時の雰 囲気は減圧でも大気圧以上の圧力であってもよい。成長させるべき半導体層の組成 に応じて最適な圧力に切り換えても良い。また、成長層の原料を基板に供給するた めのキャリアガスとしては、窒素(N )または水素(H )等の不活性ガスを含むガスを用 Hereinafter, a method for manufacturing a semiconductor laser device in the present embodiment will be described with reference to FIG. In the present embodiment, the MOVPE method is used for crystal growth, but the atmosphere during crystal growth may be a reduced pressure or a pressure higher than atmospheric pressure. The pressure may be switched to an optimum pressure depending on the composition of the semiconductor layer to be grown. Also, to supply the growth layer material to the substrate As the carrier gas, a gas containing an inert gas such as nitrogen (N) or hydrogen (H) is used.
2 2 twenty two
レ、ることができる。 I can.
[0034] まず、 n—GaN基板 101を用意し、有機溶剤や酸によって n—GaN基板 101の表 面を清浄化する。その後、 n_GaN基板 101を MOVPE装置の成長室内のサセプタ 一上に設置し、成長室内の雰囲気ガスを十分に Nで置換する。 N置換が終了した First, an n-GaN substrate 101 is prepared, and the surface of the n-GaN substrate 101 is cleaned with an organic solvent or acid. After that, the n_GaN substrate 101 is placed on the susceptor in the growth chamber of the MOVPE apparatus, and the atmosphere gas in the growth chamber is sufficiently replaced with N. N substitution finished
2 2 twenty two
後、 N雰囲気中において n— GaN基板 101の加熱を行い、 10°C/10秒の昇温レー Then, the n-GaN substrate 101 is heated in an N atmosphere, and the temperature rise rate is 10 ° C / 10 seconds.
2 2
トで 1000°Cまで昇温する。その後、 Nを Hキャリアガスに切り替え、同時にアンモニ To 1000 ° C. Then switch N to H carrier gas and simultaneously
2 2 twenty two
ァ(NH )を供給し、 5分間基板表面のクリーニングを行う。このクリーニングの後、トリ Supply NH (NH) and clean the substrate surface for 5 minutes. After this cleaning,
3 Three
メチルガリウム(TMG)およびモノシラン(SiH )を供給し、 V/III比 = 6000の条件 Supplying methylgallium (TMG) and monosilane (SiH), V / III ratio = 6000
4 Four
下で、 厚の n— GaN層 102を成長させる。引き続いて、トリメチルアルミニウム( TMA)をカロえ、 1. 厚の n_Al Ga Nクラッド層 103を成長させる。 Below, a thick n-GaN layer 102 is grown. Subsequently, trimethylaluminum (TMA) is removed and 1. A thick n_AlGaN cladding layer 103 is grown.
0.05 0.95 0.05 0.95
[0035] 次に、 TMAの供給を停止し、 n—GaN光ガイド層 104を厚さ 0. 1 μ mまで成長さ せる。 n— GaN光ガイド層 104の成長後、キャリアガスを H力 Nに切り換え、 NH Next, the supply of TMA is stopped, and the n-GaN optical guide layer 104 is grown to a thickness of 0.1 μm. After the growth of n—GaN optical guide layer 104, the carrier gas is switched to H force N, NH
2 2 3 の供給を停止し、成長温度を 800°Cまで降温する。成長温度が 800°Cで安定後、ま ず NHを供給し、続いて TMGとトリメチルインジウム(TMI)を供給し、 V/III比 = 30 Stop supplying 2 2 3 and lower the growth temperature to 800 ° C. After the growth temperature is stabilized at 800 ° C, NH is supplied first, followed by TMG and trimethylindium (TMI), and the V / III ratio = 30
3 Three
000の条件下で、 Ga In N/Ga In N—量子井戸活性層 105を成長する。 G Under the condition of 000, a Ga In N / Ga In N—quantum well active layer 105 is grown. G
0.90 0.10 0.98 0.02 0.90 0.10 0.98 0.02
a In N井戸層厚は 5nm、Ga In N障壁層の厚さは 6nmであり、井戸層数は 2 a In N well layer thickness is 5 nm, Ga In N barrier layer thickness is 6 nm, and the number of well layers is 2
0.90 0.10 0.98 0.02 0.90 0.10 0.98 0.02
である。活性層 105には、意図的な不純物ドーピングは行っていない。 It is. The active layer 105 is not intentionally doped with impurities.
[0036] 引き続いて 25nm厚のノンドープ Ga In N第 1光ガイド層 106、および 50nm厚 [0036] Subsequently, a non-doped Ga In N first optical guide layer 106 having a thickness of 25 nm and a thickness of 50 nm
0.98 0.02 0.98 0.02
のノンドープ GaN第 2光ガイド層 107を成長した後、いったん TMGの供給を停止す る。 After the non-doped GaN second optical guide layer 107 is grown, the supply of TMG is once stopped.
[0037] その後、 Nおよび NHの供給を行いながら、迅速に 1000°Cまで昇温し、成長温度 [0037] Thereafter, while supplying N and NH, the temperature was rapidly raised to 1000 ° C, and the growth temperature
2 3 twenty three
力 1000°Cに到達した後、キャリアガスを Nおよび Hの混合ガスに変更する。 N After reaching the force of 1000 ° C, change the carrier gas to a mixed gas of N and H. N
2 2 2、 H 2 2 2, H
2 2
、および NHを供給しつつ、直ちに TMGと TMAを供給して、 V/III比 = 8000の条 While supplying NH and NH, immediately supply TMG and TMA, and V / III ratio = 8000.
3 Three
件下で、 10nm厚のノンドープ Al Ga N第 3光ガイド層 108を成長させる。 Under the conditions, a 10 nm-thick non-doped AlGaN third optical guide layer 108 is grown.
0.01 0.99 0.01 0.99
[0038] 次に、 Mg原料としてのビスシクロペンタジェニルマグネシウム(Cp Mg)と、 C原料 [0038] Next, biscyclopentagenenyl magnesium (Cp Mg) as an Mg raw material, and a C raw material
2 2
としてのメタン(CH )を添加し、 p-Al Ga N第 1クラッド層 109を lOnm成長させ Methane (CH 3) was added as a p-AlGaN first cladding layer 109 by lOnm growth.
4 0.20 0.80 4 0.20 0.80
る。 p— Al Ga N第 1クラッド層 109は、 Ga In N/Ga In N—量子井戸活 The The p—Al Ga N first cladding layer 109 is composed of Ga In N / Ga In N—quantum well actives.
0.20 0.80 0.90 0.10 0.98 0.02 性層 105からの電子のオーバーフローを抑制する機能を発揮する。このとき、 C濃度 が Mg濃度よりも低くなるようにガス流量を調節する。 0.20 0.80 0.90 0.10 0.98 0.02 The function of suppressing the overflow of electrons from the conductive layer 105 is exhibited. At this time, the gas flow rate is adjusted so that the C concentration is lower than the Mg concentration.
[0039] p-Al Ga N第 1クラッド層 109の成長後、すばやくキャリアガスを Hのみに切り 替え、 0. 厚の p_Al Ga N第 2クラッド層 110、および 50nm厚の p_GaN コンタクト層 111を順次積層する。 Mgおよび Cのドーピングは、 p—Al Ga N第 1 クラッド層 109に対して行った条件と同様の条件で行う。 [0039] After the growth of the p-AlGaN first cladding layer 109, the carrier gas is quickly switched to only H, and the 0.thick p_AlGaN second cladding layer 110 and the 50 nm thick p_GaN contact layer 111 are sequentially formed. Laminate. Mg and C are doped under the same conditions as those for the p-AlGaN first cladding layer 109.
[0040] ρ— GaNコンタクト層 111の成長後、積層構造が形成された η— GaN基板 101を M OVPE装置から取り出し、フォトリソグラフィおよびエッチング技術による微細加工ェ 程を実行する。具体的には、 P—A1 Ga N第 1クラッド層 109、p_Al Ga N第[0040] After the growth of the ρ-GaN contact layer 111, the η-GaN substrate 101 on which the laminated structure is formed is taken out of the MOVPE apparatus, and a microfabrication process using photolithography and etching techniques is performed. Specifically, P-A1 Ga N first cladding layer 109, p_Al Ga N first
2クラッド層 110、 p— GaNコンタクト層 111を図 1に示すようにストライプ状に加工し、 メサストライプを形成する。 2 Cladding layer 110 and p-GaN contact layer 111 are processed into stripes as shown in FIG. 1 to form mesa stripes.
[0041] 次に、半導体積層構造の上面のうち、メサストライプの上面以外の領域を Si〇層 1 [0041] Next, in the upper surface of the semiconductor multilayer structure, the region other than the upper surface of the mesa stripe is formed in the Si layer 1
2 2
14で覆う。 SiO層 114によって覆われてレ、なレ、部分(SiO層 114の開口部)で、メサ ストライプの上面、すなわち、ストライプ状に加工された p— GaNコンタクト層 111の上 面が露出する。ストライプ幅は 1 · 4〜: ! · 8 /i m程度である。 Cover with 14. The upper surface of the mesa stripe, that is, the upper surface of the p-GaN contact layer 111 processed into the stripe shape is exposed at a portion (opening portion of the SiO layer 114) covered with the SiO layer 114. The stripe width is about 1 · 4 ~:! · 8 / im.
[0042] SiO絶縁層 114の開口部を覆うように p電極 112を形成すると、 p電極 112と p— Ga[0042] When the p-electrode 112 is formed so as to cover the opening of the SiO insulating layer 114, the p-electrode 112 and p-Ga
Nコンタクト層 111の上面とが Si〇層 114の開口部を介して接触する。なお、 p— GaThe upper surface of the N contact layer 111 is in contact with the upper surface of the Si layer 114. P-Ga
Nコンタクト層 111には、 p電極 112とのコンタクト抵抗を低減するため、濃度 1 X 102° cm— 3から 2 X 102°cm— 3の Mgがドープされている。 The N contact layer 111, in order to reduce the contact resistance with the p electrode 112, the concentration 1 X 10 2 ° cm- 3 from 2 X 10 2 ° cm- 3 of Mg is doped.
[0043] 次に、 n— GaN基板 101を裏面側力 研磨し、 n— GaN基板 101の厚さを 90 μ m 程度にまで薄くした後、 n— GaN基板 101の裏面に n電極 113を形成する。 [0043] Next, the n-GaN substrate 101 is polished on the back side to reduce the thickness of the n-GaN substrate 101 to about 90 μm, and then an n-electrode 113 is formed on the back surface of the n-GaN substrate 101. To do.
[0044] 本実施形態では、 GaN第 2光ガイド層 107を成長した後、 Al Ga N第 3光ガイド 層 108を成長するまでの間に、いったん TMGの供給を停止して、 Nと NHを供給し た状態ですばやく昇温し、かつ途中でキャリアガスを Nと Hの混合ガスに変更してい る。しかし、 TMGの供給を停止せず、 TMGを供給した状態で GaN第 2光ガイド層 1 07の結晶成長を行いながら昇温を行っても良レ、。また、 TMGおよび TMAを供給し 、A1 Ga N第 3光ガイド層 108の結晶成長を行いながら昇温を行っても良レ、。結 晶中に非発光再結合中心の原因となるような欠陥が生成されない方法であれば、ど のような昇温方法を採用してもよい。 In the present embodiment, after the GaN second light guide layer 107 is grown and before the Al Ga N third light guide layer 108 is grown, the supply of TMG is temporarily stopped, and N and NH are The temperature is quickly raised in the supplied state, and the carrier gas is changed to a mixed gas of N and H on the way. However, without stopping the TMG supply, it is acceptable to raise the temperature while growing the GaN second light guide layer 107 with the TMG supplied. Also, TMG and TMA can be supplied and the temperature can be raised while the A1 GaN third light guide layer 108 is crystal-grown. If the method does not generate defects that cause non-radiative recombination centers in the crystal, Such a temperature raising method may be adopted.
[0045] 図 2は、本実施形態の半導体レーザについての SIMSプロファイルを示すグラフで ある。図 2からわ力るように、 n— GaN光ガイド層 104、 Ga In N/Ga In N— 量子井戸活性層 105、 Ga In N第 1光ガイド層 106、および GaN第 2光ガイド層 1 FIG. 2 is a graph showing a SIMS profile for the semiconductor laser of the present embodiment. As can be seen from FIG. 2, n-GaN light guide layer 104, Ga In N / Ga In N— quantum well active layer 105, Ga In N first light guide layer 106, and GaN second light guide layer 1
07における「炭素濃度」は、 8 X 1016cm— 3〜l X 1017cm— 3である。これらの半導体層 1 05〜: 107には意図的な炭素ドーピングを行っていないため、その炭素濃度は極めて 低い。 The “carbon concentration” in 07 is 8 × 10 16 cm− 3 to l × 10 17 cm− 3 . Since these semiconductor layers 1 05 to 107 are not intentionally doped with carbon, their carbon concentration is extremely low.
[0046] また、図 2に示されるように、 A1を含有する n_Al Ga Nクラッド層 103、および In addition, as shown in FIG. 2, n_AlGaN cladding layer 103 containing A1, and
Al Ga N第 3光ガイド層 108における炭素濃度は、 l〜3 X 1017cm— 3である。これ らの半導体層 103、 808は、原料である TMAから Cがオートドーピングされるため、 意図的な炭素ドーピングを行っていないにもかかわらず、微量の Cが含有されている The carbon concentration in the Al Ga N third light guide layer 108 is 1 to 3 × 10 17 cm −3 . These semiconductor layers 103 and 808 contain a trace amount of C even though they are not intentionally carbon-doped because C is auto-doped from the raw material TMA.
[0047] なお、炭素濃度は、窒化物系半導体層の成長レートにも依存し、成長レートを低下 させると、炭素濃度は更に低下することがわかった。図 2の例に比べて、成長レートを 70%程度に低下すると、これらの窒化物系半導体層における炭素濃度は 7 X 1016c m 3以下に低下する。 [0047] It has been found that the carbon concentration also depends on the growth rate of the nitride-based semiconductor layer, and that the carbon concentration further decreases when the growth rate is decreased. Compared to the example in Fig. 2, when the growth rate is reduced to about 70%, the carbon concentration in these nitride-based semiconductor layers decreases to 7 x 10 16 cm 3 or less.
[0048] 一方、炭素ドーピングを行った p—Al Ga N第 1クラッド層 109、 p—Al Ga [0048] On the other hand, the p-AlGaN first cladding layer 109 with carbon doping, p-AlGa
N第 2クラッド層 110、および、 p— GaNコンタクト層 111における炭素濃度は、 7 X 10 17〜1 X 1018cm 3の程度の範囲にあった。これらの窒化物半導体層の場合も、その成 長レートを 70%程度に低下すると、炭素濃度は 8 X 1016cm 3〜8 X 1017cm— 3に低下 する。 The carbon concentration in the N second cladding layer 110 and the p-GaN contact layer 111 was in the range of about 7 × 10 17 to 1 × 10 18 cm 3 . In the case of these nitride semiconductor layers as well, the carbon concentration decreases from 8 × 10 16 cm 3 to 8 × 10 17 cm− 3 when the growth rate is reduced to about 70%.
[0049] 以上のように、 n型クラッド層、活性層、および p型クラッド層の炭素濃度の大小関係 は、活性層く n型クラッド層 < p型クラッド層となってレ、た。 [0049] As described above, the magnitude relationship among the carbon concentrations of the n-type cladding layer, the active layer, and the p-type cladding layer was such that the active layer was n-type cladding layer <p-type cladding layer.
[0050] 次に、 GaN層および AlGaN層(A1組成が 20%以下)に対する炭素ドーピングの役 割について説明する。 [0050] Next, the role of carbon doping for the GaN layer and the AlGaN layer (A1 composition is 20% or less) will be described.
[0051] 本実施形態における n型半導体層の成長条件 (成長温度 = 1000°C、 VZlII比 = 6000)、および p型半導体層の成長条件(成長温度 = 1000°C、 νΖΠΙ比 = 8000) のもとで、厚さ 1 β mの半導体層を成長させ、炭素ドーピングを行った。炭素濃度を 3 X 1017cm— 3〜5 X 1018cm— 3の範囲内で変化させた複数のサンプルを用意し、各サン プノレの電気特性を評価した。 [0051] The growth conditions of the n-type semiconductor layer (growth temperature = 1000 ° C, VZlII ratio = 6000) and the growth conditions of the p-type semiconductor layer (growth temperature = 1000 ° C, ν 、 ratio = 8000) in this embodiment Originally, a semiconductor layer having a thickness of 1 β m was grown and carbon doping was performed. Carbon concentration 3 Several samples were prepared in the range of X 10 17 cm— 3 to 5 X 10 18 cm— 3 , and the electrical characteristics of each sample were evaluated.
[0052] 炭素のみをドーピングした GaN層では、 n型および p型にかかわらず、作製直後の 抵抗率が I X 107 Ω cm以上であり、非常に抵抗の高レ、 n型伝導性を示すことがわか つた。なお、これらの成長条件で意図的な不純物ドーピングを全く行わずに GaN層 を作製した場合は、得られた GaN層の結晶中に残留する Siの濃度が 1〜2 X 1016c m 3程度であり、 GaN層の抵抗率は 10 Ω cm程度であった。 [0052] In a GaN layer doped with carbon only, the resistivity immediately after fabrication is IX 10 7 Ωcm or higher, regardless of n-type or p-type, and it exhibits very high resistance and n-type conductivity. I understand. When a GaN layer is fabricated without intentional impurity doping under these growth conditions, the concentration of Si remaining in the crystal of the obtained GaN layer is about 1 to 2 X 10 16 cm 3 . The resistivity of the GaN layer was about 10 Ωcm.
[0053] 炭素ドーピングを施した GaN層に対して、窒素中で 800°C、 10分間の熱処理をカロ えたところ、抵抗率の僅かな低減が確認されたものの、抵抗率は 1 X 106 Q cm以上 であり、 n型伝導性を示した。炭素濃度が 5 X 1018cm— 3以下の GaN層では、低抵抗 の n型伝導性も、 p型伝導性も示さな力 た。同様の結果は、 A1組成が 20%以下の A IGaN層におレ、ても観察された。 [0053] When the carbon-doped GaN layer was subjected to heat treatment at 800 ° C for 10 minutes in nitrogen, a slight decrease in resistivity was confirmed, but the resistivity was 1 X 10 6 Q It was over cm and showed n-type conductivity. The GaN layer with a carbon concentration of 5 × 10 18 cm– 3 or less has the power to exhibit neither low-resistance n-type conductivity nor p-type conductivity. Similar results were observed for A IGaN layers with A1 composition below 20%.
[0054] 以上のことから、本実施形態の成長条件では、クラッド層に炭素ドーピングのみを 行っても、低抵抗な n型クラッド層を得ることできず、また、 p型クラッド層を得ることもで きないことがわかる。 From the above, under the growth conditions of this embodiment, a low-resistance n-type cladding layer cannot be obtained even if only carbon doping is performed on the cladding layer, and a p-type cladding layer can also be obtained. You can see that you can't.
[0055] 一般に、 GaN層の結晶成長中に炭素ドーピングのみを施した場合、 Cが IV族元素 であるため、 Cが GaN結晶中で Gaと置換すればドナー性不純物として機能し、 Nと 置換すればァクセプタ不純物として機能する。本実施形態における成長条件で炭素 ドーピングのみを施した場合、ドーピングなしの GaN層に比べて、非常に抵抗の高い n型伝導性を示す GaN層が得られた。このこと力ら、添加した Cの大部分は GaN結 晶中で Nと置換し、ァクセプタ不純物として作用することにより、残留ドナーを補償し ていると考えられる。 GaN結晶には、ドナー源となる多くの N空孔(点欠陥)が存在す る力 ドープされたが GaN結晶中の Nを占有することにより、 N空孔の生成も抑制さ れていると考えられる。 [0055] Generally, when only carbon doping is performed during crystal growth of a GaN layer, C is a group IV element, so if C substitutes Ga in the GaN crystal, it functions as a donor impurity, and substitutes N Then, it functions as an acceptor impurity. When only carbon doping was performed under the growth conditions in this embodiment, a GaN layer showing n-type conductivity having a very high resistance was obtained compared to a GaN layer without doping. Based on this, it is considered that most of the added C is replaced with N in the GaN crystal and acts as an acceptor impurity to compensate the residual donor. The GaN crystal has many N vacancies (point defects) that serve as donor sources. It is doped, but occupying N in the GaN crystal suppresses the generation of N vacancies. Conceivable.
[0056] 図 3は、 n— GaN層の抵抗率の変化を示すグラフであり、縦軸が抵抗率、横軸が Si 濃度である。グラフ中で「秦」は、炭素濃度が 1 X 1017cm— 3のデータを示し、「△」は炭 素濃度が 8 X 1017cm— 3のデータを示している。図 4は、 ρ— GaN層の抵抗率の変化を 示すグラフであり、縦軸が抵抗率、横軸が Mg濃度である。グラフ中で「き」は、炭素 濃度が 1 X 1017cm— 3のデータを示し、「△」は炭素濃度が 8 X 1017cm 3のデータを示 してレ、る。いずれも、成長条件は上記の実施形態について説明したとおりである。 1 X 1017cm 3の炭素濃度は、意図的な Cドープを行わなかった場合のデータに対応し ている。 FIG. 3 is a graph showing the change in resistivity of the n-GaN layer, where the vertical axis represents the resistivity and the horizontal axis represents the Si concentration. In the graph, “秦” indicates data with a carbon concentration of 1 × 10 17 cm− 3 , and “△” indicates data with a carbon concentration of 8 × 10 17 cm− 3 . Fig. 4 is a graph showing the change in resistivity of the ρ-GaN layer, where the vertical axis represents the resistivity and the horizontal axis represents the Mg concentration. In the graph, “ki” is carbon. Data with a concentration of 1 X 10 17 cm- 3 are shown, and “△” indicates data with a carbon concentration of 8 X 10 17 cm 3 . In any case, the growth conditions are as described in the above embodiment. The carbon concentration of 1 X 10 17 cm 3 corresponds to the data without intentional C doping.
[0057] n型不純物として Siをドーピングした n— GaN層では、炭素濃度が 1 X 1017cm— 3の 場合に比べ、炭素濃度が 8 X 1017cm 3の場合に、抵抗率が約 50%高くなつていた。 これは、ドーピングされた Cの大部分が GaN結晶中で Nと置換し、ァクセプタ不純物 として作用するため、 Siドナーを補償するためである。 [0057] In an n-GaN layer doped with Si as an n-type impurity, the resistivity is about 50 when the carbon concentration is 8 X 10 17 cm 3 compared to 1 X 10 17 cm- 3. It was getting high. This is because most of the doped C replaces N in the GaN crystal and acts as an acceptor impurity, thus compensating for the Si donor.
[0058] 一方、 p型不純物として Mgをドーピングした p_GaN層では、炭素ドーピングを行う ことにより、抵抗率が約 10。/o程度低下した。これは、ドーピングされた Cが GaN結晶 中で Nと置換し、残留ドナーの補償や N空孔生成の低減が生じたためである。 [0058] On the other hand, the p_GaN layer doped with Mg as the p-type impurity has a resistivity of about 10 by performing carbon doping. Decreased about / o. This is because doped C replaced N in the GaN crystal, resulting in compensation of residual donors and reduction of N vacancies.
[0059] このこと力、ら、 p型窒化物系半導体層への炭素とマグネシウムの同時ドーピングによ り抵抗率の低減が実現できる力 n型窒化物系半導体層への炭素とシリコンの同時ド 一ビングでは、抵抗率が増加することが明らかとなった。従って、 n型窒化物系半導 体層の炭素濃度はできるだけ低く抑えることが望ましい。 [0059] This force is a force that can reduce the resistivity by co-doping carbon and magnesium into the p-type nitride semiconductor layer. Simultaneous carbon and silicon doping into the n-type nitride semiconductor layer It was clear that the resistivity increased at one bing. Therefore, it is desirable to keep the carbon concentration of the n-type nitride semiconductor layer as low as possible.
[0060] なお、 GaN層中に炭素ドーピングのみを施した場合は、炭素濃度が 5 X 1018cm— 3 以下であれば、平坦性の良好な GaN薄膜が実現可能である力 Cおよび Si、あるい は Cおよび Mgの同時ドーピングを行う場合は、炭素濃度が 2 X 1018cm— 3以上になる と、表面平坦性が悪化し、鏡面が得られなくなった。このため、 Cを他の不純物と同時 にドープする場合、炭素濃度は最大でも 2 X 1018cm 3以下に制御することが好ましい [0060] When only carbon doping is applied to the GaN layer, if the carbon concentration is 5 X 10 18 cm- 3 or less, the force C and Si that can realize a GaN thin film with good flatness can be realized. In the case of co-doping with C and Mg, when the carbon concentration was 2 X 10 18 cm- 3 or more, the surface flatness deteriorated and a mirror surface could not be obtained. Therefore, when C is doped with other impurities at the same time, it is preferable to control the carbon concentration to 2 X 10 18 cm 3 or less at maximum.
[0061] 図 3および図 4に示す実験結果と同様の結果は、炭素濃度が 2 X 1018cm— 3以下の 場合に得られた。また、 GaN層だけではなぐ A1組成が 20%以下の AlGaN層でも、 同様の結果が得られた。このように、炭素ドーピングには、 n型クラッド層の抵抗率を 増加させてしまう効果と、 p型クラッド層の抵抗率を低減する効果をもたらす。本実施 形態では、この効果を利用するため、 p型クラッド層に Mgおよび Cをドープしている。 [0061] Similar results to the experimental results shown in FIGS. 3 and 4 were obtained when the carbon concentration was 2 × 10 18 cm− 3 or less. Similar results were obtained with an AlGaN layer with an A1 composition of 20% or less, which is not limited to the GaN layer alone. Thus, carbon doping has the effect of increasing the resistivity of the n-type cladding layer and the effect of reducing the resistivity of the p-type cladding layer. In this embodiment, in order to utilize this effect, the p-type cladding layer is doped with Mg and C.
[0062] 炭素濃度は、 Mg濃度の 0. 8%以上 10%以下の範囲に調節することが好ましい。 [0062] The carbon concentration is preferably adjusted to a range of 0.8% to 10% of the Mg concentration.
このように炭素濃度を Mg濃度に比べて充分に低くすることにより、 Mgが Gaと置換し 、ァクセプタ不純物として作用するため、 Cが Nと効果的に置換し、ァクセプタ不純物 として作用することが可能になる。 Cが Gaではなぐ Nと置換することにより、残留ドナ 一を補償し、合わせて N空孔に起因した結晶欠陥を低減することができる。従来、こ のように他の p型不純物(Mg)よりも充分に低い濃度で炭素をドープすることは行わ れておらず、 p型窒化物系半導体の抵抗率を効果的に低減できることは知られてい なかった。 Thus, by making the carbon concentration sufficiently lower than the Mg concentration, Mg is replaced with Ga. Since it acts as an acceptor impurity, C can effectively replace N and act as an acceptor impurity. By substituting N for C instead of Ga, the residual donor can be compensated, and crystal defects caused by N vacancies can be reduced. Conventionally, carbon has not been doped at a concentration sufficiently lower than that of other p-type impurities (Mg), and it is known that the resistivity of p-type nitride semiconductors can be effectively reduced. It was not done.
[0063] 図 5 (a)は、炭素ドーピングを施した p型クラッド層を備える半導体レーザ (本実施形 態)について得られた IL特性および IV特性を示すグラフであり、図 5 (b)は、炭素ドー ピングを行わなレ、 p型クラッド層を備える半導体レーザ(比較例)について得られた IL 特性および IV特性を示すグラフである。 [0063] Fig. 5 (a) is a graph showing the IL and IV characteristics obtained for a semiconductor laser (this embodiment) having a carbon-doped p-type cladding layer. Fig. 5 (b) 4 is a graph showing IL characteristics and IV characteristics obtained for a semiconductor laser (comparative example) having a p-type cladding layer without carbon doping.
[0064] 炭素ドーピングを行うことにより、 p_Al Ga N第 2クラッド層 110の抵抗率が低 減し、 IV特性における直列抵抗成分が減少している。また、 N空孔に起因した結晶 欠陥が低減するため、活性層へのホールの注入効率が増加し、しきい値電流が減少 してレ、る。具体的には、 Cドーピングがない場合に 50mAを超えていたしきい値電流 力 ドーピングを行うことにより、約 37mAに低減されている。 [0064] By performing carbon doping, the resistivity of the p_AlGaN second cladding layer 110 is reduced, and the series resistance component in the IV characteristics is reduced. In addition, since crystal defects due to N vacancies are reduced, the efficiency of hole injection into the active layer is increased, and the threshold current is reduced. Specifically, it was reduced to about 37 mA by performing threshold current force doping that exceeded 50 mA in the absence of C doping.
[0065] p型クラッド層における抵抗率の低減を実現したことにより、高電流注入状態におけ る発熱も抑制でき、動作電流 200mAにおレ、て室温連続発振条件で 150mWの高レ、 光出力を達成できた。 [0065] By reducing the resistivity in the p-type cladding layer, it is possible to suppress heat generation in the high current injection state, with an operating current of 200mA, a high output of 150mW under room temperature continuous oscillation conditions, and light output. Was achieved.
[0066] 上記の効果を実現するためには、 p型クラッド層に Mgおよび Cをドーピングすること が重要であるが、ドーピングの際のキャリアガスとしては、 Hだけでなぐ Nが含まれ ていることが好ましい。雰囲気中に Nガスが存在することにより、窒化物系半導体結 晶中の Nサイトに Cが取り込まれやすくなるからである。 Cの Nサイトへの取り込み効 率を高めるためには、半導体レーザの電気特性に影響を与えない範囲で、成長圧力 を従来条件よりも高ぐ成長温度を低ぐ νΖπι比を低くすることが有効である。ただ し、 νΖΠΙ比を 3000以下とした場合、結晶性の低下により残留ドナー濃度が増加し 、結果的に低抵抗な ρ型クラッド層を実現することが困難となるため、 V/III比は 300 0以上にすることが望ましい。 [0066] In order to realize the above effect, it is important to dope Mg and C into the p-type cladding layer, but the carrier gas at the time of doping contains not only H but N It is preferable. This is because the presence of N gas in the atmosphere makes it easier for C to be taken into N sites in nitride-based semiconductor crystals. In order to increase the efficiency of C incorporation into the N site, it is effective to increase the growth pressure higher than the conventional conditions and lower the νΖπι ratio within a range that does not affect the electrical characteristics of the semiconductor laser. It is. However, when the νΖΠΙ ratio is 3000 or less, the residual donor concentration increases due to the decrease in crystallinity, and as a result, it becomes difficult to realize a low-resistance ρ-type cladding layer. Desirably 0 or more.
[0067] また、従来の ρ型クラッド層成長条件 (炭素ドーピングなし)を用いた場合に、 ρ型クラ ッド層またはその上に位置する p型半導体層にドープされている Mgが、結晶成長ェ 程中に光ガイド層(p側)や活性層へ拡散する問題があった。 Mgの拡散は、活性層 /光ガイド層(P側)近傍で光吸収損失を引き起こし、レーザの信頼性に悪影響を及 ぼすことになる。 [0067] Also, when the conventional ρ-type cladding layer growth condition (without carbon doping) is used, the ρ-type Mg doped in the p-type semiconductor layer or the p-type semiconductor layer positioned thereon diffuses to the light guide layer (p side) and the active layer during the crystal growth process. The diffusion of Mg causes light absorption loss near the active layer / light guide layer (P side) and adversely affects the reliability of the laser.
[0068] Mgの拡散は、 Ga In N/Ga In N—量子井戸活性層 105からノンドープ G [0068] Mg diffusion is achieved from Ga In N / Ga In N—quantum well active layer 105 to non-doped G
0.90 0.10 0.98 0.02 0.90 0.10 0.98 0.02
aN第 2光ガイド層 107までの成長温度(本実施形態では 800°C)よりも高い温度(本 実施形態では 1000°C)で p型クラッド層を成長している間に進行する。また、 Mg拡 散は、その後に行う熱処理工程や、レーザ動作時における電流印加時などの種々の 状況でも発生し得る。このような Mg拡散は、半導体積層構造を貫通する転位(貫通 転位)や、半導体積層構造中に生じた N空孔を拡散パスとして発生する。 The process proceeds while the p-type cladding layer is grown at a temperature (1000 ° C. in this embodiment) higher than the growth temperature (800 ° C. in this embodiment) up to the aN second optical guide layer 107. Mg diffusion can also occur in various situations, such as the subsequent heat treatment step or current application during laser operation. Such Mg diffusion occurs as a diffusion path by dislocations penetrating the semiconductor multilayer structure (threading dislocations) and N vacancies generated in the semiconductor multilayer structure.
[0069] 図 6は、基板における貫通転位密度と、光ガイド層(p側)/活性層中に存在する M g濃度との関係を示すグラフである。このグラフのデータは、熱処理工程等を行う前に おける結晶成長直後のウェハに対して行った評価結果に基づいている。 p型クラッド 層の炭素濃度は、 3つのレベルにある。 Mg濃度および炭素濃度は、 SIMS分析よつ て測定したものである。 FIG. 6 is a graph showing the relationship between the threading dislocation density in the substrate and the Mg concentration present in the light guide layer (p side) / active layer. The data in this graph is based on the evaluation results performed on the wafer immediately after crystal growth before the heat treatment step and the like. The carbon concentration of the p-type cladding layer is at three levels. Mg and carbon concentrations were measured by SIMS analysis.
[0070] 本実施形態では、基板と活性層の間に、低転位密度化を達成する層を特別に形成 していないため、光ガイド層(p側)/活性層における貫通転位密度は、基板における 貫通転位密度とほぼ等しい。これは、活性層と基板の力ソードルミネッセンスによる暗 点密度(暗点は貫通転位に対応)比較からも確認している。結晶成長時に Mgをドー プしてない光ガイド層(p側) /活性層中に存在する Mgの濃度は、 Mg拡散に起因し たものであるため、 Mg濃度によって Mg拡散の程度を評価することができる。 [0070] In this embodiment, since a layer that achieves a low dislocation density is not formed between the substrate and the active layer, the threading dislocation density in the light guide layer (p side) / active layer is Is almost equal to the threading dislocation density in. This is also confirmed from a comparison of dark spot density (spots correspond to threading dislocations) by active sword luminescence between the active layer and the substrate. Since the Mg concentration in the light guide layer (p-side) / active layer that is not doped with Mg during crystal growth is due to Mg diffusion, the extent of Mg diffusion is evaluated by the Mg concentration. be able to.
[0071] 図 6に示されるように、炭素ドーピングなしの p型クラッド層(炭素濃度: 1 X 1017cm_3 )を用いた場合、貫通転位密度が 3 X 105cm 2以下の基板を用いなければ、光ガイド 層(P側) Z活性層への Mg拡散を抑制することができない。一方、 p型クラッド層にお ける炭素濃度が 4 X 1017cm 3以上になると、基板の貫通転位密度が 3 X 106cm— 2程 度でも、 Mg拡散を抑制できることがわかる。 p型クラッド層に炭素ドーピングを行うこと により、 Mg拡散を抑制できる理由は、 Mgの拡散パスとして機能する N空孔が Cによ つて埋められるため、結晶成長中の高温時でも N空孔をパスとする Mg拡散が生じに くくなるためである。 [0071] As shown in FIG. 6, when a p-type cladding layer (carbon concentration: 1 × 10 17 cm_ 3 ) without carbon doping is used, a substrate having a threading dislocation density of 3 × 10 5 cm 2 or less is used. Without it, Mg diffusion to the light guide layer (P side) Z active layer cannot be suppressed. On the other hand, when the carbon concentration in the p-type cladding layer is 4 × 10 17 cm 3 or more, Mg diffusion can be suppressed even when the threading dislocation density of the substrate is about 3 × 10 6 cm− 2 . The reason why Mg diffusion can be suppressed by carbon doping the p-type cladding layer is that N vacancies functioning as Mg diffusion paths are filled with C, so that N vacancies can be formed even at high temperatures during crystal growth. Mg diffusion as a path This is because it becomes difficult.
[0072] 図 6からわかるように、 p型クラッド層に炭素ドーピングを施した場合でも、基板の貫 通転位密度が 3 X 106cm 2を超えて上昇すると、貫通転位をパスとする Mg拡散が支 配的となるため、炭素ドーピングによって N空孔を埋めることによる Mg拡散抑制効果 が現れなくなる。従って、炭素ドーピングによる Mg拡散の抑制を実現するには、貫通 転位密度が 3 X 106cm— 2以下の基板を用いることが好ましぐ貫通転位密度が 1 X 10 6cm— 2以下である基板を用いることが更に好ましい。 [0072] As can be seen from FIG. 6, even when carbon doping is applied to the p-type cladding layer, if the threading dislocation density of the substrate rises above 3 × 10 6 cm 2 , Mg diffusion using threading dislocations as a path Therefore, Mg diffusion suppression effect by filling N vacancies by carbon doping does not appear. Therefore, to achieve suppression of Mg diffusion by the carbon doping, preferably instrument threading dislocation density is to use a substrate of threading dislocation density is 3 X 10 6 cm- 2 or less is 1 X 10 6cm- 2 below substrate More preferably, is used.
[0073] 本実施形態では、 p型クラッド層にのみ炭素ドーピングを施したが、炭素濃度の大 小関係が活性層 <n型クラッド層 <p型クラッド層の関係を満足する範囲内であれば 、活性層、および n型層に炭素ドーピングを行っても良レ、。し力 ながら、活性層への 炭素ドーピングは、光吸収損失の増加を引き起こす可能性もあるので、活性層へは 炭素ドーピングを行わないことが好ましい。また、 n型クラッド層への炭素ドーピングは 、抵抗率の増加を引き起こす可能性があるので、 n型クラッド層への炭素ドーピングを 行う場合でも、その炭素濃度は 3 X 1017cm— 3以下、より好ましくは 0· 7 X 1017cm— 3以 下に調節することが好ましい。 [0073] In this embodiment, carbon doping is performed only on the p-type cladding layer. However, if the magnitude relationship of the carbon concentration is within the range satisfying the relationship of active layer <n-type cladding layer <p-type cladding layer. Also, carbon doping may be applied to the active layer and the n-type layer. However, since carbon doping in the active layer may cause an increase in light absorption loss, it is preferable not to perform carbon doping in the active layer. In addition, carbon doping into the n-type cladding layer may cause an increase in resistivity, so even when carbon doping into the n-type cladding layer is performed, the carbon concentration is 3 × 10 17 cm− 3 or less, More preferably, it is preferably adjusted to 0 · 7 × 10 17 cm− 3 or less.
[0074] 本実施形態では、 n型クラッド層および p型クラッド層の両方にバルタ結晶の AlGaN を用いているが、 n型クラッド層および p型クラッド層の少なくとも一方に、 AlGaN/G aN超格子構造層を用いてもよい。クラッド層は、 In、ホウ素(B)、砒素 (As)、リン (P) 、および/またはアンチモン(Sb)を含有していてもよぐ光とキャリアの閉じ込めを効 果的に実現できる構成であれば、他の構成を有していてもよい。また、本実施形態で は、活性層に井戸層数 2の Ga In N/Ga In N—量子井戸活性層を用いて [0074] In the present embodiment, AlGaN is used for both the n-type cladding layer and the p-type cladding layer, but AlGaN / GaN superlattice is provided in at least one of the n-type cladding layer and the p-type cladding layer. A structural layer may be used. The cladding layer has a structure that can effectively confine light and carriers even if it contains In, boron (B), arsenic (As), phosphorus (P), and / or antimony (Sb). Any other configuration may be used. In this embodiment, a Ga In N / Ga In N—quantum well active layer having two well layers is used as the active layer.
0.90 0.10 0.98 0.02 0.90 0.10 0.98 0.02
いる力 井戸層数は 3以上でも良い。また、 GalnN井戸層と GaN障壁層からなる組 み合わせでも、 GalnN井戸層と AlGalnN障壁層からなる組み合わせでも良ぐ低い 消費電力で、高い発光効率が実現できる構成であれば何でも良い。なお、これらのこ とは、後述する他の実施形態についても成立する。 The number of well layers may be 3 or more. In addition, a combination of a GalnN well layer and a GaN barrier layer, or a combination of a GalnN well layer and an AlGalnN barrier layer may be used, and any configuration capable of realizing high luminous efficiency with low power consumption can be used. These are also true for other embodiments described later.
[0075] (実施形態 2) [0075] (Embodiment 2)
次に、本発明による半導体レーザの第 2の実施形態を説明する。 Next, a second embodiment of the semiconductor laser according to the present invention will be described.
[0076] 本実施形態の半導体レーザは、図 1に示す半導体レーザと同一の構成を備えてお り、製造時におけるノンドープ Al Ga N第 3光ガイド層 108、p— Al Ga N第 1 The semiconductor laser of this embodiment has the same configuration as the semiconductor laser shown in FIG. The non-doped Al Ga N third light guide layer 108, p-Al Ga N first 1
0.01 0.99 0.20 0.80 クラッド層 109、 p-Al Ga N第 2クラッド層 110、 p— GaNコンタクト層 111の成長 0.01 0.99 0.20 0.80 Clad layer 109, p-Al Ga N second clad layer 110, p-GaN contact layer 111 growth
0.05 0.95 0.05 0.95
温度のみが実施形態 1から異なっている。実施形態 1では、これらの層の成長温度は 、 1000°Cである力 本実施形態では、 900°Cである。 Only the temperature differs from embodiment 1. In Embodiment 1, the growth temperature of these layers is 1000 ° C. In this embodiment, it is 900 ° C.
[0077] 図 7は、 p— GaN層(成長温度: 900°C)の抵抗率と Mg濃度との関係を示すグラフ である。図 4と図 7と比較することにより、成長温度の低下により、炭素ドーピングを施 した p_GaN層の抵抗率が約 6%増加した。成長温度を低下することにより、結晶性 が劣化し、残留ドナー濃度が高くなるため、 p_GaN層の抵抗率が増加すると考えら れる。し力 ながら、本実施形態で得られた p_GaN層の抵抗率は、成長温度 1000 °Cで、かつ、炭素ドーピングなしで作製したものとほぼ同等である。すなわち、本実施 形態によれば、成長温度を低下させた場合でも、炭素ドーピングの効果が得られる。 FIG. 7 is a graph showing the relationship between the resistivity of the p-GaN layer (growth temperature: 900 ° C.) and the Mg concentration. By comparing Fig. 4 and Fig. 7, the resistivity of the carbon-doped p_GaN layer increased by about 6% due to the lower growth temperature. By reducing the growth temperature, the crystallinity deteriorates and the residual donor concentration increases, so the resistivity of the p_GaN layer is thought to increase. However, the resistivity of the p_GaN layer obtained in this embodiment is almost the same as that produced at a growth temperature of 1000 ° C. and without carbon doping. That is, according to the present embodiment, the effect of carbon doping can be obtained even when the growth temperature is lowered.
[0078] 成長温度を低下させた場合に得られる炭素ドーピングによる抵抗率の低下効果は 、炭素濃度が 2 X 1018cm 3以下の場合にも現れ、 A1組成が 20%以下の AlGaN層で も得られる。 [0078] The effect of reducing the resistivity by carbon doping obtained when the growth temperature is lowered appears even when the carbon concentration is 2 × 10 18 cm 3 or less, and even in an AlGaN layer having an A1 composition of 20% or less. can get.
[0079] 図 8は、本実施形態の半導体レーザおよび実施形態 1の半導体レーザについて求 めた内部量子効率( 77 )やおよび内部損失( α .)と炭素濃度との関係を示すグラフで ある。 「秦」および「▲」は、それぞれ、実施形態 1の半導体レーザにおける内部量子 効率( 77 .)やおよび内部損失( α )を示しており、「〇」および「△」は、それぞれ、本実 施形態の半導体レーザにおける内部量子効率(77 )および内部損失(α )を示してい る。 FIG. 8 is a graph showing the relationship between the internal quantum efficiency (77) and internal loss (α.) And the carbon concentration obtained for the semiconductor laser of this embodiment and the semiconductor laser of Embodiment 1. “秦” and “▲” indicate the internal quantum efficiency (77.) and internal loss ( α ), respectively, in the semiconductor laser of Embodiment 1, and “◯” and “△” indicate the actual values, respectively. The internal quantum efficiency (77) and internal loss (α) in the semiconductor laser of the embodiment are shown.
[0080] ρ型クラッド層に対して炭素ドーピングを施すことにより、活性層へのホール注入効 率が増加し、内部量子効率が向上する。また、 ρ型クラッド層の成長温度を 900°Cに 低下することにより、 p型クラッド層の結晶成長プロセス中に生じやすい活性層の熱劣 化を抑制できるため、内部量子効率が更に改善する。ただし、炭素濃度が 2 X 1018c m 3を超えると、成長層の表面平坦性が劣化し、鏡面が得られなくなるため、炭素ドー ピングを施していても、内部量子効率はむしろ低下する。このため、炭素濃度は 2 X 1 018cm— 3以下に制御することが好ましい。 [0080] By applying carbon doping to the ρ-type cladding layer, the hole injection efficiency into the active layer is increased, and the internal quantum efficiency is improved. In addition, by reducing the growth temperature of the ρ-type cladding layer to 900 ° C, it is possible to suppress thermal degradation of the active layer that is likely to occur during the crystal growth process of the p-type cladding layer, thereby further improving the internal quantum efficiency. However, if the carbon concentration exceeds 2 X 10 18 cm 3 , the surface flatness of the growth layer deteriorates and a mirror surface cannot be obtained, so even if carbon doping is applied, the internal quantum efficiency is rather lowered. For this reason, it is preferable to control the carbon concentration to 2 × 10 18 cm− 3 or less.
[0081] 本実施形態の半導体レーザにおける内部損失の主な原因は、ノンドープ Al Ga N第 3光ガイド層 108および p— Al Ga N第 1クラッド層 109による光吸収損失で ある。 p型クラッド層の成長温度が 1000°Cの場合(実施形態 1に相当)、炭素ドーピン グの有無によって内部損失にほとんど差異は生じない。しかし、 p型クラッド層の成長 温度を 900°Cに低下させた場合、炭素ドーピングを行わないと、結晶特性が劣化す るため、光吸収損失が増加する。その結果、内部損失は、成長温度が 1000°Cに比 ベて 2倍程度に増加する。 [0081] The main cause of internal loss in the semiconductor laser of the present embodiment is non-doped Al Ga This is the optical absorption loss due to the N third optical guide layer 108 and the p-AlGaN first cladding layer 109. When the growth temperature of the p-type cladding layer is 1000 ° C (corresponding to Embodiment 1), there is almost no difference in internal loss depending on the presence or absence of carbon doping. However, when the growth temperature of the p-type cladding layer is lowered to 900 ° C, the crystal characteristics deteriorate unless carbon doping is performed, so that the light absorption loss increases. As a result, the internal loss increases about twice as high as the growth temperature of 1000 ° C.
[0082] p型クラッド層の成長温度を 900°Cに低下させた場合で、炭素ドーピングを行うと、 p -Al Ga N第 1クラッド層 109の電気特性が前述のとおりに向上するとともに、結 晶特性も改善するため、光吸収損失が減少し、内部損失も改善する。 [0082] If the growth temperature of the p-type cladding layer is lowered to 900 ° C and carbon doping is performed, the electrical characteristics of the p-AlGaN first cladding layer 109 are improved as described above, and the result is Since crystal characteristics are also improved, light absorption loss is reduced and internal loss is also improved.
[0083] 炭素濃度が 4 X 1017cm— 3、または 8 X 1017cm— 3のとき、成長温度が 900°Cの内部損 失は、成長温度が 1000°Cの場合に比べて約 20%大きいが、この差異は、内部量子 効率の改善効果と比較して、ほとんど影響の無いレベルである。すなわち、炭素濃度 力 ¾ X 1017cm— 3〜8 X 1017cm— 3の範囲にあるとき、 p型クラッド層の成長温度を 900°C 程度に低下し、しきい値電流及び動作電圧の低減を達成することができる。 [0083] When the carbon concentration is 4 x 10 17 cm— 3 or 8 x 10 17 cm— 3 , the internal loss at a growth temperature of 900 ° C is about 20 times that at a growth temperature of 1000 ° C. This difference is almost insignificant compared to the effect of improving internal quantum efficiency. That is, when the carbon concentration force is in the range of ¾ X 10 17 cm— 3 to 8 X 10 17 cm— 3 , the growth temperature of the p-type cladding layer is lowered to about 900 ° C., and the threshold current and operating voltage are reduced. Reduction can be achieved.
[0084] 本実施形態では、 p型クラッド層の成長温度を従来値から 100°C低下させているが 、 100°Cよりも大きく低下させることも可能である。本実施形態では、炭素ドーピング により、 p型クラッド層の低抵抗率化を実現しつつ、 pクラッド層の成長温度の低下に よって内部量子効率を高めることが可能になる。 p型クラッド層の成長温度を、活性層 の成長温度よりも低くすると、残留ドナー濃度が大幅に増加してしまうため、 p型クラッ ド層の抵抗が増加する。このため、 p型クラッド層の成長温度は、活性層成長温度と n 型クラッド層成長温度との間の範囲に設定することが好ましい。 In the present embodiment, the growth temperature of the p-type cladding layer is reduced by 100 ° C. from the conventional value, but it is also possible to reduce the growth temperature by more than 100 ° C. In the present embodiment, carbon doping makes it possible to increase the internal quantum efficiency by lowering the growth temperature of the p-clad layer while realizing a low resistivity of the p-type cladding layer. If the growth temperature of the p-type cladding layer is lower than the growth temperature of the active layer, the residual donor concentration increases significantly, and the resistance of the p-type cladding layer increases. For this reason, it is preferable to set the growth temperature of the p-type cladding layer in a range between the active layer growth temperature and the n-type cladding layer growth temperature.
[0085] (実施形態 3) [0085] (Embodiment 3)
以下、図 9を参照しながら、本発明による半導体レーザの第 3の実施形態を説明す る。 Hereinafter, a third embodiment of the semiconductor laser according to the present invention will be described with reference to FIG.
[0086] 本実施形態の半導体レーザは、実施形態 1の半導体レーザとほぼ同様の構成を有 しており、第一の相違点は、図 9に示すように、 p_Al Ga N第 2クラッド層 110を p The semiconductor laser of this embodiment has substantially the same configuration as that of the semiconductor laser of Embodiment 1, and the first difference is that the p_AlGaN second cladding layer 110 as shown in FIG. P
-Al Ga N (2nm厚)/ p— GaN (2nm厚)一 SLS第 2クラッド層(120ペア) 121-Al Ga N (2 nm thick) / p—GaN (2 nm thick) and one SLS second cladding layer (120 pairs) 121
0に置き換えた点にある。 [0087] また、本実施形態では、 n— Al Ga Nクラッド層 103に対しても、炭素ドーピング The point is replaced with 0. In the present embodiment, carbon doping is also applied to the n-AlGaN cladding layer 103.
0.05 0.95 0.05 0.95
を行っている。ただし、 p-Al Ga N第 1クラッド層 109および p— Al Ga N/ It is carried out. However, p-Al Ga N first cladding layer 109 and p-Al Ga N /
0.20 0.80 0.10 0.90 p— GaN— SLS第 2クラッド層 1210に対する炭素ドーピングに比べて、 [C供給量/ III族原料供給量]比を低く設定している。 n_Al Ga Nクラッド層 103、 ρ_Α1 0.20 0.80 0.10 0.90 p- GaN- SLS The second cladding layer 1210 has a lower [C supply / Group III material supply] ratio than carbon doping. n_Al Ga N cladding layer 103, ρ_Α1
0.05 0.95 0.20 0.05 0.95 0.20
Ga N第 1クラッド層 109、及び p—Al Ga N/p_GaN_ SLS第 2クラッド層 12Ga N first cladding layer 109, and p-Al Ga N / p_GaN_ SLS second cladding layer 12
0.80 0.10 0.90 0.80 0.10 0.90
10の成長温度は、いずれも、 1000°Cに設定している。 The growth temperatures for all 10 are set to 1000 ° C.
[0088] なお、 AlGaN層の結晶成長では、 AlGaN結晶中の A1含有量が多いほど (A1組成 が高いほど)、原料である TMAから Cのオートドーピングが生じやすレ、。すなわち、 [ C供給量/ III族原料供給量]比が同一であっても、 Al Ga N層よりも Al Ga [0088] In the crystal growth of the AlGaN layer, the higher the A1 content in the AlGaN crystal (the higher the A1 composition), the more likely auto-doping from TMA to C occurs as a raw material. That is, even if the [C supply amount / Group III raw material supply amount] ratio is the same, Al Ga N
0.05 0.95 0.10 0.90 0.05 0.95 0.10 0.90
N層や Al Ga N層の方が、炭素濃度が高くなる。 The carbon concentration is higher in the N layer and the AlGaN layer.
0.20 0.80 0.20 0.80
[0089] 各構成層の厚さが 2nmの Al Ga N/GaN— SLS層の場合、 A1の供給を開始 [0089] In the case of Al Ga N / GaN—SLS layers with a thickness of 2 nm for each component layer, supply of A1 started
0.10 0.90 0.10 0.90
した初期段階で一時的に炭素濃度がスパイク状に増加(パイルアップ)し、 Al Ga In the initial stage, the carbon concentration temporarily increased (pile-up) in a spike shape, and Al Ga
0.10 0.9 0.10 0.9
N層の平均炭素濃度よりも、高い炭素濃度を示す傾向がある。このように高くなつたThere is a tendency to show a higher carbon concentration than the average carbon concentration of the N layer. So high
0 0
炭素濃度は、 2nm厚の GaN層では、 GaN層(または Al Ga N層)の定常炭素濃 For the GaN layer with a thickness of 2 nm, the carbon concentration is the steady carbon concentration of the GaN layer (or AlGaN layer).
0.10 0.90 0.10 0.90
度にまで減少しない。 Al Ga N/GaN— SLS層の平均 Al組成は 5%であるが、 Does not decrease to the degree. The average Al composition of the Al Ga N / GaN— SLS layer is 5%,
0.10 0.90 0.10 0.90
炭素濃度は、結果的に Al Ga N層で同一の [C供給量/ III族原料供給量]比で As a result, the carbon concentration in the Al Ga N layer is the same [C supply / Group III raw material supply] ratio.
0.05 0.95 0.05 0.95
結晶成長した場合よりも高い値を示すことになる。 It shows a higher value than the case of crystal growth.
[0090] 本実施形態では、炭素濃度について、活性層 <n型クラッド層 <p型クラッド層の関 係を確実に成立させるため、 n—Al Ga Nクラッド層 103における [C供給量/ III In the present embodiment, in order to reliably establish the relationship of the active layer <n-type cladding layer <p-type cladding layer with respect to the carbon concentration, the [C supply amount / III in the n-AlGaN cladding layer 103 is determined.
0.05 0.95 0.05 0.95
族原料供給量]比を低くして炭素ドーピングを行っている。ただし、活性層く n型クラ ッド層く p型クラッド層の関係が達成できるのであれば、 [C供給量/ III族原料供給 量]比を高くしても構わない。 Carbon doping is carried out at a low ratio of the amount of group raw material supplied]. However, if the relationship between the active layer, the n-type cladding layer, and the p-type cladding layer can be achieved, the ratio of [C supply amount / Group III material supply amount] may be increased.
[0091] n-Al Ga Nクラッド層 103における炭素濃度が 3 X 1017cm 3以下となるように [ [0091] The carbon concentration in the n-Al Ga N clad layer 103 is 3 X 10 17 cm 3 or less [
0.05 0.95 0.05 0.95
C供給量/ III族原料供給量]比を制御すれば、 n_Al Ga Nクラッド層 103の抵 If the ratio of C supply / Group III raw material supply] is controlled, the resistance of the n_AlGaN cladding layer 103
0.05 0.95 0.05 0.95
抗率は炭素ドーピングを行わなかったときよりも約 10%程度増加するだけであり、実 用上何ら支障はなレ、。また、 n_Al Ga Nクラッド層 103における炭素濃度が 3 X The drag rate only increases by about 10% compared to when carbon doping was not performed, and there was no problem in practical use. In addition, the carbon concentration in the n_AlGaN cladding layer 103 is 3 X
0.05 0.95 0.05 0.95
1017cm 3となるように C供給量を制御し、 p— Al Ga N第 1クラッド層 109および p 10 Control the C supply rate so that it becomes 17 cm 3, and p-AlGaN first cladding layer 109 and p
0.20 0.80 0.20 0.80
-Al Ga N/p— GaN— SLS第 2クラッド層 1210の炭素濃度を 3 X 1017cm— 3以-Al Ga N / p- GaN- SLS second cladding layer 1210 3 carbon concentration of X 10 17 cm- 3 or more
0.10 0.90 上、望ましくは 4 X 10"cm—以上 l X 10lscm d以下とすることにより、 p— Al Ga N 0.10 0.90 Above, preferably 4 x 10 "cm—more than l x 10 ls cm d , p— Al Ga N
0.10 0.90 0.10 0.90
/p— GaN— SLS第 2クラッド層 1210の抵抗率を低減することができる。その結果、 I V特性における直列抵抗成分が減少し、低電圧駆動が可能になる。 The resistivity of the / p—GaN—SLS second cladding layer 1210 can be reduced. As a result, the series resistance component in the IV characteristics is reduced, and low voltage driving becomes possible.
[0092] p-Al Ga N/p_GaN_ SLS第 2クラッド層 1210の抵抗率が下がると、活性 [0092] When the resistivity of the p-AlGaN / p_GaN_SLS second cladding layer 1210 decreases, the activity decreases.
0.10 0.90 0.10 0.90
層へのホールの注入効率が増加するために、しきい値電流が減少し、高い信頼性を 有したレーザ素子を再現性良ぐ非常に高い歩留まりで実現することができる。また、 Since the efficiency of hole injection into the layer increases, the threshold current decreases, and a highly reliable laser device can be realized with a very high yield with good reproducibility. Also,
P型層における抵抗率の低減を実現したことで、高電流注入状態における発熱量も 抑制でき 150mWの光出力を室温連続発振条件下で実現できる。 By reducing the resistivity in the P-type layer, the amount of heat generated in the high current injection state can be suppressed, and a 150 mW optical output can be realized under continuous oscillation conditions at room temperature.
[0093] 本実施形態では、 p型クラッド層の成長温度を n型クラッド層の成長温度(1000°C) に等しくしているが、実施形態 2について説明したように、 p型クラッド層の成長温度 は 900°C以下でも良いし、 900°C〜: 1000°Cの範囲内でも良い。 In this embodiment, the growth temperature of the p-type cladding layer is made equal to the growth temperature of the n-type cladding layer (1000 ° C.). However, as described in the embodiment 2, the growth of the p-type cladding layer is performed. The temperature may be 900 ° C or less, and may be in the range of 900 ° C to 1000 ° C.
[0094] (実施形態 4) [0094] (Embodiment 4)
以下、本発明による半導体レーザの第 4の実施形態を説明する。 The fourth embodiment of the semiconductor laser according to the present invention will be described below.
[0095] 本実施形態の半導体レーザは、実施形態 2の半導体レーザとほぼ同様の構成を有 しており、相違点は、 n— Al Ga Nクラッド層 103に対しても炭素ドーピングを行う The semiconductor laser according to the present embodiment has substantially the same configuration as that of the semiconductor laser according to the second embodiment. The difference is that the n-AlGaN cladding layer 103 is also carbon-doped.
0.05 0.95 0.05 0.95
点にある。 n— Al Ga Nクラッド層 103に対する炭素ドーピング時の [C供給量 /I In the point. [C supply / I at the time of carbon doping to n— Al Ga N cladding layer 103
0.05 0.95 0.05 0.95
II族原料供給量]比は、 p— Al Ga N第 1クラッド層 109および p— Al Ga N第 Group II raw material supply ratio] is determined by the p-AlGaN first cladding layer 109 and p-AlGaN first
0.20 0.80 0.05 0.95 0.20 0.80 0.05 0.95
2クラッド層 110に対する炭素ドーピング時の [C供給量/ III族原料供給量]比と同 一レベルに設定する。 2 Set to the same level as the [C supply / Group III material supply] ratio during carbon doping of the cladding layer 110.
[0096] n-Al Ga Nクラッド層 103の成長温度は 1000°C、 p— Al Ga N第 1クラッ [0096] The growth temperature of the n-Al Ga N cladding layer 103 is 1000 ° C, and the first cladding layer of p-Al Ga N
0.05 0.95 0.20 0.80 0.05 0.95 0.20 0.80
ド層 109および p— Al Ga N第 2クラッド層 110の成長温度は 920°Cである。結晶 The growth temperature of the cladding layer 109 and the p-AlGaN second cladding layer 110 is 920 ° C. Crystal
0.05 0.95 0.05 0.95
成長温度が低いほど、結晶中に cが取り込まれやすくなる傾向があり、 [c供給量 Ζιι The lower the growth temperature, the easier it is for c to be incorporated into the crystal, and [c supply amount Ζιι
I族原料供給量]比が同一であれば、成長温度が 1000°Cの Al Ga N層よりも、成 If the Group I feed rate is the same, the growth rate is higher than the Al Ga N layer with a growth temperature of 1000 ° C.
0.05 0.95 0.05 0.95
長温度 920°Cの Al Ga N層の方力 炭素濃度は高くなる。 The directional carbon concentration of the AlGaN layer at 920 ° C is increased.
0.05 0.95 0.05 0.95
[0097] n-Al Ga Nクラッド層 103における炭素濃度が 3 X 1017cm 3以下となるように [ [0097] The carbon concentration in the n-Al Ga N clad layer 103 is 3 × 10 17 cm 3 or less [
0.05 0.95 0.05 0.95
C供給量/ III族原料供給量]比を制御すれば、 n_Al Ga Nクラッド層 103の抵 If the ratio of C supply / Group III raw material supply] is controlled, the resistance of the n_AlGaN cladding layer 103
0.05 0.95 0.05 0.95
抗率は炭素ドーピングを行わなかったときと比べて、実用上何ら支障はない程度にし か増加せず、デバイス特性には大きな影響は及ぼさなレ、。 [0098] n-Al Ga Nクラッド層 103における炭素濃度が 3 X 1017cm ^なるように C供 給量を制御したところ、 p— Al Ga N第 1クラッド層 109および p— Al Ga N第Compared to the case where carbon doping is not performed, the resistivity is increased only to the extent that there is no practical problem, and the device characteristics are not greatly affected. [0098] When the C supply amount was controlled so that the carbon concentration in the n-AlGaN cladding layer 103 was 3 × 10 17 cm ^, the p-AlGaN first cladding layer 109 and the p-AlGaN first layer
2クラッド層 110における炭素濃度は 8 X 1017cm 3となり、炭素ドーピングを行わない 場合よりも抵抗の低い P型クラッド層を形成できた。 The carbon concentration in the two cladding layers 110 was 8 × 10 17 cm 3 , and a P-type cladding layer having a lower resistance than that without carbon doping could be formed.
[0099] p型クラッド層に炭素ドーピングを施すことにより、 Mgァクセプタを活性化するため に必要な水素の濃度を、炭素ドーピングが行われない場合に比べて低減することも 可能である。 p型クラッド層を活性化するために、熱処理や電子線照射処理、プラズ マ照射などが必要であるが、炭素ドーピングを行わない場合に比べ、炭素ドーピング を施した p型クラッド層では、 Mgと水素の結合エネルギーが小さぐ通常よりも低いパ ヮ一で活性化させることが可能である。この効果は、 n型クラッド層にも炭素ドーピング を施すことにより、顕著になる。 [0099] By applying carbon doping to the p-type cladding layer, the concentration of hydrogen necessary to activate the Mg acceptor can be reduced as compared with the case where carbon doping is not performed. In order to activate the p-type cladding layer, heat treatment, electron beam irradiation treatment, plasma irradiation, etc. are required, but in the case of p-type cladding layer with carbon doping, Mg and It is possible to activate with a lower hydrogen bond energy than usual. This effect becomes significant by applying carbon doping to the n-type cladding layer.
[0100] 活性化処理後も半導体レーザ素子中に若干の水素が残留すると、残留していた水 素がレーザ動作中に活性層へ移動し、非発光再結合中心を活性層中に形成する可 能性がある。このような非発光再結合中心が活性層中に形成されると、素子寿命が 著しく短縮することになる。し力 ながら、炭素ドーピングを施すことにより、 Cが形成 する欠陥準位に水素がトラップされるため、活性層中への水素の移動を抑制すること ができ、信頼性が向上する効果も得られる。 [0100] If some hydrogen remains in the semiconductor laser device even after the activation treatment, the remaining hydrogen moves to the active layer during laser operation, and non-radiative recombination centers can be formed in the active layer. There is a potential. When such a non-radiative recombination center is formed in the active layer, the device lifetime is remarkably shortened. However, by applying carbon doping, hydrogen is trapped in the defect level formed by C, so that the movement of hydrogen into the active layer can be suppressed, and the effect of improving reliability can be obtained. .
[0101] このように本実施形態では、 p—Al Ga N第 1クラッド層 109、 p— Al Ga N 第 2クラッド層 110の抵抗率を低減することができ、 IV特性における直列抵抗成分が 減少する。その結果、低消費電力でのレーザ動作が可能になった。 p型クラッド層に おける抵抗率の低減を実現したことにより、高電流注入状態における発熱量も抑制 できるため、 150mWの光出力を室温連続発振条件下で実現できた。また、本実施 形態によれば、長寿命のレーザ素子を再現性良ぐ高い歩留まりで製造することが可 肯 になる。 [0101] Thus, in this embodiment, the resistivity of the p-AlGaN first cladding layer 109 and the p-AlGaN second cladding layer 110 can be reduced, and the series resistance component in the IV characteristics is reduced. To do. As a result, laser operation with low power consumption is possible. By realizing a reduction in resistivity in the p-type cladding layer, the amount of heat generated in the high current injection state can also be suppressed, so that an optical output of 150 mW was achieved under room temperature continuous oscillation conditions. Further, according to this embodiment, it is possible to manufacture a long-life laser element with a high yield with good reproducibility.
[0102] 本実施形態では、 p型クラッド層の成長温度を 920°Cに設定しているが、実施形態 [0102] In this embodiment, the growth temperature of the p-type cladding layer is set to 920 ° C.
2について説明したように、 p型クラッド層の成長温度は 900°C以下でも良いし、 900 °C〜1000°Cの範囲内でも良い。 As described in (2), the growth temperature of the p-type cladding layer may be 900 ° C. or less, or may be in the range of 900 ° C. to 1000 ° C.
[0103] なお、上記の各実施形態では、 p型クラッド層の炭素濃度を 3 X 1017cm 3以上に調 整している力 その場合の p型クラッド層の成長レートは、 10nm/分程度であった。 本発明者の実験によると、この成長レートを 6〜7nm/分程度に低下させた場合、 p クラッド層における炭素濃度の好ましい範囲は、 8 X 1016cm— 3以上 1 X 1018cm— 3以下 、更に好ましい範囲は 1 X 1017cm 3以上 1 X 1018cm— 3以下になることがわ力、つた。た だし、 Mgなどの p型不純物の濃度は上述した実施形態における値に維持している。 したがって、 p型クラッド層の炭素濃度は、炭素以外の p型不純物の濃度に対して 0. 8%以上 10%以下の範囲にあることが好ましぐ 1%以上 10%以下の範囲にあること が更に好ましい。 In each of the above embodiments, the carbon concentration of the p-type cladding layer is adjusted to 3 × 10 17 cm 3 or more. Adjusting force In that case, the growth rate of the p-type cladding layer was about 10 nm / min. According to the experiments of the present inventors, when this growth rate is reduced to about 6 to 7 nm / min, the preferable range of the carbon concentration in the p-cladding layer is 8 × 10 16 cm− 3 or more and 1 × 10 18 cm− 3 In the following, it was found that the more preferable range was 1 × 10 17 cm 3 or more and 1 × 10 18 cm− 3 or less. However, the concentration of p-type impurities such as Mg is maintained at the value in the above-described embodiment. Therefore, the carbon concentration of the p-type cladding layer is preferably in the range of 0.8% to 10% with respect to the concentration of p-type impurities other than carbon, and preferably in the range of 1% to 10%. Is more preferable.
[0104] 以上、本発明の好ましい実施形態を説明してきたが、本発明は上記実施形態に限 定されるものではなレ、。例えば、上記の各実施形態では、 GaN基板を用いているが 、基板は GaN力、ら形成されている必要はなぐ AlGaN、 InGaN、または AlGalnN等 の窒化物系半導体から形成されていてもよい。また、窒化物系半導体以外の材料か ら形成された基板(サファイア基板、 SiC基板、 Zn〇基板、 Si基板、 GaAs基板など) の上に GaN等の窒化物系半導体層を形成した基板を用いても良い。 [0104] While the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, in each of the above embodiments, a GaN substrate is used. However, the substrate may be formed of a nitride-based semiconductor such as AlGaN, InGaN, or AlGalnN, which does not need to be formed. In addition, a substrate in which a nitride semiconductor layer such as GaN is formed on a substrate (sapphire substrate, SiC substrate, ZnO substrate, Si substrate, GaAs substrate, etc.) formed from a material other than a nitride semiconductor is used. May be.
[0105] また、上記各実施形態では、高い導電性を有する n— GaN基板を用いているため 、 n電極を基板裏面に形成しているが、導電性の低い基板または絶縁性基板を用い てもよレ、。その場合、基板表面に形成した半導体積層構造の一部を n— GaN層まで エッチングし、そのエッチング面上に n電極を形成することになる。なお、導電性を有 する基板(例えば n— GaN基板)を用いる場合でも、半導体積層構造上に n電極およ び p電極の両方を形成しても良い。 [0105] In each of the above embodiments, since an n-GaN substrate having high conductivity is used, the n electrode is formed on the back surface of the substrate. However, a substrate having low conductivity or an insulating substrate is used. Moyore. In that case, a part of the semiconductor multilayer structure formed on the substrate surface is etched to the n-GaN layer, and an n-electrode is formed on the etched surface. Even when a conductive substrate (for example, an n-GaN substrate) is used, both the n electrode and the p electrode may be formed on the semiconductor stacked structure.
[0106] 上記の各実施形態では、 Gaの原料として TMG、 A1の原料として TMA、 Inの原料 として TMI、 Mgの原料として Cp Mg、 Nの原料として NH、 Cの原料として CHを用 いている力 他の原料を用いてもよい。例えば、 Gaの原料としてトリェチルガリウム (T EG)や塩化ガリウム(GaClや CAC1 )、 A1の原料としてトリェチルアルミニウム(TEA [0106] In each of the above embodiments, TMG is used as the Ga material, TMA is used as the A1 material, TMI is used as the In material, Cp Mg is used as the Mg material, NH is used as the N material, and CH is used as the C material. Force Other raw materials may be used. For example, triethyl gallium (TEG) and gallium chloride (GaCl and CAC1) as raw materials for Ga, and triethylaluminum (TEA) as raw materials for A1
)ゃジメチルアルミハイドライド(DMAH)、ジメチルアルミクロライド(DMAC1)、トリメ チルアミンァラン(TMAA)、 Inの原料としてトリェチルインジウム(TEI)、 Mgの原料 としてビスェチルシクロペンタジェニルマグネシウム(EtCp Mg)やビスメチルシクロ ペンタジェニルマグネシウム(MeCp Mg)、 Nの原料としてヒドラジン(N H )やモノメ チルヒドラジン(MMH)、ジメチルヒドラジン(DMH)、 Cの原料として臭化炭素(CBr ) N-dimethylaluminum hydride (DMAH), dimethylaluminum chloride (DMAC1), trimethylaminealane (TMAA), triethylindium (TEI) as the raw material for In, bisethylcyclopentadienylmagnesium (EtCp Mg) as the raw material for Mg, Bismethylcyclopentadienylmagnesium (MeCp Mg), hydrazine (NH) as a raw material for N Carbon bromide (CBr) as a raw material for Cylhydrazine (MMH), Dimethylhydrazine (DMH), C
4 Four
)、塩化炭素(CC1 )、二硫化炭素(CS )、アセチレン(C H )、プロパン(C H )、ネ ), Carbon chloride (CC1), carbon disulfide (CS), acetylene (C H), propane (C H), ne
4 2 2 2 3 8 ォペンタン (C H )を用いても良い。本発明を効果的に実現するためには、 Mgドー 4 2 2 2 3 8 o pentane (C H) may be used. In order to effectively realize the present invention, Mg
5 12 5 12
ビングと同時に Cを効率良くドーピングすることが重要であり、使用可能な範囲ででき るだけ分解効率の高レ、原料を用いることが望ましレ、。 It is important to efficiently dope C at the same time as bing, and it is desirable to use raw materials with as high a decomposition efficiency as possible within the usable range.
[0107] 本発明で用いることのできる p型ァクセプタ不純物は、 Mgに限定されず、他の p型 不純物、例えば亜鉛 (Zn)、ベリリウム(Be)、カドミウム(Cd)を用いてもよい。 The p-type acceptor impurity that can be used in the present invention is not limited to Mg, and other p-type impurities such as zinc (Zn), beryllium (Be), and cadmium (Cd) may be used.
[0108] 本発明の窒化物系半導体素子は、半導体レーザ素子に限定されず、発光ダイォ ード素子ゃ受光素子など P型窒化物系半導体層を有する全ての窒化物系半導体素 子に適用され得る。なお、窒化物系半導体は、 BAlGalnN混晶半導体や、 As、 P、 S bを含有する AlGalnNAsPSb混晶化合物半導体を広く含むものとする。 The nitride-based semiconductor element of the present invention is not limited to a semiconductor laser element, but is applied to all nitride-based semiconductor elements having a P-type nitride-based semiconductor layer such as a light-emitting diode element and a light-receiving element. obtain. Nitride semiconductors widely include BAlGalnN mixed crystal semiconductors and AlGalnNAsPSb mixed crystal compound semiconductors containing As, P, and Sb.
産業上の利用可能性 Industrial applicability
[0109] 本発明は、光ディスク装置用の半導体レーザ素子、照明用発光ダイオード、通信 · 情報処理用バイポーラ型電子素子などに好適に用いられる。 The present invention is suitably used for semiconductor laser elements for optical disk devices, light emitting diodes for illumination, bipolar electronic elements for communication / information processing, and the like.
Claims
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