WO2007013257A1 - Nitride semiconductor device - Google Patents

Abstract

Disclosed is a nitride semiconductor device comprising a substrate (101) and a multilayer structure formed on the substrate (101). The multilayer structure has an n-type nitride semiconductor layer (103), a p-type nitride semiconductor layer (109), and a nitride semiconductor layer (105) arranged between the n-type nitride semiconductor layer (103) and the p-type nitride semiconductor layer (109). The p-type nitride semiconductor layer (109) is doped with carbon and a p-type impurity other than carbon. The carbon concentration of the p-type nitride semiconductor layer (109) is lower than the concentration of the p-type impurity other than carbon, but higher than the carbon concentration of the n-type nitride semiconductor layer (103).

Description

 Specification

 Nitride semiconductor device

 Technical field

 [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.

 Background art

 [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] 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] 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

LECTRONICS, VOL. 9, NO. 5, 1252-1259 (2003)

 Disclosure of the invention

 Problems to be solved by the invention

 [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] 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] 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.

 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] 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] 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] 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.

 Means for solving the problem

[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.

 In a preferred embodiment, the p-type impurity other than carbon doped in the p-type nitride-based semiconductor layer is magnesium.

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.

In 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.

It is in the range of 10% to 10%.

In a preferred embodiment, the substrate includes gallium nitride, aluminum gallium nitride (

Selected from the group consisting of Al Ga Ν (0 <χ≤1)), sapphire, silicon carbide, and zinc oxide 1

 It is formed from the finished material.

In a preferred embodiment, the average value of threading dislocation density in the substrate is 3 × 10 ⁶ cm or less.

 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.

 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] 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.

 The invention's effect

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] 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] 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] 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.

 Brief Description of Drawings

 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.

 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.

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.

 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.

 Explanation of symbols

 [0026] 101 n— GaN substrate

 102 n— GaN layer

 103 n-Al Ga N cladding layer

 104 n— GaN optical guide layer

 105 Ga In N / Ga In N quantum well active layer

 106 Ga In N 1st light guide layer

 107 GaN second light guide layer

 108 Al Ga N 3rd light guide layer

 109 p-Al Ga N 1st cladding layer

 110 p-Al Ga N second cladding layer

 111 p— GaN contact layer

 112 p electrode

 113 n electrode

 114 SiO

 1210 p-Al Ga N / p— GaN— SLS second cladding layer

 BEST MODE FOR CARRYING OUT THE INVENTION

[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.

 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—Quantum well active layer 105, Non-doped Ga In N

1 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, and ρ-GaN contact layer 111.

[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.

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 electrode 113 is formed.

[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

Gain occurs at 5, and laser oscillation occurs at a wavelength of 410 nm.

[0031] 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.

 [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.

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.

 twenty two

 I can.

 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

 twenty two

 Then, the n-GaN substrate 101 is heated in an N atmosphere, and the temperature rise rate is 10 ° C / 10 seconds.

2

 To 1000 ° C. Then switch N to H carrier gas and simultaneously

 twenty two

 Supply NH (NH) and clean the substrate surface for 5 minutes. After this cleaning,

Three

 Supplying methylgallium (TMG) and monosilane (SiH), V / III ratio = 6000

 Four

 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

 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

 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

 Three

 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

 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

 It is. The active layer 105 is not intentionally doped with impurities.

[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

 After the non-doped GaN second optical guide layer 107 is grown, the supply of TMG is once stopped.

 [0037] Thereafter, while supplying N and NH, the temperature was rapidly raised to 1000 ° C, and the growth temperature

 twenty three

 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

While supplying NH and NH, immediately supply TMG and TMA, and V / III ratio = 8000.

 Three

 Under the conditions, a 10 nm-thick non-doped AlGaN third optical guide layer 108 is grown.

 0.01 0.99

 [0038] Next, biscyclopentagenenyl magnesium (Cp Mg) as an Mg raw material, and a C raw material

 2

 Methane (CH 3) was added as a p-AlGaN first cladding layer 109 by lOnm growth.

 4 0.20 0.80

 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 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] 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] 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 Cladding layer 110 and p-GaN contact layer 111 are processed into stripes as shown in FIG. 1 to form mesa stripes.

[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

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] 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

The upper surface of the N contact layer 111 is in contact with the upper surface of the Si layer 114. P-Ga

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] 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.

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.

 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

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.

 In addition, as 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.

[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] On the other hand, the p-AlGaN first cladding layer 109 with carbon doping, p-AlGa

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] 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] Next, the role of carbon doping for the GaN layer and the AlGaN layer (A1 composition is 20% or less) will be described.

[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] 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] 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%.

 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] 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.

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] 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] 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] 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] 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] 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] The carbon concentration is preferably adjusted to a range of 0.8% to 10% of the Mg concentration.

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] 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] 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] 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] 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] 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 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

 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.

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] 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] 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] 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] 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] 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

 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] (Embodiment 2)

 Next, a second embodiment of the semiconductor laser according to the present invention will be described.

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 Clad layer 109, p-Al Ga N second clad layer 110, p-GaN contact layer 111 growth

 0.05 0.95

 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.

 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] 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.

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] 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] 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] 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] 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.

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] (Embodiment 3)

 Hereinafter, a third embodiment of the semiconductor laser according to the present invention will be described with reference to FIG.

 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 (2 nm thick) / p—GaN (2 nm thick) and one SLS second cladding layer (120 pairs) 121

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

 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 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

Ga N first cladding layer 109, and p-Al Ga N / p_GaN_ SLS second cladding layer 12

0.80 0.10 0.90

 The growth temperatures for all 10 are set to 1000 ° C.

 [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

The carbon concentration is higher in the N layer and the AlGaN layer.

 0.20 0.80

 [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

 In the initial stage, the carbon concentration temporarily increased (pile-up) in a spike shape, and Al Ga

 0.10 0.9

There is a tendency to show a higher carbon concentration than the average carbon concentration of the N layer. So high

0

 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

 Does not decrease to the degree. The average Al composition of the Al Ga N / GaN— SLS layer is 5%,

 0.10 0.90

 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

 It shows a higher value than the case of crystal growth.

 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

 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] 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

 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

 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

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

-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 Above, preferably 4 x 10 "cm—more than l x 10 ^ls cm ^d , p— Al Ga N

 0.10 0.90

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] When the resistivity of the p-AlGaN / p_GaN_SLS second cladding layer 1210 decreases, the activity decreases.

 0.10 0.90

 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,

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.

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] (Embodiment 4)

 The fourth embodiment of the semiconductor laser according to the present invention will be described below.

 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

 In the point. [C supply / I at the time of carbon doping to n— Al Ga N cladding layer 103

 0.05 0.95

 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

2 Set to the same level as the [C supply / Group III material supply] ratio during carbon doping of the cladding layer 110.

 [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

 The growth temperature of the cladding layer 109 and the p-AlGaN second cladding layer 110 is 920 ° C. Crystal

 0.05 0.95

 The lower the growth temperature, the easier it is for c to be incorporated into the crystal, and [c supply amount Ζιι

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

 The directional carbon concentration of the AlGaN layer at 920 ° C is increased.

 0.05 0.95

[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

 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

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

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] 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] 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] 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] In this embodiment, the growth temperature of the p-type cladding layer is set to 920 ° C.

 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.

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] 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] 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] 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

) 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

 Four

), Carbon chloride (CC1), carbon disulfide (CS), acetylene (C H), propane (C H), ne

 4 2 2 2 3 8 o pentane (C H) may be used. In order to effectively realize the present invention, Mg

 5 12

 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.

 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. obtain. Nitride semiconductors widely include BAlGalnN mixed crystal semiconductors and AlGalnNAsPSb mixed crystal compound semiconductors containing As, P, and Sb.

 Industrial applicability

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

The scope of the claims  [1] A nitride-based semiconductor device comprising a substrate and a laminated structure formed on the substrate,  The laminated structure is  an n-type nitride-based semiconductor layer;  a p-type nitride semiconductor layer;  A nitride-based semiconductor layer positioned between the n-type nitride-based semiconductor layer and the p-type nitride-based semiconductor layer;  Have  The p-type nitride semiconductor layer is doped with a p-type impurity other than carbon and carbon, and the carbon concentration of the p-type nitride semiconductor layer is higher than the concentration of the p-type impurity other than carbon. Nitride-based semiconductor device having a lower carbon concentration than the n-type nitride-based semiconductor layer [2] The nitride-based semiconductor device according to [1], wherein the p-type impurity other than carbon doped in the p-type nitride-based semiconductor layer is magnesium. [3] The nitride semiconductor device according to [2], wherein the carbon concentration of the p-type nitride semiconductor layer is 8 × 10 ¹⁶ cm ³ or more and 1 × 10 ¹⁸ cm− ³ or less. [4] The carbon concentration of the p-type nitride semiconductor layer is 0.8% or more and 10% or less with respect to the concentration of p-type impurities other than carbon doped in the p-type nitride semiconductor layer. The nitride-based semiconductor device according to claim 2 or 3, wherein the nitride-based semiconductor device is in a range. [5] The substrate is made of gallium nitride, aluminum gallium nitride (AlGa (0 <χ≤1)),  The nitride-based semiconductor device according to claim 1, wherein the nitride-based semiconductor device is formed of a material selected from the group consisting of 1-fire, silicon carbide, and zinc oxide. 6. The nitride-based semiconductor device according to claim 5, wherein an average value of threading dislocation densities in the substrate is 3 × 10 ⁶ cm ² or less. [7] 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, The n-type nitride semiconductor layer and the p-type nitride semiconductor layer are each 2. The nitride-based semiconductor device according to claim 1, which functions as a cladding layer for the active layer. [8] The p-type nitride-based semiconductor layer and the n-type nitride-based semiconductor layer contain at least a part of an anorium,  8. The nitride semiconductor device according to claim 7, wherein the nitride semiconductor layer located between the P-type nitride semiconductor layer and the n-type nitride semiconductor layer contains indium at least in part.  9. The nitride semiconductor device according to claim 1, wherein the n-type nitride semiconductor layer is doped with at least one element selected from the group consisting of silicon, germanium, and oxygen.