DE19943405B4 - A method of fabricating a laterally monolithically integrated light emitting semiconductor device and light emitting semiconductor device - Google Patents

Abstract

Method for producing a visible mixed-color radiation emitting semiconductor chip, in which
a) a mask layer (100) is applied to a semiconductor substrate (1),
b) forming a number of differently sized window openings (200) in the mask layer (100),
c) the mask layer (100) and the window openings (200) are subjected to organometallic compounds by organometallic vapor phase epitaxy such that an active semiconductor layer sequence (2) of ternary or quaternary material contains a pn junction (21) in the window openings (200). is grown, wherein the semiconductor layer sequences (2) in the window openings (200) are each formed with the same material components but with different compositions of the ternary or quaternary material, wherein the applied in step a) mask layer (100) has a plurality of subregions (A-D ), in which in each case a group of equally large window openings (200) is formed and the partial areas have different sized window openings (200), so that the active semiconductor layer sequences of the different groups emit at different wavelengths.

Description

method for producing a laterally monolithically integrated light-emitting semiconductor component and light emission semiconductor device

The The invention relates to a method for producing a laterally monolithic integrated, electroluminescent at different wavelengths Light-emitting semiconductor device. In particular, the Invention A Method of Manufacturing a Light Emitting Semiconductor Device its individual components on a common semiconductor substrate are integrated laterally monolithic. The process is essentially based on that by organometallic gas phase epitaxy in window openings different Size that are formed in a mask layer, ternary or quaternary semiconductor compounds depending on the size of the window opening in grown in different composition.

The increasingly broad application of light emitting semiconductor devices leaves it as desirable appear to develop a monolithic LED chip, the electromagnetic radiation with different wavelengths can emit. Such a development would make significant progress especially in display technology, because with it could In any case, in principle, an integration of all three primary colors succeed in a single LED chip. But also other applications, like display and control lamps, could save costs in terms of production, Processing, etc. on a single semiconductor substrate monolithic to get integrated.

multicolored However, emitting LED chips are still predominantly made up of three individual, composed of monochrome emitting semiconductor devices, in a common housing be installed. So far, it is only known, for example Gallium phosphide (GaP) light emission on semiconductor devices with adjustable color by mixing two emitted wavelengths to produce. In the book "Semiconductor Optoelectronics" by M. Bleicher, appeared in the Dr. Alfred Huthig Verlag, Heidelberg, 1986, is on pages 157, 158 such a Two-color light emitting diode (LED) described. It contains between its front, which is the light exit side, and its back two surface emitting light emitting diodes. These are formed by epitaxial growth of p-type, differently impurity-doped GaP layers produced on an n-type GaP substrate, thereby two at the front and back the substrate formed pn junctions arise. The upper p-type GaP layer is doped with nitrogen, while the lower p-type GaP layer is doped with oxygen and zinc. Of the thus formed by the upper GaP epi layer pn junction thus emitted electrical stimulation in the green Spectral range while through the lower GaP epilayer formed pn junction emitted in the red spectral range. The shaped in this way Diodes are operated with two voltage sources whose common Negative pole with the n-side of both pn junctions, ie with the n-type GaP substrate, is connected. By separately adjusting the diode currents can thus the color spectrum of red over orange and yellow to green be varied. The red radiation penetrates the entire crystal and passes through the same area like the green one Radiation, whereby a good spatial mixture is achieved.

Of the Structure and structure of such an arrangement, however, brings with that only electromagnetic radiation of two wavelengths can be emitted. Since in addition the electromagnetic radiation of both pn transitions by one and the same area exits the semiconductor device is always a spatial Mixture of the two wavelengths brought about. Another disadvantage of the semiconductor device described is in that one pn junction on the back side is arranged and the radiation emitted by this pn junction must penetrate the entire crystal. Half of the radiation will also towards the back of the semiconductor device and thus can generally not for a front emission can be used.

In the US 5,795,798 A a method for producing a monolithic luminescent semiconductor device is described. Thereby, individual electromagnetic radiation generating LED chips are formed on a single substrate using selective epitaxy. It is described that the radiation intensity of each LED chip can be set individually by a selective selection of its lateral extent as a function of the radiation intensity to be expected. The device emits white light. In addition, it is taught that light of any desired color can be produced by individually controlling the brightness of the LED chips.

It It is an object of the present invention to provide a process for the preparation a laterally monolithic integrated electroluminescent at several different wavelengths Specify light emitting semiconductor device. Such a light emitting semiconductor device should in particular be able to electromagnetic radiation emit at two or more different wavelengths front.

This task is performed by a procedure or solved by a device according to the independent claims.

• a) auf ein Halbleitersubstrat eine Maskenschicht aufgebracht,
• b) in die Maskenschicht eine Anzahl Fensteröffnungen unterschiedlicher Größen geformt, und
• c) die Maskenschicht und die Fensteröffnungen durch metallorganische Gasphasenepitaxie mit metallorganischen Verbindungen derart beaufschlagt, daß in den Fensteröffnungen jeweils eine aktive, elektrolumineszierende Halbleiterschichtenfolge aus ternärem oder quarternärem Material enthaltend einen pn-Übergang aufgewachsen wird, wobei die Halbleiterschichtenfolgen in den Fensteröffnungen mit unterschiedlichen Zusammensetzungen des ternären oder quarternären Materials gebildet werden. Die im Verfahrensschritt a) aufgebrachte Maskenschicht weist bei dem Verfahren eine Mehrzahl von Teilbereichen auf, in denen jeweils eine Gruppe von gleich großen Fensteröffnungen ausgebildet wird und die untereinander verschieden große Fensteröffnungen aufweisen, so daß die aktiven Halbleiterschichtenfolgen der verschiedenen Gruppen mit unterschiedlichen Wellenlängen emittieren.

In a method according to the invention for producing a light emission semiconductor component electroluminescent at a number of different wavelengths, accordingly

• a) a mask layer is applied to a semiconductor substrate,
• b) formed in the mask layer a number of window openings of different sizes, and
• c) the metal-organic vapor phase epitaxy with organometallic compounds so acted upon by the mask layer and the window openings, that in the window openings in each case an active, electroluminescent semiconductor layer sequence of ternary or quaternary material containing a pn junction is grown, the semiconductor layer sequences in the window openings with different compositions of the ternary or quaternary material. In the method, the mask layer applied in method step a) has a plurality of partial areas, in each of which a group of equally large window openings is formed and which have window openings of different sizes, so that the active semiconductor layer sequences of the different groups emit at different wavelengths.

In the method according to the invention, selective epitaxy and organometallic gas phase epitaxy (MOCVD or MOVPE) are thus combined with one another. The general principle of selective epitaxy is described in JJ Coleman, Metalorganic Chemical Vapor Deposition for Optoelectronic Devices, Proceedings of the IEEE, Vol.85, No.11, November 1997, pp. 1715-1729, and in B. Korgel, RF Hicks, A diffusion model for selective-area epitaxy by metalorganic chemical vapor deposition, J. of Crystal Growth 151 (1995) 204-212. From the DE 44 29 772 C2 For example, it is known to make an integrated modulator semiconductor laser device utilizing selective epitaxy.

As is known, predefined structures can be produced by selective epitaxy. Selective layer deposition occurs when the substrate surface is partially covered with materials of different electronegativity. In order to achieve selective layer deposition, a mask layer consisting of, for example, SiO ₂ or a silicon nitride compound Si _x N _1-X is deposited on a semiconductor substrate. In this mask layer Fens teröffnungen are formed to the substrate in which the predefined structures are to be produced. These window openings are preferably produced by an etching step. Thus, a structured substrate surface is generated, which is partially covered with the mask material and partially with the semiconductor substrate. Now, when a semiconductor growth process is performed in which a suitable semiconductor material is epitaxially grown on this substrate surface, selective layer deposition occurs, which preferably proceeds in the window openings of the mask layer. The shape and size of the desired predefined structures thus depend essentially on the structures of the window openings in the mask layer and on the epitaxy parameters.

In the method according to the invention becomes as epitaxy the organometallic gas phase epitaxy applied. An essential feature of the method according to the invention lies in the fact that the Mask opening, i.e. The relationship of open substrate surface to masked area, decisively the deposition conditions of organometallic gas phase epitaxy certainly. this leads to to that in ternary or quaternary Semiconductor compounds the composition ratio of the grown semiconductor layer for given epitaxy parameters, depends on the size of the window opening. Consequently can by the size of the window opening the emission wavelength of a growing up in the window opening pn junction be set. The structure-size-dependent variation in the composition of the semiconductor material is ultimately based on a variation in the growth rate of the various components of the ternary or quaternary Semiconductor compound that differs from the different diffusion ratios of the individual components in the MOVPE process on the mask material becomes. Determine the chemical potentials on the surface of the mask material the bonding of this single component, such as Ga and / or In on this same mask surface. By simple variation of the mask opening size can be in this way all by the chosen ternary or quaternary Set semiconductor connection achievable wavelengths.

In an embodiment of the present invention is referred to as the material of the semiconductor substrate InP selected and the material of the semiconductor layer sequences is either the ternary Compound GaInAs or the quaternary compound GaInAsP. at These combinations of materials, it turns out that with increasing size of the window openings the share ratio Ga: In in the deposited semiconductor material increases, so that the bandgap accordingly increases and a formed from this material pn junction emits an electromagnetic radiation correspondingly shorter wavelength.

It may further be provided that in method step a) on the semiconductor substrate first a Bragg reflector layer sequence is applied, which is composed of a number of reflector layer pairs, each pair of individual layers having two layers with different refractive indices, and then the mask layer is applied to this Bragg reflector layer sequence. This has the advantage that the radiation emitted by the active, electroluminescent layer sequence in the direction of the substrate rear side is reflected by the Bragg reflector layer sequence in the direction of the substrate front side and thus can likewise be used.

Further can the individual light-emitting semiconductor devices as vertical resonator laser diodes (VCSELs) may be formed. In this case, except the already mentioned substrate-side Bragg reflector layer sequence yet another Light exit side, partially transparent Bragg reflector layer sequence provided. Through the two Bragg reflector layer sequences becomes a laser resonator for in the pn junction generated laser radiation formed.

in the Following are embodiments of the inventive method closer to the figures explained. Show it:

1 an intermediate product of the method according to the invention immediately after the formation of the window openings in the mask layer;

2 one according to 1 finished light emitting semiconductor device;

3 a plan view of an embodiment of a light emitting semiconductor device with regions of different wavelength emission.

To 1 is on a semiconductor substrate 1 first a Bragg reflector layer sequence 16 deposited on the then a mask layer 100 is applied. The Bragg reflector layer sequence 16 serves to do this from an electroluminescent pn junction 21 (S. 2 ) to reflect light emitted towards the back of the substrate and to redirect it to the front of the substrate so that this portion of the light can also be used for front emission. The mask layer 100 , which may consist of SiO ₂ or SiN, for example, is structured by means of photolithography and etching technique such that cylindrical window openings 200 different size, for example, of different diameters, are formed. The 1 thus shows a cross section along a plane through the window openings 200 ver runs. The window openings 200 accordingly in 1 circular cross-section, this choice of shape is by no means mandatory. It is also possible, for example, to choose rectangular cross-sectional shapes.

The Bragg reflector layer sequence 16 However, it can also be omitted, so that the mask layer 100 is applied directly to the substrate.

In the window openings 200 the mask layer 100 Subsequently, a semiconductor layer sequence is grown by means of metal-organic vapor phase epitaxy.

The embodiment of an in 2 illustrated finished processed LED chips 20 thus has a plurality of juxtaposed radiation decoupling elements 5 on. Each of the radiation decoupling elements 5 has the shape of a cylinder 6 on, whose longitudinal central axis (AZ) parallel to a main emission direction 9 of the LED chip 20 lies.

Under the main direction of radiation 9 of the LED chip 20 is the one to understand the direction in which much of the in the chip 20 generated electromagnetic radiation 3 out of this exit.

In each of the cylinders 6 is above the Bragg reflector layer 16 an active layer sequence 2 with an emission zone 4 arranged in the main emission direction 9 first a current aperture layer 14 with a current passage opening 15 and this in turn a contact layer 17 is subordinate.

The active layer sequence 2 has at least one electroluminescent pn junction 21 on and consists for example of InGaAlP.

On the of the active layer sequence 2 opposite side of the substrate 1 is contact metallization over the entire surface 19 applied.

The current aperture layer 14 serves to control the current flow through the active layer sequence 2 and thus by the electroluminescent pn junction 21 to the area of the desired emission zone 4 narrow. It consists for example of AlAs and is down to the Stromdurchlaßöffnung 15 oxidized, ie electrically insulating, but for those in the emission zone 4 generated radiation permeable.

On the top surface 10 every cylinder 6 there is a ring contact 11 essentially only that portion of the cylinder 6 covered by the total internal reflection at the interface between cylinders 6 and little or no radiation would be coupled out to the surrounding medium. The ring contacts 11 the single cylinder 6 can be interconnected by electrically conductive webs.

An essential element of the invention be is that in the epitaxy step of the growth of the semiconductor layer sequence, the components of the semiconductor compound in dependence on the size of the window opening 200 be incorporated with different proportions in the crystal lattice. This causes each of the cylinders 6 in the region of the electroluminescent pn junction 21 is formed of different semiconductor material, so that the pn junctions 21 have different band gaps. In the case of the ternary semiconductor compound GaInAs or the quaternary semiconductor compound GaAlInAs, with increasing window size, more Ga is incorporated in the lattice relative to In. In any case, this leads to an increase in the band gap and thus to a reduction in the emission wavelength. Accordingly, with this choice of material, the three radiation decoupling elements illustrated are used 5 three different emission wavelengths occur, the representation of 2 the wavelength increases from right to left.

The incorporation of the various components of the semiconductor compounds depends essentially on the diffusion behavior on the mask material. If this is known, it can easily be found by experiment, as with a given semiconductor compound, the size of the window opening 200 must be selected to achieve a certain composition ratio of an active electroluminescent layer sequence. Then, by composing a number of different window openings on a chip, a desired number of corresponding emission wavelengths can be achieved.

This in 2 illustrated embodiment shows an LED chip 20 in which only in the lower area a Bragg reflector layer sequence 16 is present, the all radiation decoupling elements 5 is common. However, it may also be provided that above the pn junction 21 a further Bragg reflector layer sequence is provided, which is partially transparent and with the first-mentioned Bragg reflector layer sequence 16 forms a laser resonator. In this way, a vertical cavity laser diode (VCSEL) is formed, which is composed of a plurality of individual laterally monolithically integrated laser diodes.

In 3 Finally, a practical embodiment according to the present invention is shown. Herein, an LED chip is divided into four quadrants, each having a plurality of radiation decoupling elements 5A -D have within a quadrant of equal diameter and between the quadrants have different diameters. Thus, within one quadrant, the emission wavelength is constant in operation while varying from quadrant to quadrant. The radiation decoupling elements 5 Each quadrant are electrically with each other using the already described ring contacts 11 connected to the top surface 10 of every cylinder 6 are applied.

As shown, the quadrant D contains the cylinders 6 with the largest cross section, while the quadrant A is the cylinder 6 Contains the smallest cross-section. In turn, if such semiconductor materials are used, in their epitaxial growth, the emission wavelength of the respective pn junction with increasing size of the window opening 200 and thus of the cylinder 6 During operation, the shortest emission wavelength in the quadrant D and the longest emission wavelength in the quadrant A are established.

1

Semiconductor substrate

2

active layer sequence

3

electromagnetic radiation

4

emission zone

5

Strahlungsauskoppelelement

5A-D

quadrant

6

cylinder

9

main radiation

10

cover surface

11

ring Contact

14

current aperture

15

current passage

16

Bragg reflector layer sequence

17

contact layer

19

contact metallization

20

LED chip

21

pn junction

100

mask layer

200

window opening

Claims (9)

Method for producing a visible mixed-color radiation-emitting semiconductor chip, in which a) on a semiconductor substrate ( 1 ) a mask layer ( 100 ), b) in the mask layer ( 100 ) a number of window openings ( 200 ) of different sizes, c) the mask layer ( 100 ) and the window openings ( 200 ) are acted upon by organometallic gas phase epitaxy with organometallic compounds such that in the window openings ( 200 ) an active semiconductor layer sequence ( 2 ) of ternary or quaternary material containing a pn junction ( 21 ), wherein the semiconductor layer sequences ( 2 ) in the window openings ( 200 ) each with the same material components but with different compositions of the ternary or quaternary material, the mask layer applied in process step a) ( 100 ) has a plurality of subregions (A-D), in each of which a group of equal size window openings ( 200 ) is formed and the subregions mutually different sized window openings ( 200 ) so that the active semiconductor layer sequences emit the different groups of different wavelengths. Method for producing a visible mixed-color radiation-emitting semiconductor chip, in which a) on a semiconductor substrate ( 1 ) a mask layer ( 100 ), b) in the mask layer ( 100 ) a number of window openings ( 200 ) of different sizes, c) the mask layer ( 100 ) and the window openings ( 200 ) are acted upon by organometallic gas phase epitaxy with organometallic compounds such that in the window openings ( 200 ) an active semiconductor layer sequence ( 2 of material based on GaN, InN, AlN and all mixed compounds thereof containing a pn junction ( 21 ), wherein the semiconductor layer sequences ( 2 ) in the window openings ( 200 ) are each formed with the same material components but with different compositions of ternary or quaternary material, the mask layer applied in process step a) ( 100 ) has a plurality of subregions (A-D), in each of which a group of equal size window openings ( 200 ) is formed and the subregions mutually different sized window openings ( 200 ) so that the active semiconductor layer sequences emit the different groups of different wavelengths. Method according to Claim 1, in which the material of the semiconductor substrate ( 1 ) is based on InP and the radiation-emitting zone comprises GaInAs or GaInAsP. Method according to claim 1, in which - the material of the semiconductor substrate ( 1 ) based on ZnO, Si, sapphire with AlC surface orientation, SiC, GaN, AlN, Al _x Ga ₁ -xN, Ga _x In _1-x N, and - the material of the semiconductor layer sequences on GaAsN, InAsN, AlAsN, GaPN, InPN , AlPN and all mixed compounds thereof. Method according to one of the preceding claims, in which the material of the mask layer ( 100 ) SiO ₂ or a silicon nitride compound Si _X N _1-X . Method according to one of the preceding claims, in which - before the method step a) on the semiconductor substrate ( 1 ) first a Bragg reflector layer sequence ( 16 ), consisting of a number of reflector layer pairs of layers with different refractive index, is applied, and - on the Bragg reflector layer sequence ( 16 ) the mask layer ( 100 ) is applied. Method according to one of the preceding claims, in which the window openings ( 200 ) have a cylindrical shape. Mixed-color light-emitting luminescence diode chip ( 20 ), in which on a common epitaxial substrate ( 1 ) a plurality of separate luminescence diode layer sequences ( 2 ) are grown side by side, whose radiation-emitting zones ( 4 ) have ternary or quaternary material and at the same time by means of organometallic gas phase epitaxy in different sized window openings ( 200 ) a mask layer ( 100 ) are deposited, so that all luminescence diode layer sequences ( 2 ) have the same material components and the compositions of the ternary or quaternary material of the radiation-emitting zones ( 4 ) depending on the size of the window openings ( 200 ) are different and in operation emit light of different color, wherein on the substrate ( 1 ) is provided a plurality of juxtaposed partial areas (A-D), in each of which a group of the same size Lumineszenzdioden layer sequences ( 2 ), and the subregions have mutually different luminescence diode layer sequences ( 2 ) so that the different groups emit at different wavelengths. Luminescence diode chip according to Claim 8, in which, on a common substrate ( 1 ) a plurality of adjacent luminescence diode layer sequences ( 2 ) in the form of radiation decoupling elements ( 5 ) is arranged, whose longitudinal center axes (AZ) parallel to a main radiation direction ( 9 ) of the LED chip ( 20 ), wherein in each radiation decoupling element ( 5 ) an active layer sequence ( 2 ) with a radiation-emitting zone ( 4 ) having a current aperture layer ( 14 ) with a current passage opening ( 15 ), which regulates the flow of current to the region of the desired radiation-emitting zone ( 4 ) limited.