JPH10303505A - Gallium nitride semiconductor light emitting device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to uniformly apply good laser oscillation characteristics on a substrate wafer surface, by specifying the thickness of the substrate on which an active layer of quantum well structure held between nitride semiconductor clad layers and/or guide layers and consisting of a indium and gallium contained nitride semiconductor. SOLUTION: A sapphire substrate 1 of 50 to 180 μm in thickness is disposed on a heating element within a predetermined growth furnace. A GaN buffer layer, an Si doped n-GaN type contact layer, an Si doped n-AlGaN clad layer and an Si doped n-GaN guide layer 5 are sequentially grown on the sapphire substrate 1. Next, an InGaN quantum well layer 14, an InGaN barrier layer 15 and an InGaN quantum well layer 14 are sequentially grown, whereby an active layer 6 of multiple quantum well structure is formed. Further, an AlGaN evaporation protective layer 7 is grown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride based semiconductor light emitting device, and more particularly, to a gallium nitride based light emitting device having a quantum well structure active layer made of a nitride semiconductor and a method of manufacturing the same.

[0002]

2. Description of the Related Art A gallium nitride based semiconductor (GaInAlN) is used as a semiconductor material for a semiconductor laser device (LD) or a light emitting diode device (LED) having an emission wavelength in a wavelength range from ultraviolet to green. A sapphire substrate, G
An aAs substrate, a SiC substrate, a MgO substrate, a Si substrate, a spinel substrate, or the like is used, and a vapor phase growth such as a metal organic chemical vapor deposition (MOCVD) or a molecular beam epitaxy (MBE) is performed on this substrate. A light emitting portion made of a gallium nitride based semiconductor is formed by a method. When a gallium nitride-based semiconductor is formed by vapor phase growth using a sapphire substrate, the thickness of the substrate may be, for example, as disclosed in JP-A-5-16.
No. 6923, usually 300 to 500
A thickness of μm was used.

On the other hand, recently, a quantum well structure has been used as an active layer of such a gallium nitride based semiconductor light emitting device. For example, a blue LD is Applied
Physics Letters, vol. 69, N
o. 10, p. 1477-1479,
FIG. 5 shows a cross-sectional view thereof. In FIG. 5, 101 is a sapphire substrate, 102 is a GaN buffer layer, and 103 is n-
GaN contact layer 104 is n-In _0.05 Ga _0.95 N
Layer 105, n-Al _0.05 Ga _0.95 N cladding layer, 10
6 is an n-GaN guide layer, 107 is a multiple quantum well structure active layer composed of an In _0.2 Ga _0.8 N quantum well layer and an In _0.05 Ga _0.95 N barrier layer, 108 is a p-Al _0.2 Ga _0.8 N layer,
109 is a p-GaN guide layer, 110 is p-Al _0.05 G
a _0.95 N cladding layer, 111 is a p-GaN contact layer, 112 is a p-side electrode, 113 is an n-side electrode, 114 is S
It is an iO ₂ insulating film. Here, the multi-quantum well structure active layer 107 is composed of 5 nm thick In _0.2 Ga _0.8 N quantum well layers.
The barrier layer is composed of a total of 9 layers, that is, four layers of In _0.05 Ga _0.95 N barrier layers having a thickness of 6 nm, and quantum well layers and barrier layers are formed alternately. The temperature during the crystal growth is 510 ° C. for the GaN buffer layer 102, and the multiple quantum well structure active layer 1
07 is 830 ° C., and other layers are 1020 ° C. In addition, Japanese Patent Application Laid-Open No. 8-316528 similarly discloses a blue LD using a gallium nitride-based semiconductor having a quantum well structure active layer. Was created without particular attention.

A blue LED is described, for example, in the above-mentioned Japanese Patent Application Laid-Open No. 8-316528, and a cross-sectional view thereof is shown in FIG. In FIG. 6, 121 is a sapphire substrate, 122 is a GaN buffer layer, 123 is an n-GaN contact layer, 124 is an n-Al _0.3 Ga _0.7 N second n-type cladding layer, and 125 is n-In _0.01 Ga _0.99 GaN first n
Type cladding layer 126 is 3 nm thick In _0.05 Ga _0.95 N
Single quantum well structure active layer, 127 is p-In _0.01 Ga
_0.99 GaN first p-type cladding layer, 128 is p-Al _0.3
Ga _0.7 N second p-type cladding layer, 129 is a p-GaN contact layer, 130 is a p-side electrode, and 131 is an n-side electrode. The temperature during the growth of these crystals depends on the GaN buffer layer 1
22 is 500 ° C., and the single quantum well structure active layer 126 is 80 ° C.
The temperature is 0 ° C., and that of each of the other layers is 1050 ° C. Also in such a blue LED, the thickness of the substrate at the time of crystal growth has been produced without particular consideration.

[0005]

However, in the conventional blue LD and blue LED device using the quantum well structure active layer, the distribution of light emission characteristics in the plane of the substrate wafer used during crystal growth is very large. There was a problem. That is, in a blue LD, the oscillation wavelength greatly differs between the central portion and the peripheral portion of the substrate wafer, and the yield for obtaining a desired oscillation wavelength is greatly reduced. For example, when a sapphire substrate having a diameter of 2 inches is used, the oscillation wavelength has a difference of 150 nm between the central portion and the peripheral portion of the substrate wafer. Furthermore, the conventional blue LD has an oscillation threshold current value of 1
Since it is as high as 00 mA or more, it has been necessary to drastically reduce the oscillation threshold current value for practical use for information processing of optical disks and the like.

Although blue LEDs have already been put into practical use, the emission wavelengths are significantly different between the central portion and the peripheral portion of the substrate wafer as in the case of the blue LD, and the yield for obtaining the desired emission wavelength is greatly reduced. There is a problem of doing it. LEs with the same emission wavelength, like a large full-color display using LEDs
In an application that requires a large amount of D, if the yield of blue LEDs is reduced due to the large in-plane distribution of the emission wavelength, the cost of a full-color display will increase. For this reason, realization of a blue LED that can be manufactured with the same emission wavelength with high yield has been desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and solves the above-mentioned problems in the gallium nitride-based semiconductor light emitting device to provide a semiconductor laser having uniform and good laser oscillation characteristics within the surface of a substrate wafer. It is an object of the present invention to provide an element and a method of manufacturing the same, and a light emitting diode element having a uniform emission wavelength within a substrate wafer surface and a method of manufacturing the same.

[0008]

In order to achieve the above object, a gallium nitride based semiconductor light emitting device according to the present invention is sandwiched between a cladding layer and / or a guide layer made of a nitride semiconductor by a vapor growth method. When forming a quantum well structure active layer made of a nitride semiconductor containing at least indium and gallium, the thickness of the substrate is set to 50 μm or more and 180 μm or more.
It is manufactured by the following.

In finding such a present invention,
The present inventor has conducted a detailed investigation on the cause of the problem in the conventional device, and as a result, the distribution of the surface temperature within the surface of the substrate wafer during the crystal growth when forming the quantum well layer revealed that It has been found that the distribution of the light emission characteristics in the inside occurs. That is, in the InGaN material used as the quantum well layer in the gallium nitride based semiconductor light emitting device, the In composition greatly changes depending on the temperature of the substrate surface on which InGaN is formed. Especially InGa
Immediately after the start of the N crystal growth, the change in the In composition depending on the temperature of the substrate surface is large. Therefore, when a quantum well layer having a very thin layer is formed of InGaN,
It has been found that the influence immediately after the start of the crystal growth of nGaN increases, and that when the substrate surface temperature decreases, the In composition sharply increases. Since the emission wavelength of an InGaN material changes depending on the In composition, the emission wavelength becomes longer as the In composition increases.

Further, it has been found that the distribution of the surface temperature in the substrate wafer surface is affected by uneven heat conduction due to the warpage of the substrate during crystal growth. In crystal growth of a gallium nitride based semiconductor, the temperature of the substrate wafer is set to 500 ° C. to 110 ° C.
Although the crystal growth is performed at 0 ° C., the temperature of the substrate is increased by heat conduction from a heating element in contact with the bottom surface of the substrate to increase the temperature of the substrate. In this case, in the conventional gallium nitride based semiconductor light emitting device in which the thickness of the substrate is 180 μm or more, a temperature difference occurs between the bottom surface and the surface of the substrate because the substrate is thick, and the temperature of the bottom surface is higher than the surface. .
As a result, the bottom surface of the substrate has a larger thermal expansion than the surface, and the substrate wafer 150 is warped as shown in FIG. 7, so that only the center portion is in contact with the heating element 151 and the peripheral portion is separated from the heating element 151. It will be in a state of being left. Therefore, the heat from the heating element 151 is not easily transmitted to the peripheral portion, and the temperature of the peripheral portion is lower than that of the central portion. For this reason, when InGaN was crystal-grown, the In composition became large in the peripheral portion, causing the distribution of the light emission characteristics in the plane of the substrate wafer 150.

That is, in a blue LD, the oscillation wavelength is InG.
Since the In composition of the aN quantum well structure active layer is determined by the In composition in the central portion and the peripheral portion of the substrate wafer, the oscillating wavelength varies greatly due to the difference in In composition, and the yield for obtaining a desired oscillating wavelength is greatly reduced. I was Furthermore, the In inside the resonator structure of one blue LD element also
Since the distribution of the In composition of the GaN quantum well layer occurs,
The optical gain obtained at a constant emission wavelength is reduced, and the oscillation threshold current is increased. On the other hand, the emission wavelength of the blue LED is significantly different between the central portion and the peripheral portion of the substrate wafer, similarly to the blue LD, and the yield for obtaining the desired emission wavelength has been greatly reduced.

Therefore, according to the present invention, a quantum well structure active layer made of a nitride semiconductor containing at least indium and gallium sandwiched between a clad layer and / or a guide layer made of a nitride semiconductor is formed by a vapor phase growth method. By reducing the thickness of the sapphire substrate to 50 μm or more and 180 μm or less, the temperature difference between the bottom surface and the surface of the substrate during the crystal growth of InGaN is eliminated, and the warpage of the substrate wafer during the crystal growth is suppressed. As a result, the substrate wafer comes into contact with the heating element on the entire bottom surface, so that the surface temperature distribution in the substrate wafer surface was suppressed. Thereby, the distribution of the In composition in the InGaN quantum well layer could be reduced.

As a result, the gallium nitride based semiconductor laser device having an improved emission characteristic distribution from the InGaN quantum well structure active layer, a uniform oscillation wavelength within the substrate wafer surface and a low oscillation threshold current value, and a substrate wafer surface A gallium nitride-based light emitting diode device having a uniform emission wavelength within the device has been realized.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a sectional view showing a gallium nitride based semiconductor laser device according to a first embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a portion A in FIG. . In this figure, 1 has a c-plane as a surface and a thickness of 150 μm.
m, sapphire substrate 2 inches in diameter, 2 is GaN
Buffer layer, 3 is an n-GaN n-type contact layer, 4 is n
-Al _0.1 Ga _0.9 Nn type clad layer, 5 is an n-GaN guide layer, 6 is a multiple quantum well composed of two In _0.2 Ga _0.8 N quantum well layers 14 and one In _0.05 Ga _0.95 N barrier layer 15. A structure active layer, 7 is an Al _0.2 Ga _0.8 N evaporation preventing layer,
8 is a p-GaN guide layer, 9 is p-Al _0.1 Ga _0.9 Np
Type cladding layer, 10 is a p-GaN p-type contact layer, 1
1 is a p-side electrode, 12 is an n-side electrode, and 13 is a SiO ₂ insulating film.

In the present embodiment, the thickness of the sapphire substrate 1 is set to 150 μm, but the thickness is not limited as long as it is between 50 μm and 180 μm. The surface of the substrate is a
Other plane orientations such as a plane, an r plane, and an m plane may be used. Further, not only a sapphire substrate but also a SiC substrate, a spinel substrate, a MgO substrate, a Si substrate, and a GaAs substrate can be used. In particular, the SiC substrate is more easily cleaved than the sapphire substrate, and thus has an advantage that the laser resonator end face can be easily formed by the cleavage. The buffer layer 2 is not limited to GaN as long as a gallium nitride-based semiconductor can be epitaxially grown thereon, and another material such as AlN or AlGaN ternary mixed crystal may be used.

N-type cladding layer 4 and p-type cladding layer 9
Is an AlG having an Al composition other than n-Al _0.1 Ga _0.9 N
An aN ternary mixed crystal may be used. In this case, when the Al composition is increased, the energy gap difference and the refractive index difference between the active layer and the cladding layer increase, and carriers and light are effectively confined in the active layer, further reducing the oscillation threshold current and improving the temperature characteristics. I can do it. Also, if the Al composition is reduced to such an extent that the confinement of carriers and light is maintained, the mobility of carriers in the cladding layer increases, and thus there is an advantage that the device resistance of the semiconductor laser device can be reduced. Further, these cladding layers may be quaternary or higher mixed crystal semiconductors containing trace amounts of other elements, and the composition of the mixed crystals in the n-type cladding layer 4 and the p-type cladding layer 9 may not be the same.

The guide layers 5 and 8 are made of a material whose energy gap has a value between the energy gap of the quantum well layer constituting the multiple quantum well structure active layer 6 and the energy gap of the cladding layers 4 and 9. If so, other materials such as a ternary mixed crystal such as InGaN or AlGaN or an InGaAlN quaternary mixed crystal may be used without being limited to GaN.
It is not necessary to dope the entire guide layer with a donor or an acceptor.
Only a part of the side may be non-doped, and further, the entire guide layer may be non-doped. In this case, there are advantages that the number of carriers existing in the guide layer is reduced, light absorption by free carriers is reduced, and the oscillation threshold current can be further reduced.

Two In _0.2 Ga _0.8 N quantum well layers 14 and one In _0.05 G layer constituting the multiple quantum well structure active layer 6 are formed.
The composition of the a _0.95 N barrier layer 15 may be set according to the required laser oscillation wavelength. If the oscillation wavelength is desired to be longer, the In composition of the quantum well layer 14 is to be increased, and if the shorter wavelength is desired, the quantum well layer 14 is required. Is reduced. Further, the quantum well layer 14 and the barrier layer 15 may be a quaternary or higher mixed crystal semiconductor containing a small amount of another element in the InGaN ternary mixed crystal. Further, the barrier layer 15 may simply use GaN.

Next, a method for fabricating the gallium nitride based semiconductor laser will be described with reference to FIGS. In the following description, the case where MOCVD (metal organic chemical vapor deposition) is used is shown, but any growth method capable of epitaxially growing GaN may be used, such as MBE (molecular beam epitaxy) or HDVPE (hydride vapor phase epitaxy). Other vapor phase epitaxy methods such as the method described above.

First, the sapphire substrate 1 having a thickness of 300 μm or more and a diameter of 2 inches, which is conventionally used and having a c-plane as a front surface, was polished to obtain a sapphire substrate 1 having a thickness of 150 μm. Subsequently, on the sapphire substrate 1 provided on a heating element in a predetermined growth furnace, the GaN buffer layer 2 was grown at a growth temperature of 600 ° C. using trimethylgallium (TMG) and ammonia (NH ₃ ) as raw materials. 35n
m.

Next, the growth temperature is raised to 1050 ° C., and a 3 μm-thick Si-doped n-GaN n-type contact layer 3 is grown using TMG, NH ₃ and silane gas (SiH ₄ ) as raw materials. Subsequently, trimethyl aluminum (TMA) was added to the raw material, and the growth temperature was 1050 ° C.
0.7 μm thick Si-doped n-Al _0.1 Ga
_{A 0.9} Nn-type cladding layer 4 is grown. Subsequently, the TMA is removed from the raw material, and the Si-doped n-GaN guide layer 5 having a thickness of 0.05 μm is grown at a growth temperature of 1050 ° C.

Next, the growth temperature is lowered to 800 ° C.
, NH ₃ , and trimethylindium (TMI) as raw materials and an In _0.2 Ga _0.8 N quantum well layer (5 nm thick)
14, In _0.05 Ga _0.95 N barrier layer (5 nm thick) 15,
An In _0.2 Ga _0.8 N quantum well layer (thickness: 5 nm) 14 is sequentially grown to form a multiple quantum well structure active layer (total thickness: 15 nm) 6. Further, using TMG, TMA and NH ₃ as raw materials, an Al _0.2 Ga _0.8 N evaporation preventing layer 7 having a thickness of 10 nm is grown at a growth temperature of 800 ° C.

Next, the growth temperature is raised again to 1050 ° C., and TMG, NH ₃ , and cyclopentadienyl magnesium (Cp ₂ Mg) are used as raw materials to a thickness of 0.05 μm.
An m-doped Mg-doped p-GaN guide layer 8 is grown. Subsequently, TMA was added to the raw material, and the growth temperature was kept at 1050 ° C., and the Mg-doped p-Al _0.1 Ga _0.9 layer having a thickness of 0.7 μm was formed.
The Np-type cladding layer 9 is grown. Subsequently, except that TMA was removed from the raw material, the growth temperature was kept at 1050 ° C. and the thickness was 0.2 mm.
A μm Mg-doped p-GaN p-type contact layer 10 is grown to complete a gallium nitride based epitaxial wafer.

Thereafter, the wafer is annealed in a nitrogen gas atmosphere at 800 ° C. to lower the resistance of the Mg-doped p-type layer.

Further, using the usual photolithography and dry etching techniques, the p-GaN p-type contact layer 10 is stripped from the outermost surface of the p-GaN p-type contact layer 10 to a width of 200 μm.
-Etching is performed until the GaN n-type contact layer 3 is exposed. Next, using the same photolithography and dry etching techniques as described above, the p-GaN p-type contact layer is formed on the outermost surface of the remaining p-GaN p-type contact layer 10 so as to form a ridge structure in a stripe shape having a width of 5 μm. 10 and p-Al _0.1 Ga _0.9 Np type clad layer 9 are etched.

Subsequently, a 200 nm thick SiO ₂ insulating film 13 is formed on the side surfaces of the ridge and on the surface of the p-type layer other than the ridge. A p-side electrode 11 made of nickel and gold is formed on the surface of the SiO ₂ insulating film 13 and the p-GaN p-type contact layer 10, and an n-GaN n-type contact layer 3 exposed by etching is formed on the surface of the n-GaN n-type contact layer 3. The side electrode 12 is formed to complete a gallium nitride based LD wafer.

Thereafter, the wafer is cleaved in a direction perpendicular to the ridge stripe to form a laser cavity end face.
It is further divided into individual chips. Then, each chip is mounted on a stem, each electrode is connected to a lead terminal by wire bonding, and a gallium nitride based semiconductor laser device is completed.

The blue LD device manufactured as described above has laser characteristics of an oscillation wavelength of 430 nm and an oscillation threshold current of 40 mA. Further, the distribution of the oscillation wavelength in the plane of the substrate wafer was reduced, and the difference in the oscillation wavelength between the central portion and the peripheral portion of the wafer, which was conventionally 150 nm, was reduced to 10 nm. Thus, according to the present invention, InGaN
The distribution of the emission characteristics from the quantum well active layer was improved, and a gallium nitride based semiconductor laser device having a uniform oscillation wavelength and a low oscillation threshold current value within the surface of the substrate wafer was realized.

FIG. 3 shows a change in the difference in oscillation wavelength between the center and the periphery of the wafer due to the thickness of the sapphire substrate having a diameter of 2 inches in the gallium nitride based semiconductor laser device, and And a graph showing a change in the oscillation threshold current value. The structure of each semiconductor laser is
It is the same as the gallium nitride based semiconductor laser device according to the first embodiment of the present invention except that the thickness of the sapphire substrate during the crystal growth is different. As you can see from this figure,
The thickness of the sapphire substrate during crystal growth is 180 μm
Is exceeded, the in-plane distribution of the oscillation wavelength increases rapidly, and the oscillation threshold current value also increases. Therefore, the reason why the emission wavelength is uniform in the wafer surface and a low oscillation threshold current value can be obtained is that the thickness of the sapphire substrate during crystal growth is 50 μm or more and 180 μm or less in the first embodiment of the present invention. Only the gallium nitride based semiconductor laser device according to the example is used. If the thickness of the substrate is 50 μm or less, the mechanical strength of the substrate is reduced, so that the substrate is easily broken,
500 ° C. to 1100 ° C. due to the difference in thermal expansion coefficient between the substrate and the gallium nitride based semiconductor formed on the substrate
After the crystal growth was performed at the temperature, when the temperature was lowered to room temperature, the substrate was warped and damaged.

In this embodiment, the quantum well layer 14 constituting the multiple quantum well structure active layer 6 has two layers.
It may have a multiple quantum well structure of three or more layers or a single quantum well structure of only one layer. Further, in this embodiment, the thicknesses of the quantum well layer 14 and the barrier layer 15 are both set to 5 nm.
These layer thicknesses need not be the same and may be different. Further, the thickness of the quantum well layer is not limited to this embodiment.

In this embodiment, the Al _0.2 Ga _0.8 N evaporation preventing layer 7 is formed so as to be in contact with the active layer 6 having a multiple quantum well structure. However, the growth temperature of the quantum well layer 14 is increased. This is to prevent evaporation in between. Therefore, any material that protects the quantum well layer 14 can be used as the evaporation prevention layer 7 and has another Al composition.
You may use 1GaN ternary mixed crystal or GaN. The evaporation preventing layer 7 may be doped with Mg. In this case, there is an advantage that holes are easily injected from the p-GaN guide layer 8 and the p-Al _0.1 Ga _0.9 Np type clad layer 9. Further, when the In composition of the quantum well layer 14 is small, the quantum well layer 14 does not evaporate even if the evaporation prevention layer 7 is not formed. The characteristics of the system semiconductor laser device are not impaired.

In this embodiment, the injection current is constricted by forming a ridge stripe structure. However, other current constriction methods such as an electrode stripe structure may be used. Further, in the present embodiment, the cavity facet of the laser is formed by cleavage, but the cavity facet can also be formed by dry etching.

Further, in this embodiment, since the sapphire substrate is used, the n-side electrode 12 is formed on the surface of the n-GaN n-type contact layer 3 exposed by etching.
When a SiC substrate, a Si substrate, a GaAs substrate, or the like having conductivity of the type is used as a substrate during crystal growth, n
The side electrode 12 may be formed. Further, the p-type and n-type configurations may be reversed.

(Embodiment 2) FIG. 4 is a sectional view showing a gallium nitride based semiconductor light emitting diode device according to a second embodiment of the present invention. In this figure, 21 is a sapphire substrate having a c-plane as a surface, a thickness of 100 μm, and a diameter of 2 inches, 22 a GaN buffer layer, 23 an n-GaN n-type contact layer, and 24 an n-Al _0.1 Ga
_0.9 Nn-type cladding layer, 25 is an n-GaN guide layer, 2
Reference _numeral 6 denotes an active layer having a single quantum well structure comprising an In _0.2 Ga _0.8 N quantum well layer; 27, an Al _0.2 Ga _0.8 N evaporation preventing layer;
Is a p-GaN guide layer, 29 is p-Al _0.1 Ga _0.9 Np
Type clad layer, 30 is a p-GaN p-type contact layer, 3
1 is a p-side electrode and 32 is an n-side electrode.

In the present embodiment, the thickness of the sapphire substrate 21 is set to 100 μm. However, the thickness is not limited as long as it is between 50 μm and 180 μm. The surface of the substrate may have another plane orientation such as an a-plane, an r-plane, or an m-plane.
Further, not only a sapphire substrate but also a SiC substrate, a spinel substrate, a MgO substrate, a Si substrate, and a GaAs substrate can be used. In particular, in the case of the SiC substrate, the cleavage is easier than in the case of the sapphire substrate, and therefore, there is an advantage that the LED element can be easily divided into chips. The buffer layer 22 is not limited to GaN as long as a gallium nitride based semiconductor can be epitaxially grown thereon.
For example, a ternary mixed crystal of AlN or AlGaN may be used.

The n-type cladding layer 24 and the p-type cladding layer 2
9 is Al having an Al composition other than n-Al _0.1 Ga _0.9 N.
A GaN ternary mixed crystal or simply GaN may be used. In this case, when the Al composition is increased, the energy gap difference between the active layer and the cladding layer increases, and the carriers are effectively confined in the active layer, thereby improving the temperature characteristics. Further, when the Al composition is reduced to such an extent that the confinement of the carriers is maintained, the mobility of the carriers in the cladding layer is increased, so that there is an advantage that the element resistance of the light emitting diode element can be reduced. Further, these cladding layers may be quaternary or higher mixed crystal semiconductors containing trace amounts of other elements, and the composition of the mixed crystals in the n-type cladding layer 24 and the p-type cladding layer 29 may not be the same.

The guide layers 25 and 28 are made of a material whose energy gap has a value between the energy gap of the quantum well layer constituting the single quantum well structure active layer 26 and the energy gap of the cladding layers 24 and 29. If GaN is not limited to other materials, such as InGaN / Al
GaN ternary mixed crystal, InGaAlN quaternary mixed crystal, or the like may be used. Further, it is not necessary to dope the entire guide layer with a donor or an acceptor, and only a part on the single quantum well structure active layer 26 side may be non-doped, and further, the entire guide layer may be non-doped. In this case, there is an advantage that the number of carriers existing in the guide layer is reduced, light absorption by free carriers is reduced, and light output is further improved. The guide layers 25 and 28 have an advantage that electrons and holes can be easily injected from the n-type cladding layer 24 and the p-type cladding layer 29 into the single quantum well structure active layer 26, respectively. 25 and 2
Since the LED element characteristics are not significantly deteriorated without providing the guide layer 8, the guide layers 25 and 28 may be omitted.

I constituting the single quantum well structure active layer 26
The composition of the n _0.2 Ga _0.8 N quantum well layer may be set according to the required emission wavelength. If the emission wavelength is desired to be longer, the In composition of the quantum well layer 26 is to be increased. 26 is reduced in In composition. Further, the quantum well layer 26 may be a quaternary or higher mixed crystal semiconductor containing a small amount of another element in an InGaN ternary mixed crystal.

Next, a method for fabricating the gallium nitride based semiconductor light emitting diode will be described with reference to FIG. In the following description, the case where MOCVD (metal organic chemical vapor deposition) is used is shown, but any growth method capable of epitaxially growing GaN may be used, such as MBE (molecular beam epitaxy) or HDVPE (hydride vapor phase epitaxy). Other vapor phase epitaxy methods such as the method described above.

First, the sapphire substrate 21 having a thickness of 300 μm or more and a diameter of 2 inches was polished to obtain a sapphire substrate 21 having a thickness of 100 μm. Subsequently, TMG was placed on the sapphire substrate 21 installed on a heating element in a predetermined growth furnace.
A GaN buffer layer 22 is grown to a thickness of 35 nm at a growth temperature of 600 ° C. by using GaN and NH ₃ as raw materials.

Next, the growth temperature is raised to 1050 ° C., and a 3 μm-thick Si-doped n-GaN n-type contact layer 23 is grown using TMG, NH ₃ and SiH ₄ as raw materials. Subsequently, TMA was added to the raw material, and the growth temperature was kept at 1050 ° C., and the Si-doped n-
An Al _0.1 Ga _0.9 Nn-type clad layer 24 is grown. Subsequently, the TMA is removed from the raw material, and the Si-doped n-GaN guide layer 25 having a thickness of 0.05 μm is grown at a growth temperature of 1050 ° C.

Next, the growth temperature was lowered to 800 ° C.
, NH ₃ , and TMI as raw materials, and a 3 nm-thick I
To create a n _0.2 Ga _0.8 N single quantum well structure active layer 26 comprising a quantum well layer. Continue with TMG, TMA and N
Using H ₃ as a raw material, an Al _0.2 Ga _0.8 N evaporation preventing layer 27 having a thickness of 10 nm is grown at a growth temperature of 800 ° C.

Next, the growth temperature is raised again to 1050 ° C., and a 0.05 μm-thick Mg-doped p-GaN guide layer 28 is grown using TMG, NH ₃ and Cp ₂ Mg as raw materials. Subsequently, TMA was added to the raw material, and the growth temperature was kept at 1050 ° C., and a 0.3 μm-thick Mg-doped p-
An Al _0.1 Ga _0.9 Np type clad layer 29 is grown. Subsequently, the TMA is removed from the raw material, and the Mg-doped p-GaN p-type contact layer 30 having a thickness of 0.2 μm is grown at a growth temperature of 1050 ° C. to complete a gallium nitride-based epitaxial wafer.

Thereafter, the wafer is annealed in a nitrogen gas atmosphere at 800 ° C. to reduce the resistance of the Mg-doped p-type layer.

Further, the n-GaN n-type contact layer 23 is exposed from the outermost surface of the p-GaN p-type contact layer 30 to a predetermined region for manufacturing an LED element by using ordinary photolithography and dry etching techniques. Perform etching.

Subsequently, the p-GaN p-type contact layer 30
A p-side electrode 31 made of nickel and gold on the surface of
An n-side electrode 3 made of titanium and aluminum is provided on the surface of the n-GaN n-type contact layer 23 exposed by etching.
2 is formed to complete a gallium nitride-based LED wafer.

Thereafter, the wafer is divided into individual chips. Then, each chip is mounted on a stem, each electrode is connected to a lead terminal by wire bonding, and a gallium nitride based semiconductor light emitting diode device is completed.

The blue LED device manufactured as described above exhibited light emission characteristics of a light emission wavelength of 430 nm and a light output of 4 mW at a forward current of 20 mA. Example 1
Similarly to the above, the distribution of the emission wavelength in the surface of the substrate wafer becomes smaller, and the center of the wafer and the peripheral portion are conventionally 150 nm.
The difference in the emission wavelength was reduced to 8 nm. As described above, according to the present invention, the distribution of the light emission characteristics from the InGaN quantum well active layer is improved, and a gallium nitride based semiconductor light emitting diode element having a uniform light emission wavelength within the surface of the substrate wafer can be realized.

In this embodiment, the number of In _0.2 Ga _0.8 N quantum well layers constituting the single quantum well structure active layer 26 is set to 1 and the thickness is set to 3 nm. A structure active layer may be used, and the layer thickness of the quantum well layer is not limited to this embodiment.

In this embodiment, the Al _0.2 Ga _0.8 N evaporation preventing layer 27 is in contact with the single quantum well structure active layer 26.
Is formed to prevent the quantum well layer 26 from evaporating while the growth temperature is being increased. Therefore, any material that protects the quantum well layer 26 can be used as the evaporation prevention layer 27, and an AlGaN ternary mixed crystal or GaN having another Al composition may be used. The evaporation preventing layer 27 may be doped with Mg. In this case, the p-GaN guide layer 28 or the p-Al _0.1
There is an advantage that holes are easily injected from the Ga _0.9 Np type cladding layer 29. Further, In of the quantum well layer 26
When the composition is small, the quantum well layer 26 does not evaporate without forming the evaporation preventing layer 27, and therefore, even if the evaporation preventing layer 27 is not formed, the characteristics of the gallium nitride based semiconductor light emitting diode element of the present embodiment are It is not spoiled.

[0051]

As described above, the gallium nitride based semiconductor light emitting device according to the present invention contains at least indium and gallium sandwiched between a cladding layer and / or a guide layer made of a nitride semiconductor by a vapor growth method. By reducing the thickness of the substrate when forming the quantum well structure active layer made of a nitride semiconductor to 50 μm or more and 180 μm or less, the temperature difference between the bottom surface and the surface of the substrate during crystal growth of InGaN is eliminated. Since the warpage of the substrate wafer during crystal growth is suppressed, the substrate wafer comes into contact with the heating element on the entire bottom surface, so that the surface temperature distribution in the substrate wafer surface is suppressed. Thereby, In
The distribution of the In composition in the GaN quantum well layer could be reduced.

As a result, the distribution of the emission characteristics from the InGaN quantum well active layer is improved, and the gallium nitride based semiconductor laser device having a uniform oscillation wavelength and a low oscillation threshold current value in the substrate wafer surface, and A gallium nitride-based light emitting diode device having a uniform emission wavelength was realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a portion A of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 3 shows the dependence of the difference in the oscillation wavelength between the central part and the peripheral part of the wafer on the thickness of the sapphire substrate and the thickness of the oscillation threshold current value of the sapphire substrate in the gallium nitride based semiconductor laser device. FIG. 4 is a graph showing dependency.

FIG. 4 is a sectional view showing a semiconductor light emitting diode device according to a second embodiment of the present invention.

FIG. 5 shows a conventional blue LD using a gallium nitride based semiconductor.
FIG.

FIG. 6 shows a conventional blue LE using a gallium nitride-based semiconductor.
It is sectional drawing of D.

FIG. 7 is a diagram showing the warpage of a substrate when the temperature of a conventional substrate wafer placed on a heating element is increased.

[Explanation of symbols]

1 sapphire substrate 2 GaN buffer layer 3 n-Gann type contact layer 4 n-Al _0.1 Ga _0.9 Nn type cladding layer 5 n-GaN guide layer 6 multiple quantum well structure active layer 7 Al _0.2 Ga _0.8 N evaporation preventing layer 8 p- GaN guide layer 9 p-Al _0.1 Ga _0.9 Np-type cladding layer 10 p-GaN p-type contact layer 11 p-side electrode 12 n-side electrode 13 SiO ₂ insulating film 14 In _0.2 Ga _0.8 N quantum well layer 15 In _0.05 Ga _0.95 N barrier layer

Claims (2)

[Claims] 1. A substrate for forming a quantum well structure active layer made of a nitride semiconductor containing at least indium and gallium sandwiched between a clad layer and / or a guide layer made of a nitride semiconductor by a vapor growth method. Thickness of 50μ
A method for manufacturing a gallium nitride based semiconductor light emitting device, wherein the thickness is not less than m and not more than 180 μm. 2. A substrate for forming a quantum well structure active layer made of a nitride semiconductor containing at least indium and gallium sandwiched between a clad layer and / or a guide layer made of a nitride semiconductor by a vapor phase growth method. Thickness of 50 μm
A gallium nitride-based semiconductor light emitting device having at least one quantum well layer, which is obtained by adjusting the thickness to 180 μm or less.