JP2980379B2 - Gallium nitride based compound semiconductor light emitting device and method of manufacturing gallium nitride based compound semiconductor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gallium nitride-based compound semiconductor light-emitting device that emits light in a blue region to an ultraviolet region, and a method of manufacturing a gallium nitride-based compound semiconductor used for the light-emitting device.

BACKGROUND ART Light-emitting elements that emit light in a wavelength region shorter than blue are expected as full-color displays and light sources for optical disks capable of recording at high density. As semiconductors used for such light emitting devices, II-VI compound semiconductors such as ZnSe and III-V compound semiconductors such as SiC and GaN are known. Research on these semiconductors is being actively conducted. Recently, GaN and In _x Ga _1-x N (0 <x <1, hereinafter referred to as InGa
A blue light emitting diode is realized by using a compound semiconductor such as N), and a light emitting element using a gallium nitride-based compound semiconductor is receiving attention (Japanese Patent Application Laid-Open No. 7-162038).

A conventional gallium nitride-based compound semiconductor light emitting device will be described with reference to FIG. This light-emitting element has a GaN buffer layer 101 and an n-type buffer layer on a sapphire (single crystal Al ₂ O ₃ ) substrate 100.
Al _x Ga ₁ -xN (0 <x <1, hereinafter abbreviated as AlGaN) cladding layer 102, InGaN active layer 103, p-type AlGaN cladding layer 10
4, and a structure in which a p-type GaN contact layer 105 is sequentially laminated. A p-side electrode (Au electrode) 107 is formed on the p-type GaN contact layer 105, and the n-type AlGaN cladding layer 10 is formed.
An n-side electrode (Al electrode) 108 is formed on a part of the portion 2 exposed.

Hereinafter, a method of manufacturing a gallium nitride-based compound semiconductor used in the above-described conventional light emitting device will be described with reference to FIGS.

In general, metal organic chemical vapor deposition (MOVPE) or molecular beam epitaxy (MBE) is used to form a gallium nitride-based compound semiconductor. Here, for example, MOVPE
A method for forming a gallium nitride-based compound semiconductor using the method will be described.

Sapphire (single crystal Al ₂ O) as shown in FIG.
₃ ) After placing the substrate 121 in a reaction furnace of a MOVPE apparatus (not shown), an organic metal trimethylgallium (TMG) and ammonia (NH ₃ ) are supplied onto the substrate 121 at a temperature of about 600 ° C. The carrier gas is hydrogen. Thus, the polycrystalline GaN layer 122a is deposited on the substrate 121.

Next, a GaN single crystal layer is formed on the GaN polycrystalline layer 122a. FIG. 2B shows a growth sequence of the GaN single crystal layer. Hereinafter, this step will be described in more detail.

The supply of TMG, which is a Ga raw material, was stopped, and the temperature of
After the temperature is raised to about 00 ° C., TMG is supplied onto the substrate again.
As a result, as shown in FIG. 20B, nuclei 122b of the GaN single crystal having high orientation along the crystal axis are formed.
GaN single crystal nuclei 1 formed at such a temperature (1000 ° C)
The range of the particle size of 22b is about several μm to several hundred μm.

Next, when the supply of TMG and NH ₃ is continued while maintaining the substrate temperature at 1000 ° C., as shown in FIG. 20C, the GaN single crystal nucleus 122b mainly grows two-dimensionally. . As a result, the nuclei 122b are connected to each other to form a GaN single crystal layer 122c as shown in FIG. GaN polycrystalline layer
122a and GaN single crystal layer 122c constitute GaN buffer layer 122.

Next, on the GaN buffer layer 122, by MOVPE method,
Another gallium nitride based semiconductor layer (not shown) is grown.

According to the above growth method, the GaN single crystal layer 122c is formed by one-stage crystal growth at 1000 ° C.

Hereinafter, a method for manufacturing the light emitting device of FIG. 19 will be described with reference to FIG.

As shown in FIG. 21, after a GaN polycrystalline layer is deposited on a sapphire substrate 100 at 600 ° C. by the above method, a GaN single crystal layer is grown thereon at 1000 ° C., and a GaN buffer layer is formed.
Form 101.

Thereafter, a gallium nitride-based compound semiconductor laminated structure 109 is grown on the GaN buffer layer 101. More specifically, first, an n-type AlGaN cladding layer 102 is grown at 1000 ° C. using TMA (trimethylaluminum), TMG (trimethylgallium), SiH ₄ (monosilane), and ammonia. Next, the substrate temperature is decreased to 700 ° C., and the InGaN active layer 103 is grown using TMI (trimethyl indium), TMG and NH ₃ . Thereafter, the substrate temperature was again raised to 1000 ° C., and p-type A was added using TMA, TMG, Cp2Mg (cyclopentadienyl magnesium) and NH _3.
The lGaN cladding layer 104 is grown. In addition, TMG, Cp2Mg
The p-type GaN contact layer 105 is grown by using NH ₃ and NH ₃ .

Next, as shown in FIG. 19, the n-type AlGaN cladding layer 1
InGaN active layer 103, p-type AlGaN until part of 02 is exposed
The clad layer 104 and the p-type GaN contact layer 105 are partially dry-etched using plasma or the like.

Next, a p-side electrode (Au electrode) 107 is formed on the p-type GaN contact layer 105, and an n-side electrode (Al electrode) 108 is formed on a partially exposed portion of the n-type AlGaN cladding layer 102.

In the above conventional technique, the GaN buffer layer 101 is formed on a sapphire substrate by one-stage (1000 ° C.) crystal growth.
The method of growing a GaN single crystal layer cannot achieve high quality of the GaN single crystal layer. That is, it is not possible to improve all properties of the GaN single crystal layer, such as electrical, optical, and crystal structures.

The reason is as follows. According to the above-described conventional method, a GaN single crystal nucleus 122b is formed on the GaN polycrystalline layer 122a at a relatively high temperature (1000 ° C.), and as shown in FIG. The nucleus 122b has a variation in the orientation. Therefore, the finally obtained GaN single crystal layer 1
The structure 22c is divided into regions having different orientations as shown in FIG. 20 (d).

As described above, the structure of the GaN single crystal layer 122c is divided into a plurality of regions having different orientations.
Many defects are present at the interface between 22c and another semiconductor single crystal layer formed thereon. In these defects, non-radiative recombination of electrons and holes occurs, and it is difficult to manufacture a light-emitting element having a high injection current density.

Further, conventionally, since the sapphire substrate used as the substrate of the nitride-based compound semiconductor light emitting device is insulative, as shown in FIG. 19, the n-type AlGaN cladding layer 102,
InGaN active layer 103, p-type AlGaN cladding layer 104, and p-type
The GaN contact layer 105 is partially etched away,
A step of forming the n-side electrode 108 on the partially exposed n-type AlGaN cladding layer 102 was required.

The present invention has been made in view of the above circumstances,
The objectives are (1) to provide a method for producing a gallium nitride-based semiconductor having excellent properties such as electrical, optical, and crystal structures; and (2) to provide a semiconductor for forming an n-side electrode. An object of the present invention is to provide a gallium nitride-based semiconductor light-emitting device which does not require a step of etching and removing a part of a laminated structure and has a low operating voltage.

DISCLOSURE OF THE INVENTION The method for producing a gallium nitride-based compound semiconductor according to the present invention comprises the steps of: forming a nitride polycrystalline layer on a substrate in a first temperature range; Forming a gallium nitride single crystal core layer in a temperature range of 2;
In a third temperature range, the crystals of the core layer of the gallium nitride single crystal are connected to each other in a direction parallel to the surface of the substrate,
Growing a nuclei layer of the gallium nitride single crystal;
Growing the gallium nitride single crystal nucleus layer in a direction perpendicular to the surface of the substrate in the above temperature range, thereby achieving the above object.

In one embodiment, the second temperature range, the third temperature range, and the fourth temperature range are higher than the first temperature range.

In one embodiment, the second temperature range is 1000 ° C. or less.

In one embodiment, the fourth temperature range is higher than the third temperature range, and the third temperature range is higher than the second temperature range.

In one embodiment, the substrate is formed from sapphire.

In one embodiment, the nitride polycrystalline layer contains aluminum nitride and is formed by ECR-CVD or ECR sputtering.

In one embodiment, the nitride polycrystalline layer is formed of Al _x Ga _1-x
It contains N (0 ≦ x ≦ 1) and is formed by MOVPE.

A method for manufacturing a gallium nitride-based compound semiconductor device according to the present invention includes a step of forming a conductive aluminum nitride layer on a surface of a silicon carbide substrate, and a step of forming a gallium nitride-based compound semiconductor laminated structure on the aluminum nitride layer. And the step of forming the above is achieved, thereby achieving the above object.

In one embodiment, the surface of the silicon carbide substrate includes:
[11-] at a first angle from the (0001) plane of the silicon carbide substrate.
20].

In one embodiment, the first angle is between about 1 ° and 18 °.
Up to ゜. In one embodiment, the first angle is
It is about 5 ゜ to 12 ゜.

In one embodiment, the step of forming the aluminum nitride layer is performed at a temperature from about 800C to 1200C.

In one embodiment, the aluminum nitride layer is made of a single crystal.

In one embodiment, on the aluminum nitride layer,
The method further includes the step of forming a gallium nitride single crystal layer.

In one embodiment, silicon is doped as an impurity in the aluminum nitride layer.

A gallium nitride-based compound semiconductor light emitting device according to the present invention includes a silicon carbide substrate, a conductive aluminum nitride layer formed on a surface of the silicon carbide substrate, and a gallium nitride-based compound layer provided on the aluminum nitride layer. And a compound semiconductor laminated structure, whereby the object is achieved.

In one embodiment, the surface of the silicon carbide substrate includes:
[11-] at a first angle from the (0001) plane of the silicon carbide substrate.
20].

In one embodiment, the first angle is between about 1 ° and 18 °.
Up to ゜. In one embodiment, the first angle is
It is about 5 ゜ to 12 ゜.

In one embodiment, the semiconductor device further comprises an electrode provided above the stacked structure, and an In _x Ga having a conductivity type opposite to that of the substrate between the stacked structure and the electrode.
_1-xN (0 <x <1) layers are provided. In one embodiment, the electrode is formed from platinum.

The method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to the present invention includes a method of manufacturing an Al _x Ga _y In _z N (0 ≦ x
<1, 0 ≦ y <1, 0 <z ≦ 1, x + y + z = 1) A gallium nitride-based compound semiconductor laminated structure including an active layer is provided, and the active layer is formed in a first temperature range. And GaN for suppressing the evaporation of In on the active layer.
Forming a cap layer; and performing a heat treatment on the active layer at a second temperature range higher than the first temperature range, thereby achieving the above object. .

In one embodiment, the step of forming the GaN cap layer is performed in the first temperature range.

In one embodiment, the step of forming the GaN cap layer is performed while increasing the temperature from the first temperature range to the second temperature range.

In one embodiment, the thickness of the GaN cap layer is about 1
nm or more and 10 nm or less.

In certain embodiments, the first temperature range is between about 500-800.
℃, the second temperature range is 1000 ℃ or more.

The gallium nitride-based compound semiconductor light-emitting device according to the present invention comprises an Al _x Ga _y In _z N (0 ≦ x <1, 0
≦ y <1, 0 <z ≦ 1, x + y + z = 1) a gallium nitride-based compound semiconductor multilayer structure including an active layer, wherein GaN for suppressing evaporation of In is provided on the active layer. A cap layer is formed, thereby achieving the above object.

The GaN cap layer has a thickness of about 1 nm or more and 10 nm or less.

A gallium nitride-based compound semiconductor light emitting device according to the present invention includes a gallium nitride-based compound semiconductor laminated structure provided on a substrate, wherein the laminated structure includes an active layer and a pair of layers sandwiching the active layer. , And carbon is used as the p-type dopant of the p-type cladding layer, thereby achieving the above object.

In one embodiment, a p-type guide layer is provided between the active layer and the p-type clad layer, and carbon is used as a p-type dopant of the p-type guide layer.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (a) to 1 (d) are views showing steps of manufacturing a gallium nitride based semiconductor according to the present invention.

FIG. 2A is a diagram showing a crystal growth sequence according to the present invention, and FIG. 2B is a diagram showing a crystal growth sequence according to the prior art.

3 (a) and 3 (b) show the surface state of the GaN single crystal layer grown by the manufacturing method of the present invention, and FIG. 3 (c).
FIG. 3D is a diagram showing a surface state of a GaN single crystal layer grown by a conventional manufacturing method.

FIG. 4A is a diagram showing room temperature photoluminescence of the InGaN layer grown by the manufacturing method of the present invention, and FIG. 4B is a diagram showing room temperature photoluminescence of the InGaN layer grown by the conventional manufacturing method.

5 (a) to 5 (d) are views showing the steps of manufacturing a gallium nitride based semiconductor according to the present invention.

FIG. 6 is a diagram showing a crystal growth sequence according to the present invention.

FIG. 7 is a diagram showing the relationship between the surface roughness of the AlGaN layer and the composition of Al when a silicon carbide substrate is used.

FIG. 8 is a diagram showing a relationship between the inclination angle of the silicon carbide substrate and the surface roughness of the AlGaN layer.

FIG. 9 shows Mg in the AlGaN layer when a silicon carbide substrate is used.
FIG. 3 is a view showing the relationship between the incorporation rate of Al and the Al composition.

FIG. 10A is a TEM photograph showing a cross section of an InGaN / GaN / AlN multilayer film formed on a (0001) just silicon carbide substrate, and FIG. In
4 is a TEM photograph showing a cross section of a GaN / GaN / AlN multilayer film.

FIG. 11 is a cross-sectional view showing a configuration of a light emitting device using a sapphire substrate according to the present invention.

FIG. 12 is a diagram showing a crystal growth sequence for manufacturing a light emitting device according to the present invention.

FIG. 13 (a) shows the interface between the undoped GaN cap layer according to the present invention and the InGaN active layer / p-type GaN guide layer. FIG. 13 (b) shows the conventional InGaN active layer / p-type GaN guide layer. It is a figure which shows the interface with.

FIG. 14 is a diagram showing the relationship between the luminous efficiency of the InGaN layer according to the present invention and the time of the heat treatment.

FIGS. 15A and 15B are diagrams showing a sequence for forming an undoped GaN cap layer according to the present invention. FIG. 15A shows a case where crystal growth is interrupted, and FIG. 15B shows a case where crystal growth is not interrupted.

FIG. 16 is a cross-sectional view showing a configuration of a light emitting device using a silicon carbide substrate according to the present invention.

FIG. 17 is a diagram showing a configuration of a multiple quantum well light emitting device according to the present invention.

FIG. 18 shows carbon (dopant according to the invention) and Mg
FIG. 9 is a diagram showing a depth profile of an impurity (differential dopant) indicating diffusion into an active layer.

FIG. 19 is a cross-sectional view illustrating a configuration of a light-emitting element using a conventional sapphire substrate.

20 (a) to (d) are views showing the steps of manufacturing a conventional gallium nitride-based semiconductor.

 FIG. 21 is a diagram illustrating a manufacturing process of a conventional light emitting device.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. In addition,
In the present specification, "gallium nitride based compound semiconductor"
The semiconductor of Ga gallium nitride (GaN) is replaced partially other group III element, for _{example, In s Ga 1-s N} (0 ≦
s <1) and Al _t Ga _1-t N (0 ≦ t <1), and also includes a semiconductor in which a part of each constituent atom is replaced by a Dobant atom or the like and a semiconductor to which another impurity is added. Shall be considered. In _s Ga _1-s N and Al _t Ga _1-t N, respectively "InGaN"
And “AlGaN”.

Further, in this specification, the “semiconductor light emitting device” includes a light emitting diode and a semiconductor laser.

First Embodiment A method of manufacturing a gallium nitride-based compound semiconductor according to the present invention will be described with reference to FIGS. More specifically, a method for forming a GaN single crystal layer on a sapphire substrate will be described. In this embodiment, a metal organic chemical vapor deposition (MOVPE) method is used to form the crystal layer.

1A to 1D are cross-sectional views illustrating a method for growing a GaN single crystal layer according to the present invention. FIG. 2A shows a growth sequence of a GaN single crystal layer.

First, sapphire (single crystal Al ₂ O
₃ ) The C-plane substrate 10 is placed on a susceptor in a reactor of a MOVPE apparatus (not shown), evacuated, and then heated at 1050 ° C. for 15 minutes in a hydrogen atmosphere of 70 Torr to obtain a substrate.
A cleaning process is applied to the surface of No. 10.

Next, as shown in FIG. 2A, after cooling the substrate to about 600 ° C., trimethylgallium (TMG) was
By supplying mol / min, ammonia at 2.5 L / min and carrier hydrogen at about 2 L / min, a GaN layer (GaN polycrystalline layer) 11a in a polycrystalline state as shown in FIG. . The temperature range (first temperature range) for depositing the GaN polycrystalline layer 11a is preferably about 500 to 600 ° C.

Next, in order to form a good GaN single crystal layer on the GaN polycrystalline layer 11a, the following three stages of crystal growth steps are performed.

The first stage is a process of forming a GaN single crystal nucleus layer. After stopping only the supply of TMG and raising the substrate temperature to about 950 ° C., as shown in FIG.
Mol / min to deposit a GaN single crystal nucleus layer 11b. 95
The formation time of the GaN single crystal nucleus layer 11b at 0 ° C. is about 3 minutes. The temperature range (second temperature range) for forming the GaN single crystal nucleus layer 11b is preferably 700 ° C. or more and 1000 ° C. or less. If the temperature is lower than 700 ° C, ammonia cannot be sufficiently decomposed. If the temperature is higher than 1000 ° C., single crystallization of the GaN polycrystalline layer 11a proceeds, and irregularities are formed on the surface of the GaN polycrystalline layer 11a.
Therefore, the surface flatness is high on the GaN polycrystalline layer 11a.
The GaN single crystal core layer 11b cannot be grown. This will be described in more detail below. The range of the crystal grain size of the GaN single crystal nucleation layer 11b formed by the present invention is about several μm.
~ Several hundred μm.

Next, a second stage of crystal growth is performed. In this step, following the first step, while supplying TMG, the substrate temperature is raised from 950 ° C. to about 1050 ° C. (third temperature range) (heating time: 2 minutes). Hold for a minute.

Next, a third stage of crystal growth is performed. In this step, following the second step, while supplying TMG, the substrate temperature is raised from about 1050 ° C. to about 1090 ° C. (fourth temperature range) (heating time: 2 minutes), and this temperature is reduced to about 10 minutes. Hold for 60 minutes.

By the steps of the second and third steps, the GaN single crystal nucleus layer 11b formed in the first step grows into a GaN single crystal layer 11c as shown in FIG. 1 (d). GaN single crystal layer 11c
Has a thickness of about 0.1 μm or more and 5 μm or less. In order to obtain good crystallinity, the second and third growth temperatures (10
(50 ° C. and 1090 ° C.) is preferably set at 1000 ° C. or more and 1200 ° C. or less.

Finally, only the supply of TMG is stopped, and the substrate is cooled to room temperature in a mixed atmosphere of ammonia and hydrogen.

As described above, the GaN single crystal layer 11c is formed on the GaN polycrystalline layer 11a.
Is formed. GaN polycrystalline layer 11a and GaN single crystal layer 11c
Constitute the GaN buffer layer 11. This GaN buffer layer 11
A gallium nitride based semiconductor multilayer structure for emitting light is deposited on the substrate. In the present embodiment, GaN is used as the polycrystalline layer constituting the buffer layer 11, but Al _x Ga _1-x N (0 <x ≦ 1) may be used instead of GaN.

An important point of the present invention is that the crystal growth is performed in a plurality of stages (three stages) in forming the GaN single crystal layer 11c. Thus, a high quality GaN single crystal layer 11c is obtained.

The formation mechanism of the GaN single crystal layer 11c will be described in more detail below.

According to the present invention, the GaN single crystal nucleus layer 11b is deposited on the GaN polycrystalline layer 11a at a relatively low temperature, that is, at a temperature lower than 1000 ° C. (950 ° C.) in the first stage. By using such a low deposition temperature, the nuclei of the GaN single crystal nucleus layer 11b are small in size and can be formed densely over the entire surface of the substrate. For this reason, the flatness of the surface of the GaN single crystal nucleus layer 11b is improved. In addition, since the deposition temperature is low, the crystal orientation of the GaN single crystal nucleus layer 11b is low, and it is oriented in multiple directions.

In the second step (1050 ° C.), the GaN single crystal nucleation layer 1
Among the nuclei 1b, the nuclei having the orientation of the surface of the substrate 10 grow largely two-dimensionally in a direction parallel to the surface of the substrate 10, as shown in FIG. 1C. As a result, adjacent nuclei with low orientation are also taken in, and the nuclei are two-dimensionally connected in a direction parallel to the surface of the substrate 10 to form GaN with high orientation.
A single crystal nucleus layer is formed. That is, the nucleus crystal of the nucleus layer 11b of the GaN single crystal, which was randomly oriented in various directions,
It grows so as to be oriented in the same direction along a direction parallel to the surface of the substrate 10.

In the third stage, when the crystal growth proceeds at a higher temperature (1090 ° C.), as shown in FIG.
The GaN single crystal nucleus layer 11c having a high orientation in a direction parallel to the surface of the substrate 10 grows in a direction perpendicular to the surface of the substrate 10. That is, the GaN single crystal layer 11c that is strongly oriented along the C axis is formed over a wide area on the substrate 10 along the orientation of the surface of the substrate 10. The GaN single crystal layer 11c thus formed is
Has high surface flatness.

In order to evaluate the crystallinity of the GaN single crystal layer 11c formed according to the present embodiment, the full width at half maximum of the diffraction peak in two-crystal X-ray diffraction was measured. The crystal of the GaN single crystal layer 11c exhibits a full width at half maximum of 3 minutes. On the other hand, conventional one stage (1000 ℃)
The crystal of the GaN single crystal layer formed by the crystal growth method has a full width at half maximum as high as 5 minutes. From this, it is understood that according to the present embodiment, a good GaN single crystal layer having excellent crystallinity can be obtained.

Further, a photograph of the surface of the GaN single crystal layer 11c formed according to the present embodiment was taken using an optical microscope, and the flatness thereof was examined. The results are shown in FIGS. 3 (a) and (b). FIGS. 3C and 3D show the surface state of a GaN single crystal layer obtained by a conventional technique as a comparative example. Third (a) and (c) are plan views of the GaN single crystal layer. FIGS. 3 (b) and (d) correspond to lines 3B-3B and 3D-3D of FIGS. 3 (a) and 3 (c), respectively.
2 shows the state of the cross section along the line.

According to the conventional technique, irregularities are observed on the surface of the GaN single crystal layer within a distance of approximately 300 μm, which is the size of the light emitting element (FIG. 3C). Further, as can be seen from FIG. 3D, the roughness of the surface of the GaN single crystal layer is about 100 angstroms. Since the flatness of the surface of the GaN single crystal layer is poor, it is difficult to deposit a gallium nitride based semiconductor multilayer film having a steep interface thereon.

On the other hand, according to the present embodiment, as shown in FIG. 3A, a GaN single crystal layer having a uniform and flat surface is obtained. Further, as can be seen from FIG. 3B, no surface irregularities can be detected in the GaN single crystal layer 11c obtained according to the present embodiment. Since the inspection limit of the optical microscope used for the measurement was 50 angstroms, it was estimated that the surface roughness of the GaN single crystal layer 11c obtained by the present embodiment was 50 angstroms or less. According to the present embodiment, since the surface of the GaN single crystal layer 11c shows excellent flatness,
A gallium nitride-based semiconductor multilayer film having good crystallinity and a steep interface can be formed thereon.

On the GaN single crystal layer 11c obtained by the present embodiment,
A gallium nitride based semiconductor multilayer film including an InGaN layer was deposited by MOVPE, and its room temperature photoluminescence was observed. The observation result is shown in FIG. FIG. 4 (a)
As can be seen from FIG. 7, only band edge emission appears near 410 nm. This indicates that a gallium nitride based semiconductor multilayer film having high quality is formed.

FIG. 4B shows the results of observation of room temperature fault luminescence when a GaN single crystal layer is formed by a conventional technique and a gallium nitride based semiconductor multilayer film including an InGaN layer is deposited thereon. As can be seen from this figure, in addition to the band-edge emission near 410 nm, emission from a deep level attributable to defects is observed near 550 nm. this is,
This is because the quality of the InGaN layer has deteriorated.

Second Embodiment A method for forming a GaN single crystal layer on a SiC substrate 210 will be described as a second embodiment of the present invention with reference to FIGS.

In the present embodiment, as a material of the substrate 210, SiC having a 6H structure is used. SiC substrate 210 is doped with nitrogen and has n-type conductivity. SiC substrate 210
Is inclined about 3.5 degrees from the (0001) plane in the [11-20] direction. In the present specification, such a substrate is referred to as an “inclined substrate” or “off-oriented substrate”.
Called.

Further, in the present embodiment, the deposition of a polycrystalline layer for forming a GaN single crystal layer on the substrate 210 is performed by an electric cyclotron resonance CVD method (ECR-CVD method) or an electron cyclotron resonance sputtering method (ECR sputtering method). Is used. Note that AlN is used as a material for forming the polycrystalline layer.

5A to 5D are cross-sectional views illustrating a method for growing a GaN single crystal layer according to the present invention. FIG. 6 shows a growth sequence of the GaN single crystal layer.

First, in order to perform crystal growth, the silicon carbide substrate 210 is placed on a susceptor in a reaction furnace of an ECR-CVD or ECR sputtering device (not shown), and after evacuation, in a hydrogen atmosphere of 70 Torr, at 1050 ° C. for 15 minutes. By heating, the surface of the substrate 210 is subjected to a cleaning process.

Next, as shown in FIG. 6, after cooling the substrate 210 to about 200 ° C., solid Al (purity 6N) and nitrogen gas are mixed with ECR-C.
Supply into a VD or ECR sputter reactor. ECR-CVD
Alternatively, the pressure in the reactor for ECR sputtering is 1 × 10 ⁻³ Torr
It is. Next, a microwave of 2.45 GHz and 500 W is applied, and an AlN layer (AlN polycrystalline layer) 211a in a polycrystalline state is deposited to a thickness of about 50 nm as shown in FIG. The range of the size of the crystal grains of the AlN polycrystalline layer 211a thus obtained is several
~ Several thousand m2.

Next, the substrate 210 on which the AlN polycrystalline layer 211a was deposited was
It is installed in the reactor of the apparatus and heat-treated at about 1000 ° C for 10 minutes in a mixed atmosphere of ammonia and hydrogen. AlN polycrystalline layer 211
In order to enhance the conductivity of a, heat treatment temperature should be about 800 ° C or more
It is preferable to set the temperature to 1200 ° C. or lower. By this processing, as shown in FIG. 5B, the C-axis orientation of the AlN polycrystalline layer 211a is improved.

Next, in order to form a good GaN single crystal layer on the AlN polycrystalline layer 211a, a process substantially similar to the three-stage crystal growth process described in the first embodiment is performed. This will be described in more detail below.

In the first stage, the substrate temperature is maintained at 1000 ° C., and TMG and ammonia are supplied using hydrogen gas as a carrier gas. As a result, as shown in FIG. 5C, the GaN single crystal nucleus layer 2 having a strong C-axis orientation is formed on the AlN polycrystalline layer 211a.
Form 11b. The formation time of the GaN single crystal nucleus layer 211b is about 2 minutes.

In the second stage, the substrate temperature is raised to about 1050 ° C. to grow the GaN polycrystalline layer 211a. In the third stage, the substrate temperature is raised to about 1090 ° C. and the GaN polycrystalline layer 211 is increased.
a is further grown, and as shown in FIG.
A single crystal layer 211c (thickness: about 0.1 μm to 5 μm) is formed. Other crystal growth conditions by the MOVPE method in the second and third stages are the same as those in the first embodiment.

The AlN polycrystalline layer 211a and the GaN single crystal layer 211c constitute a buffer layer 211. On this buffer layer 211, a gallium nitride based semiconductor multilayer structure for emitting light is deposited.

AlN polycrystalline layer using ECR-CVD or ECR sputtering
Depositing 211a has the following advantages. According to the ECR-CVD or ECR sputtering method, the AlN polycrystalline layer 211a is heated to 200 ° C.
It can be deposited at such a low temperature. On the other hand, according to the MOVPE method, ammonia, which is a nitrogen
N polycrystalline layers cannot be deposited at 200 ° C.

In the present embodiment, since the AlN polycrystalline layer 211a is formed at a temperature of about 200 ° C. by using the ECR-CVD or the ECR sputtering method, the size of the crystal grains of the AlN polycrystalline layer 211a (several Å to
Thousands) are small. By performing a heat treatment on the crystal grains having such a small size to improve the orientation of the AlN polycrystalline layer 211a, a GaN single crystal having a high density and a high orientation is formed on the AlN polycrystalline layer 211a. Nuclei can be formed. On the other hand, temperature by MOVPE method (about 600 ℃)
When using the AlN polycrystalline layer deposited by ECR-CVD,
Alternatively, it is more difficult to form a GaN single crystal nucleus having high density and high orientation on the AlN polycrystalline layer as compared with the case where the ECR sputtering method is used. According to the present invention,
If the temperature is in the range of 150 to 250 ° C., the AlN polycrystalline layer 211a functioning sufficiently as a polycrystalline layer can be deposited. In the above description, silicon carbide is used as the substrate, but sapphire may be used instead of silicon carbide.

In order to evaluate the crystallinity of the GaN single crystal layer 211c formed according to the present embodiment, the full width at half maximum of the diffraction peak in two-crystal X-ray diffraction was measured. The GaN single crystal layer 11c exhibits a full width at half maximum of two crystal X-ray diffraction of 3 minutes. From this, according to the present embodiment, Ga with a very flat surface and high quality can be obtained.
It can be seen that an N single crystal layer 211c is obtained.

Hereinafter, the reason for using the inclined SiC substrate as the substrate 210 will be described. In the present embodiment, [11]
An n-type SiC substrate polished so as to be inclined by 3.5 degrees in the [-20] direction is used. This allows the SiC substrate, especially A
When lGaN mixed crystal is deposited, the flatness of the surface of AlGaN mixed crystal is improved. Note that 3.5 in the [1-100] direction from the (0001) plane
Even if an n-type SiC substrate polished so as to be inclined at an angle is used, the same effect as described above can be obtained.

FIG. 7 shows the relationship between the roughness of the surface of the AlGaN layer deposited on the inclined SiC substrate and the composition of Al in AlGaN. The horizontal axis shows the composition of Al in AlGaN, and the vertical axis shows the roughness of the surface of the AlGaN layer. In FIG. 7, a dotted line indicates a case where a (0001) just substrate is used. In the present specification,
The “(0001) just substrate” indicates a substrate that is not inclined in any direction from the (0001) plane. The solid line in FIG. 7 shows a case where a substrate inclined by 3.5 degrees from the (0001) plane in the [11-20] direction is used. The greater the value corresponding to the vertical axis, the greater the roughness of the AlGaN surface, indicating that the surface lacks flatness. As can be seen from FIG. 7, when the inclined substrate is used, the flatness of the surface of the AlGaN layer is not inferior even if the composition of Al increases to about 30%.

FIG. 8 shows the relationship between the surface roughness of the AlGaN layer and the tilt angle of the substrate. The surface roughness of the AlGaN layer is shown on the horizontal axis. The tilt angle indicates an angle at which the substrate tilts from the (0001) plane in the [11-20] direction, and is shown on the vertical axis in FIG.

As shown in FIG. 8, the surface roughness of AlGaN decreases as the inclination angle increases. As can be seen from FIG. 8, when the inclination angle ranges from about 1 degree to 18 degrees, the AlGa
The surface of the N layer is kept flat.

When the inclination angle of the substrate is in the range of about 5 degrees to 15 degrees, the rate of incorporation of the p-type dopant into AlGaN described below is also improved.

When a (0001) just substrate is used for manufacturing a p-type AlGaN layer, the incorporation rate of Mg, which is a p-type dopant, decreases with an increase in the Al composition, and the resistance of the element increases. It was found by the present inventor. According to the present embodiment, the above problem can be solved by using the inclined substrate.

FIG. 9 shows the relationship between the incorporation rate of Mg as a dopant into the AlGaN layer and the Al composition of AlGaN when a silicon carbide tilted substrate is used. The horizontal axis indicates the Al composition of AlGaN, and the vertical axis indicates the rate of Mg taken into the AlGaN layer. As shown in FIG. 9, the rate of incorporation of Mg into AlGaN when a tilted substrate is used is different from that of AlGaN when a just substrate is used.
Higher than the incorporation rate of g.

Further, as can be seen from FIG. 9, as the Al composition increases, the Mg incorporation rate when the just substrate is used decreases, but the Mg incorporation rate when the inclined substrate is used does not decrease. This tendency is not limited to the case where Mg is used as the dopant, but is the same even when Zn, C, and Ca are used as the dopant.

As described above, according to the present embodiment, since the concentration of the p-type dopant in the gallium nitride-based semiconductor can be increased, the operating voltage of the light emitting element can be reduced.

In the present embodiment, an inclined substrate is used, but a (0001) just substrate may be used instead. In this case, n-type AlN is used as a polycrystalline layer constituting the buffer layer.
By using the layer, the resistance can be reduced and the operating voltage of the light-emitting element can be reduced.

One advantage of using a tilted substrate is that crystal defects near the InGaN active layer formed on the substrate can be reduced.

FIG. 10A is a TEM (transmission electron microscopy) photograph showing a cross section of an InGaN / GaN / AlN multilayer film formed on a (0001) just silicon carbide substrate. FIG. 10B shows [11-2] at 3.5 degrees from the (0001) plane.
InGaN / G formed on silicon carbide substrate inclined in [0] direction
4 is a TEM photograph showing a cross section of the aN / AlN multilayer film.

As shown in FIG. 10A, when a just substrate is used, a crystal defect portion (branched pattern) in the GaN film is
Exists along a direction (C-axis direction) perpendicular to the surface of the substrate,
It reaches the InGaN layer. On the other hand, as shown in FIG. 10B, when an inclined substrate is used, the crystal defect portion in the GaN film exists to bend in a direction perpendicular to the C-axis direction. For this reason, the amount of defects near the InGaN layer is reduced. This is considered to be because the lattice relaxation of the crystal occurs due to the steps on the surface of the inclined substrate.

The method of manufacturing a gallium nitride-based compound semiconductor described in the first and second embodiments is not limited to the manufacture of a light-emitting element, but can be applied to the manufacture of a light-receiving element.

Third Embodiment A method for manufacturing a gallium nitride-based compound semiconductor light emitting device using the method for manufacturing a gallium nitride-based compound semiconductor described in the first and second embodiments with reference to FIGS. Will be described. In the present embodiment, sapphire is used as the material of the substrate. Note that the MOVPE method is used for forming the crystal layer. FIG. 12 shows a growth sequence of the crystal layer.

First, sapphire (single crystal Al ₂ O
₃ ) The C-plane substrate 10 is placed on a susceptor in a reactor of a MOVPE apparatus (not shown), evacuated, and then heated at 1050 ° C. for 15 minutes in a hydrogen atmosphere of 70 Torr to obtain a substrate.
A cleaning process is performed on the surface of the 10 (FIG. 12).

Next, after cooling the substrate 10 to 600 ° C.,
It is supplied at a flow rate of 2.5 L / min for one minute to nitride the surface of the substrate 10 (FIG. 12). Thereafter, as shown in FIG. 11, 20 μmol / min of trimethylgallium (TMG) and 2.5 μm of ammonia were added.
L / min and carrier hydrogen are supplied at about 2 L / min to deposit a polycrystalline GaN layer (GaN polycrystalline layer) 11a of about 50 nm (FIG. 12).

Next, in order to form a good GaN single crystal layer on the GaN polycrystalline layer 11a, the three-stage crystal growth process described in the first and second embodiments is performed (FIG. 12). That is,
After only stopping the supply of TMG and raising the substrate temperature to 950 ° C., TMG is supplied at 20 μmol / min to deposit a GaN single crystal nucleus layer (first stage). Next, the substrate temperature is increased stepwise from 950 ° C. to about 1050 ° C. and 1090 ° C. while supplying TMG to grow the GaN single crystal layer 11c (second and third steps). GaN polycrystalline layer 11a and GaN single crystal layer 11c constitute GaN buffer layer 11 shown in FIG.

Next, monosilane (hydrogen base 50 ppm) is additionally supplied at 10 cc / min and trimethyl aluminum (TMA) is additionally supplied at 2 μmol / min to deposit an n-type AlGaN cladding layer 12 (FIG. 12).
of).

Next, only the supply of TMG, TMA and monosilane was stopped, and the substrate temperature was reduced to 70 in a mixed atmosphere of ammonia and hydrogen.
After the temperature was lowered to 0 ° C. and the substrate temperature became constant, trimethylindium (TMI) was 200 μmol / min and TMG was 20 μmol / min.
Then, an active layer 13 made of InGaN mixed crystal is deposited to a thickness of 10 nm (FIG. 12). The temperature range for forming the InGaN active layer 13 may be 500 ° C. or more and 800 ° C. or less. The active layer is Al
_{x Ga y In z N (0} ≦ x <1,0 ≦ y1,0 <z ≦ 1, x + y +
z = 1).

Next, only the supply of TMI was stopped, the flow rates of TMG and ammonia were maintained as they were, and the undoped GaN cap layer (InG
An evaporation suppression layer (aN active layer) 30 of about 1 nm is deposited (FIG. 12).
of). At this time, the flow rate of TMG may be changed.

Next, the supply of TMG was also stopped, and the temperature of the substrate was raised to about 1000 to 90 ° C. in a mixed atmosphere of ammonia and hydrogen.
Heat treatment for one minute (FIG. 12).

Next, TMA and TMG are supplied at the same flow rate as above, and cyclopentadienyl magnesium (Cp2Mg) is further supplied at 0.1 μmol / min to deposit the p-type AlGaN cladding layer 14 (FIG. 12). After that, only supply of TMA was stopped and p-type G
An aN contact layer 15 is deposited (FIG. 12). Next, TM
The supply of G and Cp2Mg was stopped, the substrate temperature was lowered to 600 ° C., and then TMG, TMI and Cp2Mg were supplied again, and p-type In _x
An intermediate layer 31 made of Ga _1-x N (0 <x <1) (thickness: 0.01 μm)
(about m-1 μm) (FIG. 12). p-type InCa
Since the band gap of the N intermediate layer 31 is small, the Schottky barrier between the p-type InGaN intermediate layer 31 and the p-type electrode (Pt) formed thereon can be reduced, and the resistance is significantly reduced. be able to.

Next, in a mixed atmosphere of ammonia and hydrogen,
After cooling to ° C., the supply of ammonia is stopped, and heat treatment is performed for 5 minutes in a hydrogen atmosphere (FIG. 12).

Finally, using a known technique, the n-type AlGaN cladding layer 1
2, InGaN active layer 13, undoped GaN cap layer 30, p-type A
lGaN cladding layer 14, p-type GaN contact layer 15, and p
The n-type InGaN intermediate layer 31 is partially etched away to form an n-type electrode (Al) 18 on the n-type AlGaN cladding layer 12 which is partially exposed. Further, on the p-type InGaN intermediate layer 31, a p-side electrode (Pt) 17 is formed.

As shown in FIG. 13A, the InGaN active layer 13 and the p-type A
A P-type GaN guide layer 33 may be formed between the n-type AlGaN clad layer 12 and the P-type GaN guide layer 33 between the lGaN clad layer 14.

Hereinafter, the reason for forming the undoped GaN cap layer 30 will be described.

By providing the undoped GaN cap layer 30 on the InGaN active layer 13, I can be several orders of magnitude higher in vapor pressure than the InGaN active layer 13.
The re-evaporation of n can be suppressed. As shown in FIG. 13A, by depositing a few atomic layers (about 1 nm) of the undoped GaN cap layer 30 at the same temperature as the deposition temperature of the InGaN active layer 13, that is, 700 ° C., as in this embodiment. In addition, a steep active layer / guide layer interface can be realized.

FIG. 13B shows a conventional undoped GaN cap layer 3.
0 is not formed, the InGaN active layer 103 and the InGaN
An n-type layer 132 and a p-type layer 13 sandwiching the active layer 103
3 shows a cross section. As shown in FIG.
The interface between the active layer 103 and the p-type GaN guide layer 133 is not a sharp interface but lacks flatness.

Further, by forming the undoped GaN cap layer 30, In can be effectively mixed into the InGaN active layer. Since the InGaN active layer 13 is deposited at a low temperature of 700 ° C., the InGaN active layer 13 has poor crystallinity such as orientation. As in the present embodiment, the substrate temperature is raised to 1090 ° C. by providing the In reevaporation suppressing layer (undoped GaN cap layer) 30 on the InGaN active layer 13 at a low temperature of 700 ° C.
The heat treatment can be sufficiently performed on the N active layer 13.
Thereby, the orientation of the InGaN active layer 13 can be improved.

FIG. 14 shows the relationship between the room-temperature photoluminescence intensity of the InGaN active layer 13 and the heat treatment time for the InGaN active layer 13. As the heat treatment time increases, the luminous intensity increases by about one digit, confirming that the luminous efficiency is significantly improved.

In the above description, as shown in FIG.
After forming the undoped GaN cap layer 30 at a temperature of about 00 ° C. (), the supply of TMG is temporarily stopped, that is, crystal growth is stopped, and then the substrate temperature is raised to about 1000 to 1090 ° C. to perform heat treatment. Was done. Instead, as shown in FIG. 15B, after forming the InGaN active layer 13 at a temperature of about 500 to 800 ° C., the supply of only TMI is stopped, and at the same time, the substrate temperature is reduced to 1000 to 900 The temperature may be raised to ° C.
That is, the undoped GaN cap layer 30 is grown while increasing the temperature.

The thickness of the undoped GaN cap layer 30 may be 10 nm or less. A more preferable range of the thickness of the undoped GaN cap layer 30 is about 1 to 3 nm. If the thickness of the undoped GaN cap layer 30 is too small (1 nm or less),
Evaporation cannot be suppressed. If the thickness of the undoped GaN cap layer 30 is too large (3 nm), the series resistance of the device increases, and a sufficient current cannot be supplied to obtain light emission. The GaN cap layer 30 may be doped with impurities as long as In can suppress evaporation of In from the InGaN active layer 13.

Fourth Embodiment Hereinafter, a gallium nitride-based compound semiconductor light emitting device will be described as a fourth embodiment with reference to FIG. In this embodiment, as a material of the substrate 410, silicon carbide (SiC) having a 6H structure is used without using sapphire. SiC substrate 410 is doped with nitrogen and has an n-type conductivity. The SiC substrate 410 has [1] at 3.5 degrees from the (0001) plane.
1-20] direction. SiC substrate 410 is (0001)
Similar effects can be obtained even if the plane is inclined by 3.5 degrees in the [1-100] direction from the plane.

FIG. 16 schematically shows a cross section of the semiconductor light emitting device of the present embodiment. As shown in FIG. 16, the semiconductor light emitting device includes a silicon carbide substrate 410, and an AlN substrate formed on the substrate 410.
A buffer layer 411, a semiconductor multilayer structure 419 provided on the buffer layer 411, a p-type InGaN intermediate layer 31 formed on the semiconductor multilayer structure 419, and a current (drive current) required for light emission And a pair of electrodes 417 and 418.

The semiconductor multilayer structure 419 includes, in order from the side close to the buffer layer 411, the n-type AlGaN cladding layer 12, the n-type GaN guide layer 32,
It includes an InGaN active layer 13, a p-type GaN guide layer 33, a p-type AlGaN cladding layer 14, and a p-type GaN contact layer 15.

Next, a method for manufacturing the gallium nitride-based compound semiconductor light emitting device will be described. In the present embodiment, the buffer layer 41
1 and 2 so that 1 has good conductivity.
The buffer layer 411 is deposited by a method different from the method of forming the buffer layer described in the embodiment. In the present embodiment, metal organic chemical vapor deposition (MOVPE) is used to deposit a semiconductor crystal layer on the substrate 410.

First, in order to perform crystal growth, a 6H silicon carbide substrate 410 is placed on a susceptor in a reactor of a MOVPE apparatus (not shown),
After evacuation, in a hydrogen atmosphere of 70 Torr, 1050 ° C
The surface of the substrate 410 is cleaned by heating for 15 minutes.

Next, after the substrate temperature is lowered to 1000 ° C., ammonia is supplied at a flow rate of 2.5 L / min for 1 minute to nitride the surface of the substrate 410. Then, as shown in FIG. 16, 10 μmol / min of trimethylaluminum (TMA), 2.5 L / min of ammonia,
Monosilane (50 ppm based on hydrogen) is supplied at 10 cc / min, and carrier hydrogen is supplied at about 2 L / min to provide an n-type AlN buffer layer 411.
Is deposited to a thickness of about 200 nm.

By making the buffer layer 411 n-type, even if an n-side electrode is provided on the back surface of the substrate 410, the electric resistance does not increase.
Since the n-type AlN buffer layer 411 is deposited at a high temperature of about 1000 ° C., the n-type AlN buffer layer 411 has almost no crystal defects, is almost single crystal, and has good conductivity. A preferred range of the temperature for depositing the n-type AlN buffer layer 411 is 800 ° C. or more and 1200 ° C. or less. If the deposition temperature is lower than 800 ° C., the orientation of the n-type AlN buffer layer 411 becomes poor, and good crystallinity cannot be obtained.
If the deposition temperature is higher than 1200 ° C., the crystallinity of the n-type AlN buffer layer 411 will be poor due to the re-evaporation of Al and N.

A GaN single crystal layer may be formed on the AlN buffer layer 411 by using the method described in the second embodiment. In this case, the AlN buffer layer and the GaN single crystal layer form the buffer layer 411.

Next, the supply amount of trimethylaluminum (TMA) was
At the same time as changing to μmol / min, 10 cc / min of monosilane (50 ppm based on hydrogen) and 20 ml of trimethylgallium (TMG)
An additional supply of μmol / min is provided to deposit the n-type AlGaN cladding layer 12.

Next, only the supply of TMA is stopped, and the n-type GaN guide layer 32 is deposited. Thereafter, only the supply of TMG and monosilane was stopped, and the substrate temperature was reduced in a mixed atmosphere of ammonia and hydrogen.
After the temperature is lowered to 700 ° C. and the substrate temperature becomes constant, trimethylindium (TMI) is supplied at 200 μmol / min and TMG is supplied at 20 μmol / min to deposit an active layer 13 of InGaN crystal with a thickness of 10 nm. The temperature range for forming the InGaN active layer 13 is 500
It is sufficient that the temperature is not lower than 800C and not higher than 800C. The active layer is composed of Al _x Ga _y In _z N
(0 <x <1, 0 ≦ y <1, 0 <z ≦ 1, x + y + z =
It may be formed from 1).

Next, only the supply of TMI was stopped, the flow rates of TMG and ammonia were maintained as they were, and the undoped GaN cap layer (InG
An evaporation suppression layer (aN active layer) 30 is deposited to a thickness of about 1 nm. At this time, the flow rate of TMG may be changed.

The reason for forming the undoped GaN cap layer 30 after depositing the InGaN active layer 13 is as follows. By providing the undoped GaN cap layer 30, the InGaN active layer
Re-evaporation of In several orders of magnitude higher than 13 in vapor pressure can be suppressed. As in the present embodiment, at the same temperature as the deposition temperature of the InGaN active layer 13, that is, 700 ° C., the undoped GaN cap layer
By depositing about 30 several atomic layers (1 nm), a steep interface can be realized between the active layer and a guide layer formed later.

Next, the supply of TMG was also stopped, and the temperature of the substrate was raised to about 1000 to 90 ° C. in a mixed atmosphere of ammonia and hydrogen.
Heat treatment for minutes. Since the InGaN active layer 13 was deposited at a low temperature of about 700 ° C., the crystallinity such as the orientation was poor. This heat treatment is for increasing the orientation of the InGaN active layer 13. As in the present embodiment, the substrate temperature is raised to 1000 ° C. by providing the In reevaporation suppressing layer (undoped GaN cap layer) 30 at a low temperature of 700 ° C. on the InGaN active layer 13. Can be sufficiently heat-treated. Thereby, the orientation of the InGaN active layer 13 can be improved.

FIG. 14 shows the relationship between the room-temperature photoluminescence intensity of the InGaN active layer 13 and the heat treatment time for the InGaN active layer 13. As the heat treatment time increases, the luminous intensity increases by about one digit, confirming that the luminous efficiency is significantly improved.

Next, 20 μmol / min of TMG and 0.1 μmol / min of cyclopentadienyl magnesium (Cp2Mg) are supplied to deposit the p-type GaN guide layer 33.

Next, TMA is added at the same flow rate as when forming the n-type AlGaN cladding layer 12, and the p-type AlGaN cladding layer 14 is added.
Is deposited. After that, only supply of TMA was stopped and p-type G
An aN contact layer 15 is deposited.

Next, supply of TMG and Cp2Mg was stopped, and the substrate temperature was reduced to 60 ° C.
After cooling to 0 ° C., TMG, TMI and Cp2Mg are supplied again to supply an intermediate layer 31 (thickness: p <x <1 <x <1) of p-type In _x Ga ₁ -xN.
(About 0.01 μm to 1 μm). Since the band gap of the p-type InGaN intermediate layer 31 is small, the p-type InGaN intermediate layer 3
The Schottky barrier between 1 and the p-type electrode (Pt) formed thereon can be reduced, and the resistance can be significantly reduced.

The p-type InGaN intermediate layer 31 can be formed by depositing p-type InGaN and then performing heat treatment at about 500 ° C. in a reduced-pressure hydrogen atmosphere of 70 Torr. In a reduced-pressure hydrogen atmosphere, activation of the p-type impurity can be achieved by a heat treatment at 400 ° C. or higher. Taking into account the suppression of dissociation of nitrogen atoms, the heat treatment temperature is 50
A low temperature of about 0 ° C. is preferred.

Then, the substrate is placed in a mixed atmosphere of ammonia and hydrogen for 50 minutes.
After cooling to 0 ° C., the supply of ammonia is stopped, and heat treatment is performed for 5 minutes in a hydrogen atmosphere.

Finally, an n-type electrode 418 is formed on the n-type SiC substrate 410 using titanium (Ti), and a p-type electrode 417 is formed on the p-type InGaN intermediate layer 31 using platinum (Pt). Pt was selected because Pt has a large work function, so that the barrier to the p-type InGaN layer 31 can be reduced.

When a current is injected into the gallium nitride-based compound semiconductor light emitting device manufactured as described above and laser oscillation is performed, the operating voltage is as low as 5 V. On the other hand, according to the conventional light emitting device, the operating voltage is about 30V. That is, according to the present embodiment, the operating voltage of the light emitting element can be significantly reduced.

As in the present embodiment, a low-resistance n-type AlN buffer layer 411 is provided on an n-type SiC substrate 410, and a conductive substrate 41
An electrode 418 is formed on the back surface of 0. This allows
Unlike the related art, it is not necessary to etch a semiconductor multilayer film epitaxially grown on a substrate in order to form an n-side electrode.

In the second embodiment and the present embodiment, the silicon carbide substrate is used, but the present invention is not limited to this. It is sufficient that a silicon substrate is used instead of the silicon carbide substrate, and a silicon carbide film is formed on the surface of the silicon substrate by carbonization. In addition, the silicon substrate is (11
1) If it is inclined in the [110] direction at about 3.5 degrees from the plane, the same effect as when a silicon carbide substrate is used can be obtained.

In the above description, the active layer is a bulk or a single quantum well of InGaN, but the present invention is not limited to this. The active layer may be an InGaN-based multi quantum well, as shown in FIG. The multiple quantum well type light emitting device can achieve higher performance of the light emitting device.

The method described above is used for manufacturing a multiple quantum well light emitting device. The InGaN-based multiple quantum well light emitting device is formed as follows. N-type Al formed on substrate
An n-type GaN guide layer (thickness: about 0.1 μm) is grown on the GaN clad layer (thickness: about 0.5 μm).
_0.2 Ga _0.8 N well layer (thickness: about 30 mm) and In _0.02 Ga
_{A 0.98} N barrier layer (thickness: about 50 °) is alternately and repeatedly grown nine times, and then a tenth In _0.2 Ga _0.8 N well layer is grown. Next, an undoped GaN cap layer (thickness: about 10 to 30 °), a p-type GaN guide layer (thickness: about 0.1 μm), and a p-type AlG are sequentially formed on the tenth In _0.2 Ga _0.8 N well layer.
An aN cladding layer (thickness: about 0.5 μm) and a p-type GaN contact layer (thickness: about 0.3 μm) are grown.

Fifth Embodiment Hereinafter, a gallium nitride-based compound semiconductor light emitting device will be described as a fifth embodiment. The light emitting device of this embodiment is different from the light emitting device of the above embodiment in that carbon (C) is used instead of Mg as the p-type dopant of the p-type GaN guide layer and the p-type AlGaN cladding layer. .

The p-type GaN guide layer is formed by supplying TMG at 20 μmol / min and propane at 0.5 μmol / min. The formation of the p-type AlGaN cladding layer is performed by adding 2 μmol / min of TMA, 20 μmol / min of TMG,
Propane is supplied at 0.5 μmol / min. Other deposition conditions are the same as in the above embodiment.

FIG. 18 shows a depth profile of the p-type impurity concentration in the p-type GaN guide layer and the InGaN active layer. As shown in FIG. 18, in the conventional light emitting device, Mg, which is a p-type impurity, diffuses toward the active layer during the growth of the GaN guide layer. On the other hand, in the light emitting device of this embodiment, carbon, which is a p-type impurity, hardly diffuses toward the active layer during the growth of the GaN guide layer. It turns out that carbon is a good p-type dopant.

Also, by using carbon as a p-type dopant also for the p-type AlGaN cladding layer, it is possible to prevent the p-type dopant from diffusing into the active layer via the GaN guide layer and improve device reliability. Can be. When the GaN guide layer is undoped, only the AlGaN cladding layer may be doped with carbon. Further, using carbon as a p-type dopant is effective not only in the case of a light emitting device using an inclined substrate but also in the case of a light emitting device using a (0001) just substrate.

Industrial Applicability According to the present invention, the following effects can be obtained.

(1) A high-quality GaN single crystal layer having excellent orientation and surface flatness can be formed on a substrate. When a gallium nitride based semiconductor multilayer film is deposited on this GaN single crystal layer, a high quality multilayer film can be grown. Therefore, a light-emitting element with high efficiency can be manufactured.

(2) Since the n-type AlN polycrystalline layer constituting the buffer layer can be deposited at a low temperature of about 200 ° C., a denser GaN single crystal nucleus can be formed on the n-type AlN polycrystalline layer. Therefore, a GaN single crystal layer having high orientation can be grown.

(3) Since the silicon carbide substrate is inclined in the [11-20] direction from the (0001) plane, a GaN single crystal layer having excellent surface flatness can be grown on the substrate. Further, in the p-type AlGaN layer formed on the silicon carbide substrate, when the Al composition increases, it is possible to suppress a reduction in the efficiency of taking in the p-type dopant.

(4) The electric resistance can be reduced by using the n-type AlN buffer layer doped with Si. Moreover, n-type SiC
Since the n-side electrode can be formed directly on the substrate side, the steps in the manufacture of the light emitting element can be greatly simplified.

(5) Since the undoped GaN cap layer is formed on the InGaN active layer, the InGaN active layer / p-type GaN guide layer,
Alternatively, the steepness of the interface between the InGaN active layer and the p-type AlGaN cladding layer can be improved. For this reason, defects can be reduced, and the efficiency and reliability of the light emitting element are dramatically improved.

(6) By performing a heat treatment on the InGaN active layer, the orientation of the InGaN active layer is improved. Therefore, the luminous efficiency of the light emitting device according to the present invention is ten times or more than that of the conventional light emitting device.

(7) Since the p-type InGaN layer is provided under the p-side electrode, the contact resistance of the p-side electrode can be reduced, and the operating voltage of the light emitting element can be reduced to about 1/6.

(8) By using carbon as the p-type dopant of the p-type AlGaN cladding layer, diffusion of the dopant into the InGaN active layer can be suppressed, so that the reliability and luminous efficiency of the light emitting device can be greatly improved.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Isao Kidoguchi 4-6-40 Midoridai, Kawanishi-shi, Hyogo (56) References JP-A-6-268259 (JP, A) JP-A-7-249795 (JP, A JP-A-5-29220 (JP, A) JP-A-3-218625 (JP, A) JP-A-8-330630 (JP, A) JP-A-8-2933643 (JP, A) Jpn. J. Appl. Phys. 30 [8] (1991) p. 1620-1627 Appl. Phys. Lett. 67 [3] (1995) p. 401-403 (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 33/00 H01S 3/18

Claims (23)

(57) [Claims] 1. A step of forming a nitride polycrystalline layer on a substrate at a first temperature range, and forming a gallium nitride single crystal at a second temperature range on the nitride polycrystalline layer. A step of forming a nucleus layer, and forming the gallium nitride single crystal nucleus layer in a third temperature range such that the crystals of the gallium nitride single crystal nucleus layer are connected to each other in a direction parallel to the surface of the substrate. A method for producing a gallium nitride-based compound semiconductor, comprising: a growing step; and a step of growing a gallium nitride single crystal nucleus layer in a direction perpendicular to a surface of the substrate in a fourth temperature range. A method for producing a gallium nitride-based compound semiconductor, wherein the first to fourth temperature ranges have a relationship of first temperature range <second temperature range <third and fourth temperature ranges. 2. The second temperature range is equal to or lower than 1000 ° C.
A method for manufacturing a gallium nitride-based compound semiconductor according to claim 1. 3. The method of manufacturing a gallium nitride-based compound semiconductor according to claim 1, wherein said fourth temperature range is higher than said third temperature range. 4. The method according to claim 1, wherein the substrate is formed of sapphire. 5. The method of manufacturing a gallium nitride-based compound semiconductor according to claim 1, wherein said nitride polycrystalline layer contains aluminum nitride and is formed by ECR-CVD or ECR sputtering. 6. The method according to claim 1, wherein the polycrystalline nitride layer is composed of Al _x Ga ₁ -xN (0 ≦
2. The composition according to claim 1, wherein x ≦ 1) is included and formed by MOVPE.
3. The method for producing a gallium nitride-based compound semiconductor according to item 1. 7. A step of forming a conductive aluminum nitride layer on a surface of a silicon carbide substrate having a surface inclined at a first angle in a [1-100] direction from a (0001) plane; Forming a gallium nitride-based compound semiconductor laminated structure on the aluminum nitride layer. 8. The method according to claim 7, wherein the first angle is about 1 ° to 18 °. 9. The method according to claim 7, wherein the first angle is about 5 ° to 12 °. 10. The method according to claim 7, wherein the step of forming the aluminum nitride layer is performed at a temperature of about 800 ° C. to 1200 ° C. 11. The method for manufacturing a gallium nitride-based compound semiconductor device according to claim 7, wherein said aluminum nitride layer is made of a single crystal. 12. The method for manufacturing a gallium nitride-based compound semiconductor device according to claim 7, further comprising a step of forming a gallium nitride single crystal layer on said aluminum nitride layer. 13. The method for manufacturing a gallium nitride-based compound semiconductor device according to claim 7, wherein said aluminum nitride layer is doped with silicon as an impurity. 14. A silicon carbide substrate having a surface inclined at a first angle in the [1-100] direction from a (0001) plane, and a conductive aluminum nitride layer formed on the surface of the silicon carbide substrate. And a gallium nitride-based compound semiconductor multilayer structure provided on the aluminum nitride layer. 15. The gallium nitride-based compound semiconductor light emitting device according to claim 14, wherein said first angle is from about 1 ° to 18 °. 16. The gallium nitride based compound semiconductor light emitting device according to claim 14, wherein said first angle is about 5 ° to 12 °. 17. The semiconductor device according to claim 17, further comprising an electrode provided above the multilayer structure, wherein an electrode is provided between the multilayer structure and the electrode.
In _x Ga _1-x N having a conductivity type opposite to the conductivity type of the substrate
15. The gallium nitride-based compound semiconductor light emitting device according to claim 14, wherein a (0 <x <1) layer is provided. 18. The gallium nitride based compound semiconductor light emitting device according to claim 17, wherein said electrode is formed of platinum. 19. An Al _x Ga _y In _z N (0 ≦ 0) provided on a substrate.
x <1, 0 ≦ y <1, 0 <z ≦ 1, x + y + z = 1) A method of manufacturing a gallium nitride based compound semiconductor light emitting device including a gallium nitride based compound semiconductor laminated structure including an active layer, comprising: A step of forming the active layer in a temperature range of 1; a step of forming a GaN cap layer on the active layer to suppress evaporation of In; a second step of forming a second layer higher than the first temperature range; Performing a heat treatment on the active layer in a temperature range, wherein the step of forming the GaN cap layer is performed in the first temperature range. A gallium nitride-based compound semiconductor light emitting device, wherein the temperature is raised to a second temperature range. 20. The GaN cap layer has a thickness of about 1 nm or more.
20. The method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to claim 19, wherein the thickness is 10 nm or less. 21. The method according to claim 19, wherein the first temperature range is about 500-800 ° C., and the second temperature range is 1000 ° C. or higher. 22. A gallium nitride-based compound semiconductor light emitting device comprising a gallium nitride-based compound semiconductor laminated structure provided on a substrate, wherein the laminated structure comprises an active layer and a pair of layers sandwiching the active layer. A p-type cladding layer and an n-type cladding layer, and a p-type contact layer provided above the p-type cladding layer, wherein magnesium is used as a p-type dopant of the p-type contact layer, A gallium nitride-based compound semiconductor light-emitting device in which carbon is used as a p-type dopant of a mold cladding layer. 23. A p-type guide layer is provided between the active layer and the p-type clad layer, and carbon is used as a p-type dopant of the p-type guide layer.
3. The gallium nitride-based compound semiconductor light-emitting device according to item 1.