JPH0870139A - Crystal growth method for n-type gallium nitride-based compound semiconductor - Google Patents

Abstract

(57) [Summary] [Objective] When an n-type nitride semiconductor is grown on the surface of a substrate that is not lattice-matched by a vapor phase growth method such as MOVPE or MBE, lattice defects in the n-type nitride semiconductor layer. By providing a method of growing the nitride semiconductor layer with a reduced amount, the crystallinity of the other nitride semiconductor grown on the surface of the n-type nitride semiconductor layer is improved, and the efficiency of the light emitting element, the light receiving element and the like is improved. A second n-type nitride semiconductor layer 33 (In _a Al _b Ga _1-ab N, 0) having a composition different from that of the n-type nitride semiconductor layer 3 ′ is grown during growth of the n-type nitride semiconductor layer 3 ′. ≤ a, 0 ≤ b, a
+ B ≦ 1) is grown in at least one layer or the n-type nitride semiconductor layer 3 ′ is grown in a film thickness of at least 5 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an n-type gallium nitride compound semiconductor (In _X Al _Y Ga _1-XY N, _0≤X , used for electronic devices such as light emitting diodes and laser diodes.
0 ≦ Y, X + Y ≦ 1, and hereinafter the gallium nitride-based compound semiconductor is referred to as a nitride semiconductor. ) Crystal growth method,
The present invention relates to a method for growing an n-type nitride semiconductor crystal directly on a substrate or via a buffer layer.

[0002]

2. Description of the Related Art Nitride semiconductors (In _{X ')} are used as materials for laser diodes and light emitting diodes that emit blue and ultraviolet light.
_{Al Y 'Ga 1-X'-} Y' N, 0 ≦ X ', 0 ≦ Y', X '+ Y' ≦ 1)
, And a blue light emitting diode with a luminous intensity of 1 cd has recently been put into practical use with this material. As shown in FIG. 1, this blue light emitting diode has a substrate 1 made of sapphire, a buffer layer 2 made of GaN, and a Ga layer.
N-type layer 3 made of N, n-type cladding layer 4 made of AlGaN, active layer 5 made of InGaN, and AlGaN
The p-type clad layer 6 made of GaN and the p-type contact layer 7 made of GaN are sequentially stacked.

[0003] Nitride semiconductor devices are generally MOVPE
(Metal organic vapor phase epitaxy) method, MBE
HDVPE (Hydride vapor phase epitaxy) method
Nitriding on the substrate surface using vapor phase growth method such as
It is obtained by stacking the semiconductor layers. On the board
Materials such as sapphire, ZnO, SiC, GaAs, MgO
Fees are used. N on the surface of the substrate via a buffer layer
Type nitride semiconductor (In _XAl_YGa_1-XYN, 0 ≦ X, 0
≦ Y, X + Y ≦ 1, especially n-type GaN and n-type Al
There are many GaN. ) Is grown. In addition, SiC, ZnO
When using a substrate with a lattice constant close to that of a nitride semiconductor, such as
In this case, the n-type nitride is directly formed on the substrate without forming the buffer layer.
Sometimes semiconductors are grown. Basically, the board table
By first growing an n-type nitride semiconductor layer on the surface,
Nitride semiconductor devices such as light emitting devices and light receiving devices are manufactured.
It

According to the MOVPE method, for example, a nitride semiconductor uses, as a source gas, an organometallic compound gas serving as a Ga source, an Al source, an In source, and an ammonia gas serving as an N source. The raw material gas is decomposed by bringing these raw material gases into contact with the heated substrate surface, and a nitride semiconductor is epitaxially grown on the substrate. Normally G for the buffer layer
aN, AlN, GaAlN, etc. are selected and 300 ° C to 9
It is grown to a thickness of 10 Å to 0.1 μm at a temperature of 00 ° C. The n-type nitride semiconductor layer grown on the buffer layer has a temperature of 900.degree.
It is grown to a thickness of less than μm.

[0005]

It is known that a nitride semiconductor is a crystal that is very difficult to grow epitaxially because there is no substrate that is completely lattice-matched. Therefore, conventionally, epitaxial growth has been performed by using a substrate having a lattice constant close to that of the nitride semiconductor to be grown, such as a SiC substrate, or by interposing a buffer layer that relaxes the lattice mismatch.

FIG. 2 shows an example of a schematic cross-sectional view of an n-type nitride semiconductor crystal grown on the surface of a substrate that is not lattice-matched. This is the Journal of Crystal Growth {Jounal of Crystal Growth, 115, (1991) P628−63.
3}, n-type GaN is epitaxially grown on the surface of the sapphire substrate via a buffer layer made of AlN, and its cross section is TEM (transmission e).
TEM image, and schematically shows the crystal structure from the TEM image. According to this figure, a buffer layer having a non-oriented orientation is grown in a columnar shape on the substrate, and when GaN is epitaxially grown on the buffer layer, a part of the buffer layer acts as a seed crystal. As a result, it is shown that the GaN layer with improved crystallinity is grown by gradually adjusting the orientation of GaN.

However, Ga completely free of crystal defects
It is difficult to grow N, and many crystal defects as shown by the broken line in FIG. 2 extend from the interface between the buffer layer and the GaN layer to reach the surface of the GaN layer. Some of these defects stop inside the crystal, but the number of defects reaching the GaN layer surface is, for example, 10 ⁷ to 10 ⁹ / cm ² . Similarly, also in the light emitting diode element of FIG. 1, the same phenomenon occurs in the crystal of the n-type layer 3.

When a large number of crystal defects are present on the surface of the n-type nitride semiconductor layer grown on the surface of the substrate, the defects are inherited to all the semiconductor layers such as the clad layer and active layer growing on the surface of the n-type layer. Therefore, there is a problem that the entire device structure is adversely affected. An element having many crystal defects has a drawback that it adversely affects element performance such as light emission output and life when it is used as a light emitting diode as described above.

When growing an n-type nitride semiconductor layer on the surface of a substrate, it is very important to grow an n-type crystal with few crystal defects. If it can be realized, it grows on the n-type crystal. Since the number of crystal defects in the clad layer, the active layer and the like to be reduced is reduced, it is possible to improve the performance of any device made of a nitride semiconductor. Therefore, the present invention has been made in view of such circumstances, and MOV
When growing an n-type nitride semiconductor layer on the surface of a substrate that is not completely lattice-matched by a vapor phase growth method such as PE or MBE, the n-type nitride semiconductor layer is grown with fewer lattice defects. The purpose is to provide a method of doing.

[0010]

The first aspect of the method of the present invention
Directly on the substrate surface by vapor phase epitaxy or
N-type nitride semiconductor (In_XAl_YGa_1-XY
Method of growing crystal of N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1)
In the step of growing the n-type nitride semiconductor layer,
Second nitride semiconductor layer having a composition different from that of the nitride semiconductor layer
(In_aAl_bGa _1-abN, 0 ≦ a, 0 ≦ b, a + b ≦ 1)
Is grown at least one layer or more.

The second aspect of the method of the present invention is that the n-type gallium nitride-based compound semiconductor (In _X Al _Y Ga) is directly applied to the substrate surface by vapor phase epitaxy or via a buffer layer.
_{In the} method of growing a crystal of _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1), the n-type gallium nitride based compound semiconductor layer is grown to a film thickness of at least 5 μm or more.

[0012]

In the first aspect, when a second nitride semiconductor layer having a different composition is formed in the n-type nitride semiconductor layer,
Since the second nitride semiconductor acts as a buffer layer, that is, a buffer layer, it is considered that crystal defects can be relaxed in the buffer layer (hereinafter, the second nitride semiconductor layer is referred to as a second buffer layer). ). More specifically, when the n-type nitride semiconductor layer is grown on the substrate, a large mismatch between the substrate and the nitride semiconductor causes a crystal defect as shown by a broken line in FIG. 2 in the crystal during the growth. . However, by interposing the second buffer layer having a different composition from that of the n-type nitride semiconductor layer to be grown as an intermediate layer, continuous crystal defects in the n-type nitride semiconductor layer have a different composition. It temporarily stops at the buffer layer. Next, when the n-type nitride semiconductor is grown on the surface of the second buffer layer, the second buffer layer acts like a substrate with a small number of mismatches, so that it grows on the second buffer layer. It is assumed that the crystallinity of the n-type nitride semiconductor to be improved is improved.

The second buffer layer may be formed in one or more layers, and the thickness of each layer is 10 angstrom (0.001 μm) or more and 1 μm or less, and more preferably 0.001 μm or more and 0.1 μm or less. It is desirable to adjust. If the thickness is less than 0.001 μm, it tends to be difficult to stop the crystal defects in the second buffer layer. On the other hand, if the thickness is more than 1 μm, new crystal defects tend to be generated from the second buffer layer. The second buffer layer may also be a multilayer film in which one layer has a thickness of several tens of angstroms and two or more layers are laminated.

The second buffer layer is In _a Ga _1-a N (0 <
a ≦ 1), or Al _b Ga _1-b N (0 <b ≦ 1), or Al _b Ga _1-b N (0 ≦ b ≦ 1) having different compositions. desirable. More preferably, In _a Ga _1-a N having an _a value of 0.5 or less or Al _b Ga _1-b N having a b value of 0.5 or less is grown. Because
In a nitride semiconductor, the ternary mixed crystal has better crystallinity than the quaternary mixed crystal semiconductor layer. Among them, in In _a Ga _1-a N and Al _b Ga _1-b N of the ternary mixed crystal, the buffer layer having the a value and the b value adjusted to the above range can have a better crystallinity. The crystal defects of the second buffer layer are reduced, and the crystal defects of the n-type nitride semiconductor layer grown on the second buffer layer are reduced. further,
When the second buffer layer is a multilayer film, crystal defects can be stopped very well. The most preferred combination is n
-Type nitride semiconductor layer is n-type GaN (GaN has the least lattice defects), and the second buffer layer is n-type In _a Ga _{1 -a} N
(0 <a ≦ 0.5) or n-type Al _b Ga _1-b N
(0 <b ≦ 0.5) or Al _b Ga with different composition
Multilayer film (superlattice) in which _1-b N (0 ≦ b ≦ 1) thin films are stacked
Is.

Further, the electron carrier concentration of the second buffer layer is almost the same as that of the n-type nitride semiconductor layer formed previously,
Or it is desirable to adjust it larger. 3 and 4 show an n-type clad layer 4 ', an active layer 5', a p-clad layer 6 ', and a p-contact layer 7'laminated on the n-type nitride semiconductor layer 3 "obtained by the method of the present invention. 3 is a view showing a structure of the light emitting element as a cross-sectional view as an actual light emitting element, in which the second buffer layer 33 is more active than the etching surface of the n-type layer for forming the negative electrode. 4 is different from that on the layer 5 ′ side in that the second buffer layer 33 is formed on the substrate 1 ′ side with respect to the etching surface, for example, to realize a light emitting device as shown in FIG. In that case, that is, in the case of realizing an element in which the position of the second buffer layer 33 is closer to the active layer side than the etching surface on which the negative electrode is to be formed, the electron carrier concentration of the second buffer layer 33 is Is smaller than the n-type layer 3 ′, the second buffer layer supplies n to p. Electrons are blocked and p from the n-type layer is blocked.
It becomes difficult for current to flow through the layers, and the device performance deteriorates. On the contrary, when the electron carrier concentration of the second buffer layer 33 is higher than that of the n-type layer 3, the electrons are likely to spread uniformly in the second buffer layer 33, and uniform light emission can be obtained. On the other hand, in the case of the device as shown in FIG. 4, even if the electron carrier concentration of the second buffer layer 33 is small, the current flows through the n-type layer 3 ″ having a high electron carrier concentration, so that the characteristics of the light emitting device are improved. Has almost no effect, on the contrary, when the electron carrier concentration of the second buffer layer 33 is high, the current easily flows to the second buffer layer 33, and uniform light emission is obtained. The electron carrier concentration of the second buffer layer 33 is preferably adjusted to be substantially the same as or larger than that of the n-type nitride semiconductor layer formed previously.

Next, in the second aspect of the present invention, by growing the n-type nitride semiconductor layer to a thickness of more than 5 μm,
Crystal defects reaching the surface can be reduced. In FIG. 2, the broken line stopping in the middle of the n-type layer indicates that the crystal defect stops halfway. A closer study of the crystal defects that stopped in the middle of the process revealed that many of the n-type nitride semiconductor layers stopped about 4 μm from the substrate. Therefore,
If the same material is continuously grown, it is possible to gradually stop crystal defects during the growth.
By growing the layer, crystal defects reaching the surface of the n layer can be reduced. In the second aspect, the more preferable thickness of the n-type nitride semiconductor layer is 7 μm.
That is all.

In the first and second aspects of the present invention, an n-type nitride semiconductor (In _x A) grown on a substrate is used.
L _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) is Al _Y Ga _1-Y N having a Y value in the range of 0 ≦ Y ≦ 0.5, and more preferably 0.3 or less. Al _Y Ga _1-Y N, most preferably Y =
0 GaN is grown. This is because the ternary mixed crystal nitride semiconductor has fewer crystal defects than the quaternary mixed crystal nitride semiconductor as described above. Further, when using an n-type nitride semiconductor as an electronic device such as a light emitting element or a light receiving element, first, an n-type nitride semiconductor grown on a substrate is AlGaN having a larger band gap than InGaN having a smaller band gap. This is because GaN is more convenient for realizing various structures such as single hetero and double hetero. Among them, especially AlGaN tends to have more crystal defects as the content of Al increases.
Has a tendency to grow an n-type nitride semiconductor layer having the least crystal defects.

Furthermore, in the first and second aspects of the method of the present invention, the substrate is sapphire or GaA.
Materials such as s, Si, ZnO, and SiC can be used, but sapphire is generally used. When sapphire is used as the substrate, it is preferable to grow the buffer layer on the substrate, but it is possible to grow without the buffer layer depending on the plane orientation of the sapphire substrate. By preferably growing the buffer layer, it is possible to obtain a smooth and mirror-like n-type nitride semiconductor crystal capable of measuring lattice defects. Further, the n-type of the nitride semiconductor can be realized in a non-doped state or by doping a donor impurity such as Si, Ge, or C during crystal growth.

[0019]

The method of the present invention by the MOVPE method will be described in detail below. Example 1 First, a well-cleaned sapphire substrate is placed on the susceptor in the reaction vessel. After evacuating the inside of the container,
While flowing hydrogen gas into the container, the substrate is heated at 1050 ° C. for about 20 minutes to remove the oxide on the surface, and the substrate is cleaned. After that, the temperature of the susceptor was adjusted to 500 ° C., and TMG (trimethylgallium gas) as a Ga source and ammonia gas as an N source were flown on the surface of the substrate at 500 ° C., and the buffer layer made of GaN was 0.0
Grow with a film thickness of 2 μm.

Next, the TMG gas was stopped and the temperature was raised to 10
After the temperature is raised to 50 ° C., TMG gas and SiH ₄ gas are caused to flow to grow a Si-doped n-type GaN layer with a film thickness of 2 μm.

Next, the TMG gas and SiH ₄ gas are stopped and the temperature is raised to 800 ° C. When the temperature reaches 800 ° C., the carrier gas is switched to nitrogen, TMG gas, TMI (trimethylindium), and SiH ₄ gas are caused to flow, and a Si-doped n-type In0.1Ga0.9N layer is added as a second buffer layer to 0.01.
Grow with a film thickness of μm.

After the growth of the In0.1Ga0.9N layer, the temperature is raised again to 1050 ° C., the carrier gas is returned to hydrogen, TMG gas and SiH ₄ gas are caused to flow, and S is similarly added.
An i-doped n-type GaN layer is grown to a film thickness of 2 μm. The carrier concentration of the second buffer layer and the carrier concentration of this n-type GaN layer were set to be substantially the same.

After the growth, the substrate was taken out of the reaction vessel, the surface of the uppermost n-type GaN layer was measured by TEM, and its TE was measured.
When the number of crystal defects per unit area was measured from the M image, it was about 1 × 10 ⁴ / cm ² .

In the process of [Example 2] and the n-type nitride semiconductor layer, TMG, TMA (trimethylaluminum), and SiH ₄ gas were used, and Si-doped n-type Al was used.
The same procedure as in Example 1 is performed, except that a 0.3 Ga0.7 N layer is grown to a thickness of 2 μm to sandwich the second buffer layer. As a result, when measured in the same manner, Si
The number of crystal defects reaching the surface of the doped n-type Al0.3Ga0.7N layer was about 5 × 10 ⁵ / cm ² . Note that Si
The electron carrier concentration of the doped n-type Al0.3Ga0.7N layer was almost the same as that of the second buffer layer.

A Si-doped n-type GaN layer is grown to a film thickness of 1 μm in the same manner as the n-type nitride semiconductor layer process of [Example 3]. Similar to the next step for the second buffer layer, Si-doped n-type In0.
A 1 Ga 0.9 N layer is grown to a thickness of 50 Å. Further, similarly to the step of forming the n-type nitride semiconductor layer, similarly, a Si-doped n-type GaN layer is sequentially grown to a film thickness of 1 μm.

Further, in the same manner as the step on the Si-doped n-type GaN layer, a Si-doped n-type In0.1Ga0.9N layer as a third buffer layer was grown again to a film thickness of 50 angstroms, and then, Similar to the last step, a Si-doped GaN layer is grown to a film thickness of 2 μm. That is, in Example 3, the GaN buffer layer 200 angstrom, the n-type GaN layer 1 μm,
A Si-doped n-type In0.1Ga0.9N second buffer layer 50 angstrom, an n-type GaN layer 1 μm, a Si-doped n-type In0.1Ga0.9N third buffer layer 50 angstrom, and an n-type GaN layer 2 μm were sequentially stacked.

As a result, the final layer of Si-doped n-type GaN
The number of crystal defects reaching the surface of the layer is about 1 × 10 ⁴
The number was pieces / cm ² . The electron carrier concentrations of the second buffer layer, the third buffer layer, and the Si-doped n-type GaN layer were substantially the same.

In the step of forming the second buffer layer of [Example 4], TMG, TMA (trimethylaluminum), and SiH ₄ gas were used without changing the growth temperature, and the Si-doped n-type Al0.3Ga0.7N layer was reduced to 0. The same procedure as in Example 1 is performed except that the second buffer layer is formed by growing the film with a thickness of 0.01 μm. As a result, when measured in the same manner, Si
The number of crystal defects reaching the surface of the doped n-type GaN layer was about 1 × 10 ⁴ / cm ² . The electron carrier concentration of the second buffer layer was almost the same as that of the Si-doped n-type GaN layer.

In the step of forming the second buffer layer in [Example 5], TMG, TMA, and Si were used without changing the growth temperature.
First, using H ₄ gas, Si-doped n-type Al0.02Ga0.98
The N layer is grown to a film thickness of 30 Å. Next, the TMA gas is stopped and a Si-doped n-type GaN layer is grown to a film thickness of 30 Å. Then, this operation is repeated 5 times to form a multilayer film in which 30 angstroms of Si-doped n-type Al0.02Ga0.98N layer and 30 angstroms of n-type GaN layer are alternately laminated in five layers. The procedure is the same as in Example 1 except that the second buffer layer is formed as described above. As a result, when lattice defects were measured in the same manner, Si-doped n-type G
The number of crystal defects reaching the surface of the aN layer is approximately 5 × 10.
^{It was 3} pieces / cm ² . The electron carrier concentration of the multilayer film, which is the second buffer layer, was almost the same as that of the Si-doped n-type GaN layer.

[Sixth Embodiment] In the process of the second embodiment, Si-doped n-type Al0.1GaGa is used as the second buffer layer.
A Si-doped n-type Al0.3Ga0.7N layer was grown in the same manner except that 0.9N was grown to a film thickness of 0.01 μm.
As a result, the number of lattice defects reaching the n-type Al0.3Ga0.7N layer on the outermost surface was about 1 × 10 ⁵ / cm 2. It should be noted that the electron carrier concentrations in this example were also substantially the same.

Comparative Example 1 In Example 1, the Si-doped n-type GaN was continuously grown without growing the second buffer layer.
When the layer was grown to a film thickness of 4 μm, the number of crystal defects reaching the surface of the n-type GaN layer was about 1 × 10 ⁷ / cm ² .

[Embodiment 7] An embodiment of the structure of an actual light emitting device will be described. Following the steps of Example 1, the following steps were added. After growth of the Si-doped n-type GaN layer, TMA (trimethylaluminum) gas is newly added, and the temperature is also 1050 ° C.
Then, as the n-clad layer, Si-doped n-type Al0.2Ga0.8
The N layer is grown to a film thickness of 0.1 μm.

After growing the n-clad layer, TMG, TM
A, stop the SiH ₄ gas, set the temperature to 800 ° C. again, and flow DEZ (diethyl zinc) in addition to TMG, TMI, SiH ₄ gas, and Si and Zn-doped In0.05Ga0.95N layer as an active layer. Grow with a film thickness of 0.1 μm.

After growth of the active layer, TMG, TMI, Si
After stopping the H ₄ and DEZ gases and setting the temperature to 1050 ° C.,
TMG, TMA, and Cp2Mg (cyclopentadienylmagnesium) gas are flown to grow a Mg-doped p-type Al0.1Ga0.9N layer as a p-clad layer to a thickness of 0.1 μm.

After growth of p-type Al0.1Ga0.9N layer, TM
The gas A is stopped, and a Mg-doped p-type GaN layer is grown to a thickness of 0.3 μm as a p-contact layer at 1050 ° C.

The element obtained as described above was etched to grow n-type GaN next to the second buffer layer.
The layer was exposed and electrodes were formed on the p-contact layer and the exposed Si-doped n-type GaN layer. That is, a light emitting diode element having a structure as shown in FIG. 4 was used. Further, this element was attached to a lead frame and molded with resin. This light emitting diode had a Vf of 3.6 V and an emission wavelength of 450 nm at 20 mA, a luminous intensity of 3.0 cd, and an emission output of 3.5 mW.

[Comparative Example 2] The same steps as in Example 7 were performed on the Si-doped GaN layer grown in Comparative Example 1 to obtain a light emitting diode device having a structure as shown in FIG. Diode is Vf3.6 at 20mA
V, emission wavelength was 450 nm, but luminous intensity was 1.0 cd
And the emission output was only 1.2 mW.

Thus, according to the first method of the present invention,
Since the n-type layer having few crystal defects is obtained, the number of crystal defects in the clad layer, the active layer and the like laminated thereon is reduced. In particular, since the thickness of the active layer is as thin as about 0.2 μm or less, it is very important to grow a crystal with few crystal defects.
Therefore, since a crystal with few crystal defects can be grown, it is possible to realize a light emitting diode element having a luminous intensity of 1 cd or more and a superior luminous output in the related art.

[Embodiment 8] A concrete embodiment of the second aspect of the present invention will be described below. Since this example also shows a method of growing by MOVPE as in the first method, there is no great difference in the basic operation. A buffer layer made of GaN is grown to a thickness of 0.02 μm on the surface of the sapphire substrate in the same manner as in the process of the first embodiment.

Similar to the process of Example 1, a Si-doped n-type GaN layer is grown to a thickness of 10 μm on the buffer layer.

After the growth, the substrate was taken out of the reaction vessel and n
Type GaN layer surface was measured by TEM, and from the TEM image,
When the number of crystal defects per unit area was measured, it was about 1 × 10 ⁵ defects / cm ² .

[Embodiment 9] Crystal growth was performed in the same manner as in Embodiment 5 except that the film thickness of the Si-doped n-type GaN layer was 5 μm. The number of crystal defects on the surface of the n-type GaN layer was about 5. The number was × 10 ⁶ .

[Embodiment 10] In the process of Embodiment 5, as in Embodiment 2, Si-doped n-type Al0.3
Crystal growth was performed in the same manner except that a Ga0.7N layer was continuously grown to a thickness of 10 μm.
The number of crystal defects on the a0.7N layer surface is about 3 × 10 ⁶ /
It was cm ² .

[Embodiment 11] An n-clad layer, an active layer, a p-clad layer and a p-contact layer are laminated on the Si-doped GaN layer obtained in Embodiment 5 in the same manner as in Embodiment 7, and the same. When a light emitting diode was manufactured as described above, its characteristics were almost the same as those of Example 7.

[0045]

As described above, according to the method of the present invention, the n-type nitride semiconductor layer having few crystal defects can be grown on the surface of the substrate. Therefore, the method of the present invention is very useful for a nitride semiconductor having no lattice-matched substrate to stack crystals with few crystal defects and realize an electronic device such as a light emitting device or a light receiving device.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing one structure of a conventional light emitting diode element.

FIG. 2 is a schematic cross-sectional view showing a crystal structure when an n-type GaN layer is grown on the surface of a substrate via an AlN buffer layer.

FIG. 3 is a schematic cross-sectional view showing one structure of a light emitting diode element having an n-type nitride semiconductor layer obtained by the method of the present invention.

FIG. 4 is a schematic cross-sectional view showing one structure of a light emitting diode element having an n-type nitride semiconductor layer obtained by the method of the present invention.

[Explanation of symbols]

1, 1 '... Substrate 2, 2'
..Buffer layers 3, 3 ', 3 "... N-type nitride semiconductor layers 4, 4' ..
..N-type cladding layers 5 and 5 '... active layers 6 and 6'
..P cladding layer 7, 7 '... p contact layer 33 ... second buffer layer (second nitride semiconductor layer)

Claims (4)

[Claims] 1. An n-type gallium nitride compound semiconductor (In _X Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1 directly on the surface of the substrate by a vapor phase growth method or via a buffer layer. )
In the method of growing a crystal, the second n-type gallium nitride compound semiconductor layer (In _a Al _b) having a different composition from the n-type gallium nitride compound semiconductor layer is grown during the growth of the n-type gallium nitride compound semiconductor layer. Ga _1-ab N, 0 ≦ a, 0
A crystal growth method for an n-type gallium nitride-based compound semiconductor, which comprises growing at least one layer of ≦ b, a + b ≦ 1). 2. The crystal growth method of an n-type gallium nitride compound semiconductor according to claim 1, wherein the thickness of each second n-type gallium nitride compound semiconductor layer is 1 μm or less. . 3. The second n-type gallium nitride based compound semiconductor layer is In _a Ga _{1 -a} N (0 <a ≦ 1), or Al _b
Ga _1-b N (0 <b ≦ 1) or AlbG with different composition
The crystal growth method for an n-type gallium nitride compound semiconductor according to claim 1 or 2, which is a multilayer film in which thin films of a1-bN (0≤b≤1) are laminated. 4. An n-type gallium nitride-based compound semiconductor (In _X Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1 directly on the substrate surface or via a buffer layer by a vapor phase growth method. )
In the method for growing a crystal, the n-type gallium nitride based compound semiconductor layer is grown to a thickness of 5 μm or more.