JP2000040842A - Gallium nitride compound semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve crystallinity of a light emitting element and enhance emission characteristics by employing a polycrystalline buffer layer. SOLUTION: In a light emitting diode 10 as an inventive element, a polycrystalline buffer layer 3 is provided on a substrate 2. The buffer layer 3 is a 100-1000 Å thick aluminum nitride(AlN) layer formed preferably in a temperature range from room temperature to 500 deg.C. Consequently, crystallinity of each layer (first N layer 4, second N layer, I layer 5) to be formed subsequently on the buffer layer 3 is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gallium nitride-based compound semiconductor light emitting device which emits blue light.

[0002]

2. Description of the Related Art Conventionally, Ga has been used as a blue light emitting diode.
A device using an N-based compound semiconductor is known. The GaN-based compound semiconductor has attracted attention because of its direct transition, which has high luminous efficiency, and that one of the three primary colors of light, blue, is used as the luminescent color. A light emitting diode using such a GaN-based compound semiconductor grows an N layer made of an N-conductivity-type GaN-based compound semiconductor on a sapphire substrate directly or with a buffer layer made of aluminum nitride interposed therebetween. GaN of I conductivity type on N layer
It has a structure in which an I layer made of a system compound semiconductor is grown.

[0003]

Incidentally, in order to increase the number of carriers contributing to light emission, it is desirable that the thickness of the N layer be as large as possible in order to increase the light emission luminance of the light emitting diode. Also, in order to obtain high quality I layer crystals, it is desirable that the N layer be thick.

On the other hand, to make the operating voltage uniform, I
The thickness of the layer needs to be thin and uniformly controlled with high accuracy.
However, if the crystal is grown only by the conventional MOVPE method, there is a problem that the crystal growth rate is slow and it takes time to form a thick N layer.

On the other hand, N-type Ga
There is also a method of growing N, I-type GaN by the halide vapor phase epitaxy method. However, in the halide vapor phase epitaxy method, the growth rate is high and it is difficult to make the thickness of the I layer thin and uniform.

As a result of repeated studies on the crystal growth of GaN, the present inventors have found that most of N
After growing the layer, it has been found that by growing the upper layer thinly by the MOVPE method, an I layer having good crystallinity can be grown thereon by the MOVPE method.
Also, by forming a polycrystalline buffer layer on the substrate,
Al _x Ga _1-x N containing GaN formed thereon (x =
(Including 0).

The present invention has been made based on such conclusions, and an object of the present invention is to improve the crystallinity of a light emitting device and to improve light emitting characteristics by using a polycrystalline buffer layer.

[0008]

According to a first aspect of the present invention, there is provided a gallium nitride-based compound semiconductor light emitting device having a polycrystalline buffer layer formed on a substrate. This is a gallium nitride-based compound semiconductor light emitting device.

The invention according to claim 2 is characterized in that the buffer layer is made of aluminum nitride (AlN). The invention according to claim 3 is characterized in that the buffer layer is formed in a range from room temperature to 500 ° C. The invention according to claim 4 is characterized in that the buffer layer has a thickness of 100 to 1000 °.

The invention according to claim 5 is characterized in that the buffer layer is formed by molecular beam epitaxy (MBE). A sixth aspect of the present invention is characterized in that the semiconductor device has an N-conductivity type N layer formed on the buffer layer. According to a seventh aspect of the present invention, the N layer is a gallium nitride-based compound semiconductor (Al _x Ga
_1-X N; including X = 0). The invention according to claim 8 is characterized in that the N layer is gallium nitride (GaN). The invention according to claim 9 is characterized in that the substrate is a sapphire substrate. The invention of claim 10 is
The main surface of the sapphire substrate is a c-plane (0001).

[0011]

According to the present invention, since a polycrystalline buffer layer is formed on a sapphire substrate, the crystallinity of each layer above a buffer layer formed thereafter is improved. As a result, the light emitting characteristics of the light emitting element were improved.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. (First Embodiment) FIG. 1 is a sectional view showing a structure of a light emitting diode 1 according to a specific embodiment of the present invention.

After cleaning the sapphire substrate 2 having the main surface as the c-plane ((0001) plane) with nitric acid, the substrate was further cleaned with acetone.
And after washing, after spraying nitrogen gas and drying,
The sapphire substrate 2 was mounted on a susceptor of a halide vapor deposition apparatus. Thereafter, the temperature of the reaction chamber was set to 900 ° C., HCl gas was passed through the metal Ga placed on the upstream side of the gas flow, and GaCl obtained as a reaction product of the two was obtained.
NH ₃ and carrier gas N ₂ were flowed toward the sapphire substrate 2 heated to 1000 ° C. Flow rate is 10ml of GaCl
/ Liter, NH ₃ was 1.0 liter / minute, and N ₂ was 2.0 liter / minute. The thickness of the first N layer 4 made of N-type GaN grown on the sapphire substrate 2 was 20 μm, and the growth rate was about 1 μm / min.

Next, the sapphire substrate 2 on which the first N layer 4 has been grown is taken out from the halide vapor phase epitaxy apparatus, and
It was placed on the susceptor in the reaction chamber of the device. Then, the sapphire substrate 2 is heated to 1000 ° C., and H _{2 is used} as a carrier gas.
Was supplied at a rate of 2.5 liter / min, NH ₃ was supplied at a rate of 1.5 liter / min, and trimethylgallium (TMG) at a rate of 20 ml / min for 12 minutes to form a second N layer 8 of N-type GaN having a film thickness of about 2 μm.

Next, the sapphire substrate 2 is heated to 900 ° C.
The H ₂ 2.5liter / min, the NH ₃ 1.5liter / min, TM
G is supplied at a rate of 15 ml / min and diethylzinc (DEZ) at a rate of 5 × 10 ⁻⁶ mol / min for 5 minutes.
Layer 5 was formed to a thickness of 1.0 μm.

Next, aluminum electrodes 6 and 7 were deposited on the side walls of the first N layer 4 and the second N layer 8 and on the upper surface of the I layer 5 to form light emitting diodes. Photomicrographs of cross sections of the first N layer 4, second N layer 8 and I layer 5 of the light emitting diode 1 thus obtained, reflection diffraction by high energy electron beam
(RHEED) showed that good crystallinity was obtained.

In particular, since the first N layer 4 is grown at a high speed by the halide vapor phase epitaxy method and the second N layer 8 precisely grown by the MOVPE method is formed thereon, the crystallinity of the I layer 5 becomes N
The layers were better than those grown by halide vapor deposition alone.

The spectrum of the light emission peak of the light emitting diode 1 is 480 nm, and the light emission intensity (luminance on the axis) is 10 nm.
mcd.

(Second Embodiment) FIG. 2 is a sectional view showing the structure of a light emitting diode 10 according to a second embodiment. In the same manner as in the first embodiment, the sapphire substrate 2 whose main surface is the c-plane ((0001) plane) was washed with nitric acid, and further washed with acetone. After cleaning, the substrate was dried by blowing nitrogen gas, and then the sapphire substrate 2 was mounted on a susceptor of a MOVPE apparatus. Thereafter, the sapphire substrate 2 is heated to 600 ° C., and H ₂ is used as a carrier gas at ₂ liter / min.
H ₃ at 1.5 liter / min, trimethyl aluminum (TM
A) was supplied at a rate of 15 ml / min for 6 minutes to form a buffer layer 3 of AlN having a thickness of about 0.1 μm. Then, the first N-layer 4, the second N-layer 8,
The light emitting diode 10 was formed by sequentially forming the I layer 5.

The light emitting diode 10 manufactured as described above
Micrographs of the cross sections of the first N layer 4, the second N layer 8, and the I layer 5, and reflection diffraction by a high energy electron beam (RHEED) showed that good crystallinity was obtained. The spectrum of the light emission peak of the light emitting diode 1 was 480 nm, and the light emission intensity (on-axis luminance) was 10 mcd.

(Third Embodiment) In this embodiment, the buffer layer 3 shown in FIG. 2 is formed by molecular beam epitaxy (MBE) in the second embodiment. After cleaning the sapphire substrate 2 whose main surface is the c-plane ((0001) plane) in the same manner as in the second embodiment, the sapphire substrate 2 was attached to the susceptor of the MBE apparatus. Then, the sapphire substrate 2
By heating to 500 ° C. and evaporating aluminum in a nitrogen gas plasma, a buffer layer 3 made of aluminum nitride (AlN) was formed on the main surface of the sapphire substrate 2 to a thickness of about 500 °. Thereafter, the first N layer 4, the second N layer 8, I
The method of forming the layers 5, the electrodes 6, 7 is the same as in the first embodiment.

The micrograph of the cross section of the first N layer 4, the second N layer 8 and the I layer 5 of the light emitting diode obtained as described above, and good crystallinity was obtained by reflection diffraction method using a high energy electron beam (RHEED). Was obtained. or,
The emission peak spectrum of this light emitting diode 1 is 480n
m, and the emission intensity (on-axis luminance) was 10 mcd.

According to the study of the present inventors, in the buffer layer 3 formed by MBE, the nucleus of GaN growth of the first N layer 4 is larger than that in the buffer layer 3 grown by MOVPE. It is thought that the single crystallinity of the first N layer 4, the second N layer 8, and the I layer 5 was improved. The buffer layer 3 was polycrystalline because the sapphire substrate 2 was formed by MBE at 500 ° C.

The present inventors also concluded that the buffer layer 3 grown in polycrystal was more than the first Nth than that grown in single crystal.
It has also been found that the layer 4, the second N layer 8, and the I layer 5 have good single crystallinity. For this purpose, it is effective to grow the buffer layer 3 by MBE.
500 ° C is desirable. In addition, the first N layer 4, the second N layer 8, and I
In order to improve the single crystallinity of the layer 5, the thickness of the buffer layer 3 is desirably 100 to 1000 °. In the above embodiment, the first N layer 4, the second N layer 8, and the I layer 5 are formed of GaN, but may be formed of Al _x Ga ₁ -xN.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a light emitting diode according to another embodiment.

[Explanation of symbols]

 1, 10: light-emitting diode 2: sapphire substrate 3: buffer layer 4: first N layer 8: second N layer 5: I layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Katsuhide Shinbe 1 Ochiai Nagahata, Kasuga-mura, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. No. 1 Toyoda Gosei Co., Ltd. (72) Inventor Akira Mabuchi Aichi Ochiai, Kasuga-mura, Nishi-Kasugai-gun, Aichi Prefecture No. 1 Toyoda Gosei Co., Ltd. Inside the university (72) Inventor Hiroshi Amano Naoichi-shi, Aichi

Claims (10)

[Claims] 1. A gallium nitride-based compound semiconductor light-emitting device, comprising a polycrystalline buffer layer formed on a substrate. 2. The gallium nitride based compound semiconductor light emitting device according to claim 1, wherein the buffer layer is made of aluminum nitride (AlN). 3. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the buffer layer is formed in a temperature range from room temperature to 500 ° C. 4. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the buffer layer has a thickness of 100 to 1000 °. 5. The gallium nitride based compound semiconductor light emitting device according to claim 1, wherein the buffer layer is formed by molecular beam epitaxy (MBE). 6. The semiconductor device according to claim 1, further comprising an N-type N layer formed on said buffer layer.
The gallium nitride-based compound semiconductor light-emitting device according to any one of the above items. 7. The gallium nitride based compound semiconductor light emitting device according to claim 6, wherein said N layer is a gallium nitride based compound semiconductor (Al _x Ga ₁ -xN; including X = 0). . 8. The gallium nitride-based compound semiconductor light emitting device according to claim 6, wherein the N layer is gallium nitride (GaN). 9. The gallium nitride based compound semiconductor light emitting device according to claim 1, wherein the substrate is a sapphire substrate. 10. The main surface of the sapphire substrate is c-plane (0
001), wherein the gallium nitride-based compound semiconductor light-emitting device according to claim 9, wherein