JP3402460B2 - Gallium nitride based compound semiconductor growth method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a blue light emitting gallium nitride compound semiconductor light emitting device.

[0002]

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

[0003]

In order to improve the light emission brightness of the above light emitting diode, it is desirable that the thickness of the N layer is as large as possible in order to increase the number of carriers that contribute to light emission. Further, in order to obtain a good quality I-layer crystal, it is desirable that the N-layer be thick.

On the other hand, in order to make the operating voltage uniform, I
The film thickness of the layer needs to be thin and uniformly and accurately controlled.
However, when crystals are 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 is sequentially formed on the sapphire substrate.
There is also a method of growing N, I-type GaN by a halide vapor phase epitaxy method, but the halide vapor phase epitaxy method has a high growth rate and it is difficult to make the thickness of the I layer thin and uniform.

As a result of repeated research on GaN crystal growth, the present inventors have found that most N
It has been found that by growing the layer and then growing the upper layer thinly by the MOVPE method, the I layer having good crystallinity can be grown thereon by the MOVPE method.
It was also found that when a buffer layer is formed on a substrate at room temperature to 500 ° C. and each layer is formed thereon, the crystallinity of each layer is improved.

The present invention has been made based on the above conclusion, and its object is gallium nitride having improved crystallinity.
The purpose is to grow a compound semiconductor .

[0008]

The invention according to claim 1 for solving the above-mentioned problems is directly or indirectly on a substrate.
In addition, an N-type gallium nitride-based compound semiconductor (Al _x Ga
_1-X N; _X = 0 consists of including) the thickness of the thick first 1N layer c
It is formed by the ride vapor deposition method , and N is formed on the first N layer.
Type gallium nitride-based compound semiconductor (Al _X Ga _1-X N;
The second thin N-layer consisting of (including X = 0) is metallized.
It is a method for growing a gallium nitride-based compound semiconductor, which is characterized by being formed by a compound vapor phase epitaxy method (MOVPE) .

According to a second aspect of the present invention, the substrate is a saf
A sapphire substrate and a first N layer
A buffer layer is formed between the two. Claim
The invention according to Item 3 is characterized in that the buffer layer is polycrystalline. The invention according to claim 4 is from room temperature to 500
It is characterized in that it is formed in the range of ° C. The invention according to claim 5 is characterized in that the buffer layer is formed to a thickness of 100 to 1000Å. The invention according to claim 6 is characterized in that the buffer layer is formed by a molecular beam epitaxy (MBE) method. In the invention according to claim 7 , the buffer layer is
It is characterized by being aluminum nitride (AlN).

The invention described in claim 8 is characterized in that the main surface of the sapphire substrate is a c-plane (0001). Contract
The invention according to claim 9 is the first N layer and / or the second N layer.
The layer is characterized in that it is gallium nitride (GaN).

[0011]

Most of the N layer is formed by the halide vapor deposition method.
Since a thick N layer is obtained at a high speed,
Manufacturing speed has been improved. The second N layer above the N layer is M
Since it was formed by the OVPE method, the layer to be grown on top of
The crystallinity was good and the layer thickness was controlled uniformly. That conclusion
As a result, for example, the light emission characteristics are improved. Also, on the sapphire substrate
By forming a buffer layer on the substrate, the crystallinity of each layer above it
Was able to improve. Especially, the buffer layer is polycrystalline
By setting the above, the first N layer, the second N layer, and the
And the crystallinity of each of the layers grown thereon was improved. Ba
The buffer layer can be formed in the range of room temperature to 500 ° C, or MB
By forming by E method, single crystallinity of each layer on the buffer layer
The optimum polycrystal can be used to improve
Further, by setting the thickness of the buffer layer to 100 to 1000Å, the first N layer, the second N layer on the buffer layer, and the upper layer
The single crystallinity of each of the grown layers was improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below 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.

The sapphire substrate 2 having the c-plane ((0001) plane) as the main surface was washed with nitric acid and then further washed with acetone.
Then, after cleaning, after blowing nitrogen gas to dry,
The sapphire substrate 2 was attached to the susceptor of the halide vapor phase growth apparatus. After that, the temperature of the reaction chamber was set to 900 ° C., HCl gas was flown through the metallic Ga placed on the upstream side of the gas flow, and GaCl obtained as a reaction product of the both,
NH ₃ and carrier gas N ₂ were flown toward the sapphire substrate 2 heated to 1000 ° C. Flow rate of GaCl is 10 ml
/ Min, NH ₃ was 1.0 liter / min, and N ₂ was 2.0 liter / min. 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 grown is taken out from the halide vapor phase growth apparatus, and MOVPE
It was placed on the susceptor in the reaction chamber of the instrument. Then, the sapphire substrate 2 is heated to 1000 ° C. and H _{2 is used} as a carrier gas.
Of 2.5 liter / min, NH ₃ at 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 thickness of about 2 μm.

Next, the sapphire substrate 2 is set to 900 ° C.,
_2.5 liter / min for H ₂ , 1.5 liter / min for NH ₃ , TM
G of 15 ml / min and diethylzinc (DEZ) were supplied at a rate of 5 × 10 ⁻⁶ mol / min for 5 minutes to form I-type GaN I
Layer 5 was formed to a thickness of 1.0 μm.

Next, aluminum electrodes 6 and 7 were deposited on the sidewalls of the first N layer 4 and the second N layer 8 and the upper surface of the I layer 5 to form a light emitting diode. A micrograph of a cross section of the first N layer 4, the second N layer 8 and the I layer 5 of the light emitting diode 1 thus obtained, a reflection diffraction method using a high energy electron beam
(RHEED) revealed that good crystallinity was obtained in each case.

In particular, since the first N layer 4 was grown at a high speed by the halide vapor phase epitaxy method and the second N layer 8 was precisely grown thereon by the MOVPE method, the crystallinity of the I layer 5 was N.
The layers are 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 (on-axis luminance) is 10
It was mcd.

(Second Embodiment) FIG. 2 is a sectional view showing a structure of a light emitting diode 10 according to a second embodiment. Similar to the first embodiment, the main surface is c
The sapphire substrate 2 to be the surface ((0001) surface) was washed with nitric acid and then further washed with acetone. Then, after the cleaning, a nitrogen gas is blown to dry the sapphire substrate 2
Was attached to the susceptor of the MOVPE device. After that, the sapphire substrate 2 is heated to 600 ° C., H ₂ is supplied as a carrier gas at ₂ liters / minute, NH ₃ is supplied as 1.5 liters / minute, and trimethylaluminum (TMA) is supplied at a rate of 15 ml / minute for 6 minutes, and then AlN is supplied. The formed buffer layer 3 to a thickness of about 0.1 μ
formed to m. Then, in the same procedure as in the first embodiment,
The 1st N layer 4, the 2nd N layer 8, and the I layer 5 were formed one by one, and the light emitting diode 10 was created.

The light emitting diode 10 manufactured in this way
It was found by the photomicrographs of the cross sections of the first N layer 4, the second N layer 8 and the I layer 5 and the reflection diffraction method (RHEED) using a high energy electron beam that good crystallinity was obtained, respectively. The spectrum of the emission peak of this light emitting diode 1 was 480 nm, and the emission intensity (on-axis luminance) was 10 mcd.

(Third Embodiment) In this embodiment, the buffer layer 3 shown in FIG. 2 is prepared by the molecular beam epitaxy method (MBE) in the second embodiment. Similar to the second embodiment, the main surface is c-plane ((000
After cleaning the sapphire substrate 2 (1) surface), the sapphire substrate 2 was attached to the susceptor of the MBE apparatus.
Then, the sapphire substrate 2 is heated to 500 ° C. to evaporate aluminum in the nitrogen gas plasma, and the buffer layer 3 made of aluminum nitride (AlN) is formed on the main surface of the sapphire substrate 2 to a thickness of about 500Å. Formed. The subsequent method of forming the first N layer 4, the second N layer 8, the I layer 5, the electrodes 6 and 7 is the same as in the first embodiment.

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

According to the consideration of the present inventors, in the buffer layer 3 formed by MBE, the nuclei of GaN growth of the first N layer 4 are larger than those of the buffer layer 3 grown by MOVPE. It is considered that the single crystallinity of the first N layer 4, the second N layer 8 and the I layer 5 was improved because of the uniform dispersion. The buffer layer 3 was polycrystalline because it was formed by MBE with the sapphire substrate 2 at 500 ° C.

In addition, the inventors of the present invention have found that the buffer layer 3 grown in a polycrystalline form has a first N-thickness rather than a single crystal.
It was also found that the layer 4, the second N layer 8 and the I layer 5 have good single crystallinity. For this reason also, it is effective to grow the buffer layer 3 by MBE, and the growth temperature for polycrystal growth is from room temperature to
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 preferably 100 to 1000Å. Although the first N layer 4, the second N layer 8 and the I layer 5 are made of GaN in the above embodiment, they may be made of Al _x Ga _{1 -x} N.

[Brief description of 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 ... Layer I

─────────────────────────────────────────────────── ─── Continuation of the front page (73) Patent holder 391012224 President of Nagoya University Furomachi, Chikusa-ku, Nagoya City, Aichi Prefecture (No address) (72) Inventor Katsuhide Mabe Kasugamura, Aichi Prefecture Ochiai, Nagahata Within Toyoda Gosei Co., Ltd. (72) Inventor Kuki Kaji, Nishikasugai-gun, Aichi Prefecture Ochiai, Nagahata No. 1 At Toyoda Gosei Co., Ltd. Incorporated (72) Inventor Yu Akasaki Furo-cho, Chikusa-ku, Nagoya, Aichi Prefecture (no street number) Inside Nagoya University (72) Inventor, Hiroshi Amano Furo-cho, Chikusa-ku, Nagoya City, Aichi Prefecture (no street number) Nagoya University ( 56) References JP-A-2-81483 (JP, A) JP-A-60-173829 (JP, A) JP-A-52-23600 (JP, A) JP-A-62 219614 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) H01L 33/00

Claims (9)

(57) [Claims] 1. A thick first film made of an N-type gallium nitride-based compound semiconductor (Al _X Ga _{1 -X} N; including X = 0) directly or indirectly on a substrate . Halide vapor phase growth of 1N layer
Formed on the first N layer, and an N-type gallium nitride compound semiconductor is formed on the first N layer.
(Al _X Ga _1-X N; including X = 0)
The second N layer is formed by metalorganic vapor phase epitaxy (MOVPE)
A method for growing a gallium nitride-based compound semiconductor, comprising: 2. The substrate is a sapphire substrate,
A buffer layer between the sapphire substrate and the first N layer.
The gallium nitride according to claim 1, wherein the gallium nitride is formed.
Method for growing um-based compound semiconductor. 3. The method for growing a gallium nitride-based compound semiconductor according to claim 2 , wherein the buffer layer is polycrystalline. 4. The buffer layer has a temperature range from room temperature to 500 ° C.
It is formed in an enclosure. In Claim 2 or Claim 3, characterized in that
A method for growing a gallium nitride-based compound semiconductor according to claim 1. 5. The buffer layer comprises 100 to 1000 Å
5. The thickness according to claim 2 , characterized in that
The method for growing a gallium nitride-based compound semiconductor according to any one of items . 6. The method of claim 2乃 said buffer layer, characterized in that the forming by molecular beam epitaxy (MBE)
The method for growing a gallium nitride-based compound semiconductor according to claim 5 . 7. The buffer layer is made of aluminum nitride (A
1N), The method for growing a gallium nitride-based compound semiconductor according to any one of claims 2 to 6 . 8. The main surface of the sapphire substrate is a c-plane (00
01) The method for growing a gallium nitride compound semiconductor according to any one of claims 2 to 7 . 9. The first N layer and / or the second N layer
The method for growing a gallium nitride-based compound semiconductor according to any one of claims 1 to 8, wherein the layer is gallium nitride (GaN).