JPH0281484A - Gallium nitride-based compound semiconductor light-emitting element - Google Patents

Abstract

PURPOSE:To obtain a thick N-layer whose crystal property is good by a method wherein an AlN buffer layer is formed on a sapphire substrate and an N-layer composed of an N-type GaN-based compound semiconductor is formed on it by a halide vapor growth method. CONSTITUTION:A sapphire substrate 2 is attached to a susceptor of an MOVPE apparatus; an AlN buffer layer 3 is formed; after that, an N-type GaN layer 4 is formed at a growth speed of about 1mum/min by using a halide vapor growth apparatus. Then, a second N-type layer 8 of N-type GaN and an I-type GaN layer 5 are formed by an MOVPE method; electrodes 6, 7 are evaporated; a light-emitting diode is completed. When the second N-layer 8 which has been grown precisely by the MOVPE method is formed on the first N-layer 4, a crystallinity of the I-layer 5 can be made much better.

Description

[Detailed description of the invention] [Industrial application field]

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

[Prior art]

Conventionally, blue light emitting diodes using GaN-based compound semiconductors are known. The GaN-based compound semiconductor is attracting attention because it has high luminous efficiency due to direct transition, and because it emits blue light, which is one of the three primary colors of light. Such a light emitting diode using a GaN-based compound semiconductor is produced by growing NF3 made of an N-conductivity type GaN-based compound semiconductor on a sapphire substrate, and growing a single-conductivity type GaN-based compound on the N layer. It has a structure in which a single layer of semiconductor is grown. As the growth method, organic all-optical compound vapor phase epitaxy (MOVPE) and halide vapor phase epitaxy are adopted.

[Problem to be solved by the invention]

By the way, in order to improve the luminance of the light emitting diode described above, it is desirable that the thickness of the N layer be as thick as possible in order to increase the number of carriers contributing to light emission. Further, in order to obtain a high-quality single-layer crystal, it is desirable that the N layer be thick. On the other hand, in order to make the operating voltage uniform, the thickness of one layer needs to be thin, uniform, and accurately controlled. However, when crystal growth is performed using only the conventional MOVPE method, the crystal growth rate is slow and it takes time to form a thick N layer. On the other hand, there is a method in which N-type GaN and I-type GaN are sequentially grown directly on a sapphire substrate by halide vapor phase epitaxy, but halide vapor phase epitaxy has a fast growth rate and allows the thickness of one layer to be thin and uniform. It was difficult to do so. Furthermore, it was not possible to obtain thick NI•Δ with good crystallinity. As a result of repeated research on GaN crystal growth, the present inventors have found that aluminum nitride (Aj!) is grown on a sapphire substrate.
It has been found that the crystallinity of the N layer can be improved by forming a buffer layer made of N) and then growing the N layer by halide vapor phase epitaxy. The present invention was made based on such a conclusion, and its purpose is to improve the manufacturing speed and light emitting characteristics of a light emitting device.

[Means to solve the problem]

The structure of the invention for solving the above problems includes a sapphire substrate and an N-type gallium nitride compound semiconductor (A 1 x
G a 1-XN ; including X=0), and a ■-type gallium nitride compound semiconductor grown on the N layer (A I2 X G a 1-XN ; including X=0). aluminum nitride (A47N) between the sapphire substrate and the N layer.
) is grown, and an N layer is grown on the buffer layer by halide vapor phase epitaxy.

【Effect of the invention】

A buffer layer made of aluminum nitride was formed on a sapphire substrate, and NZ made of an N-type gallium nitride compound semiconductor was formed on the buffer layer by halide vapor phase epitaxy, so a thick N layer with good crystallinity was formed. Obtained at high speed. Therefore, the manufacturing time of the light emitting element was shortened, and a thick N layer with good crystallinity could be created, so that the luminous intensity could be improved. Furthermore, since the N layer had good crystallinity, the crystallinity of the first layer could also be improved.

【Example】

The present invention will be described below based on specific examples. A first embodiment diagram shows a light emitting diode 1 according to a specific embodiment of the present invention.
FIG. Sapphire substrate 2 whose main surface is the 0 plane ((0001) plane)
was washed with nitric acid and then further washed with acetone. After cleaning and blowing nitrogen gas to soften the rock,
The sapphire substrate 2 was attached to a susceptor of a MOVPE device. Thereafter, the sapphire substrate 2 is heated to 600°C, and H2 is added as a carrier gas to 21! /min, N Hs
was supplied for 1.517 minutes, and trimethylaluminum (TMA) was supplied for 6 minutes at a rate of 1.517 minutes to form a buffer layer 3 made of AIN to a thickness of approximately 0.14 mm. Thereafter, the sapphire substrate 2 was taken out from the MOVPE apparatus and attached to a susceptor of a halide vapor phase epitaxy apparatus. After that, the temperature of the reaction chamber was set to 900°C, and HCA' gas was flowed over the metal Ga placed on the upstream side of the gas flow, and GaCA' and NH3 obtained as reaction products between the two,
A carrier gas N was flowed toward the sapphire substrate 2 heated to 1000°C. The flow rate is 10rnI for GaCl.
! /min, NH, 1.01/min, and N, 2.01/min. The thickness of the first N layer 4 made of N-type GaN grown on the sapphire substrate 2 was 2 m, and the growth rate was about 1 m/min. Next, the sapphire substrate 2 on which the first N layer 4 had been grown was taken out from the halide vapor phase epitaxy apparatus and placed on a susceptor in the reaction chamber of the MOVPE apparatus. Then, the sapphire substrate 2 is heated to 1000°C, and Hl is used as a carrier gas.
was supplied at a rate of 2.511/min, NH at 1.51/min, and trimethyl gallium (TMG) at a rate of 15 d/min for 12 minutes to form a second N layer 8 made of N-type GaN with a film thickness of 27a. did. Next, the sapphire substrate 2 is heated to 900°C, and H2 is heated to 2.
511/min, NH, 1.5I! /min, TMG 15d
/min, diethylzinc (DEZ) was supplied at a rate of 10-'mff1/min for 5 minutes to form an I layer 5 formed from ■-type GaN.
The film thickness is 1. Formed at oAa. Next, aluminum electrodes 6.7 were deposited on the side walls of the first N layer 4 and the second N layer 8 and on the top surface of the first layer 5 to form a light emitting diode. The first Nat of the light emitting diode 1 thus obtained
4. 2nd Na18 and 1115 (FIFi surface (73S
It was found that good crystallinity was obtained by fllfi mirror photography and high-energy electron beam reflection diffraction method (RII[!ED). In particular, since the first N layer 4 was grown on the buffer layer 3 by halide vapor phase epitaxy, a thick N layer with good crystallinity could be obtained at high speed. In the above embodiment, a thin second N layer grown by the MOVPE method is provided, but this second N layer is not necessarily necessary if the crystallinity of the first layer 5 can be sacrificed to some extent. However, when the second N layer 8 is precisely grown using the MOVPE method on the WIN layer 4, the crystallinity of the first layer 5 is lower than that of the N layer grown only using the halide vapor phase epitaxy method. It got even better. Furthermore, the emission peak spectrum of this light emitting diode 1 is 480 nm, and the emission intensity (on-axis brightness) is 10 cd.
Met. Second Embodiment In this embodiment, the buffer layer 3 shown in the figure in the first embodiment was created by molecular beam epitaxy (MBE). In the same manner as in the first embodiment, a sapphire substrate 2 having a 0 (0001) principal surface was cleaned, and then the sapphire substrate 2 was attached to a susceptor of an MBE apparatus. Thereafter, the sapphire substrate 2 is heated to 500°C to evaporate aluminum in nitrogen gas plasma, and a buffer N3 made of aluminum nitride (AlN) is formed on the main surface of the sapphire substrate 2 to a thickness of approximately 500 mm. Formed. Subsequent 1N layer 4. 2nd N layer8. I layer 5. Electrode 6.7
The method for creating is the same as in the first embodiment. The first N layer 4 of the light emitting diode thus obtained.
Micrograph of the cross section of the second N layer 8 and the first layer 5, by reflection diffraction method using high energy electron beam (RIIEIED),
It was found that good crystallinity was obtained. The emission peak spectrum of this light emitting diode 1 is 480 nm, and the emission intensity (on-axis brightness) is 10 cd.
Met. According to the inventors' considerations, in the buffer layer 3 formed by MBE, the growth nuclei of GaN in the first N layer 4 are more uniform than in the buffer layer 3 grown by MOVPE. It is considered that the single crystallinity of the 'JIN layer 4, the second N layer 8, and the first layer 5 was improved because of the dispersion. Further, the buffer layer 3 was polycrystalline because it was formed by MBE at 500° C. on the sapphire substrate 2. In addition, the present inventors have found that when the buffer layer 3 is grown as a polycrystalline layer, the first N layer 4 and the second N layer 3 are
It was also found that layer 8 and layer 1 5 had good single crystallinity. For this reason, it is effective to grow the buffer layer 3 by MBE, and the growth temperature for making it polycrystalline is from room temperature to 500°C.
is desirable. Furthermore, in order to improve the single crystallinity of the MIN layer 4, the second N layer 8, and the first layer 5, the thickness of the buffer layer 3 should be 100 to 10
00 people is desirable. In the above embodiment, the first N layer 4, the second N layer 8 and the IF
Although jI5 is formed of GaN, it may be formed of Al x GaN.

[Brief explanation of the drawing]

The figure is a configuration diagram showing the configuration of a light emitting diode according to a specific example of the present invention. Light emitting diode 2 ・Sapphire substrate buffer N 4
1st N layer 8-2nd N layer 5/1 layer Patent applicant Toyoda Gosei Co., Ltd. Nagoya University President New Technology Development Corporation

Claims (1)

[Claims] A sapphire substrate, an N-type gallium nitride compound semiconductor (Al_xGa_1
____xN;
_xGa_1_-_xN; including X=0), and aluminum nitride (
1. A gallium nitride-based compound semiconductor light emitting device, characterized in that a buffer layer made of (AlN) is grown, and the N layer is grown on the buffer layer by a halide vapor phase epitaxy method.