JPS63188938A - Method for vapor growth of gallium nitride compound semiconductor - Google Patents

Abstract

PURPOSE:To realize the vapor growth of a gallium nitride compound semiconductor thin film by a method wherein a buffer layer composed of aluminum nitride is grown on an a-plane of a sapphire substrate. CONSTITUTION:A single-crystal sapphire substrate 24, which has been cleaned by an organic cleaning method and a heat treatment and whose main plane is an a-plane, is mounted on a susceptor; the sapphire substrate 24 is vapor- etched while H2 is flowing into a reaction chamber through a first reaction-gas pipe 25 and a second reaction-gas pipe 26. Then, after the temperature has been lowered, the substrate is heat-treated while H2, NH3 and trimethylaluminum are fed through the first reaction-gas pipe 25. During this heat treatment, a buffer layer 30 composed of AlN is formed. Because a gallium nitride compound semiconductor thin film is formed vapor growth on this buffer layer, the crystallinity is improved and it becomes easy to supply the sapphire substrate.

Description

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

The present invention relates to a vapor phase growth method that improves the crystallinity of a gallium nitride compound semiconductor grown on a sapphire substrate.

[Prior art]

Conventionally, organometallic compound vapor phase epitaxy (hereinafter [MOVPEJ
gallium nitride-based compound semiconductor (AA
Research has been conducted on vapor phase growth of thin films (XGa+-xN; including x=o) on sapphire substrates. This method is carried out using a vapor phase growth apparatus as shown in FIG. In the vapor phase growth apparatus, a quartz reaction tube 7
A manifold 6 is connected to the manifold 6, and the manifold 6 has a supply system A for NHs, a supply system B for Ha and N2, and a supply system C for trimethyl gallium (hereinafter referred to as rTMGJ), an organometallic compound gas. , a supply system for trimethylaluminum (hereinafter referred to as rTMAJ), which is an organometallic compound gas, and a supply system E for diethylzinc (hereinafter, referred to as rDEZJ), which is a reactive gas containing a doping element (hereinafter simply referred to as "dopant gas"). is connected. Furthermore, a graphite susceptor 9 for high-frequency heating is disposed inside the quartz reaction tube 7, and a sapphire substrate 10 is placed on the susceptor 9. heated by. Reaction gases and carrier gases are mixed in a manifold 6 from each supply system, and the mixed gas is led to a quartz reaction tube 7 and sprayed onto a sapphire substrate 10, thereby forming a thin film of AlxGa, -8N on the sapphire substrate 10. grow up. Then, by changing the mixing ratio of each organometallic compound gas, the composition ratio can be changed, or by doping with zinc, an insulating (type I) Aj! A thin film of xGa+-xN can be formed.

[Problems to be solved by the invention]

In conventional growth methods, it has been considered that the 0 main plane of the sapphire substrate, which is involved in crystal growth, is best. However, it was found that by forming a buffer layer of AIN on the a-plane of a sapphire substrate and growing a thin film of AlxGaI-XN on the buffer layer, the crystallinity of Al1xGa, -xN improved. . Therefore, it is possible to manufacture a blue light emitting diode using a sapphire substrate having an a-plane main surface, which is easy to supply.

[Means to solve the problem]

The structure of the invention for solving the above problems is to grow a buffer layer made of aluminum nitride on the a-plane of a sapphire substrate in a vapor phase growth method of a gallium nitride-based compound semiconductor thin film using organic gold scrap compound gas, A gallium nitride-based compound semiconductor (Alx Ga+
-x N ; containing X=O) was grown in a vapor phase.

【Example】

The present invention will be described below based on specific examples. FIG. 1 is a sectional view showing the configuration of a vapor phase growth apparatus. In a reaction chamber 20 surrounded by a quartz reaction tube 21, a susceptor 22 is supported by an operating rod 23, and the position of the susceptor 22 is adjusted by the operating rod 23. Further, on the main surface 22a of the susceptor 22, a sapphire substrate 24 whose main surface 24a has an a-plane crystal plane is disposed. Note that 8 is a high frequency coil for heating the sapphire substrate 24. On the other hand, on the gas inflow side of the reaction chamber 20, a first reaction gas pipe 25 and a second reaction gas pipe 26 are arranged. The first reaction gas pipe 25 is arranged concentrically with the second reaction gas pipe 26 inside the second reaction gas pipe 26 . The first reaction gas pipe 25 is connected to the seventeenth second hold 27, and the second reaction gas pipe 26 is connected to the second manifold 28. The first manifold 27 has an NH3 supply system H.
and carrier gas supply system I and TMG supply system J and T
is connected to the MA supply system, and the second manifold 28
A carrier gas supply system I and a DEZ supply system are connected to. With this device configuration, a mixed gas of NH, TMG, TMA, and H3 flows into the reaction chamber 20 from the opening 25a of the first reaction gas pipe 25, and flows out from the opening 26a of the second reaction gas pipe 26. , a mixed gas of DEZ and H2 enters the reaction chamber 20.
leaks to. When forming an N-type AlxGa+-xN thin film, it is sufficient to flow out the mixed gas only from the first reaction gas pipe 25, and the ■-type Aj! In the case of forming an xGa+-xN thin film, it is sufficient to cause the respective mixed gases to flow out from the first reaction gas pipe 25 and the second reaction gas pipe 26. ■Mold Al1xG
When forming an at-xN thin film, the dopant gas DEZ is first mixed with the reaction gas flowing out from the first reaction gas pipe 25 in the reaction chamber 20a near the sapphire substrate 24. Then, DEZ is sprayed onto the sapphire substrate 24 and thermally decomposed, and the dopant element is doped into the growing Aj2XGa+-xN, forming a ■-type A
l1xGa+-xN is obtained. In this case, the first reaction gas pipe 25 and the second reaction gas pipe 26 separate the reaction gas and the dopant gas, and the reaction gas and dopant gas are guided to the reaction chamber 25a near the sapphire substrate 24. Since the reaction between DEZ and TMG or TMA is suppressed, good doping is achieved. Note that the openings 25a of the first reaction tube 25 and the second reaction tube 26
And the distance between 26a and the sapphire substrate 24 is 10 to 60
Preferably set in the mouth. Further, the inclination angle θ of the susceptor 22 with respect to the flow direction X of the reaction gas is set to 45 degrees. By tilting the susceptor 22 in this manner, better crystals were obtained than when the susceptor 22 was configured perpendicular to the gas flow. Next, using this vapor phase growth apparatus, a GaN thin film was formed on a sapphire substrate having the a-plane as its main surface as follows. First, a single-crystal sapphire substrate 24 having an a-plane main surface that has been cleaned by organic cleaning and heat treatment is attached to the susceptor 22 . Next, H2 was supplied to the first reaction gas pipe 2 at a rate of 0.31/min.
The sapphire substrate 24 was subjected to vapor phase etching at a temperature of 1100° C. while flowing into the reaction chamber 20 from the reaction gas pipes 26 and 26. Next, the temperature was lowered to 950°C, and H7 was fed from the first reaction gas pipe 25 at 31/min, NH gas was fed at 21/min, and TM
A was supplied at a rate of 7×10 −6 mol/min and heat treated for 1 minute. Through this heat treatment, a buffer layer of AIN was formed on the sapphire substrate 24 to a thickness of about 0.1-. When one minute has passed, the supply of TMA is stopped and the sapphire substrate 24 is removed.
The temperature of H is maintained at 970°C, and H is
3 was supplied at a rate of 2.51/min, NH was supplied at a rate of 5117 min, and TMG was supplied at a rate of 1.7×10 −' mol/min for 60 minutes to form a GaN thin film having a film thickness of 7 A1 m. FIG. 2 shows a microscopic photograph of the surface of the GaN thin film thus formed, and FIG. 4 shows the light emission characteristics due to photoluminescence. On the other hand, a GaN thin film was also grown on a sapphire substrate having a C-plane ((0001)) as its main surface in the same manner as above. FIG. 3 shows a microscopic photograph of the surface of the thin film, and FIG. 5 shows the light emission characteristics due to photoluminescence. As can be seen from the micrograph, the GaN thin film grown on the a-plane sapphire substrate has larger and more hexagonal crystals, and has better crystallinity than the GaN thin film grown on the c-plane sapphire substrate. A hexagonal crystal is obtained. On the other hand, regarding the characteristics based on photoluminescence intensity, the half-width is 4.6 meV when grown on the C-plane, and 6 meV when grown on the a-plane. From this,
As far as the photoluminescence intensity is concerned, the crystallinity is almost the same as that grown on the C-plane. Next, a method for producing a light emitting diode by growing GaN crystals on the a-plane of a sapphire substrate will be described. First, a single-crystal sapphire substrate 24 having an a-plane main surface that has been cleaned by organic cleaning and heat treatment is attached to the susceptor 22 . Next, apply H2 for 0.317 minutes to the first reaction gas pipe 2.
The sapphire substrate 24 was vapor-phase etched at a temperature of 1100 tl'' while flowing into the reaction chamber 20 from the 5 and second reaction gas pipes 26.Then, the temperature was lowered to 950°C, and the first
Heat treatment was performed for 1 minute by supplying H2 at 31/min, NH at 21/min, and TMA at 7×10 −6 mol/min from the reaction gas pipe 25. Through this heat treatment, the AIN buffer layer 30 was formed to a thickness of about 0.1 um. T when 1 minute has passed
Stop the supply of MA and lower the temperature of the sapphire substrate 24 to 9.
The temperature is maintained at 70°C, and 2.5 liters of H2 is supplied from the first reaction gas pipe 25.
1/min, NH, 1.517 min, TMG 1.7X10
-5 mol/min for 60 minutes to form eight layers 31 made of N-type GaN with a film thickness of 7 μs. Next, the sapphire substrate 24 is taken out from the reaction chamber 20', and a film thickness of about 1000 wafers is formed by photoetching, sputtering, etc.
A 3-inch film 32 was patterned. Thereafter, after cleaning this sapphire substrate 24, it was mounted on the susceptor 22 again and subjected to gas phase etching, and then the temperature of the sapphire substrate 24 was maintained at 970°C, and the first reaction gas pipe 25
From the
DEZ is supplied from the reaction gas pipe 26 at a rate of 5 x 10-6 mol/min for 5 minutes to form one layer 33 made of ■-type GaN to a thickness of 1. Formed in Owl. At this time, single-crystal type 1 GaN grows on the exposed part of GaN to obtain one layer 33, but polycrystalline G
A conductive layer 34 made of aN is formed. After that, the sapphire substrate 24 is taken out from the reaction chamber 20, and aluminum electrodes 35 and 36 are deposited on the first layer 33 and the conductive layer 34,
A light emitting diode was formed by cutting the sapphire substrate 24 into a predetermined size. In this case, the electrode 35 is an electrode of one layer 33, and the electrode 36 is an extremely thin SiO, II! electrode with the conductive layer 34. It becomes an electrode of 8 layers 31 via X32. Then, by setting the first layer 33 at a positive potential with respect to the eighth layer 31, light is emitted from the bonded surface. Furthermore, in order to form an AAXGa+-xN light emitting diode, when forming the N layer 31 and lff133,
It is sufficient to flow T M Δ from the first reaction tube 25 at a predetermined rate. For example, the temperature of the sapphire substrate 24 from the first reaction gas pipe 25 is maintained at 1105°C, H3 is 3 J/min, NH is 21/min, TMA is 7.2 × 10-' mol/min, TMG is
By supplying DEZ at a rate of 1.7X 10-' mol/min and DEZ at a rate of 5X 10-' mol/min from the second reaction gas pipe 26, a type I AAxGa+-xN semiconductor thin film of X=0.3 is produced. is obtained.

【Effect of the invention】

In the present invention, a buffer layer made of aluminum nitride is grown on eight sides of a sapphire substrate, and a gallium nitride-based compound semiconductor (A j? xGa+-xN;
Since the thin film (containing Therefore, the gallium nitride compound semiconductor light emitting device can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the configuration of one vapor phase growth apparatus for implementing the method of the present invention. FIG. 2 is a micrograph showing the surface structure of a GaN thin film grown on a sapphire substrate with eight principal crystal planes. FIG. 3 is a micrograph showing the surface structure of a GaN thin film grown on a sapphire substrate whose principal crystal plane is 0. FIG. 4 is a measurement diagram showing the photoluminescence intensity characteristics of GaNaWff grown on a sapphire substrate with eight main crystal planes. FIG. 5 is a measurement diagram showing the photoluminescence intensity characteristics of a GaN film grown on a sapphire substrate whose principal crystal plane is 0. FIG. 6 is a configuration diagram showing the configuration of a light emitting diode grown on a sapphire substrate whose main crystal plane is 0. FIG. 7 is a block diagram showing the structure of a conventional vapor phase growth apparatus. 7-Quartz reaction tube 8 ・High frequency coil 9゛Susceptor
10... Sapphire substrate 20 Reaction chamber 21 Quartz reaction tube 22-Susceptor 23° Control rod 24...
Sapphire substrate 25 First reaction gas pipe 26-second reaction gas pipe 27-first manifold 28-.-° second
72 hold 30...buffer layer 31-N layer 32
...SiO2 film 33...1 layer 34-conductive layer 3
5.36...Electrode H...NH, supply system I...
Carrier gas supply system J-・-TMG supply system
K...TMA supply system Lo...DEZ supply system Patent applicant Toyota Gosho Co., Ltd. Nagoya University Chief Attorney Osamu Fujitani Figure 2 (a) (b) xloo. Figure 3 Figure 5 Wavelength (nm)

Claims (1)

[Claims] In a vapor phase growth method of a gallium nitride compound semiconductor thin film using organometallic compound gas, a buffer layer made of aluminum nitride is grown on the a-plane of a sapphire substrate, and a gallium nitride compound semiconductor (Al
A method for vapor phase growth of a gallium nitride-based compound semiconductor thin film, characterized in that a thin film (_XGa_1_−_XN; including X=0) is grown in a vapor phase.