JPH0369879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a - group compound semiconductor aluminum indium phosphide AlInP single crystal in a gas phase by an organometallic thermal decomposition method. Among - group compound semiconductors, AlInP is an important material for obtaining short wavelength semiconductor light emitting devices. This material was first successfully synthesized in 1970 by Dr. Onton and Dr. Chikotka using the Bridgeman method (Journal of Applied Physics).
1970 vol.41.NO.10.pages 4205-4207).

However, because the binding energy between aluminum (Al) and phosphorus (P) is significantly larger than that between indium (In) and P, when Al and In are taken into the solid phase from the liquid phase, Al
Since the incorporation rate of AlxIn 1-x P was high and the composition controllability of the solid phase was extremely poor, the growth of AlxIn _1-x P by liquid phase crystal growth continued to be virtually impossible.
In 1981 (Inst.Phys.Conf.Ser.No.63
Chap12. Pages 575 to 576) Mr. Asahi et al.
(MBE)) succeeded in growing single-crystal AlInP on a gallium arsenide (GaAs) substrate crystal. The MBE method is grown under conditions that deviate greatly from thermal equilibrium, and in the AlInP system in question, the Al to In ratio in the solid phase is approximately the beam intensity ratio of the Al atomic beam and the In atomic beam. is expected to be equal to , and unlike liquid phase growth, the composition can be controlled relatively easily.

However, crystal growth of compound semiconductors containing P by the MBE method has several disadvantages that are unfavorable as an industrial crystal growth technique, such as the fact that solid P has high hygroscopicity and is flammable. There is.

The present invention solves the above-mentioned drawbacks and provides a method for forming high-quality AlInP single crystals on GaAs substrates. The production method described in the present invention is generally known as the metal organic pyrolysis method (MOCVD method), and is a system in which growth deviates significantly from thermal equilibrium, and the ratio of the gas phase composition to the solid phase composition of the raw material is is 1
One of its characteristics is that it is close to .
However, research by the authors has shown that in the growth of Al _x In _1-x P, the efficiency of Al incorporation from the gas phase to the solid phase is affected by the gas phase composition of the group generally cited as a characteristic of the MOCVD method. It has become clear that the situation is far from an approximate agreement with the solid phase composition of the and family. By examining these conditions, it was found that single crystal AlInP with good electrical and optical properties was obtained under the conditions indicated in the claims.
It has become possible to obtain it on GaAs substrates with good reproducibility.

The method for producing an aluminum/indium phosphide single crystal of the present invention is metal organic pyrolysis (MOCVD) of a - group compound semiconductor aluminum/indium phosphide single crystal using trimethylaluminum and triethylindium as feed materials for aluminum and indium, respectively. In the production method by vapor phase growth, the molar fraction of trimethylaluminum in the group raw material is set between 0.05 and 0.25,
The method is characterized in that phosphorus hydride is used as a group element raw material, and the above raw materials are thermally decomposed on a gallium arsenide substrate crystal to grow a single crystal on the substrate.

Next, embodiments of the present invention will be described using drawings and the like. A (100) GaAs substrate 4 whose surface has been cleaned by chemical etching is placed on a carbon susceptor 3 placed in a quartz reaction tube 2 shown in FIG. Approximately 3 liters of high-purity hydrogen gas is introduced per minute from the reaction tube inlet 1 to purge the atmosphere inside the reaction tube. Next, from the high frequency oscillator to the high frequency coil 5
A current is introduced into the carbon susceptor 3, and the susceptor is heated by the induced current induced on the carbon susceptor 3, thereby heating the GaAs substrate 4. Substrate temperature is 750℃
When the temperature is reached, phosphine gas (PH ₃ ) is introduced from the inlet of the reaction tube, and then an organometallic gas of group 3 is introduced into the reaction tube from the inlet of the reaction tube. Trimethylaluminum and triethylindium were used as group organic metals.

When the proportion of trimethylaluminum in the vapor pressure of all group raw materials is 15±5%, the composition x of Al _x In _1-x P deposited on GaAs falls within the range of 51±10%, and therefore, GaAs The lattice misalignment between the two is within the range of ±4%, and single crystal Al _x In _1-x P with good lattice matching can be obtained. At room temperature, GaAs
Al _x In _1-x P that has lattice matching with the substrate is x-0.51, but the Al raw material vapor in the vapor pressure of the group raw material in the gas phase is
The rate of incorporation into the solid phase is higher than that of In, and about 50% solid phase Al is deposited for about 15% Al raw material vapor. Conventionally, metal-organic pyrolysis growth method
The molar ratio of group elements in the gas phase and solid phase was said to be close to 1.

However, research by the present inventors has revealed that in the AlInP system, this ratio deviates significantly from 1.

FIG. 2 shows an experimental example of the mole fraction of trimethylaluminum in the raw material for supplying group elements in the gas phase and the mole fraction of aluminum (X) in the solid phase Al _x In _1-x P.
The broken line b shows the lattice matching condition with GaAs at room temperature, and the solid line a shows the values in the example.

In the examples, the total pressure of the gases in the reaction tube was reduced to about 70 Torr to suppress intermediate reactions between the raw material gases. A total gas pressure of 2 atmospheres or less is effective.

In this example, the growth temperature was 750°C, but a temperature between 680°C and 580°C is effective. Crystal growth temperature
A mirror-like crystal cannot be obtained below 680°C, because the mobility of elements on the crystal surface decreases as the temperature decreases, making it impossible to obtain the mobility necessary to obtain a mirror-like surface. If the substrate temperature is 850° C. or higher, the thermal decomposition of the crystal will be significant, making it impossible to obtain a good crystal. Finally, by setting the molar fraction of trimethylaluminum in the group element feed gas (trimethylaluminum and triethylindium) between 0.05 and 0.25 at a substrate temperature between 680°C and 850°C, solid-phase Al _x In _{1 -x} P can be grown within the range of x-0.51±0.2. Especially the substrate temperature
When set at 750℃ and the mole fraction of trimethylaluminum in the range of 0.15±0.05, the solid phase Al _x
The Al composition x of In _1-x P can be within the range of 0.51±0.1. At this time, the lattice deviation of Al _x In _1-x P from the GaAs substrate is ±4%. As mentioned above, GaAs can be grown by controlling the molar fraction of trimethylaluminum and the growth temperature as proposed in the present invention.
It becomes possible to grow Al _x In _1-x P single crystals on the substrate.

[Brief explanation of drawings]

FIG. 1 schematically shows the reaction tube portion where crystal growth is performed in the example, where 1 is the reaction tube inlet, 2 is the reaction tube, 3 is a carbon susceptor, and 4 is a carbon susceptor.
5 shows a GaAs substrate crystal, 5 a high frequency coil, and 6 a thermocouple for measuring the substrate temperature. 7 is an exhaust gas outlet. FIG. 2 shows the relationship between the molar fraction of trimethylaluminum and the Al composition (x) in the solid phase Al _x In _1-x P in Examples. On the vertical axis of the figure,
[Al] indicates the number of moles of Al in a unit volume of solid phase AlInP, and [In] indicates the number of moles of In. On the horizontal axis of the figure, [TMA] indicates the number of moles of trimethylaluminum in a unit volume, and [TEI] indicates the number of moles of trimethylindium. The broken line b indicates the lattice matching condition with GaAs at room temperature. The solid line a indicates the optimum fit curve of the experimental values [△ mark] in the example.

Claims (1)

[Claims] 1 In a method for producing a - group compound semiconductor aluminum/indium phosphide single crystal by organometallic pyrolysis vapor phase growth using trimethylaluminum and triethylindium as feed materials for aluminum and indium, respectively, the mole of trimethylaluminum in the group material is The fraction is set between 0.05 and 0.25, phosphorus hydride is used as the group element raw material, and on a gallium arsenide substrate crystal,
Aluminum phosphide characterized by thermally decomposing the above raw materials and growing a single crystal on the substrate.
Method for producing indium single crystal.