JPS5813486B2 - Kagobutsunogouseihouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides
-This invention relates to a method for synthesizing a group compound GaAsP.

In a sealed reaction vessel, at least one type of group ■ element is introduced through a differential pressure valve into a sealed tube containing a heated group ■ element, and other types of group
A method for synthesizing a compound, which is characterized by synthesizing a group IV compound containing multiple components with a uniform composition by simultaneously absorbing a group element and a group element, was previously proposed by the present inventors in a patent application filed in 1972.
This invention was developed as JP-A No. 50-10796.

That is, when synthesizing GaAsP, for example, a differential pressure valve is used to infuse As onto the heated Ga surface at a fixed ratio.
By supplying P and P, it was possible to synthesize a compound having a uniform composition.

However, since the compound is synthesized in a closed reaction vessel, various impurities are incorporated into the compound from the closed reaction vessel, making it difficult to increase the purity of the compound.

The present invention makes it possible to synthesize a highly pure compound with a uniform composition by supplying AsH4 and PH3 at a fixed ratio to the heated Ga surface when synthesizing GaAsP using an open tube method. It is something to do.

A description will be given below based on one embodiment.

Figure 1 shows an enlarged view of the gallium side of the gallium arsenide-gallium phosphide-gallium ternary system phase diagram for explaining the principle of the method of this invention. In the figure, the solid line is the isothermal liquidus line, and the dotted line is the precipitation line. This is the gallium phosphide isodensity line of the crystal.

FIG. 2 is a diagram showing a reaction apparatus and a temperature distribution within the reaction apparatus for specifically explaining the method of the present invention.

First, as shown at 3 in FIG. 2, gallium is placed in a vertical high-purity carbon crucible and exposed to a mixed vapor of AsH3 and PH3 at high temperature.

The vapor pressure of this mixed vapor is set to be higher than the decomposition pressure of the compound.

In this state, a thin compound is formed on the surface of the gallium solution,
It dissolves into the gallium solution.

The bottom of the solution is kept at a lower temperature than the surface of the solution, creating a temperature gradient as shown in Figure 2.

Due to the temperature difference, the solute that has melted and diffused is most likely to become supersaturated at the bottom, and crystals begin to precipitate at the bottom first.

The crystal grows automatically from this point on, and growth continues automatically until the gallium solution is finally exhausted.

This is established using the ternary system phase diagram shown in FIG.

Due to its isothermal liquidus, gallium solution can dissolve various proportions of arsenic and phosphorus at the same temperature.

For example, a solution containing only arsenic dissolved in AsH4 and P
When placed in a mixed gas of H3 and increasing the vapor pressure of PH3, the composition of arsenic and phosphorus in the solution changes along the liquidus line, and the concentration of phosphorus gradually increases until AsH4 at a certain appropriate mixing ratio. Under the vapor pressure of the mixed gas of PH3 and PH3, it has a certain composition.

When the vapor pressure of this mixed gas is higher than the decomposition pressure of the compound, the surface of the gallium solution has a certain composition as indicated by a point on the isoconcentration line of gallium phosphide indicated by the dotted line in Figure 1. A thin compound of gallium arsenide phosphide forms, which dissolves into solution.

Since the temperature at the bottom is lower than that at the surface of the solution, arsenic and phosphorus diffuse through the solution and reach the bottom.

The composition ratio of arsenic and phosphorus in the gallium solution at the bottom is determined by the crystal growth rate and the diffusion coefficients of arsenic and phosphorus in the gallium solution, but when the crystal growth rate is slow enough, the composition ratio is the same as the composition ratio at the solution surface. Become.

Therefore, crystals having the same composition as the thin gallium arsenide phosphide formed on the surface begin to precipitate at the bottom.

From this point on, if the composition of the gallium arsenide phosphide on the surface is constant, that is, if the mixing ratio of the mixed gas of AsH4 and PH3 is constant, then the gallium arsenide phosphide crystal with a constant composition will automatically form. The growth continues automatically until the gallium solution is finally exhausted.

As a result, gallium arsenide phosphide crystals with a uniform composition can be obtained.

A concrete explanation will be given below with numerical values.

The surface temperature of the gallium solution is 1150°C, and the bottom temperature is 1100°C.

The amounts of arsenic and phosphorus dissolved in a gallium solution at 1150°C are 28% and 7.4% in atom%, respectively, so for example, a thin film of gallium arsenide phosphide whose composition is 40% is dissolved in a solution. In order to obtain a solution having such a composition as to be generated on the surface, that is, a solution having the composition at point a in FIG. 1, the mixing ratio of the mixed gases should be approximately 3:2 (mole ratio of AsH4 and PH3).

That is, the molar ratio of AsH4 and PH3 is determined as follows.

From Figure 1, the amounts of arsenic and phosphorus dissolved in the gallium solution at 1150°C are 28 and 7 atom%, respectively.
．． It is 4%.

Therefore, for example, if the molar ratio of AsH4 and PH3 in the mixed gas is 1:1, the concentration ratio of arsenic and phosphorus in the gallium solution will be 28:7.4, or 3.8:1.

From the figure, the concentration ratio of arsenic and phosphorus in the gallium solution at point a in FIG. 1 is 16.2:2.8, or 5.7:1.

If the molar ratio of AsH4 and PH3 in the mixed gas at this time is X:Y, then it is 3.8X:Y=5.7:1. Therefore, X:Y is 3:2.

In FIG. 1, XGaP indicates the molar concentration of gallium phosphide in gallium arsenide phosphide.

The decomposition pressure of gallium arsenide phosphide (GaAsO.6PO.4) with a composition of 40 molar gallium phosphide at 1150°C is about 0.2 atm, so if the vapor pressure of the mixed gas is made equal to or higher than this decomposition pressure, , a thin compound forms on the surface of the gallium solution.

That is, the vapor pressure of the mixed gas need only be equal to or higher than the decomposition pressure of gallium arsenide phosphide having a specific composition and a specific temperature, and the supply rate of AsH4 and PH3 is arbitrary.

However, if the supply rate of AsH4 and PH3 is too slow, the crystal growth rate will be more limited and slow, and if it is too fast, the raw material gas will be wasted, so the vapor pressure of the mixed gas on the surface of the gallium solution will be lower than that of each gas. It is uniquely determined by the supply amount, that is, the supply speed.

This dissolves into the solution, and because there is a temperature gradient, it diffuses toward the bottom of the solution, ie, point b in FIG. 1.

Since arsenic and phosphorus become supersaturated at point b, a gallium arsenide phosphide crystal (G
aAsO. 6P0.4) is precipitated.

Thereafter, the crystal automatically grows from point b to point a.

Then, a gallium arsenide phosphide crystal having a uniform composition of 40 mol of gallium phosphide is obtained.

Next, an embodiment of the present invention will be described with reference to FIG.

Since the crystal growth apparatus is of a vertical type and it is necessary to control the mixing ratio of the AsH4 and PH3 mixed gases, each of them is supplied independently from the AsH4 supply pipe 1 and the PH3 supply pipe 2.

Metal gallium 3 is housed in a high purity carbon crucible 4,
This high purity carbon crucible 4 is heated by a high frequency coil 5 and maintained at a temperature distribution as shown in the figure.

Although 6 is a quartz reaction tube, it is not heated unlike when a compound is synthesized using a closed reaction vessel, so in the present invention, contamination from the quartz reaction tube 6 is extremely small, resulting in high purity. The compound obtained is as follows.

The diameter of a high-purity carbon crucible is 22 mmφ, and 50 g of metal gallium is used.

A with a concentration of 10 diluted with a rare gas with a surface temperature of metallic gallium of 1150°C and a bottom temperature of 1100°C.
sH4 and PH3 gases are supplied at 30 mz/min and 20 ml/min from the AsH4 supply pipe and the PH3 supply pipe, respectively.

Further, hydrogen gas was flowed at a rate of 50 ml/min into the quartz reaction tube.

If you leave it in this state for about 5 days, the diameter will be 22mmφ and the length will be about 5mm.
A 5 mm gallium arsenide phosphide crystal having a uniform composition of 40 parts is obtained.

By changing the supply ratio of AsH4 and PH3, crystals of any other composition can be obtained.

Increasing the growth temperature will increase the growth rate, but if it is too high, the decomposition pressure will increase, so
It was grown between 50°C.

In addition, if the temperature gradient of the gallium solution is increased, the growth rate will also increase, but at temperatures above 60°C/cm, the compositional change seems to become large, and below 5°C/cm, the growth rate becomes extremely slow, making it impractical. Not.

In addition, since it is necessary to increase the crystal growth rate to some extent, the supply amount of AsH4 and PH3 is 5 ml/m each.
in and 3 ml/min or more.

Also, excess supply will only be exhausted, so 100 m
l/min or less.

As described above, according to the present invention, contamination from a quartz reaction tube is prevented, and a highly pure compound of any composition can be synthesized by simply changing the supply ratio of AsU and PH3.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of the gallium side of the gallium arsenide-gallium phosphide-gallium ternary system phase diagram for explaining the principle of the present invention, showing the isothermal liquidus line and the equal concentration of gallium phosphide in the precipitated crystals. Diagram showing lines. FIG. 2 is a diagram for explaining the implementation side of this invention. 1 is an AsH4 supply pipe, 2 is a PH3 supply pipe, 3 is gallium, 4 is a high temperature carbon crucible, 5 is a high frequency coil for heating, and 6 is a quartz reaction tube.

Claims (1)

[Claims] 1. A method for synthesizing a compound in a vertical open-tube reaction vessel, in which the reaction apparatus consists of a carbon crucible containing gallium, an AsH4 supply pipe for supplying AsH4, and a PH3 supply pipe for supplying PH3, The temperature of
AsH at a feed rate of ml/min to 100 ml/min
4 and PH3 at a supply rate of 3 ml/min to 100 ml/min.