JPS6317288A - Production of gallium arsenide single crystal and quartz reaction tube - Google Patents

Abstract

PURPOSE:To stably grow a GaAs single crystal in good yield, by subjecting parts adjacent to an arsenic pressure controlling point to frosting treatment and keeping the part at the minimum temperature in growing the GaAs single crystal under a given arsenic pressure in a reaction tube by a gradient freezing (GF) method. CONSTITUTION:A thermocouple 7 for controlling an As pressure is mounted on the end part on the side opposite to the side for inserting a quartz boat 4 in a quartz reaction tube 1 and frosting processed parts 8 are formed on the inner and outer surfaces of the reaction tube 1 adjacent to the thermocouple 7. Thereby propagation of infrared rays in the parts can be reduced and kept at the minimum temperature in the reaction tube. GaAs polycrystals are then put in the quartz boat 4 and a seed crystal 2 is set on a speed shelf. The quartz boat 4 is then inserted into the reaction tube 1 to evacuate and hermetically seal the reaction tube 1. The tube 1 is then heated to melt the GaAs polycrystals and grow a single crystal by a gradient freezing (GF) method. A current is simultaneously passed through the thermocouple 7 to keep the temperature at 617 deg.C and carry out growing by keeping the interior of the reaction tube 1 at 1atm As pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a gallium arsenide (GaAs) single crystal and a quartz reaction tube used in the method.

BACKGROUND ART AND PROBLEMS Conventionally, when producing GaAs single crystals, an apparatus as shown in FIG. 3 has been used.

In the figure, 1 is a quartz reaction tube, 4 is a horizontal quartz boat, 5 is a diffusion barrier, and 7 is a thermocouple for controlling the As pressure.

GaA
The s polycrystal is melted as melt #t3, and the temperature gradient method (GF
A GaAs single crystal is grown by a method (method).

FIG. 3 also shows the temperature of each region during the growth of the GaAs single crystal. The temperature beyond barrier 5 to the middle portion is T2”C.
Furthermore, the temperature between the middle portion beyond the diffusion barrier 5 and the end of the quartz reaction tube is maintained at 73=lit 7 to 620°C.

As the As of the molten metal protrudes and the stoichiometric composition ratio (stoichiometry) of Ga:As=1:1 is lost, As
In order to prevent As from jumping out of the melt, a small amount of As is initially placed in an evaporating dish to evaporate the As and suppress this jumping out.

The AsNm pressure at the melting point of GaAs is about 1 atm, and when As is heated in a closed vacuum, its saturated vapor pressure is about 1 atm at 817°C. If the lowest temperature point is maintained at 617''C, the As pressure inside the quartz reaction tube will be maintained at 1 atm without being affected by changes in the temperature of other parts.

Therefore, if the lowest-bottom point is always maintained at 817° C., that is, if the As pressure is kept constant, GaAs can be grown stably in this environment.

Therefore, a thermocouple 7 for As pressure control is attached to the end of the quartz reaction tube 1, and this point becomes the lowest temperature point, and lit7°
If the temperature is maintained at C, the growth of the GaAs single crystal will proceed stably.

However, in the apparatus shown in FIG. 3, the heat in the high temperature section is transmitted in the quartz reaction tube or in the form of infrared rays because quartz has good infrared transmittance, and a thermocouple 7 is used to control the As pressure. There was a problem in that the temperature at the installation location was higher than that in the vicinity, making it difficult to control accurately.

[Objects and Structure of the Invention] As described above, the present invention produces GaAs from a GaAs melt in a boat in a quartz reaction tube under a constant As pressure.
In the method of growing a single crystal, the As pressure is kept constant by preventing the temperature at the temperature sensing thermocouple installation point for controlling the As pressure from becoming higher than that in the vicinity so that an accurate lowest point temperature can be detected at all times. GaAs
A single crystal is grown, and this is achieved by using a quartz reaction tube with a frosted thermocouple installation location, that is, an As pressure control point joint.

The present invention will be explained in detail below with reference to the embodiment shown in FIG. The same parts as in FIG. 3 are indicated by the same reference numerals.

The As pressure control thermocouple 7 is attached to the end of the quartz reaction tube 1 on the opposite side via the diffusion barrier 5 from the side into which the horizontal quartz boat 4 with the seed shelf is inserted, as shown in FIG. Instead, in the present invention, the frosted portion 8 is formed on the surface, inner surface, or both surfaces of the portion adjacent to the position of the thermocouple 7.

Since the frosted portion 8 is intended to roughen the surface of the quartz and diffusely reflect infrared rays, it is appropriately applied to the inner and outer surfaces as described above.

The position of the As pressure control thermocouple 7, that is, the lowest temperature point, is generally easy to set at the end of the quartz reaction tube due to the structure of the quartz reaction tube, but it is not limited to this position. do not have.

[Example 1] A quartz reaction tube with a diameter of 0 m and a length of + 500 mm was provided with a frosted part for approximately 100 ms from the end of the tube, excluding the thermocouple installation position, and adjacent to this. GaAs polycrystalline 38509 on a quartz boat
Place the seed crystal on the seed shelf, and add 140g of Si.
When I put it in and grew it using the GF method,
Growth was completed in about 180 hours, and 35003 became a single crystal. During growth, the temperature was monitored from TA to TF at the position shown in Figure 1, and the results were TA (81buC), TB, and T.
The temperature difference with C and TD was all within 0.3°C, and TA was always low.

Well, TE and TF showed temperatures 15 degrees Celsius or more lower than TA. Furthermore, when observing the fixed position of As during growth, it was found to be at the TA position. These conditions are shown in FIG.

Example 2 When growth was performed using the same GF method using the same amount of material as in Example using a 300cm-sized machine equipped with a frosted part, growth was completed in about 185 hours and 3.
2009 had become a single crystal. The temperature difference between TA (lit 8”C) and Ta, Tc, and To was within 0.2 °C, and TE and TF were at temperatures more than 15 °C higher.Also, during the entire growth process, As was higher than that of TA. It was stuck in place.

Example 3 A quartz reaction tube with the same dimensions as Example 1.2 was frosted in all areas except where the boat was located, and the same tests were conducted, but the results were almost the same as in Example 2. What song?

Comparative Example A beautiful reaction tube was used and the same amount of material was grown in the same manner.

Growth is completed in about 180 hours! 2009 became a single crystal. The rest was polycrystalline. TA (817℃) and TB,
Tc.

The temperature difference between To and each is 2.1'C, Tn, Tc+
The temperatures of To are all lower than TA, and during growth, As is TA
It was stuck to the outer periphery except for the outer part. Although the explanation has been given above using the GF method, it is also applicable to the horizontal Bridgman method using a quartz reaction tube.

All thermocouples used are chromel and alumel thermocouples.

[Effects] As explained above, in order to control the As pressure at a precisely set temperature throughout the growth period,
By frosting the area around the pressure control position, it is possible to drastically reduce the propagation of infrared rays to this area, which can be used to improve the yield of single crystallization and precisely control the composition ratio.

Furthermore, since a conventional quartz reaction tube that has been frosted can be used, the manufacturing cost will hardly increase.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the invention. FIG. 2 shows the temperature profile of each part in the embodiment of the present invention. FIG. 3 is an explanatory diagram of a conventional GaAs manufacturing method and a quartz reaction tube. 1... Quartz reaction tube, 2... Seed crystal, 3... Ga
As melt, 4... Quartz boat, 5... Diffusion barrier, 6... As57... Thermocouple for As pressure control, 8...
・Frost processing section. 1st Prisoner 2nd Figure'$ 3 Mouth

Claims (2)

[Claims] (1) In a method in which a horizontal boat is installed in a sealed quartz reaction tube and a single crystal is grown from a gallium arsenide melt in the boat under constant arsenic pressure, the portion of the quartz reaction tube adjacent to the arsenic pressure control point is frosted. A method for producing a gallium arsenide single crystal, characterized in that the arsenic pressure control point is maintained at the lowest temperature in a quartz reaction tube. (2) A quartz reaction tube used in a method in which a horizontal boat is installed in a sealed quartz reaction tube and a single crystal is grown from a gallium arsenide melt in the boat under a constant arsenic pressure, and the tube is adjacent to an arsenic control point. A quartz reaction tube characterized in that it has a frosted part on the surface or a part of the inner surface of the quartz reaction tube, or a part of the inner surface, or a part of the inner surface.