JPH0699214B2 - Method for producing gallium arsenide single crystal and quartz reaction tube - Google Patents

Description

The present invention relates to a method for producing a gallium arsenide (GaAs) single crystal and a quartz reaction tube used for the method.

[Background Art and Problems] Conventionally, when manufacturing a GaAs single crystal, 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 As pressure.

Put GaAs polycrystal in quartz boat 4 and seed crystal 2 in seed shelf.
Set, insert this into the quartz reaction tube 1, insert Si as a dopant, evacuate and seal the tube, and melt the GaAs polycrystal by melting it with a heating furnace (not shown). As a method, a GaAs single crystal is grown by the temperature gradient method (GF method).

FIG. 3 also shows the temperature of each region during the growth of the GaAs single crystal. As shown in the figure, the portion of the GaAs melt 3 diffuses from the solid-liquid interface 10 to a high temperature T ₁ ° C above the melting point. The intermediate temperature beyond the barrier 5 to the intermediate portion is T ₂ ℃, and the distance between the intermediate portion beyond the diffusion barrier 5 and the end of the quartz reaction tube is T ₃ =
It is kept at 617-620 ℃.

When heated in a furnace and the temperature rises, As in GaAs jumps out and stoichiometric composition ratio (stoichiometry) Ga: As
Since = 1: 1 is lost, a small amount of As is initially placed in the evaporation dish to evaporate As and welcome this jump so that As does not jump out of the melt.

The As dissociation 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 617 ° C.
Since the atmospheric pressure is about 1 atm, if a part of the closed quartz reaction tube as shown in Fig. 3 is kept at 617 ° C as the lowest temperature point, the quartz will not be affected even if the temperature of other parts changes, The As pressure of 1 atm is maintained in the reaction tube.

Therefore, if the lowest temperature point is always maintained at 617 ° C, that is, As
If the pressure is kept constant, GaAs can be grown stably in this environment.

Therefore, if the As pressure controlling thermocouple 7 is attached to the end of the quartz reaction tube 1 and this point becomes the lowest temperature point and is maintained at 617 ° C., the growth of the GaAs single crystal proceeds stably. .

However, in the apparatus as shown in FIG. 3, the heat of the high temperature part is transmitted as infrared rays in the quartz reaction tube or in the quartz due to its good infrared permeability, and the thermocouple 7 for controlling the As pressure is used. There was a problem that the temperature of the installation location of was higher than that of its vicinity, and it became difficult to control with high accuracy.

[Object of the invention. Configuration] The present invention is a method of growing a GaAs single crystal under a constant As pressure from a GaAs melt in a boat in a quartz reaction tube as described above, and in the temperature sensing thermocouple installation location for controlling the As pressure. The GaAs single crystal is grown by keeping the As pressure constant so that the temperature does not become higher than the neighborhood and the accurate minimum temperature can be detected at all times. In other words, it is realized by using a frosted quartz reaction tube adjacent to the As pressure control point.

The embodiment of the present invention will be described below with reference to the embodiment shown in FIG. In FIG. 3, the same parts are designated by the same reference numerals.

Regarding the quartz reaction tube 1, as shown in FIG. 3, the As pressure controlling thermocouple 7 is attached to the end portion on the opposite side of the side where the horizontal quartz boat 4 having the seed rack is inserted via the diffusion barrier 5. Instead, in the present invention, the frosted portion 8 is formed on the surface of the portion adjacent to the position of the thermocouple 7, or on the inner surface or both surfaces.

The frosted portion 8 is provided to roughen the surface of quartz and diffuse infrared rays, so that 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 itself, but it is not limited to this position. Absent.

[Example 1] Except for the thermocouple installation position from the end of a quartz reaction tube having a diameter of 60 mm and a length of 1500 mm, it extends about 100 mm from the portion adjacent to it.
Using a thing with a frosted part, 3850 g of GaAs polycrystal was put in a horizontal quartz boat, a seed crystal was set on a seed shelf, 140 mg of Si was put, and when this was grown by the GF method, The growth was completed in 180 hours, and 3500 g was single crystallized. During the growth, the temperature was monitored from T _A to T _F at the position shown in Fig. 1, and the results were that the temperature difference between T _A (617 ° C) and T _B , T _C , T _D was all within 0.3 ° C and T _A was low.

Moreover, T _E and T _F were higher than T _A by 15 ° C or more. Also, when the As fixing position was observed during growth, it was at the T _A position. These states are shown in FIG.

Example 2 A material having the same amount as that of the example was used, except that a thermocouple installation position was removed from the end of a quartz reaction tube having a diameter of 60 mm and a length of 1500 mm, and a frosted part was provided for about 300 mm from a part adjacent to this. According to the same GF method, the growth work was completed in about 185 hours, and 3200 g was single-crystallized. The temperature difference between T _A (618 ° C) and T _B , T _C , T _D was within 0.2 ° C, and T _E and T _F were higher than 15 ° C. Also, As was fixed at the position of T _A during the entire process during growth.

Example 3 The same test was carried out except that the quartz reaction tube having the same dimensions as those in Examples 1 and 2 was subjected to frosting except where the boat was located, and the results were almost the same as those in Example 2. There wasn't.

Comparative Example A quartz reaction tube having no frosted portion in Example 1 was used, and the same amount of material was used to grow the same.

The growth was completed in about 180 hours, and 1200 g was single crystallized. The rest became polycrystalline. T _A (617 ° C.) and T _B, T _C, the temperature difference between T _D each is _{2.1 ℃, T B, T C} , the temperature of T _D is lower than all T _A, growing, As the T _A portion It was adhered to the outer peripheral portion except for. Above, GF
Although the method using the method has been described, the method can also be applied to the case using the horizontal Bridgman method using a quartz reaction tube. All thermocouples were chromel. I am using an alumel thermocouple.

[Effects] As described above, in order to control the As pressure over the entire growth period at a precisely set temperature, frost processing is performed around the As pressure control position of the quartz reaction tube, and It is possible to drastically reduce the propagation of
The yield of single crystallization can be improved, and it can be used for precise control of the composition ratio.

Further, since a conventional quartz reaction tube subjected to frost processing may be used, the manufacturing cost hardly increases.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 2 shows the temperature condition of each part in the embodiment of the present invention. FIG. 3 is an explanatory view of a conventional GaAs manufacturing method and a quartz reaction tube. 1 ... Quartz reaction tube, 2 ... Seed crystal, 3 ... GaAs melt,
4 ... Quartz boat, 5 ... Diffusion barrier, 6 ... As, 7
...... As pressure control thermocouple, 8 frost processing section.

Claims (2)

[Claims] 1. A method for growing a single crystal from a gallium arsenide melt in a horizontal boat installed in a closed quartz reaction tube under a constant arsenic pressure, wherein the quartz reaction tube is adjacent to an arsenic pressure control point. A method for producing a gallium arsenide single crystal, characterized by performing frosting and maintaining the arsenic pressure control point at the lowest temperature in a quartz reaction tube. 2. A quartz reaction tube used in a method of growing a single crystal from a gallium arsenide melt in a horizontal boat installed in a closed quartz reaction tube under a constant arsenic pressure. A quartz reaction tube characterized by having a frosted portion on the surface or a part of the inner surface or a part of the inner surface or a part of the inner surface of the quartz reaction tube adjacent to the point.