JPS5934680B2 - Single crystal manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a compound semiconductor crystal having a high decomposition pressure, such as GaP or GaAs*IaP, by a liquid capsule pulling method.

The drawing is an explanatory diagram of a GaP single crystal growth apparatus using the liquid capsule method.
The aP melt 3 and the liquid encapsulant B2O34 are thermally melted by the carbon heater 5, and the liquid surface of the GaP 3 is covered with B2034.

The inside of the pressure vessel 1 is filled in advance with N2 gas by vacuum displacement, and as the temperature rises, the pressure is increased and maintained at about 70 atmospheres during melting to prevent decomposition and evaporation of GaP.

In this state, the seed crystal 6 is immersed in the GaP melt through the B2034 layer and gradually pulled up while rotating (arrow).
An aP single crystal 7 is created.

GaP has a melting point (1470°C) and a dissociation pressure of 32 atmospheres, and the GaP melt is covered with a B2O3 melt to prevent decomposition and evaporation.

B2O3 has high viscosity even in its molten state and low thermal conductivity, so a GaP solution covered with B2O3 has a small temperature gradient below the liquid surface and is easily supercooled (and often forms polycrystals during growth). .

In particular, the growth of the so-called head portion, from seed crystal attachment until the grown crystal reaches a predetermined size, progresses in B2O3, so heat dissipation is insufficient and the solution must be gradually cooled, making it more likely to be supercooled. .

When the growth of the head portion is completed, the growing crystal is exposed on B2O3, so that heat dissipation improves rapidly and rapid growth occurs.

Since the GaP solution is supercooled due to the growth of the head portion, this rapid growth is further accelerated, making diameter control extremely difficult and also causing polycrystalization.

It is extremely difficult to return to a constant diameter once it has fluctuated greatly.

In the conventional method, the rotational speeds of the seed crystal and crucible are fixed, for example, seed crystal 10 rpm crucible 20 r.

Crystal growth is performed while slowly cooling the temperature while keeping it constant at pm-.

The amount of gradual cooling from seed crystal formation to completion of pulling is approximately 50° C. at the bottom of the crucible.

It is effective to reduce the amount of temperature drop in order to reduce the supercooling of the entire solution and prevent a decrease in yield due to diameter fluctuations and polycrystalization.

The present invention provides a method for manufacturing compound semiconductor single crystals with high quality and high yield while reducing diameter fluctuations and polycrystallization.

That is, the seed crystal and the crucible are rotated in the same direction, the rotational speeds of the two are kept different, and the slower rotational speed is gradually increased as the crystal grows (thereby, the temperature distribution inside the crucible is It is possible to correct changes in the direction in which diameter fluctuations and polycrystals are likely to occur.

Due to such rotational changes, the amount of temperature drop during the crystal growth process is reduced by about 20 factors at the bottom of the crucible, which is thought to have the effect of reducing supercooling of the solution.

1 The present invention will be explained below using an example in which the present invention is applied to the production of a GaP single crystal.

Table 1 shows the rotational speed conditions and crystal growth results for Examples 1 to 3 and the conventional method.

The lifting device shown in the conventional example (drawing) was used.

As is clear from this table, the seed crystal rotation is 5 rpm.

In the conventional pm method, in which the crucible is pulled at a constant rotation of 30°, the diameter fluctuates greatly, and the average diameter was 50° in 20 pulling experiments.
The diameter of the crucible in Example 1 was φ±12, whereas in Example 1 the crucible was
The rpm is constant, and the seed crystal is set at 0.0 rpm starting from 5 rpm.
By gradually increasing the pulling rate at 5 rpm/min, the diameter increased to 50φ±5m on average over 5 times.

In Example 2, starting from the same rotation speed as the conventional example, the seed crystal was set to 0.
．． By increasing the speed at 2 rpm/min, the average of 5 times was 50φ±4.

In Example 3, the seed crystal speed was 30 rpm and the crucible speed was 5 rpm.
Starting from , the pressure point was increased at 0.1 rpm/min.

In addition, although the polycrystal generation rate was about 20 times in the conventional method, it did not occur at all in 15 times in the example.

[Brief explanation of the drawing]

The figure is a cross-sectional view of a GaP single crystal growth apparatus used in the liquid capsule method. 1... Pressure vessel, 2... Quartz crucible, 3... Ga
P melt, 4... R2O3, 5... Carbon heater, 6... Seed crystal, 7... GaP single crystal.

Claims (1)

[Claims] 1. When creating a compound semiconductor crystal by the liquid capsule pulling method, the seed crystal and the crucible are rotated in the same direction, and the rotational speed is controlled in the direction where the relative rotational speed becomes O, starting from a rotational speed with a relative difference. A method for producing a single crystal characterized by the following.