JPS598690A - Preparation of gaas single crystal - Google Patents

Abstract

PURPOSE:To prepare a GaAs single crystal having high purity and low dislocation density, by using a boat assembly composed of an inner boat made of pyrolytic boron nitride and an outer boat made of a heat-insulating rigid material. CONSTITUTION:The inner boat 1 containing GaAs 4 is made of pyrolytic boron nitride and has a thickness of about 1mm.. The outer boat 2 supporting the inner boat 1 is made of a heat-insulating rigid material, e.g. quartz having a thickness of about 5mm.. The material 5 is a heat-insulating spacer. When 2.5kg of a GaAs single crystal is grown in the boat assembly without doping, a semiinsulating crystal having a specific resistance of 10<7>-10<8> excepting about 20mm. from the rear end of the ingot can be obtained. The dislocation density of the ingot excepting 20mm. from both ends of the ingot is about <=1X10<3>/cm<3>.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a GaAs single crystal.

■- Among the V group compound semiconductors, Qa As is 3i 6
Because it has a high mobility of more than twice that, it is promising as a material for high-speed ICs and is being actively developed.

Conventionally, G (JASAs) has been generally manufactured by the horizontal boat method because it is easy to obtain single crystal dislocation density crystals.

At this time, quartz is used as the material for the boat for reasons such as thermal conductivity and strength, and therefore Si is mixed into the crystal during the crystal growth process due to the reaction between quartz and Ga or Ga AS.

However, since Si forms a shallow donor level in the QaAs crystal and has a conductivity of about 1QIN2Ωcar, conventionally the level of S1 was compensated for by doping with Cr, which forms a deep acceptor level. .

The thus obtained Cr-doped semi-insulating Qa AS substrate has Cr1 in the crystal and substrate due to the segregation of Cr.
l! As a result, the characteristics of elements formed by ion implantation or the like vary widely, which is a major hindrance to IC implementation. ■After ion implantation into a semi-insulating G11AS substrate, it is common to perform heat treatment at around 800°C to activate the ions, but since Cr diffuses at this temperature, a Si donor level appears. The substrate surface becomes conductive, and its original function as a semi-insulating substrate is lost. This was a major obstacle to the realization of GaASIC.

In order to overcome the drawbacks of semi-insulating Ga AS substrates produced by the boat method, semi-insulating Ga AS substrates have recently been developed using the high-pressure pulling method.
As *crystal growth methods are being studied.

This method can use a crucible other than quartz, such as pyrolytic boron nitrite (P-BN), and pyrolytic boron nitride does not react with Ga and GaAS.

If the pulling method is used for direct synthesis using such a crucible, impurities such as Si can be reduced, and a semi-insulating substrate with a specific resistance of 10 7 Ωapt or more can be obtained without doping with Cr or the like.

However, the Qa As crystal produced by this pull-1 method has a high dislocation density, which is about 104/C#1 at the current general technology level.

When manufactured by the horizontal boat method, it was less than 10 3 /ci, and it is clear that the characteristics of the device manufactured by the pulling method are insufficient.

As explained above, conventionally, when using the horizontal boat method, boats made of pyrolytic boron nitrite are unsuitable in terms of thermal conductivity, and quartz boats have the disadvantage that high-purity crystals cannot be obtained. , also pull-FP'1i
However, the disadvantage was that crystals with low dislocation density could not be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a manufacturing method capable of solving the above-mentioned drawbacks of the prior art and producing a GaAS single crystal with high purity and low dislocation density.

In other words, the gist of the present invention is based on the horizontal boat method, where the boat has a double structure, and the inner boat in contact with GaAs has a Q.
A cross-sectional rigid body that uses a pyrolytic boron nitride <P-BN) type boat that does not react with a and Ga AS, and is generally inscribed in the outer wall of the inner boat, and has the functions of mechanical reinforcement and heat balance. The purpose is to arrange the outer bow 1 of the material.

Pyrolytic boron nitride has excellent strength even at the melting point of Qa AS of 1238°C or higher, and
s is a substance that does not react.

Generally, pyrolytic boron nitrite is 20
00' CLX-1- is produced by a vapor phase method at a high temperature, has a wall thickness of about 1 mm or less, and has a comparative 439 flexibility. Thick walls are difficult to manufacture and are extremely expensive. Therefore, when used as a boat,
It deforms due to the weight of Qa As, and it is difficult to use it alone. In addition, during GaAS crystal growth, the thermal conductivity of the boat affects the crystallization interface shape and becomes a factor in the generation of dislocations. Even if it is thick, it cannot be used alone.

The configuration of the present invention will be specifically explained with reference to drawings showing embodiments.

1 and 2 are cross-sectional views showing examples of a vI type boat and a reaction tube used in the manufacturing method of the present invention, in which a horizontal boat with a two-layered structure, inside and outside, is arranged inside a quartz reaction tube 3. .

The inner boat 1 containing the Ga AS 4 is made of pyrolytic boron nitride and has a thickness of, for example, 1 m.
It is about m.

The outer boat 2 supporting the inner boat 1 is made of a heat insulating rigid material, for example, quartz with a thickness of about 5#. 5
is an insulating spacer.

2.5' without doping using such a boat.
When a GaAS single crystal of j was grown, a semi-insulating crystal with a specific resistance of 10' to 108 Ωα was obtained except for the 20 m at the rear end of the ingot, and a dislocation density of 1 × 103/cd was obtained except at 20 trm at each of the front and rear ends of the ingot. It was below.

There was almost no deformation of the boat, and there was almost no damage to the pyrolytic boron nitride.

As is clear from the above explanation, according to the manufacturing method of the present invention, since pyrolytic boronide is used for the inner boat that contacts QaAs, there is no need for Cr doping and high purity (3a It is possible to obtain an As single crystal, and at the same time, since it is a horizontal boat method and a heat insulating rigid material is used for the main outer boat, a GaAs single crystal with a low dislocation density can be obtained.

Such a <Z high quality GaAs single crystal has not yet been achieved by any other method, and will greatly contribute to the development of GaΔSIG and devices.

[Brief explanation of the drawing]

1 and 2 are sectional views showing two examples of a horizontal boat and a reaction tube used in the manufacturing method of the present invention. 1: Inner boat made of pyrolytic boron nitrite, 2: Outer boat, 3: Quartz reaction tube, 4: GaAS melt, 5: Heat insulating spacer. 7- Figure 1 Calculation Z

Claims (1)

[Claims] 1. In a method for producing a GaAs single crystal by disposing a horizontal boat in a quartz reaction tube 3 and storing GaAs 4 in the horizontal boat, the horizontal boat is a two-layered boat with an inner and outer layer. A method for producing a GaAs single crystal, characterized in that the inner board 1 in contact with GaAs is made of pyrolytic boron nitride, and the outer board 2 is made of a heat-insulating rigid material. 2. The method for producing a GaAs single crystal as described in the preceding paragraph, characterized in that the outer boat 2 is made of quartz.