JPS58156599A - Preparation of 3-5 group compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To obtain a high-quality single crystal, by applying a definite temperature gradient in a high temperature furnace containing a quartz boat for the growth of a III-V group compound, and shifting the boat along the direction of length keeping the temperature of the boat constant as detected by the thermocouple mounted near the boat. CONSTITUTION:A reaction tube 3 is inserted into the high temperature furnace 1 composed of a plurality of zones M, S1, S2 and S3, and a boat 4 containing molten GaAs 6 and a seed 5 is inserted into the reaction tube 3. A definite temperature gradient is formed along the reaction tube 3 by using the thermocouple T1 mounted at the zone M near the boat 4 as a reference temperature detector, and controlling the other zones with reference to the zone M. The thermocouple T2 placed near the boat 4 is shifted along the length of the boat 4 while controlling the heating current of each zone to maintain the temperature detected by the thermocouple T2 to the melting point of GaAs. A GaAs single crystal having low dislocation density can be prepared by this process, easily, economically, in high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a ■-■ group compound semiconductor single crystal by a port growth method.

(2) The case of gallium arsenide (GaAs) will be explained as an example of the method for manufacturing a V-group compound semiconductor. Horizontal Bridgman method (HB method) is a single crystal production method using the boat growth method.
is common. In this method, the quartz glass reaction tube is fixed independently of the electric furnace using a support such as a soaking tube, and the electric furnace is moved in the length direction of the port for crystallization, but it has the following drawbacks. There is.

(1) The entire device becomes long and large.

(2) A moving mechanism for the electric furnace is required, which is complicated and expensive.

(3) Supports for heat soaking tubes and the like are expensive and easily deformed by heat.

From this viewpoint, the temperature gradient method (OF method) described below has been reviewed. The OF method is a method in which a temperature gradient is provided in the length direction of the boat, and the temperature is lowered while keeping this temperature gradient constant to crystallize. That is, this is a method that only uses temperature control without moving the electric furnace or ports.

This method raises the temperature of the system to 1260-1280°C, so deformation of the reaction tube etc. is a slight problem, but since no mechanical drive is required, the equipment is simple, and the electric furnace can be moved. Vibrations caused by this do not disturb crystallization.

Further, it has the advantage that a long soaking tube is not required and only a support for installing the reaction tube in the furnace is required.

However, one of the major problems with the GF method is that it is difficult to maintain a constant crystal growth rate. That is,
An electric furnace is divided into several zones in the longitudinal direction to keep the temperature gradient constant in each part, but in reality it is difficult to obtain a uniform temperature gradient, and the temperature distribution in the longitudinal direction is uneven by the number of zones. will occur. Normally, crystallization occurs at a constant rate of cooling, so if there are irregularities in the temperature gradient, a difference will occur in the growth rate.

Furthermore, in order to obtain a low-dislocation crystal, it is necessary to control the solid-liquid interface during crystal growth to be slightly convex or flat, but such an interface shape largely depends on the growth rate. In order to keep the growth rate constant, it is necessary to control it as follows.

(1) By increasing the number of zones in the electric furnace, the temperature (
2) Detect the solid-liquid interface using the method described by Iki et al., and control the cooling rate in feedback so that the growth rate remains constant.

The following methods are conceivable, but they have the disadvantage that the equipment is complicated and expensive.

The present invention provides a method for manufacturing a group IV compound semiconductor single crystal, which can maintain a constant crystal growth rate and obtain a high-quality single crystal even if there is some unevenness in the temperature distribution in the longitudinal direction of the boat. The aim is to control the thermocouple Tl installed in zone M near the boat of the electric furnace, which has multiple zones, as the standard, and control the other zones by setting the temperature difference with zone M. In particular, the thermocouple T2 is connected to the length of the boat while controlling the heating current in each zone to create a predetermined temperature gradient and to maintain a constant temperature sensed by the other thermocouple T2 installed near the port. The purpose is to move in the direction.

FIG. 1 is a sectional view of an electric furnace in which a manufacturing method according to an embodiment of the present invention is carried out. The electric furnace is a high temperature furnace 1 and a low temperature furnace 202.
The high temperature furnace is made up of 81"83 and 4" parts.
It consists of two zones. The quartz boat 4 for GaAs growth has reeds closest to the M zone, and a thermocouple T1 is placed close to the M zone to detect the temperature.

Also, other zones 81,
Thermocouple TS1 r installed at 82 + 83
The difference (deviation) between the temperatures of TS2 and TS3 is all
82 > 83 The temperature is guided to the deviation controller of each zone and the temperature is adjusted to keep the deviation constant. Soshite Tl
and TSI, TS2 + TS3 (!: (By appropriately determining the D deviation value, a constant temperature gradient is provided in the high temperature furnace).

A quartz boat 4 in the reaction tube 3 accommodates a seed 5 and a GaAs melt 6, and an As 7 is installed at the right end of the reaction tube 3. By positioning the T2 thermometer near the quartz boat 4 and adjusting its temperature to 1280° C., which is the melting point of QaAs, the following temperature distribution is obtained.

FIG. 2 is a diagram showing the temperature distribution in the electric furnace of FIG. 1. The solid line 9 shows the temperature distribution in the electric furnace, and the tip of the thermometer T2 is set at Tm, which is the melting point of GaAs at 1238°C, and the seed 5 is
The temperature on the side is low, and by keeping the temperature on the main body side of the quartz boat 40 high, GaAa@ liquid is generated. If the temperature of the quartz boat 4 is lowered as it is, it is the same as the normal OF method, but in this embodiment, the temperature Tm is maintained while the thermometer T2 is moved in the L direction. That is, it is first melted in the state shown by the broken line 8 and then brought to the state shown by the solid line 9, and while this state is maintained, it is moved to the left.

Since the above temperature gradient is provided in the electric furnace 1,
Moving to the high temperature side (L direction) while keeping the temperature of T2 constant produces exactly the same effect as lowering the temperature while keeping the temperature distribution constant.

Furthermore, since the crystal growth rate is determined by the moving speed of T2 regardless of the degree of irregularity in the temperature distribution, the accuracy of the temperature distribution is also relaxed.

Next, an example will be described using the growth of a GaAs single crystal as an example.

(Example) Ga400f and 5i120~ as a dopant are mixed and housed in a quartz boat 4 having a length of about 23 (Ml), and a food crystal is placed at the right end of the quartz boat 4.

This was installed at the left end of the reaction tube 3 made of quartz glass, and 444 As7 was put in the other end, and the temperature was set at 5X10'Torr.
After evacuation was performed for one hour under the following reduced pressure, the product was sealed and placed in a two-barrel electric furnace as shown in FIG.

The low temperature furnace 2 on the As side is maintained at about 610° C., and the vapor pressure of As is maintained at 1 atm. On the other hand, in the high-temperature furnace 1, a thermocouple T2 is placed near the seed 5 and the temperature is raised to perform a GaAs synthesis reaction at around 1200°C, and then the temperature is further raised to bring the temperature of the thermocouple T2 to 1238°C. The temperature gradient in the GaAs melt is adjusted to 0.5 deg/crn to perform 7-dot deposition. After that, move the thermocouple T2 in the L direction by lOm/
Move at a speed of hr.

When it is confirmed that the entire crystal has solidified 30 hours after being moved to the left end of the quartz boat 4 in this manner, the crystal is cooled to room temperature at a rate of about 100 deg/hr. This results in a width of 5 crn and a length of 23 Iy.
n GaAs single crystal 8232 was obtained, and as a result of observing its crystal growth, the growth rate was tlfflo±1
wm/hr, and it was found that the solid-liquid interface remained flat and did not fluctuate.

In addition, the (1001 plane) of this single crystal was carried out, and the molten K
When the dislocation density was measured by etching with OH, it was found that the dislocation density was 500 m except for the 5 m circumference of the part in contact with the quartz boat 4.
It was confirmed that it was a single crystal with a low dislocation density (EPD) of less than 1/-.

In the method for manufacturing a GaAs semiconductor single crystal of this example, GaAs is heated using a thermometer placed close to a seed in a quartz boat.
By slowly moving the thermometer to the end of the boat while checking the melting point of You can get the effect of

Although the above embodiment describes the growth of a GaAs single crystal, application to compound semiconductors such as indium phosphide (InP) and gallium antimony (Garb) is also possible.

The method for producing a single crystal of a ■-■ group compound semiconductor of the present invention has the following Hiko effect.

(1) The difficulty of controlling the growth rate in the OF method can be improved using a simple and inexpensive method.

(2) Even if there are irregularities in the temperature distribution inside the quartz boat, the growth rate can be maintained without causing any problems to the crystallized cow.

Or it can be changed freely.

(3) Eliminates fluctuations at the solid-liquid interface during crystal growth.

(4) As a result of the above, low dislocation density GaAs single crystals can be grown with good yield.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an electric furnace for carrying out a manufacturing method according to an embodiment of the present invention, and FIG. 2 is a diagram showing the temperature distribution in the electric furnace of FIG. 1. l...High temperature furnace, 2...Low temperature furnace, 3...Reaction tube, 4
...Quartz boat, 5...Seed, 6...Ga A
s Melt, 7...A%71 Country ZP r141f M

Claims (1)

[Claims] 1゜ In a method for producing a ■-■ group compound semiconductor single crystal in which the temperature is lowered and crystallized while maintaining a constant temperature gradient in the length direction of the boat, a zone M near the above-mentioned port of an electric furnace consisting of multiple zones is used. The thermocouple T installed in the zone M is set as the standard, and the other zones are controlled by setting the temperature difference with the zone M to create a predetermined temperature gradient,
The thermocouple T2 is moved in the length direction of the boat while controlling the heating current in each zone so as to keep the temperature detected by another thermocouple T2 installed near the port constant. ■-■ Method for producing group compound semiconductor single crystal.