JPS5938186B2 - Method for producing inorganic compound single crystals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inorganic compound (hereinafter referred to as a "111-V group compound") consisting of a Group I element and a Group V element of the periodic table.

) Regarding a method for producing a single crystal. Gallium arsenide (GaAs
), indium arsenide (InAs), gallium phosphide (
-V group compound single crystals such as GaP) are used for light emitting diodes, semiconductor lasers, high frequency (mainly UHF
Widely used in manufacturing elements such as FETs and Gunn diodes for
It is used.

These IV group compound single crystals can be obtained using the temperature gradient method (GF method).
, horizontal Bridgman method (HB method) and other flat growth methods.

This is because the boat growth method allows a single crystal with a fixed shape to be obtained compared to the pulling method (CZ method).

In particular, the GF method is suitable for manufacturing large-sized single crystals because it does not require moving a heating furnace unlike the HB method.

The GF method is a type of boat growth method, and as shown in FIG. 1, a single crystal is grown by moving a temperature gradient without moving a boat or furnace.

That is, FIG. 1 is a diagram illustrating changes in temperature distribution in the GF method according to the prior art.

In FIG. 1, the vertical axis indicates temperature (arbitrary scale).

M and P are the melting points of the ■-■ group compound. The horizontal axis indicates the length (arbitrary scale) in the crystal growth direction.

1°2 and 3 are curves showing temperature distribution.

4 is a vertical cross-sectional view of the single crystal growth boat shown on the same scale as the horizontal axis.

5 is a boat 40 seed crystal installation part. When growing a single crystal by the GF method, the temperature distribution curve is lowered from 1 to 3 without changing the shape of the curve, and the solid-liquid interface is moved.

In order to form and move such a temperature distribution, it is common to divide the electric furnace into 4 to 6 parts and sequentially control each part.

In this case, a temperature gradient of about 1° C./shoulder is usually used.

However, the total length of the boat for single crystal growth is 40cn1.
If the temperature is higher than that, the temperature difference between the low-temperature part and the high-temperature part becomes large, so crystal defects are likely to occur (and contamination by boat material is likely to occur in the high-temperature part, which is a problem).

On the other hand, if the temperature gradient is made small, it becomes difficult to lower the temperature uniformly over the entire length of the boat due to errors in temperature control.

As a result, solidification begins from the part that is not in contact with the seed crystal, and it often does not become a single crystal.

The present inventors have conducted extensive research aimed at solving the problems of the prior art, and as a result, they have arrived at the present invention.

The above-mentioned object of the present invention is to provide a method for producing a single crystal of a group III-V compound by the GF method, in which the temperature of the single crystal growth boat is 15 to 15 degrees lower than the melting point of the group III-V compound.
This is achieved by a method characterized in that the temperature does not drop below a range of 0.degree.

In the method of the present invention, a seed crystal of a group ■-v compound and a polycrystal as a raw material, or a group
In order to generate a vapor pressure of the Group V element corresponding to the dissociation pressure near the melting point of the Group compound, it is sealed in a sealed tube together with the relevant Group V element.

When a Group 1 element is placed in a single crystal growth boat, it reacts with the Group V element during the single crystal growth process to produce a Group 1-V compound, and its melt is produced.

When growing a single crystal, the seed crystal portion should be kept at a temperature within 15°C, preferably 10°C, of the melting point of the -V group compound.
Set the temperature to a predetermined temperature within the range specified above, i.e., the lower limit temperature or a higher temperature within the above range, and set the temperature distribution so that it increases with a predetermined temperature gradient toward the other end of the boat. Set.

The temperature of the seed crystal part is 15°C below the melting point of the ■-v group compound.
If it is lowered beyond this value, crystal defects will increase due to distortion caused by shrinkage due to temperature changes, which is inappropriate.

The temperature gradient is preferably 0.5°C/m to 2°C/m, and 1°C
/cm to 1.5°C/rust is more preferred.

If the temperature gradient exceeds 2° C./cn1, crystal defects will increase due to thermal contraction, and if it becomes 0.5° C./1 or less, it will be difficult to control the temperature gradient, which is not appropriate.

In this case, the temperature of the high temperature part is a predetermined temperature, that is, a temperature higher than the temperature part by 20 °C or less, preferably 5 to 1
The temperature 0° C. higher, that is, the portion beyond the point where the upper limit temperature is reached (the portion far from the seed crystal) is held constant at that temperature.

When held at a higher temperature than the above temperature, the boat material (
It is not suitable because it tends to cause contamination from quartz, etc. (and it is necessary to use a special heating element such as SiC for the heating element of the electric furnace).

After reaching the predetermined temperature of each part of the quartz boat, normal GF
As in the method, the temperature is lowered to grow crystals.

The high-temperature process accompanying the above-mentioned crystal growth will be explained using drawings.

FIG. 2 is a diagram illustrating changes in temperature distribution in the GF method according to the method of the present invention.

Similar to Figure 1, the vertical axis in Figure 2 represents humidity, M, P
, indicates the melting point.

The horizontal axis represents the length in the crystal growth direction. Further, 6 is a vertical cross-sectional view of the single crystal growth boat expressed on the same scale as the horizontal axis.

7, 8 and 9 are curves showing temperature distribution.

T□ and TL written on the vertical axis are the predetermined limit temperature (upper limit temperature) of the high temperature section and the limit temperature (lower limit temperature) of the low temperature section, respectively.

As the temperature distribution changes from the state shown by curve 7 to the state shown by curve 9, the single crystal grows.

The temperature of the seed crystal part may be set higher than the lower limit temperature when starting crystal growth, but as the crystal grows, after the temperature of the part reaches TL, the temperature of that part remains constant at the lower limit temperature. Hold.

Furthermore, even after the temperature of the high-temperature part reaches a predetermined upper limit temperature frost, the part beyond that point (the part far from the seed crystal) is similarly maintained at a constant temperature.

According to the method of the present invention, the part where crystallization has finished is kept at a constant temperature for a long time, so it is not annealed.
As a result, high-quality single crystals with few polycrystalline defects can be obtained.

In addition, when growing a single crystal of a high melting point ■-V group compound such as GaAs, even if an easily controlled temperature gradient is used, the growth end (the end opposite to the side where the seed crystal is placed) 1
Since the temperature is 240 to 1,250°C, which is not around 1,300°C as in the conventional case, contamination of impurities from quartz, which is the boat material, can be prevented.

Furthermore, since superkanthal wire can be used as the heating element in the electric furnace, the heating element, which is different from SiC, can be wound into a coil, making temperature control easier.

Next, the present invention will be explained in more detail based on Examples and Comparative Examples.

Example 1 Si-doped GaAs polycrystals were placed in a quartz boat having an inner diameter of 50 mm, a total length of 450 rms, and a semicircular cross section.
I charged it.

The growth direction is set to the (111) As direction using a seed crystal.

As shown in FIG. 3, this boat was sealed together with arsenic (As) in a sealed quartz tube under reduced pressure and placed in an electric furnace.

That is, FIG. 3 is a longitudinal sectional view of the single crystal growth apparatus.

10 is a furnace tube.

11 is a sealed tube made of quartz. 12 is As and GaA
Used to prevent decomposition of s.

Reference numeral 13 denotes a partition wall that separates the quartz boat-filled part and the As-filled part of the sealed tube 11, and the partition wall 13 has a capillary-like pore that connects the two parts.

14 is a boat. Reference numeral 15 denotes an electric furnace for heating the boat 14, which is divided into five parts.

16 is an electric furnace for heating As12 to about 610° C. and generating As pressure (about 1 atmosphere).

To start crystal growth, the electric furnace 16 is heated to 610°C.
It was heated to 40°C.

After each electric furnace reaches a predetermined temperature, the temperature decrease rate is 0.6℃/
The temperature was lowered to 100 hr, and crystal growth started.

After the temperature on the low temperature side of the boat reached the lower limit temperature of 1230°C, the temperature of that part was kept constant.

The GaAs single crystal growth process was completed in 83 hours.

Of the obtained GaAs crystal rods, a portion equivalent to 60% was single crystallized.

EtchPit density (EPD) and carrier concentration are 8 x 10210 A and 6 x 101 at a portion 80 rran from the seed crystal side end, respectively.
It was 7/cdl.

Similarly, E P D 6 X 1 in the 260rrrm part
02/crAs carrier concentration 1.5 x 1018/c
It was rl.

Example 2 A quartz boat with a semicircular cross section with an inner diameter of 70 mm and a total length of 380 rrvn was coated with 3300 S' of Si-doped GaAs.
Charged polycrystal.

A GaAs single crystal was grown in the same manner as in Example 1.

The time required for single crystal growth was 70 hours. 50% of the obtained GaAs crystal rods were single crystallized.

EPD and carrier concentration are 80mm from the seed crystal installation end.
1.5X103/c4.6.2 x at each position
1017/crl, 180/crl, 1 and 2 X, respectively
103/cm, 1. It was OX1018/crA.

Example 3 Metallic gallium 1460P was placed on a quartz board similar to Example 2.
and charged with 0.22 µm of chromium (Cr).

Further, 2000 S' of As was sealed in the As sealed part of the sealed tube 11.

A single crystal was grown for 70 hours in the same manner as in Example 1.

Of the obtained crystal rods, 50% were single crystallized.

EPD is 2.5 x 1 at 80mm from the end of the seed crystal.
03/crrt, 1.1×1 in the same 200rrvn part
It was 03/ctA.

The Si content (analyzed by SIMS) is 1 at 80 mm.
．． 2 x 1015/cri, 6 x at 200mm
It was 1 o14/cd.

Example 4 G was produced in the same manner as in Example 1 except that the lower limit temperature was 1232°C, the upper limit temperature was 1240°C, and the temperature gradient was 1.5°C/shoulder.
An aAs single crystal was grown.

Of the obtained GaAs crystal rods, 55 were found to be single crystallized.

EPD9×1 at a position 80rIr1n from the seed crystal side end
02/Cmz carrier concentration is 7 x 1017/Cr
It was fl.

E P D 7 X 10 at the same 230rran position
” 7/cAz carrier concentration 2.3 x 1018/c
It was nl.

Comparative example: Temperature gradient: 1.1°C/cm, cooling rate: 0.6°C/hr
At first, the temperature of the end of the seed crystal side was set to 1234°C,
GaAs is produced using the conventional method without setting upper and lower temperature limits.
Grown single crystals.

Of the obtained crystal rods, 50 pieces were single crystallized.

EPD and carrier concentration are 80 rrm from the seed crystal side end.
At position L, 4 x 103/ca, respectively, 6
．． 5 x 10"/crll, at the same 200mm position,
2 x 10"/c4゜1, 8 x 10, respectively
It was 18/cril.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the temperature distribution of the conventional GF method. FIG. 2 is a diagram showing the temperature distribution of the GF method according to the present invention. FIG. 3 is a vertical cross-sectional model diagram of a crystal growth apparatus using the GF method. 1.2, 7.8 and 9...Temperature distribution curve, 11...
Sealed tube.

Claims (1)

[Claims] 1. In a method for producing a single crystal of an inorganic compound consisting of Group I elements and Group V elements of the periodic table by a temperature gradient method, the temperature of the single crystal growth boat is within 15°C of the lower temperature side from the melting point of the inorganic compound. A method characterized in that the temperature does not drop below that range, and the temperature difference between the high temperature part and the low temperature part of the boat is within 20°C.