JPS58176193A - Preparation of single crystal of inorganic compound - Google Patents

Abstract

PURPOSE:To obtain a single crystal of good quality with a few crystal defects of a specific inorganic compound, by preparing the single crystal of the inorganic compound with a boat for growing the single crystal at a specified temperature by the gradient freezing (GF) method. CONSTITUTION:A seed crystal of a compound of Groups III-V and a polycrystal or an element to be a raw material of Group III are introduced into a boat for growing single crystal and a corresponding element of Group V are sealed up in a sealed tube to generate the vapor pressure of the element of Group Vcorresponding to the dissociation pressure near the melting point of the compound of Groups III-V. In case the element of Group III is contained in the boat for growing the single crystal, the element is reacted with the element of Group V in the process of growing the single crystal to form a compound of Groups III-V and produce a melt thereof. For growing the single crystal, the temperature of the boat is set to be not lower than the temperature range within 15 deg.C on the low temperature side from the melting point of the above-mentioned inorganic compound and give within 20 deg.C temperature difference between the high and low temperature parts of the boat.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a single crystal of an inorganic compound (hereinafter referred to as an RI-V group compound) consisting of elements of group 4 and group V of the periodic table.

Gallium arsenide (CaA@), indium arsenide (InAs)
), gallium phosphide (GaP), and other ■-V group compound single crystals are used in light-emitting diodes, semiconductor lasers, and high-frequency (
It is mainly used for manufacturing elements such as FETs and Gunn diodes for UHF and SHF bands.

These Iff-V group compound single crystals were prepared by temperature gradient method (G
F method), horizontal Bridgman method (HB method), and other boat growth methods are often used.

According to the Boat Growth Method, this is 11%6・Fist...
...Fist/Fist e...- This is because a single crystal with a fixed shape can be obtained compared to the pulling method (CZ method). In particular, the GF method
Unlike the HB method, there is no need to move the heating furnace, so it is suitable for producing large single crystals. 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 (one arbitrary scale). M
, P, is the melting point of the [-V group compound. The horizontal axis indicates the length (arbitrary scale) in the crystal growth direction.

/, 2 and 3 are curves showing temperature distribution. 2 is a vertical cross-sectional view of a single crystal growth port shown on the same scale as the horizontal axis. This is the seed crystal installation part for Slma, Bo)+.

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 create and move such a temperature distribution, it is common to divide the electric furnace into 4-A parts and sequentially control each part. In this case, a temperature gradient of about /C/cm is usually used. However, the total length of the boat for single crystal growth is 17
When it is 9 cm or more, the difference in temperature between the low temperature part and the high temperature part becomes large, so crystal defects are likely to occur, and contamination by the 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 smaller, 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 portions that are not in contact with the seed crystal, and there are many cases where single crystals do not form.

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

The above objects of the present invention are as follows:
In the method of manufacturing by the method, the temperature of the single crystal growth port is not lower than the temperature within 15°C on the low temperature side from the melting point of the Ill-V group compound, and the temperature of the high temperature part and the low temperature part of the boat is This is achieved by a method characterized in that the temperature difference is within 20°C.

In the method of the present invention, in order to accommodate and grow a seed crystal of a group IV compound, a polycrystal serving as a raw material, or a group A group IV compound is reacted with an element of group 8 and a group 8 element, and a melt of the compound is produced.

When growing a single crystal, the seed crystal part is
- Within 15°C of the lower temperature side than the melting point of the V group compound, preferably
+'! / Set a predetermined temperature within a range of 0℃, that is, the lower limit temperature or a higher temperature within the above rt and rqh, and increase with a predetermined temperature gradient toward the other end of the boat. Set the temperature distribution as follows. It is unsuitable to lower the temperature of the seed crystal portion by more than 73° C. below the melting point of the Ill-V group compound because crystal defects will increase due to distortion caused by shrinkage due to temperature changes. The temperature gradient is preferably 0.3'C7cm -2C7cm, and 1℃
/('rn~15℃/cm is more preferable. When the temperature gradient exceeds 1℃/cm, crystal defects increase due to thermal contraction, and when it becomes less than Q, 51?: , /Crn, @ degree gradient control becomes impossible. This is not appropriate as it will be difficult.In this case, the temperature of the high temperature part is 20% higher than the predetermined temperature, that is, the temperature of the low temperature part.
The temperature higher than 5° C., preferably 5 to 10° C., that is, the portion beyond the point where the upper limit temperature is reached (the portion farther from the seed crystal) is kept constant at the temperature. When kept at a temperature higher than the above temperature, compounds with high melting points, such as GaAg
(Melting point/23 g° C.) is not suitable because contamination from the boat material (quartz, etc.) is likely to occur and it is necessary to use a special heating element such as SiC as the heating element for the electric furnace. After each part of the quartz boat reaches a predetermined temperature, normal G
Similar to the F method, crystals are grown by lowering the degree of crystal growth.

The process of temperature reduction accompanying the crystal growth described above will be explained using the 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 FIG. 1, the vertical axis in FIG. 2 represents humidity, and M and P represent melting points. Horizontal axis: ・Ma,
Represents the length in the crystal growth direction.

Further, 6 is a vertical cross-sectional view of the single crystal growth port expressed on the same scale as the horizontal axis. 7, g and 9 are curves showing temperature distribution. The letters and numbers written on the vertical axis are the predetermined limit temperature (upper limit temperature) of the high temperature portion and the predetermined limit temperature (lower limit temperature) of the low temperature portion, respectively. As the temperature distribution changes from the state shown by curve 7 to the state shown by curve 9, the single crystal is cut to length.

When starting crystal growth, the temperature of the seed crystal part is determined by one day from the lower limit temperature until it reaches a predetermined upper limit i; Similarly, use + to maintain a constant temperature.

According to the method of the present invention, the part where the 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 crystal defects can be obtained. Furthermore, when growing a single crystal of a high melting point IV 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)
Since the temperature is not as high as lλtio-i2so°C, which is around /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 of the electric furnace, unlike SiC, the heating element can be wound into a coil shape, making temperature control easier.

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

Example 1 Inner diameter 30fl, total length 11! ;0ran, Si-doped GaAs polycrystal was placed in a quartz boat with a semicircular cross section.
I charged 1. The growth direction is determined using a seed crystal (///
) As direction. As shown in FIG. 3, this boat was sealed together with arsenic (As) under reduced pressure in a sealed quartz tube and placed in an electric furnace. That is, FIG. 3 is a longitudinal sectional view of the single crystal growth apparatus. lθ is the furnace tube. 1.
/- is a sealed tube made of quartz. /2 is As and GaA
Used to prevent decomposition of s. 13 is a sealed tube //
Partition wall /3 separates the quartz boat enclosing part and the As enclosing part, and the partition wall /3 has a capillary-like pore, and the above-mentioned two parts are connected through the pore. /Q is a boat. Reference numeral 15 denotes an electric furnace for heating the boat, which is divided into five parts. 16 is an electric furnace for heating As/2 to about A10° C. to generate As pressure (about 1 atmosphere). At the start of crystal growth, the electric furnace/6 was heated to t,io℃.
The end of the boat was heated to 15°C and seed crystals were placed in an electric furnace.
It was heated until the upper limit temperature reached 2'10°C.

After each electric furnace reaches a predetermined temperature, the lifting speed is 06℃/h.
The temperature was lowered to r to promote crystal growth. 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 33 hours.

Of the obtained GaAs crystal rods, a portion corresponding to 1.0% was single crystallized. Etch P
it) density q (EpD) and carrier concentration are gX
102/cd, 4 x to17/ctd. Same (, tAo arrangement part EPD Otsu X 102/c'
! , carrier concentration 1! ;X 1018/cel
It was l.

EXAMPLE A quartz boat having a semicircular cross section with an inner diameter of 70III+ and a total length of 3 gOrm was charged with 3300f of Si-doped GaAs 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 respectively i5X/0'/(It
.

Muko x t O" / 7 s and tgorrrm each 12 x to" / cI! ”, 10X/OI8
/ It was 7.

Example 3 Metallic gallium/& Otsu 01 in a quartz boat similar to Example 3
and chromium (Cr) 0.22μ. In addition, 20001 As was sealed in the As-filled part of the sealed tube //.

A single crystal was grown for 70 hours in the same manner as in Example 1. Among the obtained crystal rods, the SO group was found to be single crystallized. EPD
is the part of gθ from the seed crystal edge, 2. SX/03
/cd, same 200rftm part /1Xto3/cr
/l. The St content (analyzed by SIMS) is
In the same torn, /2

Example 9 The lower limit temperature is / / 232'C, the upper limit temperature is 72'L
Example 1 except that the temperature gradient was 0°C and /S°C/crn.
A GaAs single crystal was grown in the same manner as above. 33% of the obtained GaAs crystal rods were single crystallized. EPD 9 Xt o at the gOrun position from the seed crystal side end
2/7. What is your career A degree? X/o 17/
It was ctd. EPD7×101 at the same 230 city location
7/7-, carrier concentration a3x to18/ crd
Met.

Comparative example: Temperature gradient: 1/1:/Cm, cooling rate: 06°C
/hr, and the temperature at the end of the initial seed crystal side is /23'IC
A GaAs single crystal was grown by the conventional method without setting an upper temperature limit or a lower limit temperature. Of the obtained crystal rods, 50% were single crystallized.

EPD and carrier concentration are g from the seed crystal side end.

- position, ti-x to3/ad, t, respectively.
s x/ 017/ cttl, same 200rlrM
(r) Position Te, Tsuretsure, KoX / 03/ 7%i
g X/0”/6d.

[Brief explanation of the drawing]

The qt diagram 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. /, ko, 7, g and evening...Temperature distribution curve l/...Sealed tube patent applicant Mitsubishi Monsan Doo Kasei Co., Ltd. Agent
Person Patent attorney Hase = (1 other person) Figure 1

Claims (1)

[Claims] (1) In a method for producing a single crystal of an inorganic compound consisting of an element of group Ⅰ and an element of group V of the periodic table by a temperature gradient method, the temperature of the single crystal growth 11'' boat is on the lower side 73 from the melting point of the inorganic compound. The temperature does not drop below the range of ℃, but the temperature difference between the hot and cold parts of the boat is 2.
A method characterized in that the temperature is within °C.