JPH05139877A - Production of compound semiconductor single crystal - Google Patents

Abstract

PURPOSE:To provide the title single crystal improved in yield. CONSTITUTION:In a method for growing CdTe single crystal using a seed crystal by vertical Bridgman technique or vertical gradient freezing technique, a crucible made up of (A) a smaller diameter portion for the seed crystal, (B) a second portion with its diameter divergent, and (C) a cylindrical portion with constant diameter is used, and the initial growth rate within the portion A after seeding is set at >=1mm/hr and the <111> orientation the greatest in growth rate is grown prior to the other orientations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a compound semiconductor single crystal by a vertical Bridgman method or a vertical gradient freeze method, and particularly to 2-6 such as CdTe.
The present invention relates to a method for growing a group compound semiconductor single crystal.

[0002]

2. Description of the Related Art There is a method of growing a compound semiconductor single crystal by using a seed crystal by a vertical Bridgman method or a vertical gradient freeze method. This method is suitable for GaAs etc.
In the case of -5 group compound semiconductor, there is not much problem, but C
Group 2-6 compound semiconductors such as dTe have a drawback that stacking fault energy is lower than that of GaAs and that defects such as twins are likely to occur during single crystal growth. Especially when a seed crystal is used, twins and the like are likely to occur in the early stage of growth,
The growth direction often changed depending on the twin crystals that occurred. The growth orientation is an important condition for obtaining a single crystal with a high yield, and changing the crystal orientation has been a problem. Further, there is also a problem that the single crystallization itself becomes difficult because the growth orientation changes.

[0003]

The present invention solves the above problems and provides a method for producing a compound semiconductor single crystal having a stable growth orientation.

[0004]

[Means and Method for Solving the Problems] That is, the present invention relates to a method for growing a compound semiconductor single crystal using a seed crystal by the vertical Bridgman method or the vertical gradient freeze method. And a crucible consisting of a straight body portion and a gradually increasing diameter, and the initial growth rate in the small diameter portion after seeding is 1
It is intended to provide a method for producing a compound semiconductor single crystal, characterized by preferentially growing the crystal orientation of the compound semiconductor having the highest growth rate of mm / h or more. The present invention can be applied to all compound semiconductors.
It is a method for producing a compound semiconductor single crystal which is effective when applied to a Group-6 compound semiconductor, particularly a ternary or quaternary mixed crystal containing CdTe and CdTe. CdTe has a zincblende-type crystal structure and has a bond parallel to the <111> axis.
Rotational twins like those rotated by 60 ° around the 111> axis are likely to enter. Since there are three other azimuths equivalent to the <111> azimuth except for the relationship between the front and back sides, twins can enter four plane azimuths, and the twins intersect at 109.5 °. For example, in the case of growing a crystal in the <111> orientation, twins entering the (111) plane perpendicular to the growth orientation do not affect the growth orientation, but twins enter other equivalent twin planes. And the growth direction is completely different from that of the twin plane. In this way, the growth orientation changes once twins enter, but if a twin with the same plane orientation as the twin initially entered enters this changed growth orientation, the growth orientation also changes. It will return to the <111> direction. In other words, even if twins enter, if twins with the same plane orientation enter again, it will return to the original plane, and even number of twins will not change the growth orientation even if the twins become defects. Become. The present inventor has paid attention to this point and considered a method of returning to the original growth orientation by inserting a twin crystal even if the twin crystal has entered once. The <111> orientation has the highest growth rate. If the crystal is grown at a slow growth rate, the crystal can be grown stably in any crystal orientation. However, by increasing the growth rate, preferentially growing the <111> orientation, which has the fastest growth rate, Even if the growth direction changes due to twins, that direction cannot grow stably,
Twinning is likely to occur again, and eventually the original <111> orientation will be restored. The present invention has been obtained as a result of experiments and research based on the above viewpoints.

[0005]

EXAMPLES As shown in FIG. 1, a cylindrical CdTe seed crystal having a <111> orientation in the longitudinal direction was etched and washed in a small diameter portion of an inner diameter of 8 mm, and the CdTe polycrystal raw material was placed in the crucible straight body portion of the inner diameter of 80 mm. Then, the crucible was put in a quartz ampoule and sealed at a vacuum degree of 10 ⁻⁶ torr. This quartz ampoule was loaded into the crystal growth furnace shown in FIG. 2, the temperature was raised to just below the melting point of CdTe, and the ampoule lengthwise direction was 2 to 10 ° C./cm.
A temperature gradient was applied, the temperature was gradually raised, and the seed crystal was melted back to the middle thereof, and then homogenized for 30 hours. The initial growth rate in the crucible small diameter part after seeding was 0.3 mm / h, 0.6 mm / h, 1 mm / h, 1.5
Under 4 conditions of mm / h, from the growth start position to 1 mm and 2
0.5mm / h after growing up to 0mm at the above speed
It was made to grow to the straight body part at the growth rate of.

As a result, 0.3 mm / h and 0.6 mm
In all the crystals grown at / h, the growth orientation was still changed by the twin crystal in the initial stage of growth. On the other hand, 1 mm
Twin crystals were generated a plurality of times in the crystals grown at / h and 1.5 mm / h, but the final growth orientation was the same <111> orientation as the seed crystal. Also, 1 mm / h and 1.
1m from the growth start position even when growing at 5mm / h
Although the material having a growth rate of 0.5 mm / h after being grown to m did not polycrystallize, the growth rate was 0.5 mm after growing from the growth start position to 20 mm.
In some of those grown as / h, the growth orientation was returned to the original one, but there were some in which crystal grains were generated from the crucible wall and polycrystallized. From the above results, it was possible to preferentially grow the crystal orientation of the compound semiconductor having the highest growth rate by setting the initial growth rate in the crucible small diameter portion after seeding to 1 mm / h or more. The range of growth at 1 mm / h or higher must be within the range of the small diameter portion of the crucible that is affected by twin crystals entering there, and it depends on the size of the small diameter portion of the crucible, but within 15 mm from the growth start position. Range is desirable.

[0007]

According to the present invention, a single crystal can be stably grown in the crystal orientation of the compound semiconductor having the highest growth rate, and the yield of the single crystal can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of a crucible. FIG. 2 is a diagram showing a crystal growth furnace.

[Explanation of symbols]

 1 pBN crucible 2 CdTe polycrystal raw material 3 CdTe seed crystal 4 crystal growth furnace 5 quartz ampoule 6 quartz cap 7 crucible support stand

Claims (3)

[Claims] 1. A method for growing a compound semiconductor single crystal using a seed crystal by the vertical Bridgman method or the vertical gradient freeze method, which comprises a small diameter portion for putting the seed crystal, a portion where the diameter gradually expands and a straight body portion. A compound semiconductor, which uses a crucible and has an initial growth rate in the small-diameter portion after seeding of 1 mm / h or more and preferentially grows the crystal orientation of the compound semiconductor having the fastest growth rate. A method for producing a single crystal. 2. A method for producing a compound semiconductor single crystal, wherein the compound semiconductor is a 2-6 group compound semiconductor. 3. A method for producing a compound semiconductor single crystal, wherein the Group 2-6 compound semiconductor is a ternary or quaternary mixed crystal containing CdTe and CdTe.