JPS5935880B2 - GaSb single crystal pulling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for pulling a GaSb single crystal by a liquid capsule pulling method, a so-called LEC method, for pulling a single crystal from a raw material melt covered with a liquid capsule.

GaSb is a type of ■-V compound semiconductor, and is used in Inl-xGaxSb mixed crystals and Inl-xGaxSb mixed crystals for functional devices.
It can be used as a substrate crystal for l-xAlxSb mixed crystal, or as a substrate crystal for GaAs1-xSbx mixed crystal or Gal-yA1yAs1-xSbx mixed crystal for light-emitting/receiving devices for optical communication, and more recently for optoelectronic composite devices and optoelectronic composite integrated circuits. Multilayer materials and superlattice materials (e.g. GaSb/
This crystal is useful as a substrate crystal for AlSb-based superlattices, etc.).

As methods for producing GaSb single crystals, the horizontal Bridgman method, band melt method, single crystal pulling method, double crucible single crystal pulling method, etc. have been known for a long time.

However, GaSb is very easily oxidized, and the oxide is GaSb.
Since it is stable at the melting point of Sb, it floats on the surface of the melt as so-called scum, causing twinning and abnormal growth. Recently, liquid capsules suitable for GaSb (
KCl/NaCl eutectic material, B2 as inert liquid)
O3/Na3AlF6 mixed materials have been developed, and GaSb single crystals can now be pulled using the so-called LEC method.

However, GaSb exhibits strong anisotropic growth, with <111>
Although pulling a single crystal in the B direction, that is, the {111}Sb plane of GaSb, has been successful, pulling a single crystal in the <100>, <311>, or <511> directions requires strong anisotropic growth. It has not been successful due to twinning, dendrite growth, etc.

Also, when growing in the <111>B direction, significant facet growth occurs reflecting this strong anisotropy. For example, when Te is doped as an n-type impurity, Te gathers in the facet region, resulting in so-called impurity-rich growth. Form the core area. For this reason, the impurity concentration between the facet part and the off-facet part varies from 3 times to 10 times in extreme cases, making it difficult to obtain a uniform and high quality single crystal. The present invention solves the above-mentioned difficulties and provides a new LEC method that makes it possible to grow high-quality single crystals by alleviating the strong anisotropy of GaSb.

The first invention of the present invention (the invention described in claim 1) is characterized in that, in the LEC method, raw material melt is converted from Ga and Sb to KCI/NaCl eutectic material, which is a liquid capsule, or B2O.
3/Na3AlF6 mixed material, and anisotropic growth characterized in that the composition ratio of Sb in the raw material melt is larger than 52.5% and smaller than 60% in terms of atomic percent. A method for pulling a relaxed GaSb single crystal is provided.

In particular, it is possible to grow in the crystallographic <100> direction, which is important for device applications, and even when Te, which is an n-type impurity, is added, uniform and high-quality GaSb single crystals can be pulled.

Also crystallographic <011>, <111>, <211>, <3
It is also possible to pull in directions such as <11>, <411>, <511>, etc., and this has effects such as alleviating facet growth and anisotropic growth (thus preventing the occurrence of twins).

Next, in the second aspect of the present invention (the invention described in claim 5), a GaSb crystal is synthesized in advance, and a raw material melt is synthesized from this and excess Sb. The composition ratio of Sb in the raw material melt is also 5 in terms of atomic percent.
The present invention provides a method for pulling a GaSb single crystal in which anisotropic growth is moderated by more than 2.5% and less than 60%.

In this method, scum is likely to be generated from the GaSb crystal, but high-quality single crystals can be easily pulled by performing sufficient pretreatment or by using a liquid capsule in the double crucible single crystal pulling method. . As for InSb, it should be noted that a method of adding 1% or less of excess Sb is known as a method of suppressing the occurrence of twin crystals (see the specification of Patent Publication No. 12151 of 1972).

Regarding GaSb, the so-called Nativedef
ct (Ga atom substituted with Sb: G
There is an example in which the Sb composition ratio was set to 60 to 73% in order to reduce the Sb (estimated to be aSb), but there have been no reports on the relaxation of anisotropic growth or the possibility of <100> growth. (F.J.Reidetal: ゛゛GasbP
repairedfrOmNOnstOichiOichiMe
tricMelts''JOumalOfElectr
Oichi Chemical Society,. Vol. ll
3▲7, 1966, pp. 713-716).

Hereinafter, the present invention will be explained in detail by examples using the drawings. Example 1 Figure 1 shows an L diagram for explaining an example of the present invention in which a high-quality single crystal of GaSb was grown by the liquid capsule pulling method.
FIG. 3 is a cross-sectional view of the EC device.

In the figure, 1 is a pressure-resistant container that can be adjusted from normal pressure to 50°C as necessary.
It can be filled with high pressure nitrogen gas or high pressure argon gas up to atmospheric pressure.

A carbon heater 4 surrounding a quartz crucible 2 and a carbon crucible 3 is installed in a pressure vessel 1, and the crucible 3 can be moved vertically and rotated by a lower drive shaft 5.
A GaSb single crystal sheet T is attached to the upper drive shaft 6, which also allows vertical movement and rotational movement. 1st
An example of pulling in the <100> direction using the device shown in the figure will be described.

First, 500 tons of Ga with a purity of 99.9999% and Sb with a purity of 99.9999% were placed in a quartz crucible 2.
Approximately 100y of KCI/NaCl eutectic material with a molar ratio of 873v and 1:1 was contained. After filling the pressure container 1 with dry nitrogen gas, it was heated to 730° C. using a carbon heater to produce a melt 9 with Ga:Sb in an atomic percent ratio of 50%:50%.

The thickness of liquid capsule 8 was approximately 5 mm. <100
The single crystal sheet 7 cut in the > direction is adjusted by lowering the upper drive shaft 6 and gradually lowering the temperature of the melt.
I did some seeding. Increase the pulling speed to 4 -127n
wL/hour, the rotation speed of the sheet T and crucible 2 was changed from 3 to 30 times/minute, and the pressure of nitrogen gas in the pressure container was changed from 1 to 50 atm. Although the relative position of the crucible 2 with respect to the heater 4 was adjusted by raising and lowering the crucible, twins were extremely likely to occur and it was difficult to grow a single crystal. So next, Ga
A melt containing 47.5%:52.5% Sb in atomic percent was produced from Ga5OOl and Sb965y and grown at a pulling rate of 6 mm/hr.

The melting point of Ga in this composition is shown in curve 11 in Figure 2.
:Sb=50%: It was not much different from the case of 50%, and twins were still likely to occur. However, as shown in FIG. 3I, the twin crystal 15 entered, but only from one side.

Considering that when Ga:Sb=50%250%, twins always entered from both sides and crystal growth was extremely difficult, this is considered to be a considerable improvement. Still, 12 in Figure 3 I
The strong anisotropic growth shown in Fig. 13 is not sufficiently relaxed.
The cross section of the portion 14 was also flat, and twins were generated from one side from the long side 16. Example 2nd Ga:S
b is 45%:55% in atomic percent
Generate from Oy and SblO67l and raise the pulling speed to 7 at first.
<1 while gradually decreasing from mm/hour to 3mm/hour.
00> direction.

As shown in FIG. 3, the grown crystal was a good single crystal with no twins. It can be seen that the growth of the shoulder 12 is gradual, and the cross section at 13, as shown in 14, shows that the strong anisotropy characteristic of GaSb has been greatly alleviated. Katta. Note that the maximum diameter of the grown portion was approximately 50 nm.

Although this crystal is doped with Te, the electron concentration at 300K is (5±0.5)×101b within the plane of the wafer 14.
Example 3 In this example, Ga:Sb was 40% in atomic percent:
A 60% melt was produced from Ga5OOy and Sbl3lOV, and a <100> single crystal of GaSb was grown under the same conditions as in Example 2.

The grown crystal was a single crystal, but as shown in Figure 3, after the shoulder 12 grew gently, the cross section also became 1 at the position 13.
As shown in Figure 4, although it is clear that the anisotropy has been relaxed, as it grows, the crystal collapses like IT, and the so-called supercooling phenomenon becomes noticeable.
However, in the section 13, there was no Te core region and the electron concentration at room temperature was uniform.

In this way, the composition ratio of Sb is 52.5% in atomic percent.
By making it larger and smaller than 60%, GaSb
It was found that the strong anisotropic growth of the <100> crystal can be alleviated, and that even when doped with Te, a high-quality single crystal with a uniform electron concentration without a core region can be obtained within the wafer plane.

Example 4 Melt having the same composition as Example 2, that is, Ga:Sb=45
%: Crystallographic directions other than <100> from 55% melt 2 <011>, <111>, <211>, <311>, <
511>.

Other growth conditions were the same as in Example 2.

Ga:Sb- Growth from 50%:50% melt <1
Although it is difficult except for <11>, in this example, <100>
Similarly, single crystal growth was easy. However, the symmetry of the cross section of the crystal changes, so it becomes closer to a triangle or pentagon. Growth conditions can be easily modified in addition to those detailed above.

For example, Se or Sn may be used as an impurity instead of Te, or Zn or Ge may be used as an impurity. Also Ga:Sb
As the ratio approaches 40% to 60%, the rate at which the composition of the melt changes with the growth of the crystal increases, so the pulling rate of the single crystal increases from the initial 4-12 k/hr to 1 as the growth progresses. It is preferable to gradually reduce the speed to -3 mm/hour. Furthermore, although Ga and Sb are used as starting materials in the above embodiments, GaSb and Sb synthesized in advance may also be used.

For example, a melt of Ga:Sb=45%:55% can be produced using GaSb 1373V and Sbl94y as starting materials.

However, since GaSb is easily oxidized in this method, it is desirable to perform pretreatment and drying in an inert gas or reducing gas, or to use a double crucible method in combination.

As detailed above, the present invention provides <100> and <Nl
GaSb in l>(n=0, 1, 2, 3, 4, 5) direction
The present invention provides a novel LEC method that not only allows the growth of single crystals with good yield, but also allows the growth of high-quality GaSb single crystals with uniform impurity distribution in the cross section, and particularly has the following effects. (I) Large <100> with a cross section of approximately 50 groups 1φ
Growth GaSb single crystals can be grown.

(Also, the yield of large <Nll> grown GaSb single crystals is greatly improved.

The variation in impurity distribution within the cross section can be improved to ±10%.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the LEC device used in the embodiment of the present invention,
FIG. 2 is a diagram showing the relationship between the composition ratio of Sb and the melting point. FIG. 3I is a diagram of the upper part of a GaSb single crystal in an example of the present invention. In the figure, 1 is a pressure container, 2 is a quartz crucible, 3 is a carbon crucible, 4 is a carbon heater,
5 is a lower drive shaft, 6 is an upper drive shaft, 7 is a single crystal sheet,
8 is a liquid capsule, 9 is a melt, 10 is a grown crystal, and 1
1 is a curve showing the melting point, 12 is the initial growth portion, 13 is the position of the cross section 14, 15 is the twin crystal, 16 is the twin position, and IT is the collapse of the crystal.

Claims (1)

[Claims] 1. In the LEC method in which a single crystal is pulled from a raw material melt covered with a liquid capsule, the raw material melt is directly synthesized from Ga and Sb under the liquid capsule, and the raw material melt is directly synthesized from Ga and Sb under the liquid capsule. The composition ratio of Sb in the melt is 52.
A method for pulling a GaSb single crystal in which anisotropic growth is moderated by more than 5% and less than 60%. 2. The method for pulling a GaSb single crystal according to claim 1, wherein the growth direction is the crystallographic <100> direction and Te, which is an n-type impurity, is further added to the raw material melt. 3. The method for pulling a GaSb single crystal according to claim 1, wherein the growth direction is the crystallographic <n11> direction and Te, which is an n-type impurity, is further added to the raw material melt. However, n is zero or a natural number of 5 or less. 4. The method for pulling a GaSb single crystal according to claim 1, wherein the pulling rate of the single crystal is gradually reduced from 4-12 mm/hour at the initial stage of growth to 1-3 mm/hour as the growth progresses. 5 In the LEC method for pulling a single crystal from a raw material melt covered with a liquid capsule, the raw material melt is synthesized from pre-synthesized GaSb crystals and Sb under the liquid capsule, and the raw material GaSb with relaxed anisotropic growth, characterized in that the composition ratio of Sb in the melt is greater than 52.5% and smaller than 60% in terms of atomic percent.
Single crystal pulling method.