JPH07257993A - Method for growing bulky single crystal - Google Patents

Abstract

PURPOSE:To provide a method for growing a bulky single crystal by which a bulky single crystal with good shape can be formed on a seed crystal in a vapor phase by a chemical transport method with a vertical growth device by covering the peripheral part of the surface of the seed crystal with a cover. CONSTITUTION:When starting material for a crystal is disposed in the upper high-temp. region of a vertical growth vessel and it is sublimed to grow a single crystal on a seed crystal disposed in the lower low-temp. region, the peripheral part of the surface of the seed crystal is covered with a cover preferably coated with a film having properties of subliming crystal nuclei and inhibiting crystal growth. Carbon or SiC is suitable for the coating material. Quartz, carbon, pBN or Al2O3 may be used for the material of the cover but the quartz is especially suitable. The starting material is disposed in the high- temp. region in cobmination with halogen if necessary. This method is fit to obtain a bulky single crystal of a II-VI compd. semiconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for vapor phase growing a bulk single crystal on a seed crystal by a chemical transport method such as a sublimation method or a halogen transport method, and more particularly to ZnSe, ZnS, II-V such as ZnSSe and CdTe
This method is suitable for growing bulk single crystals of Group I compound semiconductors.

[0002]

2. Description of the Related Art FIG. 4 is a conceptual diagram of an apparatus for vapor phase growing a bulk crystal on a seed crystal by a chemical transportation method such as a sublimation method or a halogen transportation method. A raw material container 2 is provided above a vertical growth container 1 made of quartz, crystal powder as a raw material 3 is charged therein, and a seed crystal 6 is installed at the bottom of the growth container 1. After sealing the growth container 1, the raw material 3 is heated to a temperature T ₁ , the seed crystal 6 is heated to a temperature T ₂ , and a temperature difference ΔT (= T ₁ −T ₂ ) is generated between the raw material 3 and the seed crystal 6. By providing the temperature gradient as shown in FIG. 5, the sublimated raw material gas is transported onto the seed crystal for crystal growth. Note that the above temperature difference Δ
T is usually set within 10 ° C.

[0003]

The present inventors tried crystal growth of ZnSe by the sublimation method using the vertical growth apparatus of FIG. 4, but could not obtain a bulk single crystal. When the temperature difference ΔT between the high temperature region and the low temperature region is set higher than 10 ° C., a polycrystal grows not only on the seed crystal surface but also on the inner wall surface of the growth container around it as shown in FIG. 4 to obtain a single crystal. I couldn't. In addition, the temperature difference ΔT is 0 <ΔT ≦ 1
When the crystal growth of ZnSe was tried in the range of 0 ° C., no crystal growth was observed on the inner wall surface of the growth container, but the crystals on the seed crystal were still polycrystalline.

Therefore, the present invention solves the above-mentioned drawbacks,
An object of the present invention is to provide a method for vapor-depositing a bulk single crystal having a regular shape on a seed crystal by a chemical transport method such as a sublimation method or a halogen transport method using a vertical growth apparatus.

[0005]

According to the present invention, (1) a crystal raw material is placed in a high temperature region above a vertical growth vessel for sublimation,
In a method for growing a single crystal on a seed crystal arranged in a lower temperature region, a method for growing a bulk single crystal, which comprises growing a peripheral portion of a seed crystal surface with a cover,
Alternatively, (2) the method for growing a bulk single crystal according to the above (1), characterized in that halogen such as I, Cl and Br is arranged in a high temperature region together with the crystal raw material. The halogen can be added in the elemental state or as a halide of the element constituting the crystal.

It is preferable that the cover for covering the peripheral portion of the seed crystal used in the present invention is coated with a film having a property of sublimating crystal nuclei and suppressing crystal growth. Carbon and SiC are suitable as the coating material. The cover material is quartz, carbon, pB.
N, Al ₂ O ₃ or the like can be used.

The growth method of the present invention is suitable for growing a bulk single crystal of a II-VI group compound semiconductor. In these growths, the temperature difference ΔT between the high temperature region and the low temperature region is
The larger the rate, the higher the feed rate of the raw material gas and the higher the productivity of the single crystal, but the more likely it is to be polycrystallized. It is more preferred to grow in the range of 10 to 30 ° C, especially 10 to 20 ° C when using the above film coated cover, but 0 to 10 ° C, especially 3 to 10 when using the uncoated cover. More preferably, it grows in the range of -7 ° C.

[0008]

The inventors of the present invention observed that a crystal grown on a seed crystal by a chemical transport method such as a sublimation method or a halogen transport method was cut from various angles and its cross section was observed. It was found that the seed crystal was generated from the peripheral part, especially the edge part. In this, the polycrystal generated at the edge part of the seed crystal in the initial stage of growth engulfs the single crystal grown in the central part of the seed crystal, and finally the whole is polycrystallized. Although the details of the generation of the polycrystal at the edge portion are not clear, it is considered that it is caused by a fine chipping of the peripheral portion of the seed crystal that occurs at the seed crystal preparation stage or when the seed crystal is mounted in the growth container.

Therefore, in the present invention, by covering the peripheral portion of the seed crystal with a cover and growing it, it is possible to prevent the generation of polycrystals, and it is possible to obtain a bulk single crystal having a regular shape. . Further, by keeping the surface of the cover at a temperature higher than that of the seed crystal surface, even if the crystal nuclei are once generated, they are immediately sublimated and the growth of the crystal nuclei can be suppressed. In addition, it is preferable to have a property of promoting transport of the source gas to the seed crystal by forming a temperature gradient in the radial direction of the growth container.

In the present invention, in order to secure the above characteristics,
By using a cover coated with carbon or SiC, the cover surface temperature can be kept higher than the seed crystal surface, and as a result, it is possible to prevent the generation of polycrystals and to grow a well-shaped single crystal. did. The carbon coating may cover both sides of the cover by a CVD method, a vapor deposition method, or the like. Also, the cover material is
Quartz, carbon, pBN, Al ₂ O _{3 and the} like can be used, but quartz is particularly suitable because of its high workability, relatively high purity, and easy availability.

FIG. 1 is a conceptual view of a single crystal growth apparatus for carrying out the method of the present invention, and FIG. 2 is a plan view of a cover used in FIG. FIG. 3 is a modification of FIG. 1, and differs from FIG. 1 in that a cover provided with a carbon film is used. A raw material container 2 for containing a raw material 3 is arranged above the vertical growth container 1, and a ring-shaped cover 5 is placed on the seed crystal 6 in the concave portion at the bottom, and a temperature gradient as shown in FIG. By holding, the bulk single crystal 4 is formed on the seed crystal. In FIG. 3, a quartz cover whose surface is coated with a carbon film is used.

[0012]

【Example】

(Example 1) ZnSe by sublimation method using the growth apparatus of FIG.
Bulk single crystals were grown. The cylindrical vertical growth vessel is a quartz vessel having an inner diameter of 30 mm and a height of 150 mm. As a raw material, 50 g of high-purity ZnSe powder was filled in a raw material container, and a (100) -faced ZnSe single crystal (5 × 5 mm) seed crystal was placed at the bottom of the growth container. An annular cover having an inner diameter of the central hole of 4.5 mm and a thickness of 1 mm was placed on the seed crystal to cover the peripheral portion of the seed crystal surface. Then, when the raw material was kept at 1065 ° C. and the seed crystal was kept at 1060 ° C., and growth was performed for 10 days under the condition of ΔT = 5 ° C.,
Zn with a size of 10 × 10 × 15 mm ³ and a regular shape
An Se bulk single crystal could be obtained. The same experiment was repeated, but the reproducibility was extremely good. Also,
A similar experiment was conducted by selecting ΔT in the range of 0 to 10 ° C. However, in this range, polycrystallization did not occur, and a single crystal similar to the above could be obtained.

(Example 2) In the same manner as in Example 1, except that the surface of the cover was coated with a carbon film having a thickness of about 10 μm, and the raw material was kept at 1075 ° C and the seed crystal was kept at 1060 ° C. Bulk single crystals were grown. That is, when the growth was performed for 10 days under the condition of ΔT = 15 ° C., a ZnSe bulk single crystal having a size of 15 × 15 × 20 mm ³ and a regular shape could be obtained. The same experiment was repeated, but the reproducibility was extremely good. Further, a similar experiment was conducted by selecting ΔT in the range of 10 to 30 ° C. However, in this range, polycrystallization did not occur, and a single crystal similar to the above could be obtained.

(Example 3) The plane orientations of the ZnSe seed crystals used in Examples 1 and 2 were changed from (100) to (11).
1) Crystal growth was carried out in the same manner as in Example 1 and Example 2 except that it was changed to A and (111) B, and a ZnSe bulk single crystal having a regular shape was grown in the same manner as in Example 1 and Example 2. I was able to do it.

(Example 4) Same as Example 1 except that high-purity ZnSe powder and solid iodine were filled in a raw material container and the raw material was changed to 855 ° C and the seed crystal was changed to 850 ° C. When a ZnSe bulk single crystal was grown as described above, the ZnSe having a regular shape as in Example 1 was formed.
A bulk single crystal could be obtained, and its reproducibility was extremely good. Further, a similar experiment was conducted by selecting ΔT in the range of 0 to 10 ° C. However, in this range, polycrystallization did not occur, and a single crystal similar to the above could be obtained.

(Example 5) In the same manner as in Example 1, except that the raw material container was filled with iodine together with high-purity ZnSe powder and the carbon-coated quartz cover used in Example 2 was used. When a ZnSe bulk single crystal was grown by using the same, it was possible to obtain a ZnSe bulk single crystal having a regular shape as in Example 1, and the reproducibility was extremely good. Also, within the range of 10 to 30 ° C, ΔT
Was selected and the same experiment was carried out, but within this range, a single crystal similar to the above could be obtained without polycrystallization.

[0017]

According to the present invention, by adopting the above-mentioned structure, it is possible to prevent the generation of polycrystals from the peripheral portion of the seed crystal arranged at the bottom of the vertical growth container and the inner wall of the container, and to prevent the generation of polycrystal on the seed crystal. Enabled the growth of bulk single crystals of quality.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an apparatus for growing a bulk single crystal for carrying out the method of the present invention.

FIG. 2 is a plan view of the cover used in FIG.

FIG. 3 is a conceptual diagram of a bulk single crystal growth apparatus, which is an application example of FIG. 1, using a cover having a carbon film.

FIG. 4 is a conceptual diagram of a conventional bulk single crystal growth apparatus.

5 is a graph showing a temperature distribution in the vertical growth container of FIG.

Claims (6)

[Claims] 1. A method of growing a single crystal on a seed crystal arranged in a high temperature region above a vertical growth container and sublimating the raw material, and arranging a peripheral portion of a seed crystal surface in a peripheral region of the seed crystal surface. A method for growing a bulk single crystal, characterized by covering with a cover and growing. 2. The method for growing a bulk single crystal according to claim 1, wherein halogen is arranged in a high temperature region together with the crystal raw material. 3. The bulk according to claim 1, wherein the cover covering the peripheral portion of the seed crystal surface is coated with a film having a function of sublimating crystal nuclei and suppressing crystal growth. Single crystal growth method. 4. The method for growing a bulk single crystal according to claim ₃ , wherein a cover made of quartz, carbon, pBN or Al ₂ O ₃ coated with a carbon film or a SiC film is used. 5. A method for growing a bulk single crystal of a II-VI group compound semiconductor by the method according to any one of claims 1 to 4. 6. The method for growing a bulk single crystal according to claim 5, wherein the temperature difference between the high temperature region and the low temperature region is maintained at 30 ° C. or less.