JP2712247B2 - (II)-Method for producing bulk single crystal of group VI compound - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a bulk single crystal of a II-VI group compound.

[Conventional technology]

II-VI group compound semiconductors such as ZnS, ZnSe and CdHgTe are expected to provide functions such as blue light emitting diodes and infrared detecting elements that cannot be obtained with group IV compound semiconductors such as Si or group III-V compound semiconductors such as GaAs. ing. Some of these II-VI group single crystals are utilized as so-called infrared window materials utilizing their optical characteristics.

It is known that such a bulk single crystal of a II-VI group compound can be obtained from a gas phase or a liquid phase by various methods such as a sublimation method and a high-pressure melting method, but iodine transport using iodine as a transport agent is known. Law. The iodine transport method has an advantage that the concentration of lattice defects can be reduced since low-temperature growth is possible as compared with the sublimation method, and a single crystal can be manufactured with a simple apparatus.

In such an iodine transport method, conventionally, a method of growing a single crystal in a sealed tube using a single crystal of several mm square as a seed crystal has been adopted. However, the single crystal obtained by this iodine transport method is slightly colored in a turquoise color, and the etch pit density, which is a measure of crystal defects, is 3 to 9 × 10 9
It was as high as ⁴ cm ^-2 . In addition, such crystals cannot be used for infrared window materials. Conventionally, thin films with a thickness of several mm are formed by thin film forming techniques such as vapor deposition, molecular beam epitaxy (MBE), and metal organic chemical vapor deposition (MOCVD). An extremely inefficient method of producing a thick film having a thickness of as much as possible has been taken.

In addition, it is difficult to attach a seed crystal in a sealed tube, and the growth process becomes complicated, for example, the powder of the raw material of the II-VI group compound adheres to the seed crystal and polycrystal growth is likely to occur, and industrial applications Not suitable for

[Problems to be solved by the invention]

Therefore, the present inventor has obtained a bulk single crystal of a II-VI compound without using a seed crystal, and reduced the coloring of the obtained single crystal and reduced the etch pit density to obtain a good quality semiconductor substrate. As a result of intensive studies to obtain a high quality bulk single crystal of a II-VI compound which can be used and also used as an infrared window material, the present invention has been achieved.

[Means for solving the problem]

That is, the gist of the present invention is to provide a method for producing a bulk single crystal of a II-VI compound by an iodine transport method in a sealed tube having one end in a conical shape, wherein a cross-section including a central axis in a longitudinal direction of the sealed tube is provided. A method for producing a bulk single crystal of a II-VI group compound, wherein a bulk single crystal is grown without using a seed crystal by using a sealed tube having an apex angle of a cone of 5 to 30 and a method for producing the same. A method for producing a bulk single crystal of a group II-VI compound, which comprises pretreating a raw material of a group II-VI compound with a group VI hydride at a temperature of 700 ° C or more and less than 1000 ° C.

 Hereinafter, the present invention will be described in detail.

In the present invention, as a method for obtaining a bulk single crystal of a II-VI group compound, iodine (I ₂ ) is used as a transporting agent, and the II-VI group raw material is reacted with iodine on the high temperature side in a sealed tube to obtain a volatile single crystal. A so-called iodine transport method is used in which the compound is transported to a low-temperature side single crystal growth region to grow a single crystal.

Single crystals of the desired II-VI group compound include ZnS, Z
Single crystals such as nSe, ZnTe, CaS, CdTe, CdHgTe and the like can be mentioned.

As a raw material for obtaining a single crystal, a high-purity compound or a high-purity powder or pellet of ZnS, ZnSe, CaS, CdTe, CdHgTe or the like is used. These starting compounds may have a purity of about 2N or 3N, but preferably have a purity of 5N or 6N.

Iodine is preferably as high as possible in reagent grade or higher purity.The amount of iodine is appropriately determined by the volume of the sealed tube, the temperature difference of the sealed tube during single crystal growth, the amount of the II-VI group compound, etc. 0.1 to 10 mg per 1 cc of the inner volume of the sealed tube,
From the relationship between the crystallinity of the single crystal and the doping amount of iodine in the single crystal, the content is preferably 0.5 to 2 mg per 1 cc of the internal volume.

In the present invention, usually, for the purpose of dehydration and removal of impurities, the raw material II-VI compound is placed in a vacuum, in a high-purity hydrogen stream, in a stream of an inert gas such as high-purity argon, or in a high-purity group VI. Heat treatment is performed in a hydride gas stream. As the Group VI hydride, hydrogen sulfide, hydrogen selenide, or the like is used, and a mixture thereof can also be used. However,
Water (H ₂ O) is excluded. Of these, hydrogen sulfide is particularly preferably used.

The gas used for the heat treatment is preferably as pure as possible, and it is necessary to prevent the incorporation of H ₂ O and O _{2 in} order to prevent hydrolysis and oxidation of the II-VI group compound. Is preferably set to a concentration of 0.1 ppm or less. It is preferable to provide a step for removing these impurities as necessary.

Heat treatment is a raw material powder or small agglomerate of the II-VI group compound,
Pellets and the like are placed in a processing vessel, and the inside of the vessel is once evacuated to 10 ^-3 Torr or less, and then the gas is introduced. The temperature is raised to a predetermined temperature while flowing the gas, and the state is maintained as necessary. It is done by doing.

The processing temperature is usually 700 ° C. or more and less than 1000 ° C., preferably 8 ° C.
It is selected from the range of 50 ° C to 900 ° C. The temperature may be raised rapidly or stepwise, and the holding time at a high temperature is appropriately selected from a range of about 1 hour to about 24 hours. Also,
Cooling is also performed in the gas stream, and rapid cooling or cooling may be performed.

After cooling to room temperature, II-VI group compound in the raw material is high purity Group VI hydride (H ₂ O is excluded) is preferably stored in gas or inert gas, to transfer to the single crystal growth process Can be handled in the air for a short time.

After the heat treatment, the process may be directly transferred to the single crystal growing step without cooling.

As the container for performing the heat treatment, a quartz container is usually used, but any container that does not react with the II-VI group compound may be used, and a ceramic-coated container or the like can also be used. In addition, the processing vessel can be used as it is as a sealed tube for growing a single crystal. However, in this case, care must be taken because if the inner wall of the vessel becomes dirty due to scattering of the raw material powder or the like, polycrystal is easily formed during the growth of the single crystal.

In particular, when the heat treatment is performed using a Group VI hydride, a high-quality bulk single crystal with no coloring and a small etch pit density can be obtained, which is preferable.

The heat-treated II-VI group compound is vacuum-sealed in a quartz container together with iodine (I ₂ ) to form a sealed tube for growing a single crystal.

In the present invention, a sealed tube having a conical shape at one end is used as the sealed tube for growing a single crystal, and the apex angle of the cone in a cross section including the central axis in the longitudinal direction of the sealed tube is 5 to 30 degrees. It is necessary to be. If this angle is less than 5 degrees, only small crystals can be obtained, and if it is more than 30 degrees, polynuclei are generated and polycrystallized.

FIG. 1 shows an example of a sealed tube for growing a single crystal used in the present invention. If the angle (θ in FIG. 1) of the thinnest part of the tip is 5 to 30 degrees, the tip may be gradually narrowed as shown in FIGS. 1 (b) and (c). However, in this case, it is preferable that θ ′ in FIG. 1 is usually 60 degrees or less. Also, as shown in FIG. 1 (d), when there is a constriction on the way, there is an advantage that when a single crystal is grown in a vertical type, the crystal is less likely to fall.

As a method for producing a sealed tube, one end may be filled with a II-VI compound raw material and iodine in such a conical quartz tube, and then the other end may be cut off under vacuum in a usual manner, II
After placing the -VI compound raw material and iodine in a normal quartz tube, the other end may be sealed off in a vacuum in such a shape.

In the present invention, a single crystal can be grown without using a seed crystal by using the sealed single crystal growth tube having such a specific shape.

As a single crystal growth method, there are a horizontal type and a vertical type, but either of these methods may be used, and as a temperature control method, there are a gradient freeze method, a furnace inner tube moving method, a fixed temperature difference method, and the like. Any of these methods may be used.

The temperature on the high temperature side (raw material section) of the sealed tube is usually 800 to 900
° C, preferably in the range of 840-860 ° C. Also,
The temperature of the low-temperature side single crystal growth part is 1 to higher than the high-temperature side temperature.
It is appropriately selected from a temperature as low as about 120 ° C. For example, when the raw material powder is heat-treated in vacuum, the temperature is about 100 ° C lower,
1-30 when the raw material powder is heat-treated in a hydrogen sulfide stream
It is preferable that the temperature is lower by ° C.

In addition, in order to carry out iodine-based transport constantly and obtain a homogeneous crystal, the temperature difference between the high temperature side and the low temperature side must be strictly controlled.

Single crystal growth usually requires two to three weeks, but may exceed four weeks in some cases.

The group II-VI bulk single crystal obtained by the present invention is a large cubic single crystal having a large size of about 1 cm ³ .

The bulk single crystal obtained by the present invention is naturally doped with iodine and is an n-type semiconductor.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples unless it exceeds the gist.

Example 1 10 ^-6 T of high purity ZnS powder (manufactured by Kasei Optonics Co., Ltd.)
Vacuum sintering was performed under reduced pressure of orr for 24 hours. Put 8g ZnS raw material powder and 30mg iodine in 20mm inner diameter quartz ampoule, 10 ^-6 T
It was sealed at a length of 7 cm at a sealing angle of 15 degrees under reduced pressure of orr. The internal volume was 22 cc. The ampoule was fixed in a vertical electric furnace, and the material (bottom) was cleaned by reverse growth for 12 hours at 700 ° C for the raw material part (bottom) and 850 ° C for the single crystal growth part (top). The bulk single crystal of zinc sulfide was grown by maintaining the temperature at 850 ° C. and the single crystal growth part (upper) temperature at 750 ° C. for 20 days. FIG. 2 shows a program for growing a single crystal. After cooling, split the ampoule to 1.0 cm ³
A large transparent single crystal was obtained. FIG. 3 is a diagram of the obtained single crystal. The obtained single crystal was a perfect cubic single crystal.

Example 2 20 g of high-purity ZnS powder (manufactured by Kasei Optonics Co., Ltd.) was placed in a quartz boat and placed in a horizontal electric furnace with an inner diameter of 50 mm.
It was placed in a 500 mm long quartz tube. After reducing the pressure of the quartz tube to 10 ^-4 Torr, high-purity hydrogen sulfide gas (manufactured by Nippon Sanso Corporation)
While flowing from one end of the quartz tube at 10 cc / min and discharging from the other end to the outside, the quartz tube was heated to 850 ° C. over 1 hour,
It was left for 3 hours while maintaining the temperature at 50 ° C. The mixture was allowed to cool for about 2 hours while maintaining the flow rate of hydrogen sulfide at 10 cc / min. Immediately after cooling, weigh 8 g immediately, and together with 14 mg of iodine, an inner diameter of 16 mm
Transferred to a quartz ampoule. While depressurizing the quartz ampule to about 10 ^-6 Torr, the ampule was sealed at a length of 7 cm so that the angle of the ampule was about 20 degrees. The internal volume became about 14cc. This ampoule was fixed in a vertical electric furnace, and the raw material part (bottom part) was cleaned by reverse growth at 700 ° C. and the single crystal growth part (top part) at 850 ° C. for 12 hours. The crystal growth part was kept at 830 ° C. for 20 days to grow a bulk single crystal of zinc sulfide. After cooling, the ampoule was cracked to obtain a transparent, cubic single crystal having a size of 1.5 cm ³ and without coloring.

The (111) plane of the obtained crystal was boiled with sodium hydroxide 25
After etching in a 1% aqueous solution for 1 minute, the state of the surface was observed with an optical microscope. The etch pit density is 6.0 × 10 ³ cm ^-2
Met.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, a bulk single crystal of a large and high quality II-VI compound can be easily obtained by an iodine transport method without using a seed crystal.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view (a cross-sectional view including a central axis in a longitudinal direction of the sealed tube) showing an example of a sealed tube for growing a single crystal used in the present invention. FIG. 2 is a diagram showing a single crystal growth program according to the first embodiment. A indicates a raw material part, and B indicates a single crystal growth part. FIG. 3 is a diagram showing the single crystal obtained in Example 1.

Claims (2)

(57) [Claims] 1. A method for producing a bulk single crystal of a II-VI group compound by an iodine transport method in a sealed tube having a conical shape at one end, the method comprising the steps of: A method for producing a bulk single crystal of a II-VI group compound, wherein a bulk single crystal is grown without using a seed crystal using a sealed tube having an apex angle of 5 to 30 degrees. 2. A method for producing a bulk single crystal of a II-VI compound by an iodine transport method, comprising the steps of:
After being treated with a Group VI compound at a temperature of 0 ° C. or more and less than 1000 ° C., one end is a sealed tube having a cone shape, and the apex angle of the cone in a cross section including a central axis of the sealed tube in a fixed direction. A method for producing a bulk single crystal of a II-VI compound, wherein a bulk single crystal is grown using a sealed tube having a temperature of 5 to 30 degrees without using a seed crystal.