JPH08109094A - Production of compound semiconductor single crystal - Google Patents

Abstract

PURPOSE: To enable the compositional control of a raw material melt and effectively carry out the compositional control of a grown single crystal by providing a crucible for placing a compound semiconductor raw material therein with a constitution having the air permeability capable of passing a vapor of an element for controlling the vapor pressure therethrough and growing the crystal from the melt surface downward while controlling the vapor pressure. CONSTITUTION: A simple substance or a compound comprising at least one of an element 5 for controlling the vapor pressure in constituent elements of a compound semiconductor is placed in a reservoir part 4B of a quartz ampul 4 and a raw material 2 containing at least two elements in the constituent elements of the compound semiconductor is then placed in an air-permeable crucible 1 capable of passing the vapor of the element 5 for controlling the vapor pressure therethrough. The crucible 1 is placed in the quartz ampul 4 and vacuum sealed. The quartz ampul 4 is installed in a vertical type heating furnace 6, which is subsequently used to heat the reservoir part 4B. Thereby, the vapor pressure of the element 5 is applied to the interior of the quartz ampul 4 to solidify the raw material melt from the top of the melt 2 downward while controlling the vapor pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a single crystal of a compound semiconductor by applying a crystal production technique and a vertical gradient freezing (VGF) method or a vertical Bridgman (VB) method, for example, CdTe or CdZnTe. The present invention relates to a technique useful for producing a single crystal or a mixed crystal of such II-VI group compound semiconductors.

[0002]

2. Description of the Related Art One of the methods for producing a compound semiconductor single crystal is described in Japanese Patent Publication No. 5-59873 filed by the applicant of the present invention. This is a manufacturing method to which the VGF method is applied. An ampoule in which a raw material of a compound semiconductor is enclosed is placed in a vertical heating furnace and the raw material is heated and melted. The single crystal is grown downward from the center of the surface of the melt by cooling while maintaining a state in which the temperature is higher toward the bottom and higher toward the bottom. According to this manufacturing method, it is possible to grow the crystal in a floating state without contacting the ampoule wall with the solid-liquid interface where the crystal is formed, thereby suppressing generation of thermal stress in the crystal, and Since it is possible to prevent nucleation from occurring at one place at the same time, it is possible to grow a good quality and large diameter compound semiconductor single crystal with few defects such as twins and dislocations with good reproducibility and high yield.

Further, as a method for producing a compound semiconductor single crystal, there is a method described in JP-A-64-37488. This is a manufacturing method applying the VB method, in which a single crystal growth material and a vapor pressure control element are enclosed in a reaction tube, and the reaction tube is moved in a vertical heating furnace relative to the furnace. The single crystal is grown upward from the lower part of the raw material melt while controlling the pressure. According to this manufacturing method, strict vapor pressure control is possible, and a single crystal having sufficiently controlled physical properties such as conductivity type and resistance value can be obtained with good reproducibility.

Further, in another known liquid-encapsulated Czochralski (LEC) method as another method for producing a compound semiconductor single crystal, a gas permeable filter is sandwiched between the bottoms of a quartz crucible containing a GaP melt to form a Ga. A method is known in which a GaP single crystal is grown by providing a reservoir and heating Ga to apply Ga vapor pressure (described in Japanese Patent Publication No. 56-35639). According to this, there is no dish pit and G
It is possible to obtain the effect that a high-quality GaP crystal having a few voids can be industrially put to practical use.

Furthermore, US Pat. No. 3,649,19
No. 3 synthesizes a GaAs polycrystal by covering a Ga melt contained in a crucible having a porous bottom with a sealant and diffusing As gas into the Ga melt through the porous bottom. However, a method for growing a single crystal after that is shown.

[0006]

[Problems to be Solved by the Invention] However, VGF
Method and VB method, etc.
In the case of growing a single crystal downward from the surface of the raw material melt as shown in No. 3, especially when growing a mixed crystal such as CdZnTe in which the composition variation in the growth direction is likely to occur due to segregation of Zn, the surface of the melt is increased by the grown crystal. Is almost covered,
Even if vapor pressure control is performed as in JP-A-64-37488, it becomes difficult for the vapor pressure control element (Zn in the case of CdZnTe) gas to come into contact with the raw material melt, and the effect of vapor pressure control is There is a problem that it is difficult to obtain.

The Japanese Patent Publication No. 56-35639 described above
In the LEC method, a crucible having an air-permeable filter at the bottom is used to apply Ga vapor in a Ga reservoir to the raw material melt in the crucible. The VGF method or the VB method is used to move downward from the melt surface. Not only does this suggest a vapor pressure control method of applying a vapor pressure to a raw material melt through a crucible wall when growing a crystal, but it also has a drawback that the structure of the crucible is complicated.

Further, the above-mentioned US Pat. No. 3,649,19
No. 3 diffuses As gas into a Ga melt through a porous bottom of a crucible when synthesizing a compound semiconductor polycrystal.
Not only does it suggest a vapor pressure control method of applying a vapor pressure to a raw material melt through a crucible wall when a crystal is grown downward from the melt surface by the B method,
It also has a drawback that the crucible has a complicated structure and is difficult to process.

The present invention has been made in view of the above circumstances, and an object thereof is to effectively control vapor pressure even when a crystal is grown downward from the melt surface by the VGF method or the VB method. It is therefore an object of the present invention to provide a method for producing a compound semiconductor single crystal, which enables to control the composition of the raw material melt and to effectively control the composition of the grown crystal.

[0010]

In order to achieve the above object, the present inventor has formed a crucible for growing a single crystal with a material having air permeability such that vapor of Cd or Zn can pass through the crucible. It has been found that by using C., it is possible to control the vapor pressure of Cd and Zn, thereby controlling the composition of the raw material melt and growing crystals downward from the melt surface by the VGF method or the VB method. .

The present invention has been made based on the above findings, and a simple substance or a compound made of at least one vapor pressure controlling element among the constituent elements of the compound semiconductor is provided in the reservoir portion of the quartz ampoule having the reservoir portion. And a raw material containing at least two of the constituent elements of the compound semiconductor is placed in a crucible having gas permeability that allows the vapor of the vapor pressure controlling element to pass therethrough, and the crucible is filled with the quartz ampoule. And the quartz ampoule is vacuum-sealed, the quartz ampoule is placed in a vertical heating furnace, and the reservoir is heated by the heating furnace to control the vapor pressure in the reservoir. While heating the crucible by the heating furnace to melt the raw material while controlling the vapor pressure by applying the vapor pressure to the quartz ampoule, the vertical direction in the raw material melt is obtained. The compound semiconductor by gradually cooling while holding the temperature gradient in the direction from the upper end of the melt toward the lower end of the melt so as to become higher and solidifying the raw material melt downward from the upper end of the melt. Is characterized by growing a single crystal of.

The present invention is also characterized in that the crucible is made of porous graphite, carbon, sintered boron nitride, alumina or porous quartz.

[0013]

According to the above-mentioned means, the crucible for containing the raw material of the compound semiconductor is made to have a gas permeability which allows the vapor of the vapor pressure controlling element to pass therethrough, and V is controlled while controlling the vapor pressure.
Since the crystal is made to grow downward from the melt surface by the GF method or the VB method, the melt surface is almost covered by the grown crystal and the area where the vapor of the vapor pressure controlling element and the raw material melt are in direct contact Even if the temperature becomes extremely small, the vapor and the raw material melt are sufficiently in contact with each other through the crucible wall or through the crucible wall and the crucible bottom, and the three-phase equilibrium state of gas phase, liquid phase and solid phase is reached. It is possible to grow crystals while maintaining the above. Therefore, since the composition of the raw material melt is kept constant during the crystal growth, stable crystal growth can be performed.

In addition, a crystal having a mixed crystal composition of ternary or higher is
In the case of growing while simultaneously controlling the vapor pressures of the elements above the components, for example, in the case of growing a crystal of a ternary mixed crystal semiconductor such as Cd _1-X Zn _X Te, the above-mentioned air-permeable crucible is used to produce Cd. By simultaneously controlling the vapor pressures of Zn and Zn, it is possible to prevent the Zn concentration in the raw material melt from decreasing as the crystal growth progresses due to the segregation of Zn. Can be kept constant, so that a crystal having a uniform composition in the crystal growth direction can be obtained.

[0015]

EXAMPLE An example of a method for producing a compound semiconductor single crystal according to the present invention will be described below with reference to FIGS. 1 and 2. FIG.
FIG. 2 is a vertical cross-sectional view of a state in which a raw material melt is put into a crucible used for carrying out the manufacturing method according to the present invention, and crystals are slightly grown from the surface of the melt, and FIG. 2 is a heating furnace for crystal growth of the crucible. It is the schematic which showed the state installed inside and the example of the temperature distribution of the vertical direction in this heating furnace. In both figures, 1 is a crucible, 2 is a raw material melt, 3 is a grown crystal, 4 is a quartz ampoule, 4A is a crystal growth chamber, 4B is a vapor pressure control chamber (reservoir section), 5 is a vapor pressure control element, 6 is a heater.

In the method for producing a compound semiconductor single crystal according to the present invention, vapor pressure control is performed by using a crucible 1 having gas permeability that allows passage of vapor of vapor pressure control element 5 among the constituent elements of the compound semiconductor crystal to be grown. The crystal is grown downward from the surface of the raw material melt 2 by the VGF method. That is, a raw material containing a constituent element of a compound semiconductor is placed in the crucible 1 and the crucible 1 is placed in a quartz ampoule 4.
Is installed in the crystal growth chamber 4A of
A simple substance or a compound made of the element 5 for controlling the vapor pressure is put in B, the quartz ampoule 4 is vacuum-sealed, and the quartz ampoule 4 is placed in a vertical heating furnace. The heater 6 heats the reservoir portion 4B to a predetermined temperature to control the output (supply power) of the heater 6 so that the vapor pressure of the vapor pressure controlling element 5 in the quartz ampoule 4 becomes a desired value, and the crucible 1
The raw material therein is melted to form a raw material melt 2. Then, the temperature of the crystal growth chamber 4A is adjusted to the Hani line while maintaining a temperature gradient such that the temperature of the crucible bottom is higher than the surface (upper end) of the raw material melt 2 as shown by the arrow line in FIG. Gradually cool to the side,
The raw material melt 2 is solidified from the upper part to the lower part.

Here, the crucible 1 has air permeability as described above, and is not particularly limited, but is made of, for example, porous graphite, carbon, boron nitride sintered body, alumina or porous quartz. In addition to these, any material that can be used for growing a compound semiconductor crystal and has air permeability is suitable as a material for the crucible 1. Due to the air permeability of the crucible 1 as described above, as shown in FIG. 1, even if the surface of the raw material melt 2 is almost covered with the grown crystals 3, the vapor (gas) of the vapor pressure control element 5 remains The raw material melt 2 is passed through the side wall and the bottom wall of the crucible 1, and further, the contacted gas diffuses into the raw material melt 2. Therefore, an element such as CdZnTe that is consumed from the raw material melt 2 and its concentration decreases as the crystal growth progresses due to segregation or the like (in the case of CdZnTe, Z
n), or an element such as CdTe that must be in excess of the melt composition by deviating from the stoichiometric composition of the compound semiconductor (CdTe in the case of CdTe) is selected as the vapor pressure controlling element 5. As a result, the concentration of the element during crystal growth can be maintained at a predetermined level, and thus fluctuations in the melt composition can be prevented.

Further, the heater 6 can freely set the temperature distribution in the vertical direction.
It is a heater having a multi-stage structure of stages or more. And
The electric power supplied to the heater 6 is controlled by a control device such as a computer (not shown) based on temperature data measured by temperature measuring means (not shown) such as a thermocouple (not shown) provided at one or more locations in the heating furnace. Has become
Thereby, the output of the heater 6 is adjusted so that the temperature in the furnace has a desired distribution.

Specific examples will be given below, but it goes without saying that the present invention is not limited to the following specific examples. (Specific Example 1) As the crucible 1, for example, density (bulk density)
Of 1.0-1.1 g / cm ³ , thickness of 1 mm, inner diameter of 42 mm and depth of 50 mm porous graphite (trade name VCP10)
A crucible made of was used. CdTe polycrystalline raw material input is 1
500 g, and about 10 g of Cd in the reservoir 4B.
I put it in. The temperature of the crystal growth chamber 4A is set to 1110 ° C., the temperature of the reservoir portion 4B is set to 800 ° C., and the temperature is held for 25 hours. Then, the temperature gradient in the vertical direction in the raw material melt 2 is 0.5 to 1 ° C. / Cm, and gradually cool at a cooling rate of 0.2 ° C./hour to CdT downward from the surface of the raw material melt 2.
e Single crystal was grown. When examining the obtained crystals,
It was found that the stoichiometric composition in the crystal growth direction was uniformly distributed, and a CdTe single crystal of higher quality than the conventional one was obtained.

Here, the porosity of the porous material of the crucible 1 is not particularly limited, but the larger porosity is the liquid phase (raw material melt 2) and the gas phase (vapor of vapor pressure control element 5). Since it is expected that a portion in contact with will become larger and a remarkable effect will be obtained, it is preferable that the porosity is large in a range where the raw material melt 2 does not leak.

(Specific Example 2) The same crucible 1 as in the above specific example 1.
Was used. The amount of the CdTe polycrystalline raw material charged was 250 g, and 178 g of Cd and 104 g of Zn were placed in the reservoir portion 4B (molar ratio of Cd and Zn was 1). Crystal growth chamber 4
After setting the temperature of A to 1110 ° C. and the temperature of the reservoir section 4B to 800 ° C. and holding for 25 hours,
The temperature gradient in the vertical direction in the raw material melt 2 is 0.5 to 1 ° C / cm.
Then, the ternary mixed crystal of CdZnTe was grown downward from the surface of the raw material melt 2 by gradually cooling at a cooling rate of 0.2 ° C. per hour. When the obtained crystal was examined, it was found that the composition of Zn in the crystal growth direction was 2.1 to 2.6 atomic%, which was more uniform than the Zn distribution due to segregation. It was also found that the crystal growth surface, that is, the Zn distribution in the radial direction was uniform except for the edges of the crystal.

In the above embodiments, the case of growing a single crystal of CdTe and CdZnTe has been described as an example, but other compound semiconductors such as PbTe and PbSnT are used.
e, CdS, CdSe, ZnS, ZnSe, ZnTe,
PbS, PbSe, InSb, InAs, InP, Ga
As, GaSb, GaP, HgCdTe, CdZnS
Of course, the single crystal manufacturing method of the present invention can be applied to e, ZnSSe, and the like.

Further, in the above embodiment, the present invention is applied to the V
The case where the present invention is applied to the GF method has been described, but the present invention is not limited to this, and the present invention is also applied to a VB method and a cairoporous method in which a raw material melt of a compound semiconductor is slowly cooled and solidified while being sealed with a liquid sealant. Applicable.

Further, in the above embodiment, the surface of the raw material melt 2 was opened and the crystal 3 was grown from the nuclei naturally generated on the surface of the melt, but a seed crystal having the same composition as the crystal to be grown or cooling. A heat sink for heat may be brought into contact with the surface of the raw material melt to grow crystals downward from the surface of the raw material melt.

[0025]

According to the method for producing a compound semiconductor single crystal of the present invention, at least one of the constituent elements of the compound semiconductor is used for controlling the vapor pressure in the reservoir portion of the quartz ampoule having the reservoir portion. And a raw material containing at least two elements of the constituent elements of the compound semiconductor is placed in a crucible having gas permeability that allows the vapor of the vapor pressure controlling element to pass therethrough. Is placed in the quartz ampoule and the quartz ampoule is vacuum-sealed, and then the quartz ampoule is placed in a vertical heating furnace, and the reservoir is heated by the heating furnace to vaporize the vapor in the reservoir. While controlling the vapor pressure by applying the vapor pressure of the pressure control element to the quartz ampoule,
After melting the raw material by heating the crucible by the heating furnace, the temperature gradient in the vertical direction in the raw material melt is gradually increased while maintaining the temperature from the upper end of the melt toward the lower end of the melt. In order to grow the single crystal of the compound semiconductor by solidifying the raw material melt from the upper end of the melt by cooling to the upper end of the melt, through the crucible wall,
Or, the vapor of the vapor pressure controlling element and the raw material melt are sufficiently in contact with each other through the crucible wall and the crucible bottom, and crystal growth is performed while maintaining the equilibrium state of the three phases of the gas phase, the liquid phase and the solid phase. be able to. Therefore, since the composition of the raw material melt is kept constant during the crystal growth, stable crystal growth can be performed, and crystals having a uniform composition in the crystal growth direction can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a state in which a raw material melt is put into a crucible used for carrying out a manufacturing method according to the present invention, and crystals are slightly grown from the surface of the melt.

FIG. 2 is a schematic diagram showing an example of a state in which the crucible is installed in a heating furnace for crystal growth and a temperature distribution in a vertical direction in the heating furnace.

[Explanation of symbols]

 1 Crucible 2 Raw Material Melt 3 Crystal 4 Quartz Ampoule 4B Reservoir Section 5 Vapor Pressure Control Element 6 Heater (Heating Furnace)

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[Procedure amendment]

[Submission date] November 25, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

Specific examples will be given below, but it goes without saying that the present invention is not limited to the following specific examples. (Specific Example 1) As the crucible 1, for example, density (bulk density)
Was 1.0 to 1.1 g / cm ³ , a thickness of 1 mm, an inner diameter of 42 mm and a depth of 50 mm, and a crucible made of porous carbon (trade name VCP10) was used. CdTe polycrystalline raw material input amount is 150
It was 0 g, and about 10 g of Cd was put in the reservoir portion 4B. The temperature of the crystal growth chamber 4A is set to 1110 ° C, and the temperature of the reservoir portion 4B is set to 800 ° C.
After holding for 5 hours, the temperature gradient in the vertical direction in the raw material melt 2 was set to 0.5 to 1 ° C./cm, and the raw material melt 2 was gradually cooled at a cooling rate of 0.2 ° C./hour downward from the surface. A CdTe single crystal was grown toward it. When the obtained crystal was examined, it was found that the stoichiometric composition in the crystal growth direction was uniformly distributed, and a CdTe single crystal of higher quality than the conventional one was obtained.

Claims (2)

[Claims] 1. A quartz ampoule having a reservoir portion is provided with a simple substance or a compound consisting of at least one vapor pressure controlling element among constituent elements of a compound semiconductor, and the vapor pressure controlling element A raw material containing at least two of the constituent elements of the compound semiconductor is placed in a crucible having gas permeability that allows vapor to pass through, the crucible is placed in the quartz ampoule, and the quartz ampoule is vacuum-sealed. After stopping, the quartz ampoule is installed in a vertical heating furnace, and the reservoir is heated by the heating furnace to apply the vapor pressure of the vapor pressure controlling element in the reservoir into the quartz ampoule. While controlling, after heating the crucible by the heating furnace to melt the raw material, a vertical temperature gradient in the raw material melt is changed from the melt upper end to the melt lower end. A compound semiconductor, characterized in that a single crystal of the compound semiconductor is grown by gradually cooling while holding the melt at a high temperature and solidifying the raw material melt downward from the upper end of the melt. Method for producing single crystal. 2. The method for producing a compound semiconductor single crystal according to claim 1, wherein the crucible is made of porous graphite, carbon, sintered boron nitride, alumina or porous quartz.