JP2000327496A - Production of inp single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing an InP single crystal of a high yield by suppressing the generation defects, such as polycrystals and twins, when growing the InP single crystal, thereby enhancing a single crystallization rate. SOLUTION: A crystalline body of InP having an atomic composition ratio In/InP of In and P of >=0.490 to <0.500 is used as raw material. More specifically, a crucible 1 containing the InP crystalline body having the composition described above as the raw material is installed in heating furnaces 6, 8 where the raw material heated to above its melting point and is melted and, thereafter, the raw material melt 2 is gradually cooled, by which the InP single crystal is grown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an InP compound semiconductor single crystal, and more particularly to a method for growing an InP single crystal by gradually cooling a raw material melt contained in a refractory crucible. Regarding useful techniques.

[0002]

2. Description of the Related Art In general, III-V compound semiconductors such as GaP, GaAs, and InP have a high vapor pressure near the melting point. Therefore, a liquid sealant layer made of B ₂ O ₃ or the like is formed on a raw material melt. It is manufactured industrially by the liquid sealing method covered with, especially,
The liquid-sealed Czochralski method (LEC method) is widely used. The LEC method is a method in which the crystal is pulled up as the crystal grows, and has the advantage that the crystal orientation can be controlled by seeding and a high-purity crystal can be easily obtained. However, since the temperature gradient in the melt during the crystal growth is large, the thermal stress applied to the crystal increases and the dislocation density increases, so that a semiconductor laser or photo diode using such a compound semiconductor single crystal having a high dislocation density can be used. Diodes have the disadvantage that their electrical characteristics are degraded.

On the other hand, the vertical Bridgman method (VB method)
In the vertical gradient freeze method (VGF method), the temperature gradient in the melt during crystal growth is from several degrees Celsius / cm to several tens of degrees Celsius because crystal growth is performed by gradually cooling the raw material melt in a refractory crucible.
/ Cm, which is one order of magnitude smaller than that of the LEC method, and therefore has the advantage that the thermal stress applied to the crystal is reduced and the dislocation density can be kept low.

The VGF method will be described with reference to FIG. 1 showing a crystal growth apparatus. A crystal growing apparatus shown in FIG. , A quartz cap 4 for sealing the quartz ampule, and a heating furnace comprising a cylindrical heater 6 for heating the raw material melt and a high-pressure vessel 8, and the inside of the high-pressure vessel 8 is sealed. A thermocouple 7 for temperature measurement is provided on the side of the quartz ampule so that the temperature near the crucible can be measured.
In the VGF method, by using such a crystal growth apparatus, while controlling the temperature gradient in the vertical direction in the crystal, the heater 6 is adjusted to gradually lower the temperature and grow the crystal from below the crucible 1 to above. Is the way.

[0005]

SUMMARY OF THE INVENTION However, the conventional
In the VGF method, the crucible containing the raw material is placed in a quartz ampule and hermetically sealed, and this quartz ampule is placed in a heating furnace and heated, so that the partial pressure of phosphorus vapor in the quartz ampule and the raw material melt Phosphorus evaporates from the raw material melt until the decomposition pressure equilibrates, and the raw material melt always has an atomic composition ratio In / InP of 0.500 or more and an excess of In. As described above, a shift in the atomic composition ratio of the raw material melt causes compositional supercooling during crystal growth, and as a result, polycrystals, twins, and the like have been generated. As a result, the InP single crystallization yield was often reduced.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a method for producing an InP single crystal having a high yield and a high yield of single crystal.

[0007]

According to the present invention, in order to solve the above problems, the atomic composition ratio of In to P, In / InP, is 0.490.
As described above, the InP crystal having a size of less than 0.500 is used as a raw material. Specifically, as in the VGF method, a crucible containing an InP crystal having the above composition as a raw material is placed in a heating furnace, and heated to a temperature equal to or higher than the melting point to melt the raw material. Is gradually cooled to grow an InP single crystal. In the above composition
When the P crystal is used as a raw material, the phosphorus in the raw material melt decreases as the phosphorus evaporates during heating, and the atomic composition ratio In / InP of the raw material melt was initially 0.490 or more and less than 0.500.
Is 0.500 (stoichiometric composition: Stoichiometric comp
osition), and with the phosphorus vapor pressure and the decomposition pressure of the raw material melt in equilibrium, the atomic composition ratio of the raw material melt In / InP
And the stoichiometric composition is hardly deviated, so that generation of polycrystals and twins can be prevented. further,
The crucible containing the above raw materials is sealed in a closed container,
By setting the closed type container in the heating furnace, it is possible to restrict evaporation of phosphorus from the raw material melt, and to prevent a shift in the atomic composition ratio In / InP of the raw material melt. It can be suppressed efficiently.

[0008] The following describes the progress of the research by the present inventors before reaching the present invention.

When growing a single crystal of InP, the InP is heated.
This makes it easier for phosphorus to evaporate.
It has a vapor pressure around 0 atm. For this reason, generally the LEC method
Then B ₂0₃Cover with a liquid sealant consisting of
It is raised in the atmosphere.

On the other hand, in the VGF method, a single crystal is grown by sealing the raw material melt in a quartz ampoule. Therefore, phosphorus is released from the raw material melt until the partial pressure of phosphorus vapor in the ampoule and the decomposition pressure of the raw material melt are balanced. Will evaporate. Therefore, the atomic composition ratio In / InP of the raw material melt is always 0.500 or more, and there is an excess of In. It has been found that due to the deviation of the atomic composition in the raw material melt, compositional supercooling occurs during crystal growth, and polycrystals, twins, and the like are generated. Thus, the present inventors have studied the use of a phosphorus-rich InP crystal having an atomic composition ratio In / InP of less than 0.500 as a raw material for growing an InP single crystal.

In general, an InP polycrystalline raw material is produced by the HB method, and its atomic composition ratio In / InP is 0.500 (stoichiometric composition) or 0.500 or more, so that the In composition tends to be excessive. However, the present inventors have succeeded in producing an InP polycrystalline raw material having a phosphorus excess composition even in the HB method by optimizing the production conditions. For example, phosphorus was excessively applied at a predetermined vapor pressure during the synthesis of the InP polycrystal, and was rapidly cooled to obtain an InP polycrystal having an excess phosphorus composition.

Specifically, In is heated to 1070 ° C., and phosphorus is heated to 20 atm, 30 atm, 50 atm, 75 atm, 100 atm.
After applying an atmospheric pressure and an atmospheric pressure to synthesize an InP polycrystal, each was cooled to room temperature in about 30 minutes.

Table 1 shows the result of analyzing the weight of In in the synthesized InP polycrystal and examining the atomic composition ratio. As shown in Table 1, when phosphorus is applied at 50, 75, 100, and 120 atm, an InP polycrystal having a phosphorus excess composition can be synthesized, and the value of each atomic composition ratio In / InP is 0.498, 0. 49
3, 0.490 and 0.490. When phosphorus is applied at 120 atm, it is difficult to obtain a phosphorus-rich InP polycrystal having an atomic composition ratio In / InP of 0.490 or less because phosphorus is precipitated in the InP polycrystal.

[0014]

[Table 1] When an InP single crystal was grown using this phosphorus-excess InP crystal as a raw material, the generation of polycrystals and twins was suppressed, and the single crystallization ratio was dramatically increased, thereby improving the yield.

The present invention has been made based on the above findings. In a crystal growth method for gradually cooling a raw material melt to obtain an InP single crystal, the atomic composition ratio In / InP of In / InP is 0.49.
A crystal of InP having a value of 0 or more and less than 0.500 is used as a raw material, whereby the generation of polycrystals, twins, and the like can be effectively suppressed, and the yield of InP single crystals can be reduced. Can be manufactured well.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of a crystal growth apparatus used for growing a crystal by the VGF method. The crystal growth apparatus shown in FIG. 1 is the same as the apparatus used in the conventional VGF method, and includes a pBN crucible 1 for accommodating a raw material melt 2 and a graphite crucible support 3 for supporting the crucible 1. And a quartz ampule 5 accommodating the crucible 1 and the crucible support 3
, A quartz cap 4 for sealing the quartz ampule, and a heating furnace comprising a cylindrical heater 6 for heating the raw material melt and a high-pressure vessel 8, and the inside of the high-pressure vessel 8 is sealed. A thermocouple 7 for temperature measurement is provided on the side of the quartz ampule so that the temperature near the crucible can be measured.

First, the atomic composition ratio In / InP synthesized by the HB method
Is placed in a crucible 1 made of pBN and the quartz ampule 5 is evacuated, and then the quartz ampoule 5 and the quartz cap 4 are removed as shown in FIG. It was welded with an oxyhydrogen burner, and the inside of the quartz ampule was sealed under reduced pressure. The quartz ampule was heated by the heater 6 to raise the temperature inside the heating furnace to about 1070 ° C. to melt InP. At this time, an inert gas such as argon gas was introduced into the high-pressure vessel 8 to prevent the quartz ampule 5 from being ruptured due to the decomposition pressure of InP, and the pressure was set to 35 atm.

Next, the bottom of the crucible 1 is heated to the melting point of InP (10
62 ° C.), and the temperature of the heater 6 was adjusted such that the temperature in the melt increased from the bottom to the top with a temperature gradient of 5 to 10 ° C./cm. After the temperature is sufficiently stabilized, the crystal growth rate is about 1 mm / h.
The heater 6 was adjusted and gradually cooled. After growing for about 150 hours, the crystal was cooled over 30 hours.

When InP crystals were repeatedly grown under these conditions, eight out of ten single crystals were free of polycrystals and twins, and single crystals of InP could be obtained at a high yield.

The present inventor conducted a comparative experiment under conditions deviating from the composition ratio according to the present invention in order to confirm the effects of the present embodiment.

Comparative Example 1 Atomic Composition Ratio In Synthesized by HB Method
An InP crystal was grown in the same manner as in the above example, using a crystal of InP having an InP ratio of 0.500 as a raw material. As a result, 10
Polycrystals and twins were generated in 7 of the crystals, and only 3 out of 10 single crystals in which polycrystals and twins were not generated showed that the yield was poor. .

Comparative Example 2 Atomic composition ratio In synthesized by HB method
/ InP in excess of 0.500 and less than 0.51
InP crystals were grown in the same manner as in the above example using nP crystals as a raw material. As a result, only one out of ten single crystals was a single crystal in which no polycrystal or twin crystal was generated, and the yield was far from practical use.

From the above results, the atomic composition ratio of In and P In / I
When an InP crystal having an nP of 0.490 or more and less than 0.500 is used as a raw material, the generation of polycrystals and twins can be significantly suppressed, and an InP single crystal can be produced with good yield. become.

In this embodiment, the case where the quartz ampoule is sealed to grow a single crystal to reduce the amount of phosphorus evaporated has been described. For example, a crystal is grown by placing a crucible in a high-pressure vessel. When the pressure inside the high-pressure vessel is increased, the amount of phosphorus evaporated can be suppressed to some extent without using a quartz ampoule.
According to the growing method using the crystal as a raw material, the deviation of the atomic composition ratio in the raw material melt from the stoichiometric composition can be reduced, and the generation of polycrystals and twins can be suppressed.

In this embodiment, a method for growing an InP single crystal by the VGF method has been described.
You are not restricted by law. Any method may be used as long as the raw material melt in the crucible is gradually cooled to grow an InP single crystal,
For example, as in the HB method (Horizontal Bridgman method), the temperature of the heater is adjusted so that a temperature gradient is formed in the raw material melt in the horizontal direction. Is also applicable to the method of growing.

[0027]

The effects obtained by the invention disclosed in the present application will be briefly described as follows.

That is, according to the method for producing an InP single crystal of the present invention, in the crystal growing method for gradually cooling the raw material melt to obtain an InP single crystal, the atomic composition ratio In / InP of In: P is 0.1.
Since an InP crystal having a size of 490 or more and less than 0.500 is used as a raw material, it is possible to effectively suppress the occurrence of polycrystals, twins, and the like, and to produce an InP single crystal with a high yield. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a crystal growing apparatus used in the present embodiment and a conventional VGF method.

[Explanation of symbols]

 1: Crucible 2: Raw material melt 3: Crucible support 4: Quartz cap 5: Quartz ampule 6: Heater 7: Thermocouple 8: High pressure vessel

Claims (3)

[Claims] 1. A method for producing an InP compound semiconductor single crystal, wherein an atomic composition ratio In / InP of In and P is 0.490 or more,
A method for producing an InP single crystal, characterized by using an InP crystal of less than 0.500 as a raw material. 2. A crucible containing an InP crystal having the above composition as a raw material is placed in a heating furnace, and heated to a temperature equal to or higher than the melting point to melt the raw material.
The method for producing an InP single crystal according to claim 1, wherein a P single crystal is grown. 3. The method for producing an InP single crystal according to claim 2, wherein the crucible containing the raw material is sealed in a closed container, and the closed container is set in a heating furnace.