JPS59131597A - Production of high-quality gallium arsenide single crystal - Google Patents

Abstract

PURPOSE:To produce a high-quality GaAs single crystal in high stability, by synthesizing molten GaAs in a crucible under high pressure, contacting a seed crystal to the molten liquid, and pulling the crystal under a strong magnetic field. CONSTITUTION:The crucible 3 placed in the pressure vessel 1 contains a molten B2O3 layer 6 as a liquid encapsulation agent and a molten GaAs layer 5 under the encapsulation layer 6. The pressure in the vessel 1 is decreased to <=5atm to distill and purify the molten GaAs 5. The pulling axis 8 is lowered to contact the seed crystal 7 with the molten GaAs 5, and the molten liquid is applied with strong magnetic field by the magnetic field generator 11 to suppress the convection in the molten liquid 5. The seed crystal 7 is pulled up with rotation at a definite rate of rotation in the magnetic field to effect the growth of the GaAs crystal. The interface between the solid and the liquid can be made smooth by this method, and a high-quality semi-insulating GaAs single crystal free from growth stripes can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for manufacturing high quality gallium arsenide (GaAs) single crystals.

Among the m-■ group compounds, Gaps has a high electron mobility and is being widely used as a crystal substrate for elements of ultrahigh-speed integrated circuits and opto-electronic integrated circuits.

Gaps is attracting attention because of its high quality G.
The specific resistance of aks is 10'0. It has high insulating properties of crn or higher, it has few defects in the crystal and has a uniform distribution, and it is easy to manufacture large wafers. As a method for manufacturing GaAs single crystals that satisfies such requirements, the liquid-encapsulation pulling method (LEC method) is attracting attention. This sealing pulling method is known as a low pressure sealing pulling method and a high pressure sealing pulling method. The low-pressure sealing pulling method uses Gaps polycrystals produced by the port growth method as a raw material, so the purity of the raw material is low and chromium needs to be added to make it semi-insulating, which is preferable. In addition, the high-pressure sealing pulling method, which directly synthesizes raw materials, does not require the addition of chromium, but because Ga and A8, which are crystal raw materials, and boron oxide (B20B), which is a liquid sealant, are heated and synthesized under high pressure. The crystal raw material melt melting in the crucible is in an extremely unstable state due to thermal convection, and since the crystal growth operation is performed in such an R state, the shape of the solid-liquid interface changes drastically. , minute growth striations occur in the resulting crystals due to thermal deterioration. When devices are formed using such crystal substrates, it is difficult to manufacture integrated circuits with uniform electrical and device characteristics with good reproducibility because defects formed in the crystal substrate cannot be controlled. Ta.

An object of the present invention is to provide a method for manufacturing a high-quality, additive-free (undoated) semi-insulating GaAs single crystal with good reproducibility by controlling the quality of the growing crystal.

Therefore, the method for producing high-quality semi-insulating Ga, As single crystals according to the present invention uses a high-pressure liquid sealing pulling method to produce Ga, As single crystals.
In a method for producing a single crystal, once a crystal raw material melt is synthesized in a crucible under high pressure, a seed crystal is brought into contact with and pulled up from the crystal raw material melt while applying a magnetic field of 1200 Gauss or more to perform crystal growth. It is characterized by When a magnetic field is applied in this way, the convection of the crystal raw material melt is suppressed, and crystal growth occurs in a stable state at the solid-liquid interface, resulting in the formation of high-quality GcLAs single crystals without the generation of growth stripes. .

The first equipment was installed to carry out the high-pressure liquid-sealed pulling method, which has been known as the direct synthesis method for Gaks single crystals.
To explain with a diagram, l is a high-pressure container, and a crucible 3 made of quartz, boron nitride, etc., whose outer periphery is covered with a supporting material ring such as a carbon material, is provided in this high-pressure container l.
The times the support axis? A heating furnace is provided around the crucible 3 to heat and maintain the crucible A at a predetermined temperature. A pulling shaft r with a seed crystal 7 attached to the lower end is provided in the upper part of the crucible 3, and this pulling shaft is configured to rotate and move up and down.

A magnetic field applying device // is provided on the outer periphery of the high-pressure container /, so that a magnetic field is applied to the crystal-raw material melt j inside the crucible.

In the apparatus configured as above, the crucible 3 contains Ga and A.
Add a predetermined amount of s, and add B2O as a liquid sealant.
3, place the crucible in a high-pressure container, pressurize the container with an inert gas such as argon or nitrogen, and heat the crucible in a heating furnace to a temperature higher than the melting temperature of the crystal raw material. The crystal raw material and sealant inside are melted.

In the crucible 3, by the above heat treatment, a 20g B melt layer 6 as a liquid sealant is formed in the upper layer, and a Gaps melt layer is formed in the lower layer. When the raw material in the crucible is completely melted, the pulling shaft is lowered to bring the seed crystal 7 into contact with the melt layer in the crucible 3, and the seed crystal 7 is pulled up while rotating at a predetermined speed to grow the GaAs crystal 10. However, the temperature inside the container is 20 to 60 atm and about 1260°C, and the GaAs melt inside the crucible is in an unstable state with intense thermal convection, making it difficult for crystal growth to occur under such conditions. If this is done, growth streaks are likely to be formed on the crystals generated due to thermal fluctuations.

Therefore, in this invention, the seed crystal 7 is
At the time of contact with the aAs melt, a magnetic field is applied to the melt by the magnetic field application device // (arrow %B//). The strength of the applied magnetic field is 1200 Gauss or more, and the higher the strength, the more pronounced the effect.

When a magnetic field is applied to the GcLAs melt in this way, GaA
s The thermal convection that was occurring in the melt is suppressed, and the seed crystal is
When crystal growth is performed by contacting and pulling up the As melt, the solid-liquid interface is in a gentle state, so that no growth stripes occur and a semi-insulating Gaks single crystal is generated.

As is clear from the above explanation, the method for producing a QaAs single crystal according to the present invention only involves applying a magnetic field to the GaAB melt during the crystal growth process, and is combined with the known method for producing a Gaps single crystal. By carrying out this method, even higher quality Ga, As single crystals can be obtained.

Next, embodiments of this invention will be described.

Example 1 In a single crystal production apparatus having the structure shown in FIG. 1, 500 f of gallium, $60 of arsenic, and 1801 boron oxide were placed in a pyrolithic boron nitride crucible with an inner diameter of 100 m and a depth of 100 m. Place the crucible at 150 bar, pressurize argon gas to about 50 atm, and remove the crucible to 150 bar.
After heating to 0°C and forming a B2O3゛1-melt layer at the top and a GaAs melt layer at the bottom, the pressure inside the container was set to 5 atm and left for 30 minutes. It was pressurized to atmospheric pressure and a magnetic field of 1250 gv.s was applied. Ga
The thermal fluctuation in the As melt was 15°C, but by applying the above magnetic field, it became less than 0°1°C.Next, the seed crystal was placed in the GaAs melt while the magnetic field was applied. 9111 for 1 hour while rotating the seed crystal at a rate of 6 revolutions per minute.
The pulling operation was carried out at the speed of I+ for about 10 hours, and the diameter of about 5
A GaAs single crystal with 0 darkness and a length of about 90 tea was obtained.

When this crystal was cut in a direction parallel to the growth direction and the growth stripes were observed, no irregular growth stripes due to thermal convection of the melt were observed, indicating that the crystal was growing in an extremely stable state. was shown.

Example 2 A GaAs melt was formed in the same manner as in Example 1, and without distillation purification, a magnetic field of 1250 Gauss was applied to directly grow crystals. The crystal growth conditions were the same as in Example 1, and only the application of the magnetic field was stopped when about 20 m of crystals had been formed, and the application of the magnetic field was stopped again when about 15 m of crystals had been formed.
A Gaussian magnetic field was applied to obtain a GaAs single crystal with a length of about 60 mm.

When the resistance value of this crystal in the growth direction was measured, the results shown in the graph of FIG. 2 were obtained (curve a). That is, the resistance value of the crystal that was generated while a magnetic field was applied was low, and the resistance value of the crystal that was generated when the magnetic field was stopped was significantly high.

To investigate the cause of the above, we measured crystals using photoluminescence and found that crystals created in a magnetic field had deep defect levels (crystal defects unique to GcLAs, called 'EL, #). It was found that the concentration decreased significantly. In addition, the Si concentration was measured using secondary ion mass spectrometry and was found to be 8 X I D''/i in a crystal to which a magnetic field was applied.
It was slightly higher than the crystal (3×10'n1) obtained by normal pulling. From the above, it was found that the effective segregation coefficient of impurities changes somewhat and the intrinsic defect density of Gaks decreases.

For comparison, a GaAs melt was purified by distillation in the same manner as in Example 1, and then crystal growth was performed in exactly the same manner as above, and the resistance of the resulting crystal was measured in the same manner. Values as shown in the curve were obtained.

The results show that the effect is significantly improved if the melt before crystal growth is purified to remove impurities and then a magnetic field is applied to grow the crystal.

Based on the above results, the impurity concentration in the GcLAs crystal is
It was possible to control the defect concentration and produce a uniform, high-quality GaAB single crystal with high electron mobility and high reproducibility.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of a single crystal manufacturing apparatus for carrying out the present invention, and FIG. 2 is a graph showing the resistance distribution of the produced GaAs single crystal. In the figure, l is a high-pressure vessel, c is a heating furnace, 3 is a crucible, and j is G.
aAs melt, 6 a liquid sealant, 7 a seed crystal, 10 a generated crystal, /l a magnetic field applying device. Patent Applicant: Agency of Industrial Science and Technology Director-General's Board - 158 [Written amendment (spontaneous), dated c. 17, 1932. Director of the Japan Patent Office Kazuo Wakasugi A. Case 1981 Patent Application No. 5181 39. ? Please make corrections in the specification to be amended, in the scope of claims, and in the detailed description of the invention.
Yong Ershio The scope of the claims is amended in Appendix 9, 卆i The detailed description of the invention is amended as follows. □□- (1) On page 2, line ig, "crystal substrate" was corrected to "crystal produced by the method as a substrate." (2) On page 3, line 9 to IO, "7200 Gauss or more" was corrected to "intensity that substantially suppresses convection of the melt." (3) On page 5, line 13, ``Strength of applied magnetic field'' is changed to ``The purpose of applying a magnetic field is to substantially suppress the convection of the melt. Although it varies depending on the crystal pulling conditions, for example, if the crucible diameter is about 10
0111RI, the depth and thickness of the u-crystal raw material melt is -〇m
Corrected to "If it is about m". (4) Insert the following sentence next to line I on page 5. [Please note that the raw materials in the crucible circle are completely melted and B2O is present at the top.]
When the third melt layer is formed and the GaAs melt layer is formed at the bottom, only the pressure inside the high-pressure container is reduced to below S atmosphere. As a result, many bubbles are generated from the GaA3 melt layer, rise within the melt, and diffuse into the atmosphere within the container. At this time, moisture, impurities, etc. in the melt are removed along with bubbles. In this way, by distilling and refining the GaS melt before the crystal pulling operation, the quality of the GaAs single crystal formed is further improved. ” Claims Procedure Amendment C Method) % Formula % A Case Indication Patent Application No. 5181 of 1982! 1. Title of the invention: Process for producing even-quality gallium arsenide single crystal 3. Persons making amendments: Subject of amendment Drawing = 5)

Claims (1)

[Claims] In a method of producing a gallium arsenide single crystal by a liquid confinement pulling method, the gallium arsenide single crystal is grown by pulling a seed crystal while applying a magnetic field of 1200 Gauss or more to the crystal raw material melt. Method for producing arsenic single crystal.