JPS6058199B2 - Method for manufacturing gallium arsenide single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a semi-insulating gallium arsenide (CaAs) single crystal having a resistivity of 1σΩ·cm or more.

A high-purity GaAs single crystal has a specific resistance of approximately Ω and is semi-insulating on the zero plane. Capacity can be reduced,
Since elements can be easily separated, integration density can be increased.

Up to now, methods for manufacturing semi-insulating GaAs single crystals include port growth, low-pressure sealing pulling method, and high-pressure sealing pulling method (direct synthesis method from Ga and As).
, Yo, +11↓ 4Z has silicon mixed into the material from quartz, which is the boat material, and its resistivity decreases. For this reason, chromium is usually added to make it semi-insulating. However, it has problems such as variations in properties due to non-uniform distribution of chromium and changes in properties during the heat treatment process, and the internal dislocation density distribution of the obtained crystal wafer tends to be U-shaped. Furthermore, since the low-pressure sealing and pulling up method uses GaAs polycrystals produced by the boat growth method as a raw material, the purity of the raw material is low and chromium must be added. The high-pressure seal pulling method does not require the addition of chromium, but since crystals are created under high pressure, defects are likely to occur in the crystals due to the influence of the thermal environment due to pressure, and the use of liquid sealants and high-pressure gas convection As a result, the manufacturing process is complicated, and the internal dislocation density distribution of the obtained crystal wafer tends to be W-shaped. Therefore, although it is difficult to produce high-quality semi-insulating single crystals, it is easy to produce high-purity polycrystals because the amount of molten liquid splashed into the furnace is small. I This invention does not add impurities such as chromium, that is, the resistance value is 1Ω・α without addition.
The purpose of the present invention is to provide a method for producing the above semi-insulating aAs single crystal with high yield and good reproducibility. is synthesized, this crystal is crushed, the crushed GaAs crystal is heated and melted under low pressure below the atmospheric pressure, and a GaAs single crystal is obtained by a pulling method.

To explain this invention based on the attached drawings, FIG. 1 shows an example of a single crystal manufacturing apparatus by a pulling method, in which 1 is a high-pressure container, a crucible 3 is installed in this high-pressure container 1, The crucible is rotatably supported by a support member 4, and heated to a predetermined temperature by a heater 2 provided around the crucible.

At the top of the crucible is a pulling shaft 5 with a seed crystal 6 at the tip.
is provided, and this pulling shaft is configured to rotate and move up and down. In the present invention, the crucible 3
Either quartz or pyrolyte nitride polymer may be used, but since the latter does not contain silicon, contamination with impurities can be prevented to that extent. Gallium (Ga) and arsenic (As) are placed in this crucible in such proportions that a single crystal with a desired composition ratio can be obtained. Next, B2O3 is added as a sealant in such an amount that when melted, it forms a layer with a thickness of 1C71 or more. The graphs in Figure 2 are B, O
It is clear that the higher the water content of B2O3, the greater the gettering effect of impurities due to water, and the specific resistance of 1Cf'Ω・Cm is shown. In order to obtain a GaAs single crystal, it is necessary to use wet 803 having a water content of 1200 ppm or more. As mentioned above, a predetermined amount of Ga, AS is placed in the crucible.
, B2O3, the crucible is placed in a high-pressure container 1, an inert gas such as argon or nitrogen is pressurized to create a high pressure of 5 leakage pressure or more, and the crucible 3 is heated by a heater 2. Heat to above the melting point of GaAs (approximately 1260'C).

Then, in the crucible, a GaAs melt layer 7 is formed in the lower part, and a B2O3 melt layer 8 is formed in the upper part, and the B2O3 layer acts as a high-pressure sealant to prevent evaporation of the GaAs melt. At this time, B2O3 with a high moisture content is used. In order to
Impurities, such as silicon, in the GaAs melt are gettered, and the melt is highly purified. In this state, the seed crystal 6 is brought into contact with the GaAs melt 7 and pulled up to form a GaAs crystal. In the above-mentioned pulling process, the crucible or the pulling shaft 5 is rotated and stirred at an appropriate speed in order to maintain the GaAs melt/solution homogeneous as required.
Further, since a single crystal is not manufactured, the pulling speed of the seed crystal may be about 5 to 20 W$L/h. The crystalline material thus obtained is ground into pieces of 1 an square or less by an appropriate method in order to facilitate melting. Next, an etching process is performed to remove impurities attached to the pulverized material. This etching treatment is carried out using sulfuric acid, hydrochloric acid, nitric acid, hydrogen peroxide, etc.; sulfuric acid is effective for removing organic matter adhering to the surface of the pulverized material, and hydrochloric acid and nitric acid are effective for removing heavy metals. The Ga, As crystals crushed and purified in this way are put into the crucible again together with B2O3 as a sealing agent, and the inside of the high-pressure container is heated with inert gas under medium pressure or lower pressure of 10 to 2 msec. Heating GaAs crystal and B2O
Ga. Contact with As solution, 1
By pulling at a speed of about 5 wn/h, a GaAs single crystal having a specific resistance of 1 Cf'Ω·α or more can be obtained.

B2O3 added above can be used in either wet type or dry type. Further, when pulling the seed crystal, the crucible and the pulling shaft are rotated at an appropriate speed as necessary. As is clear from the above description, the present invention uses Y! as a sealant! G that uses wet type B2O3 with high water content to remove impurities by gettering effect.
By once making an aAs crystal, and then remelting this crystal and pulling it under pressure below medium pressure, it is possible to produce a G with a specific resistance of 1 Cf'Ω・α or more without the crystal defects seen in the high-pressure method.
An aAs single crystal can be obtained with good reproducibility.

Furthermore, by using B2O3 with a water content of 1500 ppm or more and controlling the pulling speed of the seed crystal, the specific resistance can be reduced to 10.
A GaAs single crystal having a resistivity of 3Ω·α or more and having a substantially uniform resistance distribution within the crystal can be easily obtained. Next, examples of the present invention will be described.

Using a single crystal manufacturing apparatus having the structure shown in Fig. 1, the inner diameter is 100W$L1 and the height is 10c)T! r! Is the purity of N's Pyrolytec boron nitride crucible? 50% of the raw materials Ga and As
0y, then the moisture content is 2000ppm (7) B2
I put in 160f of O3.

This crucible is placed in a high-pressure container, and argon gas is pressurized to bring the pressure to about (4), while the crucible is heated to about
It was heated to 300°C. As a result of the above heating, a B2O3 melt was formed in the upper layer and a GaAs melt was formed in the lower layer in the crucible. When the GaAs is completely melted in the crucible, a seed crystal is brought into contact with the GaAs melt, and 157n! It was pulled up at a speed of n/h. During this lifting operation, the crucible is
The seed crystal was rotated five times in the opposite direction relative to the crucible at a rate of [. Approximately 50mm in diameter due to the above lifting operation.
A Ga crystal having a length of W1m1 and a length of about 100TfrIfL1 and a weight of about 900y was obtained.

Next, this GaAs crystal was crushed to a size of 1 cm square or less, etched for 5 minutes using a mixed solution of H2SO4:H2O2:H2O in a ratio of 5:1:1, and after thoroughly washing with water, HCl:HNO3: After etching was performed again for 3 minutes using a 1:1:1 H2O mixture, the substrate was thoroughly washed with pure water. The GaAs crystals crushed and purified in this way are again B
, O3, and the crucible was placed in a high-pressure container, and argon gas was injected under pressure to bring the pressure to about W atm, and the crucible was heated to about 1300 sc. When the GaAs in the crucible is completely melted, a seed crystal is brought into contact with the GaAs melt and 5T
n! It was pulled up at a rate of n/h. At this time, the crucible is 1
At a rate of 20 times per minute, the seed crystal is
rotated at a rate of 1. By the above-mentioned pulling operation, a cylindrical GaAs single crystal with a diameter of about 5" and a length of about 100 m was obtained. Next, the shoulder portion and the middle portion of this cylindrical ρAAs single crystal were cut out, and the specific resistance from one end of each wafer through the diameter to the other end was measured. The specific resistance of the shoulder wafer is shown in Figure 3a, and the specific resistance of the body wafer is shown in Figure 3.
Shown in Figure b. As is clear from the graph above, the shoulder area,
The resistivity of all the wafers in the body exceeded 1 Cf3Ω·double, and the resistance distribution was almost uniform at all points.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a single crystal production apparatus, FIG. 2 is a graph showing the relationship between the water content of B2O3 used as a capsule in the present invention and the specific resistance of the GaAs single crystal obtained, and FIG. 2 is a graph showing the specific resistance of Ga, As single crystals obtained by the method of the invention.

Claims (1)

[Claims] 1. Gallium, arsenic, and boron oxide with a water content of 1200 ppm or more are heated at a temperature higher than the melting temperature of gallium arsenide under a high pressure of 50 atmospheres or higher to form a melt in which the upper layer is a boron oxide melt and the lower layer is a gallium arsenide melt. A seed crystal is brought into contact with the gallium arsenide solution and pulled up to create a gallium arsenide crystal, and the obtained crystal is heated and melted together with boron oxide under a pressure of 10 to 20 atmospheres to melt the gallium arsenide formed in the lower layer. A method for producing a gallium arsenide single crystal, characterized by bringing a seed crystal into contact with a liquid and pulling it up.