JPS5938187B2 - Method for producing Group 3-5 compound semiconductor single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing single crystals of ■-V group compound semiconductors such as GaAs, InP, InAs, etc., and particularly relates to a method for manufacturing single crystals with a low dislocation density using a boat growth method. It is something.

In the single crystal production of ■-V group compound semiconductors using the boat growth method, the (111) plane has traditionally been grown. This is because (100) plane wafer ~ is easy to cut out, and secondly, in (111) plane growth, crystal growth tends to spread laterally and it is easy to control the crystal growth interface to be flat.

However, even when (111) plane growth is performed, it is difficult to control the crystal growth interface to be flat, especially when producing a single crystal with a large cross-sectional area.

For example, if the growth rate is slowed, the growth interface will become a convex surface, making it easier to generate Beh dislocations, and conversely, if the growth rate is increased, the growth interface will become a concave surface, making it easier to generate defects such as lineage dislocations.

These defects are caused by (111) plane growth and an attempt to forcibly control the growth interface to be flat, and the larger the crystal, the higher the rate at which defects will occur.

It is said that the difficulty in obtaining a high-quality single crystal is proportional to the square of the cross-sectional area of the crystal.

The purpose of the present invention is to provide a method for producing a -V group compound semiconductor single crystal that is suitable for growing a single crystal of good quality and a large cross-sectional area with good reproducibility. The purpose is to grow the (111) plane of the crystal at an inclination angle of 50 to 250 with respect to the plane perpendicular to the direction. Figure 1 shows ■-V manufactured using the manufacturing method that is an embodiment of the present invention.
FIG. 2 is a perspective view of a group compound semiconductor single crystal.

This single crystal has been taken out from the boat, and the right end is the seed crystal 3, which is used as the seed to grow the single crystal 4.

Although the growth direction of the single crystal 4 is the longitudinal direction, the (111) plane 2 is grown with an inclination angle 1 of 50 to 250 with respect to a plane perpendicular to the longitudinal direction. Since the furnace for growing this single crystal 4 usually uses a horizontal electric furnace, the temperature distribution inside the furnace is symmetrical. Therefore, the crystal growth interface tends to be symmetrical with respect to the crystal axis, and in the case of the above method, the (111) plane cannot extend to both sides and tends to be dogleg-shaped. FIG. 2 is a plan view showing the growth interface of the single crystal shown in FIG.

The single crystal 4 forms a bent growth interface 5 in the shape of a dogleg, grows in a growth direction 6 shown by a solid line with an arrow, and advances in the liquid melt 7. The single crystal 4 having such a growth interface 5 has the following features. (1) The peak portion of the growth interface 5 serves as a growth nucleus and also serves as the free surface of the liquid melt, making it difficult to incorporate dislocations.

(2) Since the growth is performed separately on the left and right sides with the peak position of the growth interface 5 as the boundary, it is the same as growing two crystals with small cross-sections in parallel, and a high-quality, large-sized single crystal 4 is stable. can be obtained.

(3) The growth interface 5 has a peak and is apparently convex, but unlike the convex surface when the {111} plane is aligned with the cross section in the growth direction 6, thermal strain at the growth interface There are almost no defects, and the occurrence of defects such as suberly dislocations is suppressed.

(4) Since the growth interface 5 naturally takes the shape of a dogleg, fine adjustment work for controlling the interface becomes difficult.

(6) If a heat dissipation means is added above the growth interface 5, {1
11} It is possible to grow by tilting the plane not only in the horizontal direction but also in the vertical direction.

However, it is clear that the {100} plane of the single crystal obtained by this method has a left-right asymmetric shape that extends slightly in the lateral direction compared to the case of a conventional linear growth interface.

However, the effect of improving the yield of high-quality large-sized single crystals more than compensates for these drawbacks. The method of this example is
A case where this method is applied to the production of aAs single crystal will be described next.

First, Ga4OO9 and Sil2Om9 as a dopant are placed in a quartz glass boat, and a seed crystal with a {111} plane tilted by 15 is placed at one end of the boat.

Furthermore, put As4449 at the other end of this boat and make it 5×1
After evacuation for 1 hour under reduced pressure of 6T0rr or less,
Place in a sealed state in a low temperature furnace.

This low-temperature furnace was kept at about 610°C, and the vapor pressure of As in the quartz boat was maintained at 1at0m.
After the GaAs synthesis reaction is carried out at around 0.degree. C., the temperature is further increased to adjust the seed crystal portion to 1238.degree. C. and the temperature gradient in the GaAs melt to 0.5 deg/CTn to perform seeding. After that, it was cooled at a rate of 1.7deg/Hr, and the whole solidified in 20 hours. After solidification, the mixture was cooled to room temperature at a rate of about 100 deg/hr.

In this way, width 5 cm, length 23 crrLf)Ga
As single crystal 823f! However, as shown in FIG. 2, the growth interface 5 of this crystal was shaped like a "<" with a peak, and the growth stripes (facets) also appeared in the shape of a "<".

When the {100} surface of this single crystal was planarized and dislocation density was measured by etching with Rakuten KOH, the dislocation density was found to be less than 500/d except for about 5 mm around the part in contact with the boat, which is a low value. This shows that it is a single crystal with high dislocation density (EPD).

In particular, the dislocation density at the peak portion of the growth interface 5 is low, with 100
The dislocation density was less than /d. Note that when the inclination angle is less than 5, the {111} planes connect to both sides of the boat, which is the same as normal single crystal growth.

Further, when the inclination angle was 250 or more, the shape of the {100} plane was disturbed and cutting became difficult. That is, it was confirmed through experiments that a range of 50 to 250 is appropriate. The method for producing a GaAs single crystal in this example is to
While a and the dopant are collected, a seed crystal with a {111} plane inclined by 15 degrees is placed at one end of the boat, and As is placed at the other end of the boat to reduce the pressure and then seal it off.

After heating the enclosed boat to fill it with As vapor, it is heated to a high temperature to perform a GaAs synthesis reaction, and the temperature is further increased to melt and seed the GaAs, and a temperature gradient is applied. By removing it, a single crystal with {111} planes grown in a dogleg shape can be obtained.

This single crystal is GaAs with low dislocation density and few crystal defects.
It is a single crystal, and this manufacturing method has the advantage of excellent reproducibility.

Although the above embodiment describes a method for manufacturing a GaAs single crystal, this manufacturing method can also be applied to the case where a compound semiconductor single crystal using other -V group elements is obtained by a boat growth method.

In the method for manufacturing -V group compound semiconductor single crystals of the present invention, the peak portion of the growth interface serves as a growth nucleus, and since that portion is a free surface and has little thermal strain, a high-quality single crystal with low dislocations can be produced. can get.

Furthermore, since the growth occurs separately on the left and right sides with the peak portion of the growth interface as a boundary, it is easy to control the growth interface, and a large single crystal with a high yield can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a -V group compound semiconductor single crystal manufactured using a manufacturing method that is an embodiment of the present invention, and FIG.
FIG. 2 is a plan view showing the growth interface of the single crystal shown in the figure. 1: tilt angle, 2: {111} plane, 3: seed crystal, 4: single crystal, 5: growth interface, 6: growth direction, 7: melt.

Claims (1)

[Claims] 1. A method for producing a III-V group compound semiconductor single crystal by a boat growth method, characterized in that the {111} plane of the crystal is grown at an angle of 5° to 35° with respect to a plane perpendicular to the crystal growth direction. - A method for producing a group V compound semiconductor single crystal.