JP2003212698A - Method of manufacturing gallium phosphide single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the yield of single crystals by suppressing the generation of polycrystals at a constant diameter portion and the bottom part of an obtained GaP single crystal, and controlling the shape of the solid-liquid interface in order to prevent solidification under such a condition that the solid-liquid interface forms a shape extremely protruded in the melt side during growth of the crystal, when the GaP single crystal of the (100) azimuth is manufactured by an LEC method. <P>SOLUTION: The temperature of the bottom of a crucible at the time when the diameter of the shoulder part of the GaP single crystal 7 reaches a predetermined value is defined as T1, and the protruding degree L1 (mm) of the obtained GaP single crystal 7 is obtained by measuring the shape of the solid-liquid interface at the bottom of the obtained GaP single crystal 7. (1) When the protruding degree L1 is within a range of 6 to 8 mm, the next temperature T2 of the bottom of the crucible is set to this temperature T1 of the bottom of the crucible, and (2) when the protruding degree L1 is out of the range of 6 to 8 mm, the next temperature T2 of the bottom of the crucible is obtained from following relation: T2=T1+t, wherein, t is a corrective temperature and given by following relation: t=(L1-optimum protruding degree target value)×correction temperature per 1 mm of the protruding degree. <P>COPYRIGHT: (C)2003,JPO

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 gallium phosphide single crystal by a liquid sealing pulling method, and more particularly to a gallium phosphide single crystal capable of suppressing polycrystallization and improving single crystal yield. The present invention relates to a method for producing crystals.

[0002]

2. Description of the Related Art A gallium phosphide single crystal used as a substrate for manufacturing a light emitting diode in the visible light region (hereinafter,
"GaP single crystal" is grown by a liquid sealing pulling method (hereinafter abbreviated as "LEC method").

A manufacturing apparatus using the LEC method will be described with reference to the drawings. FIG. 1 is a sectional view showing a manufacturing apparatus by the LEC method.

The manufacturing apparatus by the LEC method comprises a pressure vessel 1 that can withstand a high pressure of about 100 atm.
The P single crystal is manufactured in an inert gas such as N ₂ or Ar at 50 atm. A quartz crucible 4 is arranged in a wall 11 and a base 12 in the center of the pressure vessel 1, and a gallium phosphide polycrystal (hereinafter, referred to as " GaP polycrystal ”) and an impurity exhibiting n-type or p-type electrical characteristics in the crystal, and further B _{2 is used} as a liquid sealant 8 for preventing volatile decomposition of phosphorus when the raw material is melted. Add O ₃ . A carbon heater 2 for heating is arranged around a quartz crucible 4, and a cylindrical carbon heat insulating material 3 is provided around the carbon heater 2.

A method of growing a GaP single crystal with the manufacturing apparatus shown in FIG. 1 will be described. The melting point of gallium phosphide is 1465 ° C., and the decomposition pressure of phosphorus at this time is about 35.
Atmospheric pressure and very high.

In a high pressure inert gas atmosphere as described above,
The heating carbon heater 2 is energized to raise the temperature to the melting point of GaP. After the GaP polycrystal in the quartz crucible 4 has melted,
It was attached to the holder 10 connected to the upper shaft 5 (1
00) Face seed crystal 6 is lowered and B ₂ in quartz crucible 4
Seeding is performed by immersing in a gallium phosphide melt located under the O ₃ layer. At this time, the quartz crucible 4 contained in the wall 11 and the base 12 is rotated at a designated number of rotations while maintaining the temperature of the gallium phosphide melt compatible with the (100) face seed crystal 6 in advance. On the other hand, the (100) face seed crystal 6 is also pulled up at a predetermined speed while being rotated at a specified number of rotations to grow a GaP single crystal 7.

However, in the GaP single crystal 7 obtained by the above-mentioned method, polycrystallization is observed in the crystal straight body part and the crystal bottom part. In addition, a crystal mass sensor (not shown) that monitors the crystal mass during crystal growth gives an abnormal signal of a rapid mass increase and the operation is stopped (hereinafter abbreviated as solidification).
But sometimes it happened. The cause of this polycrystallization and solidification is that the temperature distribution in the quartz crucible 4 changes due to the deterioration of the heat insulating material 3 and the heating carbon heater 2 arranged in the pressure vessel 1, and the solid-liquid interface shape changes. It is thought to be to do.

Conventionally, to solve the problem of the temperature distribution fluctuation, crystal growth has been carried out while empirically changing the relative positions of the quartz crucible 4 and the heating carbon heater 2 (hereinafter referred to as crucible setting). . However, this measure requires several test growths in order to respond after seeing the results of growing a large number of single crystals and to confirm the single crystallization after changing the growth conditions. There were many losses, and the single crystal yield was reduced.

[0009]

DISCLOSURE OF THE INVENTION The present invention, when producing a GaP single crystal having a (100) orientation by the LEC method, prevents the polycrystallization which occurs in the straight body portion or the crystal bottom portion of the obtained GaP single crystal. For the purpose of improving the single crystal yield by controlling the shape of the solid-liquid interface so that the shape of the solid-liquid interface does not become extremely convex and solidify toward the melt during crystal growth. There is.

The height of the portion which is convex and solidified as described above, that is, the portion which is tapered from the crystal straight body portion to the crystal bottom portion is called convexity.

[0011]

A method for producing a gallium phosphide single crystal of the present invention is a liquid encapsulation pulling method using a (100) face seed crystal with boron oxide (B ₂ O ₃ ) as a liquid encapsulant. A method for producing a gallium phosphide single crystal, in which the crucible bottom temperature T1 at the time when the crystal shoulder portion of the gallium phosphide single crystal has grown to a predetermined diameter and the crystal bottom portion of the obtained gallium phosphide single crystal From the convexity L1 (unit: mm) of the gallium phosphide single crystal obtained by measuring the solid-liquid interface shape, (1) If the convexity L1 is in the range of 6 to 8 mm, The crucible bottom temperature T2 is obtained by Equation 4.

[0012]

[Formula 4] (2) When the convexity L1 is outside the range of 6 to 8 mm, the correction temperature t calculated by the equation 5 is used,

[0013]

[Formula 5] The next crucible bottom temperature T2 is obtained by Equation 6.

[0014]

[Formula 6] It is preferable that the optimum target value of the convexity of the crystal bottom of the gallium phosphide single crystal is within the range of 6 to 8 mm.

Alternatively, the angle between the ridge line of the crystal bottom of the gallium phosphide single crystal and the horizontal plane when the gallium phosphide single crystal is suspended is 13.5-17.7 °.
The optimum convexity target value of the crystal bottom of the gallium phosphide single crystal is determined.

[0016]

In order to solve the conventional problems, the present inventor has controlled the crucible bottom temperature in the initial stage of crystal growth relative to the previous crystal growth, so that the temperature during the crystal growth can be controlled. It was found that the shape of the liquid interface can be controlled extremely reproducibly. This is industrially effective in that it is unlikely to be affected by changes in temperature distribution due to deterioration of the heating carbon heater and the heat insulating material.

The present inventor utilizes the pressure vessel 1 shown in FIG. 1 and sets the pressure in the pressure vessel 1 to 50 atm to prevent the decomposition of the gallium phosphide melt while growing the first GaP single crystal. did. FIG. 3 shows a side view of the grown GaP single crystal.

The solid-liquid interface shape of the crystal bottom portion 7b of the GaP single crystal 7 grown for the first time was measured with a caliper or the like, and the convexity L1 of the crystal and the crystal bottom portion 7 were checked against the occurrence of polycrystallization or solidification.
The relationship between the angle formed by the ridgeline of b and the horizontal plane and the like was investigated.

As a result, there is a correlation between the degree of occurrence of polycrystallization and solidification and the convexity L1, and it is difficult for polycrystallization and solidification to occur when the convexity L1 is in the range of 6 to 8 mm. I found out. If the lower limit of the convexity L1 is smaller than 6 mm, polycrystallization is likely to occur in the crystal straight body portion of the obtained GaP single crystal 7, and if it is larger than 8 mm, the crystal bottom portion 7b of the obtained GaP single crystal 7 is The number of cases where the solid-liquid interface shape became extremely convex on the melt side (above interface growth) and solidified increased. In addition, the crystal bottom portion 7 of the obtained GaP single crystal 7
The angle between the ridge of b and the horizontal plane is 13.5-17.7 °.
Then, similarly to the above, it was found that polycrystallization and solidification were unlikely to occur.

Next, the inventor has conducted a number of growth tests based on the above findings, and the lower limit of the convexity L1 of the crystal bottom portion 7b of the GaP single crystal 7 in which the solid-liquid interface shape is less likely to be polycrystallized or solidified. Is 6 mm and the upper limit of the convexity L1 is 8 mm, in order to control the angle between the ridgeline of the crystal bottom portion 7b of the GaP single crystal 7 and the horizontal plane to 13.5 to 17.7 °,
As shown in FIG. 1, it has been found that a crucible temperature control method for controlling the crucible bottom temperature measured by the thermocouple 13 attached to the lower shaft 9 is important.

That is, the method for producing a gallium phosphide single crystal of the present invention employs a liquid sealing pulling method using (100) face seed crystal 6 with boron oxide (B ₂ O ₃ ) as the liquid sealing agent 8. A method for producing a gallium phosphide single crystal 7, wherein the crucible bottom temperature T1 at the time when the crystal shoulder portion 7a of the gallium phosphide single crystal 7 grows to a predetermined diameter, and the obtained crystal of the gallium phosphide single crystal 7 From the convexity L1 (unit: mm) of the gallium phosphide single crystal 7 obtained by measuring the solid-liquid interface shape of the bottom portion 7b, (1) the convexity L1 is 6
When it is within the range of ˜8 mm, the next crucible bottom temperature T2 is obtained by the equation 7.

[0022]

[Formula 7] (2) When the convexity L1 is out of the range of 6 to 8 mm, the correction temperature t calculated by the equation 8 is used,

[0023]

[Formula 8] The next crucible bottom temperature T2 is obtained by Expression 9.

[0024]

[Formula 9] The optimum convexity target value of the crystal bottom portion 7b of the gallium phosphide single crystal 7 is preferably within the range of 6 to 8 mm.

Alternatively, the angle between the ridgeline of the crystal bottom portion 7b of the gallium phosphide single crystal 7 and the horizontal plane when the gallium phosphide single crystal 7 is suspended is 13.5 to 17.7 °. The optimum convexity target value of the crystal bottom portion 7b of the gallium phosphide single crystal 7 is determined.

Hereinafter, the present invention will be described in detail with reference to the drawings by way of examples.

[0027]

EXAMPLE 1 An example of the present invention will be described in detail.

A carbon heat insulating material 3 having a high heat insulating property was installed in the pressure vessel 1, and a quartz crucible having a diameter of 100 mmΦ and a depth of 100 mm was used as the crucible 4.

First, 1100 g of a GaP polycrystalline raw material as a raw material and S (sulfur) as an additive impurity are added to the crucible 4 and 150 g of a liquid sealant B ₂ O _{3 is} further added to heat them so as to surround them. Arrange the heater 2. Pressure vessel 1
After the inside was evacuated, the carbon heater 2 for heating was energized in a high-pressure nitrogen gas atmosphere to raise the temperature above the GaP melting point of 1465 ° C., and the GaP polycrystal was melted, and then arranged in advance (100). The seed crystal 6 in the azimuth direction is rotated and lowered, and G
After soaking in the aP melt, crystal growth was started while pulling up at a speed of 10 mm / h. Maximum diameter of crystal shoulder is 40mm
The bottom temperature of the crucible at φ was 1410 ° C.

The convexity L of the crystal bottom of the obtained GaP single crystal
When 1 was measured with a caliper, it was 5 mm, so the corrected temperature t was calculated according to the equation 8. Optimal convexity target value is 7
mm, the correction temperature per 1 mm of convexity is 3 ° C / m
m.

That is, the correction temperature t = (5-7) × 3 =
It is −6 ° C., and the right side of Expression 9 is 1410 ° C. (current crucible bottom temperature T1) −6 ° C. (correction temperature t) = 1404 ° C. This is set as the next crucible bottom temperature T2.

According to the above-mentioned method, the GaP single crystal was grown to 2
I ran 00 runs.

The ratio of the convexity of the crystal bottom of 6 to 8 mm and the single crystal yield are shown in Table 1, and the frequency distribution of the convexity is shown in FIG.

As shown in Table 1, the crystal bottom has a convexity of 6 to
88.5% was within the proper range of 8 mm,
The single crystal yield was also 90% or more.

(Conventional Example) For comparison, 200 runs of GaP single crystals were grown by the conventional method without using the method of the present invention.

The ratio of the convexity of the crystal bottom of 6 to 8 mm and the single crystal yield are shown in Table 1 (the frequency distribution of the convexity is not shown).

As shown in Table 1, the crystal bottom has a convexity of 6 to
What was within the proper range of 8 mm was 60.3%,
The single crystal yield was 75.0%, confirming the effectiveness of the present invention.

[0038]

[Table 1]

[0039]

As described above, according to the method of the present invention, GaP having the (100) orientation by the liquid sealing pulling method is used.
When producing a single crystal, the problem of polycrystallization that occurs in the straight body part of the crystal or the bottom part of the crystal, and the problem that the solid-liquid interface shape is extremely convex and solidifies on the melt side during crystal growth. This was improved by controlling the convexity of the crystal bottom of the shape, the single crystal yield was greatly improved, and stable operation became possible.

[Brief description of drawings]

FIG. 1 is a sectional view showing an apparatus for producing a single crystal by the LEC method.

FIG. 2 is a bar graph showing the frequency distribution of the convexity of the crystal bottom portion in the example.

FIG. 3 is a side view showing a grown GaP single crystal.

[Explanation of symbols]

1 Pressure Vessel 2 Heating Carbon Heater 3 Heat Insulating Material 4 Quartz Crucible 5 Upper Shaft 6 (100) Orientation Seed Crystal 7 GaP Single Crystal 7a Crystal Shoulder 7b Crystal Bottom 8 Liquid Sealant (B ₂ O ₃ ) 9 Lower Shaft 10 Holder 11 Wall 12 Base 13 Thermocouple (crucible bottom temperature)

Claims (3)

[Claims] 1. A method for producing a gallium phosphide single crystal by a liquid encapsulation pull-up method using a (100) face seed crystal with boron oxide (B ₂ O ₃ ) as a liquid encapsulant.
Phosphorus obtained by measuring the crucible bottom temperature T1 at the time when the crystal shoulder of the gallium phosphide single crystal grows to a predetermined diameter and the solid-liquid interface shape of the crystal bottom of the obtained gallium phosphide single crystal. Convexity L1 of gallium single crystal (unit: m
m) and (1) when the convexity L1 is in the range of 6 to 8 mm, the next crucible bottom temperature T2 is obtained by Equation 1, and (2) When the convexity L1 is outside the range of 6 to 8 mm, the corrected temperature t calculated by the equation 2 is used to calculate Obtain the next crucible bottom temperature T2 by Equation 3 [Equation 3] A method for producing a gallium phosphide single crystal, comprising: 2. The method for producing a gallium phosphide single crystal according to claim 1, wherein the optimum convexity target value of the crystal bottom of the gallium phosphide single crystal is within a range of 6 to 8 mm. 3. The gallium phosphide so that the angle between the ridgeline of the crystal bottom of the gallium phosphide single crystal and the horizontal plane when the gallium phosphide single crystal hangs is 13.5-17.7 °. The method for producing a gallium phosphide single crystal according to claim 1, wherein an optimum convexity target value of the crystal bottom of the single crystal is determined.