JPS5819637B2 - Silicon doped gallium tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a gallium arsenide single crystal using a boat growth method, and is a useful method capable of producing a single crystal that can be highly doped with silicon and has a low dislocation density. This is what we provide.

First, we will give a typical example of the conventional manufacturing method of gallium arsenide and discuss its problems.

FIG. 1 is a diagram showing the configuration of a so-called dual-humidity horizontal Bridgman method crystal growth furnace, a temperature distribution diagram in the furnace, and a crystal growth container.

The horizontal axis shows the position inside the growth furnace, and the vertical axis shows the humidity inside the furnace.

Temperature T1. T3 is T1=1250'-1275 respectively
℃.

T3-605°-620°C.

Also, Tm is the melting point of gallium arsenide, approximately Tm = 1238
It is ℃.

In FIG. 1, 1 is a high-purity quartz container containing a high-purity quartz boat 6 that holds a gallium arsenide melt 2;
3 is a small amount of grown gallium arsenide single crystal or a high purity gallium arsenide seed crystal, and 4 is excess arsenic for controlling the vapor pressure of arsenic (As).

7 and 9 schematically show an electric furnace divided into a high temperature heating section A and a low humidity heating section C.

The container 1 is sealed in advance under a high vacuum of 10" mHg or less, but when the container 1 reaches a steady state after being inserted into the furnace, the excess arsenic 4 fills the container with arsenic vapor, creating a pressure of approximately 1 atm. is maintained.

In this state, the electric furnace 7°9 is moved to the left relative to the container 1 at a speed of 5 to 50 mm/hour, thereby single crystallizing potassium arsenide.

Here, a high temperature heating section (temperature T1) and a low temperature heating section (temperature T3)
) is as large as 10° to 50'C/Cm.

Therefore, during the cooling process after solidification, a large difference in graininess occurs in the longitudinal direction within the crystal.

When a temperature difference occurs, strain occurs due to the difference in thermal expansion (difference in lattice constant), and when this amount of strain exceeds the elastic limit of the crystal, plastic deformation occurs and dislocations are generated or multiplied.

In particular, plastic deformation is likely to occur just below the melting point of gallium arsenide, so in this method where the temperature gradient G is large just below the melting point, the dislocation density increases and even crystals with a small cross-sectional area (5 cm or less) are usually 2X 103 cm - It ends up being 2 or more.

If the cross-sectional area is 10 crA or more, it exceeds 1×10 4 crn-2.

It is also known that the following reaction occurs between gallium arsenide melt (including doped silicon) and quartz boats.

4Ga (in GaAs melt) -1-8iO□ (solid) =
2Ga20 (gas) +S i ・
・・・・・・・・・ (1) Si + 5iO3 (solid) = 2
SiO (gas)・・・・・・・・・(2)3Ga20
(Gas) +A s 4 (Gas) -〇a203 (Solid) +
4GaAs (solid) ・・・・・・・・・
・ (3) SiO (gas) = SiO (solid) ・・
(4) When doping silicon at a high concentration, equations (2) and (4) mainly contribute to the reaction.

At first, the reaction of equation (2) proceeds to the right and silicon monoxide (Si
n) generating steam;

This vapor diffuses from the high-temperature heating section to the low-temperature heating section and is condensed by the reaction of equation (4), resulting in a decrease in psio.

Here, the equilibrium constants of equations (1) and (2) are each set to 1 (
T1), 2(T1), CPGa2o, Ps
io ] 2 = 1 (TI) - 2 (TI ).

However, the activity of Ga and the activity of Si are each 1 (T1)
, included in 2 (T1) (, When Psio decreases, PG
Since a20 must increase, equation (1) will proceed to the right, and so-called "wetting" in which the melt and the quartz boat react will proceed.

As a result, a high quality single crystal cannot be obtained.

The present invention solves the above-mentioned difficulties, makes it possible to control the residual silicon concentration in the grown gallium arsenide single crystal over a wide range, and in particular, to control high concentration doping in the range of about 5 x 1017 to 5 x 101 f'cm-3, and The present invention provides a method for producing a gallium arsenide single crystal that allows the dislocation density to be approximately 2 x 103 Crrl-2 or less.

The first invention of the present invention is an improved method of the above-mentioned two-temperature horizontal Bridgman method, which was previously proposed by the present applicant (see Japanese Patent Publication No. 35861/1986). (a) The crystal growth furnace consists of a high-temperature heating section of about 1245°-1270°C, an intermediate-temperature heating section of about 1080'-1220°C, and a low-humidity heating section where the vapor pressure of arsenic is approximately 1 atm (approximately 1 atm). (b) A quartz boat is used as the boat for accommodating the gallium arsenide, and the sealed container for accommodating the quartz boat is located between a chamber for accommodating the boat, a chamber for accommodating the arsenic, and those chambers. Although it is recognized that the arsenic vapor can flow through the pores provided in the pores that inhibit the diffusion of gallium oxide and silicon oxide vapors, (c) the arsenic storage chamber in the pores and the In the manufacturing method, the distance (L2) between the boundary line of In particular, the temperature is 11000-1200'C, and the temperature gradient G between the high temperature heating section and the intermediate temperature heating section (Fig.
is about 2 to 10 C/cm, and the crystal growth rate is about 2
~10 rIrIrL/hour (thereby, the dislocation density is about 2X10''Cr11-2 or less).This is a method for producing a silicon-doped gallium arsenide single crystal with a low dislocation density.

According to the present invention, the cross-sectional area of the single crystal is 5c4 (diameter 35r
ItM), it is possible to produce a silicon-doped gallium arsenide single crystal with a low dislocation density.
Even if the crystal has a small cross-section of less than 2×1O-3Crrl-2, and the cross-sectional area is 10
cm (diameter of 50 semicircles) or more: 1 x 104 cm-2
Only GaAs crystals with dislocation densities above the above have been obtained.

As will be explained later, [Since GaAs crystals are generally grown in the <111> direction, the cross-sectional area 5c77f is a (100) cross-sectional area of about 9 cli, and the cross-sectional area 1 octA is a (100)
The area of part Ii corresponds to approximately 15c77f.

Also, T.S., Plaskett et al., T.S.
he Effect of Growth 0r
ientation on the Crystal
Perfection of Ho-rizon
tal Bridgman GrownGaAs''
.

Journal of Electrochemistry
alSoci ity, Jan, (1971) PP,
115~l 17, (according to this, even a small crystal of a semicircle with a diameter of about 15 m (cross-sectional area 0.9 crrt) <013>
direction (only this grown crystal has a dislocation density of about 1000Cr/
It is said that the number of children decreased to less than 12.

In contrast, according to the present invention, a large-area GaAs crystal with a cross-sectional area of 5c7n-2 (a semicircle with a diameter of 35 mm) or more can have a dislocation density of 2X 10'' cm-2 or less with good reproducibility. be.

Further, in the present invention, after the single crystal has finished growing and the entire single crystal has been placed in the intermediate temperature heating section, it is appropriate to stop the crystal growth furnace and lower the temperature of the furnace to slowly cool it. be.

Next, the second invention of the present invention provides a method according to the first invention in which the silicon concentration in the single crystal is set to a particularly high concentration, approximately 5×10 17 CrrL−3 to 5×10 18 Crrl−
It is characterized by being controlled within a range of 3.

Generally speaking, when impurities are doped at a high concentration, the dislocation density tends to increase rapidly, but according to the method of the present invention, on the contrary, the dislocation density tends to decrease.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 FIG. 2 shows a configuration diagram of a crystal growth furnace using a three-humidity type horizontal bridge 77 method, a humidity distribution diagram in the furnace, and a crystal growth container for manufacturing gallium arsenide single crystals according to an example of the present invention. FIG.

The horizontal axis shows the position inside the growth furnace, and the vertical axis shows the temperature inside the furnace.

Temperature T1. T2. T3 is T1=1245°~
1270℃, T2=1100'-1,200℃, T3=
605°-620°C, especially 610°C.

However, if the amount of excess arsenic 4 is extremely small, T3 can be heated to almost the same level as T2, so Cr can be omitted.

In FIG. 2, 1 is a high-purity quartz container containing a high-purity quartz boat O that holds a gallium arsenide melt 2;
3 is a small amount of grown gallium arsenide single crystal and a high purity or silicon-doped gallium arsenide seed crystal; 4 is excess arsenic for controlling the vapor pressure of arsenic (As).

The quartz boat 6 is shown in its simplest form, but when so-called seeding is performed using a seed crystal, 1 Takashi Suzuki, ``Manufacturing of compound semiconductors and problems'', lecture sponsored by the Japan Economist Center. Materials, October 20th-10th
It is possible to place a thin seed crystal on the shelf of a so-called shelf boat, which has been adopted since it was published in May 21, 1970, PP, 1-16.

Reference numeral 5 denotes a pore, which allows the flow of arsenic vapor but serves to inhibit the diffusion of gallium oxide and silicon oxide vapor.

? , 8.9 schematically show an electric furnace divided into a high temperature heating section A, an intermediate heating section B, and a low temperature heating section C.

Further, G is the humidity gradient between the high wetness heating section A and the intermediate temperature heating section B, which was approximately 2 to 10° C. 1 cm.

Inside boat 6, there is initially gallium (99.9999% purity).
Approximately 500gr of Si and 200mgr of high purity Si are stored, and arsenic (purity 99.9999
%) of about 550gr and high purity arsenic trioxide (AS203)
of 50mgr was accommodated.

The molten gallium arsenide thus generated in the boat 6,
After connecting the silicon-doped gallium arsenide seed crystal having the (111)A s direction in the longitudinal direction of the boat 6, the electric furnace I, 8°9 is turned to the left relative to the quartz container 1, and the It was moved at a speed of 10y+tm/hour.

After all the molten gallium arsenide crystals have solidified, 30~b For example, it was cooled at a rate of about 0° C./hour.

In this way, a large and long gallium arsenide single crystal with a cross-sectional area of 6-10c4 (100 cm), a cross-sectional area of 9-15 cm, and a length of about 30-40 cm was obtained, and the luster on the boat side of this crystal was Very well, no trace of "wetting" between the boat and the melt could be observed.

The total length of the crystal (to obtain a high quality crystal over the entire length, the second
In the figure, it was necessary to set L2≧L1.

Also, the ratio of the temperature gradient G (2 to 10"C/cm) to the crystal growth rate R (2 to 10B/hour), so-called G/R, is 10C,
It is desirable that it be larger than time/cyst (z) □ G51
0℃10n, R510m+++7 o'clock, G/R≦10℃,
In the case of 1/crtl, it is difficult to obtain a low dislocation density GaAs crystal with a cross section of 5 cd or more.

7. Perpendicular to the longitudinal direction of this crystal. C(111)Ga plane 3
About 1 at room humidity using H2SO4:lH2O□:lH2O
As a result of measuring the etch pit density after etching for 0 minutes, it was found that the dislocation density was approximately 500 cm@-2 at the leading end of the crystal and approximately 5oo Crrl@- at the trailing end.

Furthermore, when the (100) plane of this crystal was etched with molten KOH for about 8 minutes and the etch pit density was measured, almost the same results were obtained.

Furthermore, as a result of measuring the Hall coefficient of this crystal by the van der Para method, the carrier concentration at 295° was 2 x 1018 m-3 at the tip and 5 x 1018 Crr at the rear end.
I knew it was l-3.

The effects of Example 1 are explained as follows.

■ The temperature gradient G between the high-temperature heating section and the low-humidity heating section is 2-b.During the cooling process after solidification, the temperature difference in the longitudinal direction within the crystal is small, and the growth rate is small at 2-10 mm/hour.
Since the temperature difference in the radial direction within the crystal is also reduced, thermal strain is small and dislocations do not occur or multiply.

(2) Since the cooling rate after completion of solidification is as low as approximately 0° C./hour, the difference in humidity between the inside and outside of the crystal is small, so thermal distortion is small and dislocations do not occur or multiply.

■ The silicon monoxide vapor generated by the reaction between the silicon in the gallium arsenide melt and the quartz boat (the above-mentioned (2)) has a temperature T2 of the intermediate temperature heating section of 1100°-120°.
Because it is as high as 0°C, it does not condense.

In other words, since equation (4) does not proceed to the right, Psio does not decrease.

As a result, equation (1) does not proceed to the right, so it is considered that "wetting" does not occur.

FIG. 3 shows the role of this intermediate temperature heating zone.

FIG. 3 is a diagram explaining the range in which the concentration of residual silicon in gallium arsenide can be controlled by the present invention. The activity (asi) of silicon in the liquid is shown, and the vertical axis on the right is the concentration Ns of residual silicon in the obtained crystal.
i is shown.

The straight line 10-a in the figure represents the equation (4), and the straight line 1o-b represents the equilibrium relationship of the equation (3).

Residual silicon concentration is controlled (T2 is 1045℃)
It is necessary that 〈T2〈m, p is within the range of 1050℃〈T2〈1
The temperature needed to be 200°C.

In particular, according to the present invention, the residual silicon concentration Nsi in the crystal can be reduced to 5
X 10”cm” (Nsl〈5×1018Crr
It can be seen that in order to obtain a high quality single crystal of l-3, the temperature of T2 must be 1100°C<T2<1200°C.

Also, the silicon concentration is about 1013 Crrl-3 to 5×101
In order to be controlled within the range of 7cm-3, the temperature must be 1050℃1.
<1200°C is sufficient, but if the cross-sectional area is 5 crA or more, the dislocation density will be 2×103 Crrv2 or less (this also requires 1100°C<T2<1200°C).

In addition, the silicon concentration is approximately 1013 cm-3 ~ 5 x 1018
It is considered to be effective to control the impurity to cm-3 and dope with an impurity other than Si.

As detailed above, the method of the present invention can control the residual silicon concentration in the crystal and reduce the dislocation density by The purpose is to provide a method that can reduce the amount to 103Crrl-2 or less.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a crystal growth furnace, a humidity distribution diagram in the furnace, and a crystal growth container in the case of producing gallium arsenide crystals by a conventional method. FIG. 2 is a diagram showing a configuration diagram of a crystal growth furnace, a humidity distribution diagram in the furnace, and a container for crystal growth when producing gallium arsenide crystals according to an embodiment of the present invention. Figure 3 shows the residual silicon 7 in gallium arsenide according to the present invention.
FIG. 3 is a diagram illustrating a range in which the darkness W of the image can be controlled. In the figure, 1 is a quartz container, 2 is a gallium arsenide melt, and 3 is a quartz container.
is crystallized gallium arsenide or gallium arsenide seed crystal, 4 is excess arsenic, 5 is pore section, 6 is quartz boat, 7 is high temperature heating section, 8 is intermediate temperature heating section, ' 9 is low temperature heating section .

Claims (1)

[Claims] 1. Gallium arsenide single crystal is grown using the three-temperature horizontal Bridgman method, that is, (a) the crystal growth furnace has a high-temperature heating section of about 1245°-1270°C and an intermediate heating section of about 1080°-1220°C. It is equipped with a temperature heating section and a low humidity heating section that heats the vapor pressure of arsenic to approximately 1 atmosphere, (b) a quartz boat is used as a boat for containing gallium arsenide, and a sealed container for containing the quartz boat. The chamber housing the boat, the chamber housing the arsenic, and the chambers installed between these chambers allow the flow of arsenic vapor, but there are no restrictions that prevent the diffusion of gallium oxide or silicon oxide vapor. (c) the distance (L2) between the boundary line of the pores with the arsenic storage chamber and the lowest temperature position of the intermediate temperature heating section is approximately equal to the total length (Ll) of the boat; In the manufacturing method, the humidity of the intermediate temperature heating section is set to 1100° C. to 1200° C., and the temperature gradient G between the high temperature heating section and the intermediate temperature heating section is set (FIG. 2). is about 2 to 10 C/cm, and the crystal growth rate is about 2 to 1
By setting the rate to 0 kaku/hour, the dislocation density is approximately 2×103c.
A method for producing a silicon-doped gallium arsenide single crystal having a low dislocation density, characterized in that the dislocation density is Wl-2 or less. 2. In the method according to claim 1, the silicon concentration in the single crystal is approximately 5×10 17 crrl-3 to 5×
A method for producing a potassium arsenide single crystal doped with a high concentration of silicon and having a low dislocation density, the method comprising controlling the dislocation density to a range of 1018 Crrl-3.