JPH11268998A - Gallium arsenic single crystal ingot, its production, and gallium arsenic single crystal wafer using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the production of wafers suitable for the ion injection producible in a high yield by obtaining GaAs single crystal that has a low EL2 concentration and high uniformity from the top to the tail. SOLUTION: Seed crystal 3 of GaAs single crystal 3 is arranged in the lower part of the crucible 5 in the rack 8 and GaAs polycrystal is charged in the remaining space of the crucible 5 and the polycrystal are covered with B2 O3 as a sealant 4. Then, an inert gas is introduced into the air-tight vessel 10 and the pressure is adjusted to a prescribed value. The crucible is heated, with the heater 6 so that the temperature in the upper part may become more than 5 deg.C higher than the bottom temperature to melt the GaAs polycrystal. Then, the rack 8 is allowed to move downward with the lower shaft 19 to solidify the polycrystal melt 2 thereby growing a single crystal of GaAs. The resultant GaAs single crystal ingot has the EL concentration ranging of from 0.8 to 1.4×10<16> cm<-3> , the change rate of the EL2 concentration is <=10% at the top and the tail and the single crystal is homogeneous.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaAs single crystal ingot, a method of manufacturing the same, and a method of producing a Ga ingot using the same.
The present invention relates to an As single crystal wafer, and more particularly to a GaAs single crystal wafer used for integrated circuits and microwave devices, a GaAs single crystal ingot for collecting the wafer, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, GaAs single crystals have been mainly grown by a liquid encapsulated pulling method (liquid encapsulated pulling method).
Czochralski method (LEC method) was used.

However, when a GaAs crystal substrate grown by the LEC method is used for an integrated circuit or a microwave device, there has been a problem that device characteristics such as frequency dispersion and low-frequency oscillation occur. This is because the GaAs crystal grown by the LEC method has an EL2 concentration of about 1.5 × 1.
It was thought that one of the causes was a high value of 0 ¹⁶ cm ^-3 .

In addition, "Crystal growth and evaluation of compound semiconductors"
Part 3 (Edited by Junichi Nishizawa, Semiconductor Research 29, pp.3-p
p. 29) 1. Development of Mass Production Technology for Pulled Crystals for GaAsIC ”(Reference 1) discloses that Ga grown by the LEC method is used.
The relationship between the composition of the raw material melt and the EL2 concentration in the As crystal is disclosed.

According to Document 1, the arsenic ratio (A
When s / (Ga + As)) is 0.501, EL2
The concentration is almost constant over the entire length of the obtained ingot. However, when the arsenic ratio is higher than this, the EL2 concentration gradually increases toward the tail of the ingot, while when the arsenic ratio is lower than this, the EL2 concentration gradually decreases toward the tail of the ingot, and the head of the ingot is reduced. It is shown that the EL2 concentration changes significantly between the tail and the tail.

Japanese Unexamined Patent Application Publication No. 9-8048 (Reference 2) has an effect of suppressing frequency dispersion when used in an element by annealing a GaAs wafer to make the vicinity of the surface Ga rich. It is disclosed.

On the other hand, "Growth and properties of semi
insulating VGF-GaAs; E. Buhrig et al; Materials Sc
ience & Engineering B44 (1997) pp. 248
~ Pp. 251) (Reference 3) includes a vertical temperature gradient method (Ve
r2 in a GaAs single crystal grown by the rtical Gradient Freezing method (VGF method).
There is a ^statement that the concentration was as low as × 10 ¹⁶ cm ^-3 . Also, Japanese Patent Application Laid-Open No. HEI 3-122097 (Document 4) discloses a vertical Bridgman method: VB
Method, the EL2 concentration is 0.85 to 1.1 × 10 ¹⁶ cm ⁻³ in the GaAs single crystal grown by the method, and the EL2 concentration is 0.4 to 0.66 × in the GaAs single crystal grown by the VGF method. There was a ^statement that it was 10 ¹⁶ cm ^-3 .

[0008] However, in References 3 and 4, such an E is provided over the entire length of the single crystal ingot.
There is no description as to whether or not a low value of the L2 concentration is obtained.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device having a high yield because the EL2 concentration, which may be one of the causes of the device characteristic failure, is low and uniform from the head to the tail of the ingot. An object of the present invention is to provide a GaAs single crystal ingot, a method for manufacturing the same, and a GaAs single crystal wafer using the same, which can obtain a wafer suitable for ion implantation.

[0010]

According to the present invention, G is provided.
The aAs single crystal ingot is an ingot made of a GaAs single crystal, and has an EL2 concentration of 0.8 to 1.4 × 10 ¹⁶ c in the entire region from the head to the tail of the ingot.
m- ³ .

In the specification of the present application, the "head of the ingot" means the total length of the GaAs single crystal ingot 1 as L (cm) and the seed crystal 3 side end of the GaAs single crystal ingot 1 as shown in FIG. Assuming that the length from the part is x (cm), it means a position represented by x / L = 0.1. Here, the position represented by x / L = 0.1 is
When the solidification rate g at the end of the seed crystal 3 side of the GaAs single crystal ingot 1 is set to 0, the solidification rate g can be expressed as g = 0.1.

In the specification of the present application, the "tail of the ingot" means a position represented by x / L = 0.8. Here, the position represented by x / L = 0.8 can also be represented as a solidification ratio g = 0.8.

[0013] In the GaAs single crystal ingot according to the second aspect of the present invention, in the configuration of the first aspect of the present invention, the rate of change between the EL2 concentration at the head of the ingot and the EL2 concentration at the tail of the ingot is less than 10%. It is characterized by having.

According to a third aspect of the present invention, there is provided a GaAs single crystal ingot according to the first or second aspect of the present invention, wherein the GaAs single crystal has an average dislocation density of 10,000 cm.
⁻² , and the average residual strain of the GaAs single crystal (| Sr
−St |) is less than 1 × 10 ⁻⁵ , and the diameter of the ingot is 3 inches or more.

A GaAs single crystal wafer according to a fourth aspect of the present invention is a wafer obtained from an ingot made of a GaAs single crystal, and has an EL2 concentration of 0.8 to 1.0 in the entire region from the head to the tail of the ingot. 4 × 10 ¹⁶ cm
^-3 range.

According to a fifth aspect of the present invention, there is provided a GaAs single crystal wafer according to the fourth aspect of the present invention, wherein the EL2 concentration at the head of the ingot and the E2 concentration at the tail of the ingot.
The rate of change from the L2 concentration is less than 10%.

The GaAs single crystal wafer according to the invention of claim 6 is a plurality of wafers collected from an ingot made of GaAs single crystal, and each of the plurality of wafers has an EL2 concentration of 0.8 to 1.4 × 10 ^16. cm ^-3 , wherein the average of the rate of change in EL2 concentration between adjacent wafers of the plurality of wafers is less than 0.1%.

According to a seventh aspect of the present invention, there is provided a GaAs single crystal wafer according to any one of the fourth to sixth aspects, wherein the average dislocation density of the GaAs single crystal is 10,000 c.
m ⁻² and the average residual strain of the GaAs single crystal is 1 ×
Less than 10 ^-5 , and the diameter of the wafer is 3 inches or more.

According to the method of manufacturing a GaAs single crystal ingot according to the present invention, the GaAs single crystal has an EL2 concentration of 0.8 to 1.4 × 10 ¹⁶ cm ^-3 in the entire region from the head to the tail. A method for manufacturing an ingot, comprising: disposing a seed crystal made of a single-crystal GaAs compound on the bottom of a vertically arranged crucible; disposing a polycrystalline GaAs compound raw material on the remainder of the crucible; Disposing the GaAs compound raw material in the heating means by setting the temperature of the top of the crucible to be higher than the temperature of the bottom of the crucible by 5 ° C. or more by the heating means and heating. The GaAs compound raw material melted from the bottom of the crucible is solidified to form GaAs.
Growing a single crystal.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a view showing a VB method of producing a GaAs single crystal ingot according to the present invention.
It is sectional drawing which shows an example of an As single crystal growing apparatus.

Referring to FIG. 2, this GaAs single crystal growing apparatus 100 includes an airtight container 10, a support 8 and a heater 6.
And a heat insulating material 7. A lower shaft 19 is attached to a lower portion of the support 8 so that the support 8 can be moved in the direction of an arrow during crystal growth. Moreover, in the support stand 8,
The crucible 5 is installed.

Next, a method of manufacturing a GaAs single crystal ingot using the GaAs single crystal growing apparatus configured as described above will be described.

First, a seed crystal 3 made of a GaAs single crystal is placed below the crucible 5, and G is placed on the rest of the crucible 5.
The aAs polycrystalline raw material is accommodated. Next, for example, B ₂ O ₃ is housed as a sealant 4 on the GaAs polycrystalline raw material.

Next, an inert gas such as Ar or an N ₂ gas is introduced into the hermetic container 10 to adjust the inside of the hermetic container 10 to a predetermined pressure.

Subsequently, the crucible 5 containing the GaAs polycrystalline raw material is heated by the heater 6. In this way, the GaAs polycrystalline raw material is melted, and a raw material melt 2 is produced.

Next, the lower shaft 19 is moved downward as shown by the arrow, so that the raw material melt 2 is moved from the bottom of the crucible 5.
Is solidified to grow the GaAs single crystal 1.

Here, from melting of the GaAs polycrystalline raw material, G
At the time of heating by the heater 6 until the growth of the aAs single crystal, the temperature at the bottom of the crucible 5 is, as shown in FIG.
T slightly higher than the melting point of 1238 ° C. of GaAs single crystal
₁ (° C.), while the temperature at the top of crucible 5
T ₂ (° C.) is set higher than T ₁ (° C.).
According to this embodiment, the temperature T of the upper part of the crucible 5
₂ (° C.) is 5 degrees lower than the temperature T ₁ (° C.) at the bottom of the crucible 5.
Set higher than ℃.

In the above-described example, G in the VB method is used.
Although the growth of the aAs single crystal has been described, the GaAs single crystal ingot according to the present invention can also be manufactured by using another vertical boat method such as the VGF method.

The GaAs single crystal ingot thus obtained has an average dislocation density of less than 10,000 cm ^-2 and an average residual strain of less than 1 × 10 ^-5 even when the diameter is 3 inches or more. Become.

Further, in the entire region from the head to the tail of the GaAs single crystal ingot, the EL2 concentration is 0.8 to 0.8.
It is in the range of 1.4 × 10 ¹⁶ cm ⁻³ . In addition, GaA
The rate of change between the EL2 concentration at the head of the s single crystal ingot and the EL2 concentration at the tail of the ingot is 10
% And the EL2 concentration is uniform over the entire length of the ingot.

From such a GaAs single crystal ingot, a GaAs single crystal wafer according to the present invention is obtained.

As described above, Ga according to the present invention is
In the As single crystal ingot, the EL2 concentration is uniform over the entire length, and the EL2 concentration is low. Further, the GaAs single crystal ingot according to the present invention has stable stoichiometry (composition ratio of As in GaAs) in the crystal. As a result, a GaAs single crystal wafer having high characteristics and suitable for ion implantation with a high yield can be manufactured.

As described above, a crystal having a uniform EL2 concentration over the entire length and a stable stoichiometric crystal can be obtained according to the present embodiment by a vertical growth method such as a VB method or a VGF method in the crystal growth. This is probably because the type boat method is used. That is, as shown in FIG. 2, the GaAs single crystal 1 is protected by the raw material melt 2 during the crystal growth, so that As does not scatter from the crystal. Furthermore, in the vertical boat method, during crystal growth,
Since the raw material melt 2 is not agitated, disturbance factors in stoichiometry are extremely reduced. In addition, B ₂ O ₃
In the case where gallium oxide is generated by reacting the sealing agent composed of and the raw material melt 2, the interface between the sealing agent 4 composed of B ₂ O ₃ and the raw material melt 2 has a distance from the GaAs single crystal 1. Since they are far apart, they hardly affect the GaAs single crystal 1.

Further, according to this embodiment, since the temperature at the top of the crucible is set so as to be higher than the temperature at the bottom of the crucible by 5 ° C. or more, the natural convection in the raw material melt 2 is achieved. Is further suppressed. Therefore, it is considered that the EL2 concentration becomes uniform over the entire length of the ingot.

Next, for comparison, a method of growing a GaAs single crystal using the conventional LEC method will be described.

FIG. 4 is a sectional view showing an example of a conventional GaAs single crystal growing apparatus by the LEC method.

Referring to FIG. 4, the GaAs single crystal growing apparatus 200 includes an airtight container 20, a support 8, a pulling shaft 39, a heater 6, and a heat insulating material 7. A lower shaft 19 is attached to a lower portion of the support base 8. Lower shaft 19
Each of the pulling shafts 39 can be freely driven in the vertical direction while rotating as shown by the arrows. Further, the crucible 5 is installed in the support base 8.

Next, a method of manufacturing a GaAs single crystal ingot using the GaAs single crystal growing apparatus thus configured will be described.

First, a GaAs polycrystalline raw material is accommodated in the crucible 5. The GaAs polycrystalline raw material may include at least one of Ga and As in addition to the GaAs polycrystal. Next, for example, B ₂ O ₃ is housed as a liquid sealant on the GaAs polycrystalline raw material.

Next, an inert gas such as Ar or N ₂ gas is introduced into the hermetic container 20 to adjust the inside of the hermetic container 20 to a predetermined pressure.

Subsequently, the crucible 5 containing the GaAs polycrystalline raw material is heated by the heater 6 to melt the GaAs polycrystalline raw material to produce a raw material melt 2.

Next, a pulling shaft 39 having a seed crystal 3 made of a GaAs single crystal attached to a lower end portion is moved to the raw material melt 2.
Soak in Subsequently, the raw material melt 2 is solidified from the side of the seed crystal 3 by rotating the pulling shaft 39 as shown by the arrow, thereby growing the GaAs single crystal 1. During crystal growth, the raw material melt 2 is stirred by rotating the lower shaft 29 as shown by the arrow.

The GaAs single crystal ingot obtained as described above has an average dislocation density of 10,000 cm ^-2 or more, typically 40,000 to 400, when the diameter is 3 inches or more.
80,000 cm ^-2 and an average residual strain of 1.0 × 1
0 ^-5 or more, typically 1.0 to 2.0 × 10 ^-5 .

When a crystal is grown under the condition that a uniform EL2 concentration is obtained from the head to the tail of the GaAs single crystal ingot, the EL2 concentration becomes 1.5 × 10
^It is restricted to around ¹⁶ cm ^-3 . That is, when crystal growth is performed under the condition that the EL2 concentration is higher than 1.5 × 10 ¹⁶ cm ⁻³ , the EL2 concentration gradually increases from the head to the tail of the GaAs single crystal ingot. On the other hand, when crystal growth is performed under the condition that the EL2 concentration is lower than 1.5 × 10 ¹⁶ cm ⁻³ , the EL2 concentration decreases from the head to the tail of the GaAs single crystal ingot.

As described above, when the conventional LEC method is used, the rate of change of the EL2 concentration between the head and the tail of the GaAs single crystal ingot becomes large, and the stoichiometry in the crystal becomes small. Also tends to be unstable. This is because, when the LEC method is used, the grown GaAs single crystal 1 comes out above B ₂ O ₃ 4 as shown in FIG. It is considered that high As escapes. Further, in the LEC method, since the raw material melt 2 is stirred during the crystal growth as described above, a disturbance factor in stoichiometry increases. Further, B as a sealant
₂ O ₃ 4 of the raw material melt 2 and react if gallium oxide is generated, the interface between the B ₂ O ₃ 4 of the raw material melt 2 is GaAs
It is considered that the GaAs single crystal 1 is likely to be affected since it is located relatively close to the single crystal 1.

[0046]

(Example 1) GaAs by the VB method shown in FIG.
Using an s single crystal growing apparatus, a GaAs single crystal ingot having a diameter of 3 inches was produced as follows.

First, a seed crystal made of a GaAs single crystal was placed under a crucible made of pBN (pyrolytic boron nitride). Subsequently, As /
A GaAs polycrystal previously synthesized under the condition that the composition ratio of (Ga + As) is 0.500, and B ₂ O as a sealant
₃ was filled. Therefore, in this example, GaAs
The composition ratio of As / (Ga + As) in the entire raw material is 0.1%.
500.

Next, the crucible filled with the GaAs material and B ₂ O ₃ was vacuum-sealed in a quartz ampoule. By heating the crucible with a heater, the GaAs polycrystalline raw material is melted to produce a raw material melt, and the surface of the raw material melt is treated with B _2.
The liquid was sealed with a liquid sealant made of O ₃ .

Subsequently, by moving the lower axis downward, the raw material melt was solidified from the bottom of the crucible to grow a GaAs single crystal.

In the heating by the heater from the production of the raw material melt to the growth of the GaAs single crystal, conditions were set such that the temperature at the top of the crucible was higher by 10 ° C. than the temperature at the bottom of the crucible.

(Example 2) As a GaAs raw material, a GaAs polycrystal (As / (Ga
+ As) = 0.500), and excess Ga was used. Therefore, in this example, the composition ratio of As / (Ga + As) in the whole GaAs raw material was 0.480. The crucible filled with the raw material is placed in a high pressure chamber, and the temperature of the carbon heater is adjusted under N ₂ gas pressure of 10 atm so that the temperature at the top of the crucible is 40 ° C. higher than the temperature at the bottom of the crucible. Under these conditions, a GaAs single crystal was grown. Thus, similarly to the first embodiment,
A GaAs single crystal ingot having a diameter of 3 inches was produced.

For other manufacturing conditions, see Example 1.
The description is omitted because it is completely the same.

(Comparative Example) Ga according to the LEC method shown in FIG.
3 inch diameter GaAs using As single crystal growing equipment
A single crystal ingot was produced.

In this comparative example, Ga and As were accommodated in a crucible, and GaAs was reacted by Ga and As in the chamber.
An s raw material was prepared, and after melting, a method of starting single crystal growth was adopted. As / (Ga +
As) having a composition ratio of 0.488, 0.501, 0.5
Under the three conditions of 12, each ingot was manufactured.

(Evaluation) GaAs obtained as described above
For the s single crystal ingot, the EL2 concentration, the average dislocation density, the average residual strain, and the specific resistance were measured.

Table 1 below shows the EL at the ingot head (solidification ratio g = 0.1) measured for the GaAs single crystal ingots of Example 1, Example 2, and Comparative Example.
2 concentration (cm ^-3 ), ingot tail (solidification rate g = 0.
EL2 concentration of 8) (cm ^-3), EL2 concentration of EL2 concentration / head ratio (tail change between EL2 concentration in EL2 concentration and the ingot tail of the ingot head), the average dislocation density (cm ^-2), And average residual strain. In addition, each of the ingots had a specific resistance at room temperature of 1.0 × 10 ⁷ (Ω · cm) or more and exhibited semi-insulating properties.

For each ingot, a total of 80 mirror-polished wafers were cut and polished between the head (solidification ratio g = 0.1) and the tail (solidification ratio g = 0.8) of the ingot. Collected.

E measured at the head and tail of the ingot
From the L2 concentration, the average of the rate of change of the EL2 concentration between adjacent wafers in a series of wafers can be estimated by the following equation (1).

([EL2] _B / [EL2] _F ) ^{1 / n} (1) where n is the number of wafers collected from one ingot, and [EL2] _F is the head of the ingot (solidification rate g =
The EL2 concentration (cm ^-3) in 0.1), [EL2] _B is the tail of the ingot (EL2 concentration in solidification rate ^{g = 0.8) (cm -3)} , respectively show.

According to the above formula (1), 80 obtained from each of the ingots of Example 1, Example 2, and Comparative Example was obtained.
EL between two adjacent wafers
The average of the rate of change of the two concentrations was determined. The values are also shown in Table 1.

[0061]

[Table 1]

Although not shown in Table 1, in the GaAs single crystal ingot of Example 2, the solidification rate g ≧
For the portion represented by 0.9 (x / L ≧ 0.9), the EL2 concentration was reduced, and the solidification rate g = 0.92 (x / L
L = 0.92), the EL2 concentration was reduced to 0.6 × 10 ¹⁶ cm ⁻³ .

FIG. 5 is a diagram showing the relationship between the ingot position and the EL2 concentration for the GaAs single crystal ingots of Example 1, Example 2, and Comparative Example. In FIG. 5, the horizontal axis represents the solidification rate g, and the vertical axis represents the EL2 concentration (c
m ^-3 ).

Next, GaAs single crystal wafers were sampled from the GaAs single crystal ingots of Example 1, Example 2 and Comparative Example, and used for MES-FET (metal-semicondone).
uctor FET).

The MES-FET has a self-aligned LDD structure having a buried p-type layer, and has a gate length of 0.8 μm.
And

FIGS. 6 and 7 show the Ga sampled from the GaAs single crystal ingots of Example 1 and Comparative Example, respectively.
It is a figure which shows the drain conductance (gd) frequency dispersion in the MES-FET using an As single crystal wafer.

When the gate voltage (Vgs) is 0 V, an AC component (ΔVd) is added to the drain DC voltage (Vds) 2.0 V.
s) The AC voltage ΔVout generated in the load resistance ( _RL ) when 0.2 V is applied is shown on the vertical axis, and the applied frequency is shown on the horizontal axis. The frequency was measured in the range of 10 to 20 kHz. gd is represented by the following equation (2).

Gd = (1 / R _L ) (ΔVout / ΔVds) (2) The degree of frequency dispersion is determined by changing the low-frequency flat part gd (10 Hz,
373K) and a high frequency flat portion gd (10 kHz, 298
Gd (10 kHz, 298 K) / gd
(10 kHz, 373 K).

As is clear from FIGS. 6 and 7, when a GaAs single crystal wafer obtained from the GaAs single crystal ingot of the comparative example was used, the degree of frequency dispersion was 1.8.
On the other hand, when the GaAs single crystal wafer obtained from the GaAs single crystal ingot of Example 1 was used,
The degree of frequency dispersion was as small as 1.66. this is,
In the GaAs single crystal ingot of Example 1, EL2
This is considered to be the effect of the low concentration.

Further, it was found that the degree of frequency dispersion when the GaAs single crystal wafer obtained from the GaAs single crystal ingot of Example 2 was used was 1.50, which was a smaller value.

[0071]

As described above, according to the present invention, EL2 which can be one of the causes of the failure of the device characteristics is obtained.
A GaAs single crystal ingot having a low concentration and being uniform from the head to the tail is obtained. Therefore, GaAs suitable for ion implantation with high yield
An s single crystal wafer can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining positions of a head and a tail of a GaAs single crystal ingot.

FIG. 2 is a sectional view showing an example of a GaAs single crystal growing apparatus by a VB method used for manufacturing a GaAs single crystal ingot according to the present invention.

FIG. 3 is a diagram showing a temperature profile during the growth of a GaAs single crystal in the production of a GaAs single crystal ingot according to the present invention.

FIG. 4 is a cross-sectional view showing an example of a conventional GaAs single crystal growing apparatus by the LEC method.

FIG. 5 shows GaAs of Example 1, Example 2, and Comparative Example.
It is a figure showing the relation between the position of an ingot and EL2 density about a single crystal ingot.

FIG. 6 is a diagram showing a drain conductance (gd) frequency dispersion in an MES-FET using a GaAs single crystal wafer taken from the GaAs single crystal ingot of Example 1.

FIG. 7 is a diagram showing a drain conductance (gd) frequency dispersion in a MES-FET using a GaAs single crystal wafer taken from a GaAs single crystal ingot of a comparative example.

[Explanation of symbols]

1 GaAs single crystal 2 GaAs polycrystalline raw material melt 3 seed crystal 4 B ₂ O ₃ (sealant) 5 crucible 6 heater 7 heat insulating material 8 support table 10, 20 airtight container 19, 29, the lower shaft 39 pulling shaft 100 VB method GaAs single crystal growing device by 200 LEC method GaAs single crystal growing device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomohiro Kawase 1-1-1, Koyokita, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Itami Works

Claims (8)

[Claims] 1. An ingot made of a GaAs single crystal, wherein in an entire region from a head to a tail of the ingot,
A GaAs single crystal ingot, wherein the EL2 concentration is in a range of 0.8 to 1.4 × 10 ¹⁶ cm ⁻³ . 2. The GaAs single crystal ingot according to claim 1, wherein the rate of change between the EL2 concentration at the head of the ingot and the EL2 concentration at the tail of the ingot is less than 10%. 3. An average dislocation density of the GaAs single crystal is 1
Less than 0,000Cm ^-2, mean residual strain of the GaAs single crystal is less than 1 × 10 ^-5, the diameter of the ingot is 3 inches or more, according to claim 1
Or the GaAs single crystal ingot according to claim 2. 4. A wafer taken from an ingot made of a GaAs single crystal, wherein the whole region from the head to the tail of the ingot is:
A GaAs single crystal wafer, wherein the EL2 concentration is in the range of 0.8 to 1.4 × 10 ¹⁶ cm ⁻³ . 5. The GaAs single crystal wafer according to claim 4, wherein the rate of change between the EL2 concentration at the head of the ingot and the EL2 concentration at the tail of the ingot is less than 10%. 6. A plurality of wafers collected from an ingot made of a GaAs single crystal, wherein each of the plurality of wafers has an EL2 concentration of 0.8 to 1.4.
× 10 ¹⁶ cm ⁻³ , EL2 between adjacent ones of the plurality of wafers.
A GaAs single crystal wafer, wherein the average of the rate of change in concentration is less than 0.1%. 7. The GaAs single crystal has an average dislocation density of 1
Less than 0,000Cm ^-2, mean residual strain of the GaAs single crystal is less than 1 × 10 ^-5, the diameter of the wafer is at least 3 inches, according to one of claims 4 to claim 6 GaAs single crystal wafer. 8. EL in all regions from the head to the tail
(2) the concentration is in the range of 0.8 to 1.4 × 10 ¹⁶ cm ⁻³ ;
A method for producing a GaAs single crystal ingot, comprising: disposing a seed crystal made of a single crystal GaAs compound at the bottom of a vertically arranged crucible; and disposing a polycrystalline GaAs compound raw material at the rest of the crucible. Placing the crucible in a heating means, and heating the heating means by setting the temperature at the top of the crucible to be higher than the temperature at the bottom of the crucible by 5 ° C. or more by the heating means. , After melting the GaAs compound raw material, the molten GaAs from the bottom of the crucible.
Solidifying the compound raw material to grow a GaAs single crystal, comprising the steps of: