JPH11147799A - Method for producing compound semiconductor single crystal and compound semiconductor single crystal produced by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a group II-VI compound semiconductor single crystal having a sufficiently reduced defect density and a compound semiconductor single crystal having a sufficiently reduced defect density according to the production method. And SOLUTION: An element of the 12 (2B) group of the periodic table and the 16th element
In a method for producing a single crystal of a compound semiconductor comprising a (6B) group element, Al, Ga, N, P, As, Be, Mg,
At least one of S and Se is added as an impurity. The amount of the impurity added is 5 × 10 ¹⁵ atoms / cm
It is preferable that the density be ³ or more and 1 × 10 ²⁰ atoms / cm ³ or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ZnSe, ZnT
e, CdTe, etc., a compound semiconductor comprising a 12 (2B) group element and a 16 (6B) group element of the periodic table (hereinafter referred to as “II
-Group VI compound semiconductor ". )) And a compound semiconductor single crystal manufactured by the method.

[0002]

2. Description of the Related Art Conventionally, methods for producing single crystals of II-VI compound semiconductors include a Bridgman method and a slow cooling method (Gradient Freezing Method: G).
F method) etc.) had been applied.

In the Bridgman method, the twelfth (2)
A compound semiconductor single crystal is grown by dissolving a raw material composed of a group B) element and a group 16 (6B) element in a crucible and moving it in a temperature gradient of 10 to 50 ° C./cm to a lower temperature side. ing.

In the temperature gradient annealing method (temperature gradient method), a temperature profile is changed without moving a crucible itself in which a raw material composed of a Group 12 (2B) element and a Group 16 (6B) element is melted. By doing so, a crystal is grown in a low temperature part.

In these crystal growth methods, the defect density in the crystal is reduced by optimizing the growth conditions such as reducing the temperature gradient in the melt and reducing the temperature fluctuation in the melt. Is being planned.

On the other hand, a compound semiconductor (hereinafter referred to as "II") comprising a group 13 (3B) element and a group 15 (5B) element of the periodic table.
Group IV compound semiconductor. " In the growth method of (1), in addition to the above-mentioned growth method, an impurity having an effect of increasing the hardness of the crystal is added, so that the defect density in the crystal is reduced as a result.

That is, for example, gallium arsenide (GaAs), which is a typical example of a III-V compound semiconductor,
Silicon (Si) is effective in reducing the defect density, and indium phosphorus (InP) is effective in adding sulfur (S) and zinc (Zn). It has been reported that it can be obtained (see J. Appl. Phys. 49 (1972) 822).

[0008]

However, II-VI
In the case of group-compound semiconductors, it is difficult to grow a crystal having a sufficiently low defect density even if the growth conditions are optimized, because of the characteristics that the crystal is soft and a defect easily enters the crystal. Was.

In the case of II-VI compound semiconductors, III-V
Unlike group III compound semiconductors, suitable impurities that can reduce the defect density by addition have not been found yet.

On the other hand, since II-VI compound semiconductor bulk crystals are difficult to produce industrially, it is unavoidable to use III-V compound semiconductor bulk crystals as substrates to obtain II-VI compounds having similar lattice constants.
In many cases, group III compound semiconductors are epitaxially grown and used for devices and the like.

[0011] In the method of producing a vapor phase epitaxial single crystal of a II-VI compound semiconductor, MOVPE (Metal Organic Vapor Phase Epitaxy) and MBE (Molecular Beam Epitaxy) are used.
y: molecular beam epitaxy method).

That is, for example, in ZnSe, an epitaxial single crystal layer is grown on a GaAs substrate by using the MBE method. However, a lattice mismatch between the substrate and a slightly existing substrate and a difference in thermal expansion coefficient between the substrate and the epitaxial layer are caused. The element is deteriorated due to dislocation from the substrate interface due to thermal strain generated from the substrate, stress in the epitaxial layer, and the like, so that a short life has been a problem.

In view of the above, it is expected that a device can be formed by homoepitaxy using a II-VI group compound semiconductor as a substrate so that the lattice can be matched and the life can be prolonged. It is difficult to produce group III compound semiconductor bulk crystals on an industrial scale, and it is difficult to obtain crystals with sufficiently reduced defect density due to the fact that II-VI compound semiconductor crystals themselves tend to be soft due to their soft nature. was there.

[0014] For these reasons, it is a reality that II-VI compound semiconductors cannot stably obtain crystals with sufficiently reduced defect density.

The present invention was devised as a result of a study in view of the above circumstances, and relates to a method of manufacturing a II-VI compound semiconductor single crystal having a sufficiently reduced defect density and a method of manufacturing the same. It is a main object to obtain a compound semiconductor single crystal with a sufficiently reduced defect density.

[0016]

In order to achieve the above-mentioned object, the present invention provides a compound of Group 12 (2B) of the periodic table and a compound of the group 16 (2B).
In a method for producing a single crystal of a compound semiconductor comprising a (6B) group element, Al, Ga, N, P, As, Be, Mg,
At least one of S and Se is added as an impurity.

The amount of the impurity added is 5 × 10 ¹⁵
It is preferable that the concentration be not less than atoms / cm ^{3 and not} more than 1 × 10 ²⁰ atoms / cm ³ .

The compound semiconductor crystal to which an impurity is added includes, for example, ZnSe, ZnTe, and CdTe.
Of these, ZnTe and its compounds are particularly desirable.

The present invention is suitable for producing various semiconductor devices using a compound semiconductor single crystal obtained by the production method.

In the following, the present inventors outline the contents of study and the progress of the research up to the present invention.

As a result of the present inventors' research on overcoming the fact that the crystal defect density of a II-VI compound semiconductor single crystal cannot be sufficiently reduced as described above, Al, Ga, N, and P, As, Be, Mg, S, S
It has been found that the addition of at least one of e has a remarkable effect on the reduction of the defect density in the II-VI compound semiconductor single crystal, particularly on the reduction of the dislocation density.

This is the same as the above-mentioned report on the growth of the group III-V compound semiconductor single crystal, which is similar to the report that the addition of specific impurities hardens the crystal and reduces the dislocation density.
It is presumed to be an effect.

More specifically, when growing a II-VI group compound semiconductor single crystal, Al, Ga, N, P, As, Be,
By adding at least one of Mg, S, and Se as a predetermined amount as an impurity, the defect density of the crystal is sufficiently reduced.

As a method for growing II-VI compound semiconductors, for example, a vertical temperature gradient slow cooling method (Vertical Gradien
t Freezing Method: VGF method, Vertical Bridgman Method (VB method), or Liquid Encapsulated Czochralski Metho
d: LEC method).

As an epitaxial growth method for II-VI compound semiconductors, MOVPE (Metal Organic Vapor Method) is used.
por Phase Epitaxy: metal organic vapor phase epitaxy)
MBE (Molecular Beam Epitaxy) or the like can be employed.

The above MOVPE method or MB
MOVPE for II-VI compound semiconductor applicable to E method
In the epitaxial growth using an apparatus or an MBE apparatus, Al, Ga, N, P, As, Be, Mg, Al, Ga, N, P, As, Be and Mg are used instead of Cl or the like as a dopant for n-type crystal growth during n-type crystal growth. S,
By using a simple substance of Se or an alloy or a compound thereof, the above Al, Ga, N, P, As, Be, M
g, S, Se doping can be realized.

As the material of the substrate for epitaxial growth,
II-VI compound semiconductors can be used.
It is also possible to use a substrate made of a III-V compound semiconductor such as s.

The above Al, Ga, N, P, As,
The most effective epitaxial growth can be performed most effectively by using a substrate made of a II-VI compound semiconductor bulk crystal having a low defect density and obtained by hardening an impurity to which at least one of Be, Mg, S, and Se is added.

As described above, by adding the above impurities to the epitaxial crystal of the II-VI group compound semiconductor, the dislocation density is low, and in addition, when a device is manufactured, a high quality semiconductor device is unlikely to introduce defects during operation. It was found that an epitaxial crystal could be obtained.

According to an experiment conducted by the present inventors, when the amount of the impurity added is less than 5 × 10 ¹⁵ atoms / cm ³ , the effect of reducing the defect density is small and exceeds 1 × 10 ²⁰ atoms / cm ³ . It was found that the crystallinity deteriorated due to lattice distortion and the like, which was not preferable.

Therefore, it is effective to reduce the defect density of the II-VI group compound semiconductor single crystal, and the addition amount of the impurity which does not adversely affect the other is 5 × 10 ¹⁵ atoms / cm ³ or more and 1 ×
10 ²⁰ atoms / cm ³ or less, preferably 1 × 10 ¹⁶ atoms
It was concluded that it is desirable that the concentration be in the range of not less than 1 / cm ^{3 and not} more than 1 × 10 ¹⁸ atoms / cm ³ .

Further, as a result of conducting experiments on various methods for manufacturing compound semiconductors and epitaxial growth methods, the single crystal manufacturing method in which the above-described impurities are added is ZnSe, Z
The present invention has been completed with the conviction that it is effective in reducing the defect density in the production of single crystals of general II-VI compound semiconductors such as nTe, CdTe and its compounds.

According to the manufacturing method of the present invention, it is possible to manufacture a group II-VI compound semiconductor single crystal having a sufficiently reduced defect density. In addition, if a compound semiconductor single crystal manufactured by the method for manufacturing a single crystal according to the present invention is used, a high-quality semiconductor device can be manufactured, and the yield in the semiconductor device manufacturing process can be expected to be improved.

[0034]

Here, an example of an embodiment of the present invention will be described.

First, a group II-VI compound semiconductor material to be grown and Al, Ga, N, P, As, Be, M
g, S, Se alone or at least one of its compounds is charged into a crucible. At this time, in growing a crystal containing a highly volatile component, measures are taken to prevent the raw material from volatilizing. Specific measures include, for example, enclosing a crucible in an ampoule, or using a sealing material under high pressure.

The crucible charged with the raw material is placed in a growth furnace and heated to a temperature at which the raw material is sufficiently melted.
Then, after the raw materials are sufficiently melted, a desired temperature profile is set and crystal growth is started.

As a growing method, a Bridgman method or a temperature gradient slow cooling method (GF method) is generally applied. However, in principle, Al, Ga, N,
It is presumed that the effect of reducing the defect density by adding impurities of P, As, Be, Mg, S, and Se can be similarly obtained.

Further, Al, Ga, N, P, As, Be,
By adding Mg, S, and Se as impurities, a hardening effect of the crystal can be obtained, so that MOVPE for growing an epitaxial film as well as growing a bulk crystal can be obtained.
The method (metalorganic vapor phase epitaxy) and the MBE (molecular beam epitaxy) can be easily applied.

And, Al, Ga, N, P, As, B
By doping at least one of e, Mg, S, and Se into a crystal, a high-quality epitaxial crystal having a low dislocation density and hardly introducing defects during operation after device fabrication can be obtained.

In addition, Al, Ga, N, P, As, Be,
When the addition amount of Mg, S, and Se is less than 5 × 10 ¹⁵ atoms / cm ³ , the effect of reducing the defect density does not appear so much and 1 × 10 ²⁰ at
If it exceeds oms / cm ³ , a phenomenon in which crystallinity is deteriorated due to lattice distortion or the like is observed, which is not preferable.

Therefore, it is effective in reducing the defect density of the II-VI group compound semiconductor single crystal, and the amount of addition of the impurity which does not adversely affect other elements is 5 × 10 ¹⁵ atoms / cm ³ or more.
10 ²⁰ atoms / cm ³ or less, preferably 1 × 10 ¹⁶ atoms
It is desirable that the concentration be in the range of not less than / cm ^{3 and not} more than 1 × 10 ¹⁸ atoms / cm ³ .

[0042]

EXAMPLES (Example 1) Phosphorus (P) was added to ZnTe.
An example in which a single crystal to which is added as an impurity is produced by a vertical Bridgman method (VB method) will be described with reference to FIG.

FIG. 1 is a schematic diagram showing a configuration of a crystal growing apparatus C1 by the VB method.

In the figure, a crystal growing apparatus C 1 comprises a crucible 1 for filling a raw material 2, a quartz ampule 3 for enclosing the crucible 1, and an elevating apparatus 5 for moving the quartz ampule 3 up and down in a heater 4 of a growing furnace. It is composed of

The crucible 1 is a cylindrical one having a diameter of 2 inches formed of pBN and a conical bottom.
The crucible 1 contains 300 g of ZnTe as a raw material 2 and 1 mg of Zn as an additive of phosphorus (P).
It is filled with ₂ P _3.

The crucible 1 filled with the raw material 2 is vacuum-sealed in a quartz ampule 3, and this quartz ampule 3 is placed on a lifting device 5 and placed in a heater 4 of a growth furnace.

Here, Zn is grown by the crystal growing apparatus C1.
The step of growing a single crystal of Te will be briefly described.

First, electricity is supplied to the heater 4 so that the Zn
The temperature is raised to 1100 ° C., which is a temperature at which Te and Zn ₂ P ₃ as an additive are sufficiently dissolved, and the temperature is maintained for 24 hours.

Thereafter, a temperature profile required for the VB method, in which the lower portion has a low temperature, is set. The defect density can be reduced by setting the temperature gradient at the crystal growth position to a relatively small value of 15 ° C./cm.

Next, while maintaining the temperature gradient at the growth position, the lifting device 5 is driven at a speed of 1 mm / hr, and the quartz ampoule 3 is gradually moved to the low temperature side to start crystal growth.

Then, after the crystal was grown for 20 days, the temperature was lowered at a cooling rate of 100 ° C./hr to complete the crystal growing step.

When the grown crystal 6 was taken out of the crucible 1 and inspected, it was a single crystal except for the peripheral portion. As a result of analyzing impurities in the crystal, 5 × 10 ¹⁷ atoms were found in the crystal.
/ Cm ³ of phosphorus (P).

Under the same conditions, when compared with a crystal grown without adding Zn ₂ P ₃ as an additive, the dislocation density of the single crystal 6 grown by applying the present invention is lower by about one digit. It was confirmed that the addition of the impurity (phosphorus (P)) according to the present invention was effective in reducing the defect density.

In this embodiment, the case where phosphorus (P) is added as an impurity has been described. However, the present invention is not limited to this, and a simple substance or a compound of Al, Ga, N, As, Be, Mg, S, Se may be used. Can be added as an impurity additive.

The additive of phosphorus (P) is not limited to Zn ₂ P ₃ , and other suitable phosphorus compounds can be used.

Further, the compound semiconductor single crystal grown according to this embodiment is not limited to ZnTe, and other II-VI group compound semiconductor single crystals can also be grown.

Example 2 Next, a single crystal obtained by adding aluminum (Al) to ZnTe as an impurity was subjected to a vertical gradient freezing method (VG).
An embodiment in the case of manufacturing by the F method) will be described with reference to FIG.

FIG. 2 shows a crystal growth apparatus C2 by the VGF method.
FIG. 3 is a schematic diagram showing the configuration of FIG.

In the figure, a crystal growing apparatus C2 comprises a crucible 11 for filling a raw material 12, a quartz ampule 13 for enclosing the crucible 11, and a high-pressure vessel 15 provided with a heater 14 for installing the quartz ampule 13. Have been.

The crucible 11 has a diameter of 2 formed of pBN.
Inches, conical bottom cylinders are used. The crucible 11 contains 500 g of Z as a raw material 12.
nTe is filled together with 1 mg of Al alone as an additive.

The crucible 11 filled with the raw material 12 is vacuum-sealed in a quartz ampule 13,
Is installed in the heater 14 of the high-pressure vessel 15 constituting the growth furnace.

Here, Zn is grown by the crystal growing apparatus C2.
The step of growing a single crystal of Te will be briefly described.

First, the atmosphere in the high-pressure vessel 15 is replaced with nitrogen, and while the furnace pressure is adjusted so that the vapor pressure in the quartz ampule 13 matches the furnace pressure, the heater 14 is driven to produce the raw material 12. ZnTe and Al as an additive
The temperature is raised to 1350 ° C., which is a temperature at which is sufficiently melted, and the temperature is maintained for 24 hours.

Thereafter, required in the VGF method,
Set the temperature profile where the lower part becomes low temperature. In addition,
By setting the temperature gradient at the crystal growth position to a relatively small value of 15 ° C./cm, the defect density can be reduced.

Then, while maintaining the temperature gradient at the growth position, the temperature is lowered at a slow cooling rate of 2 ° C./hr, and the crystal is grown for 5 days. Then, the temperature was lowered at a cooling rate of 100 ° C./hr, and the crystal growth was completed.

When the grown crystal 16 was taken out of the crucible 11 and inspected, it was a single crystal except for the peripheral portion. As a result of analyzing impurities in the crystal, 5 × 10 ¹⁷ at
oms / cm ³ of aluminum (Al).

Under the same conditions, when compared with a crystal grown without adding Al as an additive, the dislocation density of the single crystal 16 grown by applying the present invention was reduced by about one digit. It has been confirmed that the addition of the impurity Al according to the present invention is effective in reducing the defect density.

In the present embodiment, the case where Al is added as an impurity has been described.
It is also possible to add a simple substance or a compound of N, As, P, Be, Mg, S, Se as an impurity additive of ZnTe.

Further, the additive is not limited to Al alone, and other suitable aluminum compounds, aluminum alloys or intermetallic compounds can also be used.

Furthermore, the compound semiconductor single crystal grown in this embodiment is not limited to ZnTe, and other II-VI group compound semiconductor single crystals can be grown.

The first and second embodiments are merely examples of the present invention, and the present invention is not limited by the present invention.

[0072]

According to the present invention, there is provided a method for producing a single crystal of a compound semiconductor comprising a group 12 (2B) element and a group 16 (6B) element of the periodic table, comprising Al, Ga, N, P, As, B
By adding at least one of e, Mg, S, and Se as impurities, there is an excellent effect that the defect density of the crystal can be sufficiently reduced.

Further, if the compound semiconductor single crystal manufactured according to the present invention is used, a high-quality semiconductor device can be manufactured and the yield in the semiconductor device manufacturing process can be expected to be improved. .

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a crystal growing apparatus by a VB method for obtaining a compound semiconductor single crystal by a manufacturing method according to the present invention.

FIG. 2 is a schematic view showing an example of a crystal growing apparatus by a VGF method for obtaining a compound semiconductor single crystal by a manufacturing method according to the present invention.

[Explanation of symbols]

C1 crystal growing device 1 pBN crucible 2 material (ZnTe), additive (Zn ₂ P ₃ ) 3 quartz ampoule 4 heater 5 elevating device 6 ZnTe single crystal C2 crystal growing device 11 pBN crucible 12 material (ZnTe), additive (Al) 13) Quartz ampoule 14 Heater 15 High pressure vessel 16 ZnTe single crystal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/368 H01L 21/368 Z

Claims (7)

[Claims] 1. An element of the 12 (2B) group of the periodic table and the 16th element
In a method for producing a single crystal of a compound semiconductor comprising a (6B) group element, Al, Ga, N, P, As, Be, Mg,
A method for producing a single crystal of a compound semiconductor, comprising adding at least one of S and Se as an impurity. 2. The method according to claim 1, wherein said impurity is added in an amount of 5 × 10 ¹⁵ atoms / c.
2. The method for producing a single crystal of a compound semiconductor according to claim 1, wherein the value is not less than m ^{3 and not} more than 1 × 10 ²⁰ atoms / cm ³ . 3. The method according to claim 1, wherein the compound semiconductor crystal to which the impurity is added is ZnSe, ZnTe, CdTe or a compound thereof. 4. The method for producing a compound semiconductor single crystal according to claim 1, wherein an epitaxial growth method is applied to the method for producing a compound semiconductor single crystal. 5. A method for producing a single crystal of a compound semiconductor according to any one of claims 1 to 4, wherein Al, Ga,
A compound semiconductor comprising a Group 12 (2B) element and a Group 16 (6B) element of the periodic table, wherein at least one of N, P, As, Be, Mg, S, and Se is added as an impurity. Single crystal. 6. The method according to claim 1, wherein the amount of impurity added is 5 ×.
A compound semiconductor single crystal comprising a Group 12 (2B) element and a Group 16 (6B) element of the periodic table, which is set to 10 ¹⁵ atoms / cm ³ or more and 1 × 10 ²⁰ atoms / cm ³ or less. 7. The compound semiconductor single crystal according to claim 5, wherein the compound semiconductor crystal to which the impurity is added is ZnSe, ZnTe, CdTe or a compound thereof.