WO2017200035A1 - Cdte epitaxial growth method - Google Patents

Abstract

The primary objective of the present invention is to provide a novel method for epitaxially growing CdTe on a single-crystal Si substrate. Another objective of the present invention is to provide a novel method for epitaxially growing CdTe on a single-crystal CdTe substrate. In order to achieve the abovementioned objectives, a method is provided for epitaxially growing CdTe on a single-crystal Si substrate or a single-crystal CdTe substrate, wherein the method has a growth step for depositing CdTe from a gas phase onto the surface of the single-crystal Si substrate or the single-crystal CdTe substrate using simple Cd and simple Te or an organic Te compound as the respective Cd source and Te source.

Description

CdTe epitaxial growth method

The present invention mainly relates to an epitaxial growth method of CdTe (cadmium telluride).

CdTe is useful as a semiconductor for radiation detectors. Currently, a bulk CdTe crystal grown by a traveling heater method is in practical use for this application. However, bulk CdTe crystals are difficult to increase in size, and it is said that the uniformity of crystallinity and electrical characteristics is not sufficient.
In order to solve such problems, attempts have been made to form a CdTe thick film on a large area substrate such as a Si substrate or a GaAs substrate by heteroepitaxial growth. For example, there is a report that a good quality CdTe layer can be epitaxially grown on a (211) Si substrate together with a GaAs piece by MOVPE (Metal-Organic Vapor Phase Epitaxy) method (Non-patent Document 1). ).

In the epitaxial growth of CdTe by the MOVPE method, an organometallic compound is used for both the Cd source and the Te source. For example, in the method disclosed in Non-Patent Document 1, dimethylcadmium (DMCd) is used as the Cd source, and diethyl tellurium (DETe) is used as the Te source.
There is a report that CdTe crystals are produced at a low temperature of 230 ° C. (DETe is stable) when elemental Cd vapor is introduced into the reactor of the MOVPE apparatus together with DETe instead of DMCd (Non-patent Document 2). ). However, no attempt has been made to use these raw materials (single Cd and organic Te compound) for epitaxial growth of CdTe.

There is a report that a CdTe film oriented along the (111) axis was deposited on an alumina (aluminum oxide) substrate by the Elemental-Vapor-Transport method using simple Cd and simple Te as raw materials (Non-patent Document 3).

The main object of the present invention is to provide a novel method for epitaxially growing CdTe on a single crystal Si substrate.
Another object of the present invention is to provide a novel method for epitaxially growing CdTe on a single crystal CdTe substrate.
Another object of the present invention is to provide a novel method for epitaxially growing CdTe on a single crystal (GaAs, sapphire, CdZnTe, CdHgTe, GaN, etc.) substrate other than CdTe.
Another object of the present invention is to provide a vapor deposition apparatus for depositing CdTe on a substrate.

Embodiments of the present invention include the following [A1] to [A14].
[A1] A method of epitaxially growing CdTe on a single crystal Si substrate, the method including the following steps: (i) a first step of preparing a single crystal Si substrate, (ii) a single unit prepared in the first step A second step of baking the crystalline Si substrate in a flow of baking gas containing H ₂ and cleaning its surface; and (iii) using elemental Cd and an organic Te compound as the Cd source and Te source, respectively. A third step of depositing CdTe from the vapor phase on the surface cleaned in the second step of the single crystal Si substrate.
[A2] The method according to [A1], wherein the baking gas flow does not contain one or both of Ga and As.
[A3] Before the third step, the single crystal Si substrate is placed in a reactor, and in the third step, simple Cd vapor and organic Te compound vapor are supplied into the reactor. A2].
[A4] The method according to [A3], wherein the elemental Cd vapor is generated from metal Cd placed in the reactor.
[A5] In the second step, the single crystal Si substrate is baked in the reactor, and the single crystal Si substrate is not removed from the reactor between the end of the second step and the start of the third step. The method according to [A3] or [A4].
[A6] The method according to any one of [A1] to [A5], wherein the single crystal Si substrate prepared in the first step has a surface oxide film.
[A7] The method according to any one of [A1] to [A6], wherein the CdTe crystal grows two-dimensionally in the third step.
[A8] The method according to any one of [A1] to [A7], wherein the single crystal Si substrate is a {211} Si substrate.
[A9] In the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the third step, the strongest peak is the CdTe {422} peak, and the intensity of the second strongest peak is the CdTe { 422} The method according to [A8], which is 1/10 or less of the intensity of the peak.
[A10] The method according to [A8] or [A9] above, wherein the peak of the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the third step is only the CdTe {422} peak.
[A11] The method according to any one of [A8] to [A10], wherein the (422) reflection ω-scan X-ray rocking curve obtained from the CdTe crystal is a single peak.
[A12] The method according to any one of [A1] to [A11], wherein the organic Te compound includes diisopropyl tellurium.
[A13] A method for manufacturing a semiconductor for a radiation detector, comprising a step of epitaxially growing CdTe on a single crystal Si substrate by the method according to any one of [A1] to [A12].
[A14] A vapor deposition apparatus for depositing CdTe on a substrate, a hot wall type reactor, a susceptor disposed in the reactor to support the substrate, and a substrate supported by the susceptor A first heater disposed outside the reactor to heat the Cd, a Cd reservoir disposed within the reactor, and a metal Cd contained in the Cd reservoir disposed outside the reactor. A vapor deposition apparatus comprising: a second heater; and a bubbler disposed outside the reactor for vaporizing the organic Te compound supplied into the reactor via a pipe.

Further, the following [B1] to [B17] are included in the embodiment of the present invention.
[B1] A method of epitaxially growing CdTe on a single crystal CdTe substrate, the method including the following steps:
(I) a first step of preparing a single crystal CdTe substrate; and
(Ii) A second step of depositing CdTe from the vapor phase on the surface of the single-crystal CdTe substrate using simple Cd and an organic Te compound as a Cd source and a Te source, respectively.
[B2] The single crystal CdTe substrate is placed in a reactor before the second step, and simple Cd vapor and organic Te compound vapor are supplied into the reactor in the second step. the method of.
[B3] The method according to [B2], wherein the elemental Cd vapor is generated from metal Cd placed in the reactor.
[B4] The method according to any one of [B1] to [B3], wherein the CdTe crystal is grown two-dimensionally in the second step.
[B5] The method according to any one of [B1] to [B4], wherein the single crystal CdTe substrate is a {211} CdTe substrate.
[B6] In the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the second step, the strongest peak is the CdTe {422} peak, and the intensity of the second strongest peak is the CdTe { 422} The method according to [B5], which is 1/10 or less of the intensity of the peak.
[B7] The method according to [B5] or [B6], wherein the peak of the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the second step is only the CdTe {422} peak.
[B8] The method according to any one of [B5] to [B7], wherein the ω-scan X-ray rocking curve of {422} reflection obtained from the CdTe crystal formed in the second step is a single peak.
[B9] The method according to any one of [B1] to [B4], wherein the single crystal CdTe substrate is a {111} CdTe substrate.
[B10] In the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the second step, the strongest peak is the CdTe {111} peak, and the intensity of the second strongest peak is the CdTe { 111} The method according to [B9], which is 1/10 or less of the intensity of the peak.
[B11] The method according to [B9] or [B10] above, wherein the peak of the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the second step is only the CdTe {111} peak.
[B12] The method according to any one of [B9] to [B11], wherein the {111} reflection ω-scan X-ray rocking curve obtained from the CdTe crystal formed in the second step is a single peak.
[B13] The method according to any one of [B1] to [B4], wherein the single crystal CdTe substrate is a {100} CdTe substrate.
[B14] In the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the second step, the strongest peak is the CdTe {400} peak, and the intensity of the second strongest peak is the CdTe { 400} The method according to [B13], which is 1/10 or less of the intensity of the peak.
[B15] The method according to [B13] or [B14], wherein the peak of the XRD pattern obtained from the 2θ / ω scan of the CdTe crystal formed in the second step is only the CdTe {400} peak.
[B16] The method according to any one of [B13] to [B15], wherein the {400} reflection ω-scan X-ray rocking curve obtained from the CdTe crystal formed in the second step is a single peak.
[B17] The method according to any one of [B1] to [B16], wherein the organic Te compound contains diisopropyl tellurium.
[B18] A method for manufacturing a semiconductor for a radiation detector, comprising a step of epitaxially growing CdTe on a CdTe substrate by the method according to any one of [B1] to [B17].

Further, embodiments of the present invention include the following [C1] to [C17].
[C1] A method of epitaxially growing CdTe on a single crystal substrate other than CdTe, the method including the following steps:
(I) a first step of preparing a single crystal substrate other than CdTe, and
(Ii) A second step of depositing CdTe from the vapor phase on the surface of a single crystal substrate other than CdTe using simple Cd and an organic Te compound as a Cd source and a Te source, respectively.
[C2] Before the second step, a single crystal substrate other than CdTe is placed in a reactor, and in the second step, simple Cd vapor and organic Te compound vapor are supplied into the reactor, [C1] The method described in 1.
[C3] The method according to [C2], wherein the elemental Cd vapor is generated from metal Cd placed in the reactor.
[C4] The method according to any one of [C1] to [C3], wherein in the second step, CdTe crystals are grown two-dimensionally.
[C5] The method according to any one of [C1] to [C4], wherein the organic Te compound includes diisopropyl tellurium.
[C6] A method for manufacturing a semiconductor for a radiation detector, comprising a step of epitaxially growing CdTe on a single crystal substrate other than CdTe by the method according to any one of [C1] to [C5].

In addition, the following [D1] to [D35] are included in the embodiment of the present invention.
[D1] A method of epitaxially growing CdTe on a single-crystal Si substrate, using simple Cd and simple Te or an organic Te compound as a Cd source and a Te source, respectively, and removing CdTe on the surface of the single-crystal Si substrate. A growth step of depositing from the phase.
[D2] The method according to [D1], including a preparation step of preparing a single crystal Si substrate, and a baking step of baking the prepared single crystal Si substrate in a reducing gas or an inert gas.
[D3] The method according to [D2], wherein the baking step is performed without volume of other components on the surface of the single crystal Si substrate.
[D4] The method according to [D2] or [D3], wherein the baking step cleans a surface of the single crystal Si substrate.
[D5] The method according to any one of [D2] to [D4], wherein the single crystal Si substrate prepared in the preparation step has a surface oxide film.
[D6] The method according to any one of [D1] to [D5], wherein the single crystal Si substrate is a {211} Si substrate.
[D7] The method according to any one of [D2] to [D5], wherein the gas used in the baking step is a gas containing H ₂ .
[D8] The method according to any one of [D1] to [D7], wherein the Te source is an organic Te compound.
[D9] The method according to any one of [D1] to [D8], wherein a CdTe deposition temperature in the growth step is 570 ° C. or higher.
[D10] The method according to any one of [D1] to [D9], wherein the strongest peak of the CdTe crystal obtained in the growth step is a CdTe {422} peak in an XRD pattern obtained from a 2θ / ω scan.
[D11] The method according to any one of [D1] to [D10], wherein the single crystal Si substrate and the CdTe crystal obtained in the growth step have the same crystal plane.
[D12] A method for manufacturing a semiconductor for a radiation detector, comprising a step of epitaxially growing CdTe on a single crystal Si substrate by the method according to any one of [D1] to [D11].
[D13] A vapor deposition apparatus for depositing CdTe on a substrate,
A hot wall reactor,
A susceptor disposed in the reactor to support a substrate;
A first heater disposed outside the reactor to heat a substrate supported by the susceptor;
A Cd reservoir disposed in the reactor;
A second heater disposed outside the reactor to heat the metal Cd contained in the Cd reservoir;
A vapor deposition apparatus comprising: a bubbler disposed outside the reactor for vaporizing an organic Te compound supplied into the reactor through a pipe.

[D14] A method of epitaxially growing CdTe on a single-crystal CdTe substrate, using simple Cd and simple Te or an organic Te compound as a Cd source and a Te source, respectively, and removing CdTe on the surface of the single-crystal CdTe substrate. A growth step of depositing from the phase.
[D15] The method according to [D14], including a preparation step of preparing a single crystal CdTe substrate, and a baking step of baking the prepared single crystal CdTe substrate in a reducing gas or an inert gas.
[D16] The method according to [D15], wherein the baking step is performed without depositing other components on the surface of the single crystal CdTe substrate.
[D17] The method according to [D15] or [D16], wherein the baking step cleans a surface of the single crystal CdTe substrate.
[D18] The method according to any one of [D15] to [D17], wherein the single crystal CdTe substrate prepared in the preparation step has a surface oxide film.
[D19] The method according to any one of [D14] to [D18], wherein the single crystal CdTe substrate is a {211} CdTe substrate.
[D20] The method according to any one of [D15] to [D18], wherein the gas used in the baking step is a gas containing H ₂ .
[D21] The method according to any one of [D14] to [D20], wherein the Te source is an organic Te compound.
[D22] The method according to any one of [D14] to [D21], wherein the CdTe deposition temperature in the growth step is 570 ° C. or higher.
[D23] The method according to any one of [D14] to [D22], wherein the strongest peak of the CdTe crystal obtained in the growth step is a CdTe {422} peak in an XRD pattern obtained from a 2θ / ω scan.
[D24] The method according to any one of [D14] to [D23], wherein the single crystal CdTe substrate and the CdTe crystal obtained in the growth step have the same crystal plane.
[D25] A method for manufacturing a semiconductor for a radiation detector, comprising a step of epitaxially growing CdTe on a single crystal CdTe substrate by the method according to any one of [D14] to [D24].
[D26] A method of epitaxially growing CdTe on a single crystal substrate other than CdTe,
A growth step of depositing CdTe from the vapor phase on the surface of a single crystal substrate other than CdTe using simple Cd and simple Te or organic Te compound as the Cd source and Te source, respectively.
[D27] The method according to [D26], including a preparation step of preparing a single crystal substrate other than CdTe, and a baking step of baking the prepared single crystal substrate other than CdTe in a reducing gas or an inert gas. Method.
[D28] The method according to [D27], wherein the baking step is performed without depositing other components on the single crystal substrate other than the CdTe.
[D29] The method according to [D27] or [D28], wherein the baking step cleans a surface of a single crystal substrate other than the CdTe.
[D30] The method according to any one of [D27] to [D29], wherein the single crystal substrate other than CdTe prepared in the preparation step has a surface oxide film.
[D31] The method according to any one of [D27] to [D30], wherein the gas used in the baking step is a gas containing H ₂ .
[D32] The method according to any one of [D26] to [D31], wherein the Te source is an organic Te compound.
[D33] The method according to any one of [D26] to [D32], wherein a CdTe deposition temperature in the growth step is 570 ° C. or higher.
[D34] The method according to any one of [D26] to [D33], wherein the single crystal substrate other than the CdTe and the CdTe crystal obtained in the growth step have the same crystal plane.
[D35] A method for manufacturing a semiconductor for a radiation detector, comprising the step of epitaxially growing CdTe on a single crystal substrate other than CdTe by the method according to any one of [D26] to [D34].

A novel method is provided for epitaxially growing CdTe on a single crystal Si substrate.
Also provided is a novel method for epitaxially growing CdTe on a single crystal CdTe substrate.
Also provided is a novel method for epitaxially growing CdTe on a single crystal substrate other than CdTe.

FIG. 1 shows a schematic diagram of a vapor deposition apparatus. FIG. 2 shows a schematic diagram of a vapor deposition apparatus. FIG. 3 shows a schematic diagram of a vapor deposition apparatus. FIG. 4 shows a schematic view of a vapor deposition apparatus. FIGS. 5A to 5E show bird's-eye SEM images of the CdTe film, respectively (drawing substitute photos). 6A and 6B show cross-sectional SEM images of the CdTe film, respectively (drawing substitute photograph). FIG. 7 is a diagram showing an arrangement of an X-ray generator, a sample (CdTe film), and an X-ray detector in XRD analysis. FIG. 8A shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 8B shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 8C shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 8D shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 8E shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 9 shows a (422) reflection ω-scan X-ray rocking curve (source: CuKα) obtained from a (211) CdTe film deposited on a Si substrate. FIG. 10A shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 10B shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 10C shows an XRD pattern of the CdTe film obtained from the 2θ / ω scan. FIG. 11 shows a bird's-eye SEM image (left) and a cross-sectional SEM image (right) of the CdTe film of Experiment 1 (drawing substitute photograph). FIG. 12 is a drawing showing the arrangement of an X-ray generator, a sample (CdTe film), and an X-ray detector in XRD analysis. FIG. 13 shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan of Experiment 1. FIG. 14 shows the (422) reflection ω-scan X-ray rocking curve (source: CuKα) obtained from the CdTe film of Experiment 1. FIG. 15 shows a bird's-eye SEM image (left) and a cross-sectional SEM image (right) of the CdTe film of Experiment 2 (drawing substitute photograph). FIG. 16 shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan of Experiment 2. FIG. 17 shows the (422) reflection ω-scan X-ray rocking curve (source: CuKα) obtained from the CdTe film of Experiment 2. FIG. 18 shows a bird's-eye SEM image (left) and a cross-sectional SEM image (right) of the CdTe film of Experiment 3 (drawing substitute photograph). FIG. 19 shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan of Experiment 3. FIG. 20 shows the (422) reflection ω-scan X-ray rocking curve (source: CuKα) obtained from the CdTe film of Experiment 3. FIG. 21 shows a bird's-eye SEM image (left) and a cross-sectional SEM image (right) of the CdTe film of Experiment 4 (drawing substitute photograph). FIG. 22 shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan of Experiment 4. FIG. 23 shows the (422) reflection ω-scan X-ray rocking curve (source: CuKα) obtained from the CdTe film of Experiment 4. FIG. 24 shows a bird's-eye SEM image (left) and a cross-sectional SEM image (right) of the CdTe film of Experiment 5 (drawing substitute photograph). FIG. 25 shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan of Experiment 5. FIG. 26 shows the (422) reflection ω-scan X-ray rocking curve (source: CuKα) obtained from the CdTe film of Experiment 5. FIG. 27 shows a bird's-eye SEM image (left) and a cross-sectional SEM image (right) of the CdTe film of Experiment 6 (drawing substitute photograph). FIG. 28 shows the XRD pattern of the CdTe film obtained from the 2θ / ω scan of Experiment 6. FIG. 29 shows the (422) reflection ω-scan X-ray rocking curve (source: CuKα) obtained from the CdTe film of Experiment 6.

1. Vapor Deposition Apparatus An example of a vapor deposition apparatus that can be preferably used for carrying out the epitaxial growth method of CdTe according to the embodiment is schematically shown in FIG.
Referring to FIG. 1, a vapor deposition apparatus 100 includes a hot wall reactor 111, a susceptor 112 disposed in the reactor to support the substrate, and a substrate supported by the susceptor. A first heater 113 disposed outside the reactor, a Cd reservoir 114 disposed within the reactor, and a second heater disposed outside the reactor to heat the metal Cd contained in the Cd reservoir. A heater 115 and a bubbler 120 disposed outside the reactor for vaporizing the organic Te compound supplied into the reactor via a pipe are provided.

The reactor 111 can be a quartz tube chamber, but is not limited thereto. The susceptor 112 can be formed of, for example, quartz, SiC (silicon carbide) or the like.
The first heater 113 surrounds the zone where the susceptor 112 is disposed in an annular shape.
The Cd reservoir 114 is made of, for example, quartz and can store molten metal Cd. In other words, the metal Cd is a simple substance Cd.
The second heater 115 surrounds the zone where the Cd reservoir 114 is disposed in an annular shape.

The reactor 111 is connected to one end of a first carrier gas supply pipe 116 whose other end is connected to a first carrier gas supply source (not shown). A first carrier gas for transporting single Cd vapor generated from the metal Cd accommodated in the Cd reservoir is supplied into the reactor 111 through the first carrier gas supply pipe 116.

A bubbler 120 for vaporizing the organic Te compound is disposed outside the reactor 111. The organic Te compound vaporized by the bubbler 120 is transported into the reactor 111 through a Te source supply pipe 117 together with a second carrier gas (bubbling gas) supplied to the bubbler from a second carrier gas source (not shown). The
In the middle of the Te source supply pipe 117, one end of a third carrier gas supply pipe 121 whose other end is connected to a third carrier gas source (not shown) is connected, and the organic Te supplied to the reactor 111 is connected. The compound vapor can be diluted with a third carrier gas.

The reactor 111 is further connected to one end of a barrier gas supply pipe 118 having the other end connected to a barrier gas source (not shown). In the reactor 111, the Te source supply pipe 117 and the barrier gas sharing pipe 118 constitute a double pipe having the former as an inner pipe and the latter as an outer pipe, and the Te source-containing gas flow released from the inner pipe is It is surrounded by a barrier gas flow released from the outer tube.
The reactor 111 is further provided with an exhaust port 119. The exhaust port 119 is usually connected to a scrubber.

Modification examples of the vapor deposition apparatus shown in FIG. 1 are illustrated in FIGS. 2 to 4, the same reference numerals are given to the components corresponding to those shown in FIG.
The vapor deposition apparatus shown in FIG. 2 is configured such that the susceptor 112 supports the substrate perpendicular to the bottom surface of the apparatus.
In the vapor deposition apparatus shown in FIG. 3, the reactor 111 is a vertical type, and the gas flow is directed from above to below in the reactor.

The method of forming an epitaxial CdTe film according to the embodiment can also be performed using a vapor deposition apparatus having the configuration shown in FIG.
Referring to FIG. 4, a vapor deposition apparatus 200 includes a hot wall type reactor 211, a susceptor 212 disposed in the reactor to support the substrate, and a substrate supported by the susceptor. A first heater 213 arranged outside the reactor is provided, and a bubbler 220 arranged outside the reactor for vaporizing the organic Te compound supplied into the reactor via a pipe.
The Cd reservoir 231 is a chamber type, and the metal Cd accommodated in the Cd reservoir is heated by the second heater 232 disposed outside the Cd reservoir.

The single Cd vapor generated in the Cd reservoir 231 is fed into the reactor 211 through the Cd source supply pipe 233 together with the first carrier gas supplied from the first carrier gas source (not shown) through the carrier gas supply pipe 234 to the Cd reservoir. To be transported to.
In addition, in the vapor deposition apparatus shown in FIGS. 1 to 4, a mechanism for rotating the susceptor can be arbitrarily provided.

2. CdTe Epitaxial Growth Method on Single Crystal Si Substrate An epitaxial growth method of CdTe on a single crystal Si substrate according to the embodiment uses single Cd and single Te or an organic Te compound as a Cd source and a Te source, respectively. A growth step of depositing CdTe from the vapor phase on the surface of the substrate.
The growth method preferably further includes a preparation step of preparing a single crystal Si substrate, and a baking step of baking the prepared single crystal Si substrate in a reducing gas or an inert gas. The preparation step and the baking step are preferably performed before the growth step.

Further, the CdTe epitaxial growth method according to the embodiment may include the following three steps as main steps.
(I) First A step of preparing a single crystal Si substrate.
(Ii) a single-crystal Si substrate prepared in said first step, a reducing gas or an inert gas, preferably baked at baking gas stream containing H _2, second A step of cleaning the surface.
(Iii) First, CdTe is deposited from the vapor phase on the surface cleaned in the second step A of the single-crystal Si substrate using simple Cd and simple Te or organic Te compound as the Cd source and Te source, respectively. Three A steps. The first A step and the second A step may be omitted.
Each step will be specifically described below.

2.1. First A Step In the first A step, a single crystal Si substrate is prepared as a substrate on which CdTe is to be epitaxially grown. A preferred single crystal Si substrate is a {211} substrate, but is not limited.
The single crystal Si substrate prepared in the first A step can have a surface oxide film. The surface oxide film here includes all silicon oxide films formed by reacting silicon derived from the Si substrate with oxygen supplied from the outside of the substrate.
The surface oxide film that the single crystal Si substrate prepared in the first A step may have can be either an unintentionally formed oxide film or an intentionally formed oxide film, and how it is formed. The oxide film formed may be an oxide film formed under any conditions.

An example of the surface oxide film that the single crystal Si substrate prepared in the first A step may have is a natural oxide film (an unintentionally formed oxide film). In general, an oxide film formed at room temperature in air, an oxide film formed by chemical cleaning such as RCA cleaning, an oxide film formed in the process of cleaning an Si wafer with ultrapure water, and the like are natural oxide films. are categorized.
Another example of the surface oxide film that the single crystal Si substrate prepared in the first A step may have is an intentional oxidation treatment such as a thermal oxide film, an oxide film formed by a treatment with an oxidizing agent such as a hot nitric acid solution, etc. This is an oxide film formed by the above. Chemical oxide films formed by the Ishizaka-Shiraki method, which is known as a surface cleaning method for Si substrates, can also be classified here. For details of the Ishizaka-Shiraki method, see A. Ishizaka, et al, “Low Temperature Surface Cleaning of Silicon and Its Application to Silicon MBE”, J. Electrochem. Soc., Vol. 133, pp 666-671 (1986). I want.

The surface oxide film that the single crystal Si substrate prepared in the first step A may have includes a part made of silicon oxide generated by unintentional oxidation, and a part made of silicon oxide formed by intentional oxidation treatment. May be included.
Furthermore, the single crystal Si substrate prepared in the first step A has a deposited film made of silicon oxide, silicon nitride, or silicon oxynitride on the surface instead of or in addition to the above-described surface oxide film. It may be formed.

2.2. Second A Step In the second A step, the single crystal Si substrate prepared in the first A step described above is baked in a reducing gas or an inert gas, preferably in a baking gas flow containing H ₂ , and the surface is baked. Clean. By executing this step, it becomes easy to epitaxially grow CdTe in the subsequent third A step.
The baking gas is preferably a reducing gas or an inert gas, more preferably only H ₂ (100% H ₂ ) as the reducing gas, but is not limited to N ₂ , noble gases (He, Ne, An inert gas such as Ar) may be contained. As long as it is not difficult to clean the surface of the single crystal Si substrate, the baking gas is allowed to contain not only H ₂ and inert gas but also other gases. Ga or As need not be present in the baking atmosphere.
The second A step is preferably performed without depositing other components on the surface of the single crystal Si substrate from the viewpoint of easy control of the carrier type of the crystal due to impurities and the carrier concentration. Specifically, the aspect of baking in the atmosphere which does not contain the component containing elements, such as Ga and As, is mentioned.

In the baking step, it is preferable to clean the surface of the single crystal Si substrate. The term “cleaning” as used in the present invention refers to removing unnecessary components in the CdTe deposition on the surface of the substrate, for example, removing a surface oxide film that may exist on the surface of the Si substrate. By sufficiently cleaning the surface of the Si substrate by the baking step, it becomes easy to deposit CdTe.
If the single crystal Si substrate has a surface oxide film, it is preferable to remove the surface oxide film, and the baking temperature and baking time are set according to the thickness.
The baking temperature, which is the temperature of the single crystal Si substrate during baking, is usually 500 ° C. or higher, preferably 700 ° C. or higher, more preferably 800 ° C. or higher, more preferably 850 ° C. or higher, particularly preferably 900 ° C. or higher, most preferably. 950 ° C. or higher and lower than the melting point of Si. It should be noted that the higher the baking temperature, the shorter the time required to clean the surface, but the faster the baking vessel will heat.
Moreover, baking time is 1 minute or more normally, Preferably it is 5 minutes or more, More preferably, it is 10 minutes or more, More preferably, it is 15 minutes or more, Most preferably, it is 20 minutes or more.
At least a part of the surface oxide film of the single crystal Si substrate may be removed by wet or dry chemical etching before the above-described baking. Preferred examples of the etching solution that can be used in the wet method include an HF aqueous solution (hydrofluoric acid) and an aqueous solution containing NH ₄ F (ammonium fluoride).

2.3. Third A Step In the third A step, CdTe is deposited from the vapor phase on the single crystal Si substrate prepared in the first A step by using simple Cd and simple Te or organic Te compound as the Cd source and Te source, respectively. .
Specifically, single Cd vapor and single Te vapor or organic Te compound vapor are supplied into a reactor in which a single crystal Si substrate is installed. The single crystal Si substrate is heated to a temperature higher than the minimum temperature required for crystallization of the deposited CdTe. When the surface of the single crystal Si substrate is cleaned in the second step described above, epitaxial growth of CdTe crystals is likely to occur on the surface.

The XRD pattern obtained from the 2θ / ω scan of the epitaxially grown CdTe crystal has a strong specific peak. For example, in the case of a CdTe crystal epitaxially grown on a {211} Si substrate, the {422} peak is the strongest in the XRD pattern obtained from the 2θ / ω scan, and the intensity of the second strongest peak is 1 / of the {422} peak. It can be less than 10 or even less than 1/100. The smaller the ratio, the higher the crystallinity of the grown CdTe, which is preferable.

In a particularly preferred example, two-dimensional growth of CdTe crystals occurs in the third A step. Two-dimensional growth refers to a growth mode in which a crystal grows so as to form a layer that seamlessly covers the substrate surface.
The in-plane variation of the layer thickness in the CdTe crystal layer formed by two-dimensional growth is preferably ± 50% with respect to the median value.
The two-dimensional growth of CdTe crystal can be realized, for example, by optimizing the deposition temperature.

The simple Te or organic Te compound used for the Te source is not particularly limited, but preferred examples of the organic Te compound include dimethyl tellurium [(CH ₃ ) ₂ Te], diethyl tellurium [(C ₂ H ₅ ) ₂ Te], and diisopropyl. Tellurium [(CH ₃ ) ₂ CH—Te—CH (CH ₃ ) ₂ ], ditertiary butyl tellurium [(CH ₃ ) ₃ C—Te—C (CH ₃ ) ₃ ] and diisopropyl ditellurium [(CH ₃ ) ₂ CH-Te-Te-CH ( CH 3) 2] and the like. The thermal decomposition temperatures of the organic Te compounds listed here are all 500 ° C. or lower.
The deposition temperature of CdTe is not particularly limited, but is usually 570 ° C. or higher, more preferably 600 ° C. or higher, and usually 730 ° C. or lower, more preferably 720 ° C. or lower.

2.4. Preferred Embodiment Here, an example in which CdTe crystals are epitaxially grown on a {211} Si substrate using the vapor deposition apparatus 100 shown in FIG. 1 will be described.
<Preparation of substrate and installation in reactor>
A {211} Si substrate having a surface oxide film is prepared. The surface oxide film may be a natural oxide film or a chemical oxide film formed by the procedure used in the Ishizaka-Shiraki method.
Next, after setting the prepared {211} Si substrate on the susceptor 112, the susceptor is placed in a zone surrounded by the first heater 113 in an annular shape in the reactor 111.
The metal Cd is introduced into the Cd reservoir before the Si substrate is installed in the reactor.

<Baking of substrate>
After the Si substrate is installed in the reactor 111, a baking gas containing H ₂ is supplied into the reactor.
It is not necessary to provide piping for baking gas in the vapor deposition apparatus 100, and the baking gas is supplied into the reactor 111 by using piping for supplying the first carrier gas, the third carrier gas, and / or the barrier gas. be able to. The composition of the first carrier gas, the third carrier gas, and / or the barrier gas may be the same as the composition of the baking gas.
After the start of the supply of the baking gas, the pressure in the reactor 111 is controlled within a range of 0.8 to 1.0 atm, for example, using an external exhaust means connected to the exhaust port 119, for example, a fan.

After the inside of the reactor is replaced with baking gas, heating of the substrate by the first heater 113 is started.
The baking temperature is preferably 900 ° C. or higher, more preferably 1000 ° C. or higher. When the reactor 111 is a quartz tube chamber, the baking temperature is preferably 1300 ° C. or lower. The object can be achieved even when the baking temperature is 1100 ° C. or lower.
Although depending on the thickness of the surface oxide film of the {211} Si substrate, the baking time is preferably 30 minutes or more.

<Deposition of CdTe>
After baking, the output of the first heater 113 is lowered to lower the temperature of the {211} Si substrate to a predetermined deposition temperature. The baking gas continues to flow while the substrate temperature is lowered. There is no need to remove the substrate from the reactor 111, and the substrate surface remains cleaned by baking until the beginning of CdTe deposition. The fact that the substrate does not have to be removed from the reactor is also advantageous in that the process can be simplified.

Simultaneously with the control of the substrate temperature, the metal Cd in the Cd reservoir 114 is heated to a predetermined temperature higher than the melting point by the second heater 115 and melted.
The temperature of the metal Cd is preferably set lower than the substrate temperature, and more preferably the temperature difference between the metal Cd and the substrate is 100 ° C. or more. By doing so, it is possible to prevent the metal Cd from being deposited on the substrate.
When the temperatures of the substrate and the metal Cd reach predetermined values, the compositions and flow rates of the first carrier gas, the third carrier gas, and the barrier gas are set to predetermined compositions and values, respectively, and the supply of the second carrier gas is started. .
The compositions of the first carrier gas, the second carrier gas, the third carrier gas, and the barrier gas are each preferably 100% H ₂ , but are not limited thereto. Each gas may contain a gas other than H ₂ as long as the epitaxial growth of the CdTe crystal is not inhibited. An example of a gas other than H ₂ is an inert gas, that is, N ₂ or a rare gas (He, Ne, Ar, etc.), but is not limited thereto.

When the supply of the second carrier gas is started, the organic Te compound vapor generated in the bubbler 120 is transported into the reactor 111 through the Te source supply pipe 117. The organic Te compound vapor carried into the reactor 111 is decomposed by being heated by the first heater 113, and reacts with simple Cd vapor generated by vaporization of the metal Cd to generate CdTe. At least a part of the generated CdTe is deposited on the {211} Si substrate. The deposition temperature at this time may be 570 ° C. or higher, and may be 600 ° C. or higher.

When the deposition conditions are set appropriately, CdTe crystals grow epitaxially on the {211} Si substrate. In a preferred example, two-dimensional growth of CdTe crystals occurs. In a particularly preferable example, the peak of the XRD pattern obtained from the 2θ / ω scan of the two-dimensionally grown CdTe crystal is only the CdTe {422} peak.

3. CdTe Epitaxial Growth Method on Single Crystal CdTe Substrate An epitaxial growth method of CdTe on a single crystal CdTe substrate according to an embodiment uses single Cd and single Te or an organic Te compound as a Cd source and a Te source, respectively. A growth step of depositing CdTe from the vapor phase on the surface of the substrate.
Preferably, the growth method further includes a preparation step of preparing a single crystal CdTe substrate and a baking step of baking the prepared single crystal CdTe substrate in a reducing gas or an inert gas. The preparation step and the baking step are preferably performed before the growth step.

3A. CdTe Epitaxial Growth Method on Single Crystal CdTe Substrate The CdTe epitaxial growth method according to the embodiment may include the following two steps as main steps.
(I) First B step of preparing a single crystal CdTe substrate.
(Ii) Second B step of depositing CdTe from the vapor phase on the surface of the CdTe substrate using simple Cd and simple Te or organic Te compound as the Cd source and Te source, respectively.
Each step will be specifically described below.

3A. 1. First B Step In the first B step, a single crystal CdTe substrate is prepared as a substrate on which CdTe is to be epitaxially grown. Preferred single crystal CdTe substrates are {211} CdTe substrate, {111} CdTe substrate, and {100} CdTe substrate from the viewpoint of availability of the substrate, but are not limited thereto.
CdTe may be a CdTe bulk substrate or a CdTe layer grown on a different substrate, and can be obtained by a commercially available method or a known method described in Non-Patent Documents 1 to 3. Also, single Cd and simple Te or organic Te compound may be used for a single crystal Si substrate as in the second B step, respectively, as a Cd source and a Te source.
When the second B step is applied to a single crystal Si substrate, the single crystal Si substrate is previously baked in a reducing gas or an inert gas, preferably in a baking gas flow containing H ₂ , and the surface is cleaned. Turn into. By executing this step, it becomes easy to epitaxially grow CdTe from simple Cd and simple Te or organic Te compound.
The baking gas is preferably a reducing gas or an inert gas, and is preferably only H ₂ (100% H ₂ ) as the reducing gas, but is not limited thereto. N ₂ , noble gases (He, Ne, Ar) Etc.) may be contained. As long as it is not difficult to clean the surface of the single crystal CdTe substrate, the baking gas is allowed to contain not only H ₂ and inert gas but also other gases. Ga or As need not be present in the baking atmosphere.
The first B step is preferably performed without depositing other components on the surface of the single crystal CdTe substrate from the viewpoint of easy control of the carrier type and carrier concentration of the crystal due to impurities. Specifically, the aspect of baking in the atmosphere which does not contain the component containing elements, such as Ga and As, is mentioned.

The baking temperature, which is the temperature of the single crystal CdTe substrate during baking, is less than the melting point of CdTe. It should be noted that the higher the baking temperature, the shorter the time required to clean the surface, but the faster the baking vessel will heat.
If the single crystal CdTe substrate has a surface oxide film, it is preferable to remove the surface oxide film, and therefore the baking temperature and baking time are set according to the thickness.
At least a part of the surface oxide film included in the single crystal CdTe substrate may be removed by wet or dry chemical etching before the above-described baking. Preferred examples of the etching solution that can be used in the wet method include an HF aqueous solution (hydrofluoric acid) and an aqueous solution containing NH ₄ F (ammonium fluoride).

3A. 2. Second B Step In the second B step, CdTe is deposited from the vapor phase on the CdTe substrate prepared in the first B step using simple substance Cd and organic Te compound as the Cd source and Te source, respectively.
Specifically, single Cd vapor and organic Te compound vapor are supplied into a reactor in which a single crystal CdTe substrate is installed. The single crystal CdTe substrate is heated to a temperature higher than the minimum temperature required for crystallization of the deposited CdTe.

The XRD pattern obtained from the 2θ / ω scan of the epitaxially grown CdTe crystal has a strong specific peak. For example, in the case of a CdTe crystal epitaxially grown on a {211} CdTe substrate, the {422} peak is the strongest in the XRD pattern obtained from the 2θ / ω scan, and the intensity of the second strongest peak is 1 / of the {422} peak. It can be less than 10 or even less than 1/100. The smaller the ratio, the higher the crystallinity of the grown CdTe, which is preferable.

For example, in the case of a CdTe crystal epitaxially grown on a {111} CdTe substrate, the {111} peak is the strongest in the XRD pattern obtained from the 2θ / ω scan, and the intensity of the second strongest peak is the {111} peak. It can be less than 1/10, or even less than 1/100. The smaller the ratio, the higher the crystallinity of the grown CdTe, which is preferable.

Also, for example, in the case of a CdTe crystal epitaxially grown on a {100} CdTe substrate, the {400} peak is the strongest in the XRD pattern obtained from the 2θ / ω scan, and the intensity of the second strongest peak is the {400} peak It can be less than 1/10, or even less than 1/100. The smaller the ratio, the higher the crystallinity of the grown CdTe, which is preferable.

In a particularly preferred example, two-dimensional growth of CdTe crystals occurs in the second B step. Two-dimensional growth refers to a growth mode in which a crystal grows so as to form a layer that seamlessly covers the substrate surface.
The in-plane variation of the layer thickness in the CdTe crystal layer formed by two-dimensional growth is preferably ± 50% with respect to the median value.
The two-dimensional growth of CdTe crystal can be realized, for example, by optimizing the deposition temperature.

The simple Te or organic Te compound used for the Te source is not particularly limited, but preferred examples of the organic Te compound include dimethyl tellurium [(CH ₃ ) ₂ Te], diethyl tellurium [(C ₂ H ₅ ) ₂ Te], and diisopropyl. Tellurium [(CH ₃ ) ₂ CH—Te—CH (CH ₃ ) ₂ ], ditertiary butyl tellurium [(CH ₃ ) ₃ C—Te—C (CH ₃ ) ₃ ] and diisopropyl ditellurium [(CH ₃ ) ₂ CH-Te-Te-CH (CH ₃ ) ₂ ]. The thermal decomposition temperatures of the organic Te compounds listed here are all 500 ° C. or lower.
The deposition temperature of CdTe is not particularly limited, but is usually 570 ° C. or higher, more preferably 600 ° C. or higher, and usually 730 ° C. or lower, more preferably 720 ° C. or lower.

3B. CdTe Epitaxial Growth Method on Single Crystal Substrate Other than CdTe The CdTe epitaxial growth method according to another embodiment is a method of epitaxially growing CdTe on a single crystal substrate (GaAs, sapphire, CdZnTe, CdHgTe, GaN, etc.) other than CdTe. And has the following two steps as main steps.
(I) First C step of preparing a single crystal substrate other than CdTe.
(Ii) A second C step in which CdTe is deposited from the vapor phase on the surface of the single crystal substrate using simple Cd and an organic Te compound as a Cd source and a Te source, respectively.

3B. 1. First C Step In the first C step, a single crystal substrate other than CdTe is prepared as a substrate on which CdTe is to be epitaxially grown. A preferable single crystal substrate is a substrate of GaAs, sapphire, CdZnTe, CdHgTe, GaN or the like, but is not limited thereto. In addition, it is preferable that Si single crystal is not contained in single crystals other than CdTe in a 1st C step.

3B. 2. Second C Step In the second C step, CdTe is deposited from the vapor phase on the substrate prepared in the first C step using simple Cd and simple Te or organic Te compound as the Cd source and Te source, respectively.
Specifically, single Cd vapor and organic Te compound vapor are supplied into a reactor in which a substrate is installed. The substrate is heated to a temperature higher than the minimum temperature required for crystallization of the CdTe to be deposited.

The XRD pattern obtained from the 2θ / ω scan of the epitaxially grown CdTe crystal has a strong specific peak. For example, in the case of a CdTe crystal epitaxially grown on a {211} GaAs substrate, the {422} peak is the strongest in the XRD pattern obtained from the 2θ / ω scan, and the intensity of the second strongest peak is 1 / of the {422} peak. It can be less than 10 or even less than 1/100. The smaller the ratio, the higher the crystallinity of the grown CdTe, which is preferable.

For example, in the case of a CdTe crystal epitaxially grown on a {111} GaAs substrate, the {111} peak is the strongest in the XRD pattern obtained from the 2θ / ω scan, and the intensity of the second strongest peak is the {111} peak. It can be less than 1/10, or even less than 1/100. The smaller the ratio, the higher the crystallinity of the grown CdTe, which is preferable.

For example, in the case of a CdTe crystal epitaxially grown on a {100} GaAs substrate, the {400} peak is the strongest in the XRD pattern obtained from the 2θ / ω scan, and the intensity of the second strongest peak is the {400} peak. It can be less than 1/10, or even less than 1/100. The smaller the ratio, the higher the crystallinity of the grown CdTe, which is preferable.

In a particularly preferred example, two-dimensional growth of CdTe crystals occurs in the second C step. Two-dimensional growth refers to a growth mode in which a crystal grows so as to form a layer that seamlessly covers the substrate surface.
The in-plane variation of the layer thickness in the CdTe crystal layer formed by two-dimensional growth is preferably ± 50% with respect to the median value.
The two-dimensional growth of CdTe crystal can be realized, for example, by optimizing the deposition temperature.

The simple Te or organic Te compound used for the Te source is not particularly limited, but preferred examples of the organic Te compound include dimethyl tellurium [(CH ₃ ) ₂ Te], diethyl tellurium [(C ₂ H ₅ ) ₂ Te], and diisopropyl. Tellurium [(CH ₃ ) ₂ CH—Te—CH (CH ₃ ) ₂ ], ditertiary butyl tellurium [(CH ₃ ) ₃ C—Te—C (CH ₃ ) ₃ ] and diisopropyl ditellurium [(CH ₃ ) ₂ CH-Te-Te-CH (CH ₃ ) ₂ ]. The thermal decomposition temperatures of the organic Te compounds listed here are all 500 ° C. or lower.
The deposition temperature of CdTe is not particularly limited, but is usually 570 ° C. or higher, more preferably 600 ° C. or higher, and usually 730 ° C. or lower, more preferably 720 ° C. or lower.

3C. Preferred Embodiment Here, an example of epitaxially growing a CdTe crystal on a {211} CdTe substrate using the vapor deposition apparatus 100 shown in FIG. 1 will be described.
<Preparation of substrate and installation in reactor>
A {211} CdTe substrate is prepared.
Next, after the prepared {211} CdTe substrate is set on the susceptor 112, the susceptor is placed in a zone surrounded by the first heater 113 in an annular shape in the reactor 111.
The metal Cd is charged into the Cd reservoir before the {211} CdTe substrate is installed in the reactor.

<Deposition of CdTe>
After installing the {211} CdTe substrate, the temperature of the {211} CdTe substrate is adjusted to a predetermined deposition temperature.

Simultaneously with the control of the substrate temperature, the metal Cd in the Cd reservoir 114 is heated to a predetermined temperature higher than the melting point by the second heater 115 and melted.
The temperature of the metal Cd is preferably set lower than the substrate temperature, and more preferably the temperature difference between the metal Cd and the substrate is 100 ° C. or more. By doing so, it is possible to prevent the metal Cd from being deposited on the substrate.
When the temperatures of the substrate and the metal Cd reach predetermined values, the compositions and flow rates of the first carrier gas, the third carrier gas, and the barrier gas are set to predetermined compositions and values, respectively, and the supply of the second carrier gas is started. .
The compositions of the first carrier gas, the second carrier gas, the third carrier gas, and the barrier gas are each preferably 100% H ₂ , but are not limited thereto. Each gas may contain a gas other than H ₂ as long as the epitaxial growth of the CdTe crystal is not inhibited. An example of a gas other than H ₂ is an inert gas, that is, N ₂ or a rare gas (He, Ne, Ar, etc.), but is not limited thereto.

When the supply of the second carrier gas is started, the organic Te compound vapor generated in the bubbler 120 is transported into the reactor 111 through the Te source supply pipe 117. The organic Te compound vapor carried into the reactor 111 is decomposed by being heated by the first heater 113, and reacts with simple Cd vapor generated by vaporization of the metal Cd to generate CdTe. At least a portion of the generated CdTe is deposited on the {211} CdTe substrate. The deposition temperature at this time may be 570 ° C. or higher, and may be 600 ° C. or higher.

When the deposition conditions are set appropriately, CdTe crystals grow epitaxially on a {211} CdTe substrate. In a preferred example, two-dimensional growth of CdTe crystals occurs. In a particularly preferable example, the peak of the XRD pattern obtained from the 2θ / ω scan of the two-dimensionally grown CdTe crystal is only the CdTe {422} peak.

4). Applications By using the CdTe epitaxial growth method according to the embodiment, CdTe crystal layers having various thicknesses can be grown on a single crystal Si substrate.
In one example, a bulk CdTe crystal that can be used as a free-standing substrate can be obtained by removing the single crystal Si substrate from the CdTe crystal layer that has been grown thick by the method according to the embodiment.
In another example, a CdTe crystal layer grown by the method according to the embodiment can be used in a state of being bonded to a single crystal Si substrate to form a semiconductor device such as a radiation detector or a solar cell. .

In the above applications, the use of the method according to the embodiment for the growth of CdTe crystals is advantageous in terms of cost compared to the method of growing CdTe crystals using an organic Cd compound as a Cd source. This is because simple Cd is used as a raw material as it is without going through the synthesis process of the organic Cd compound. High-purity simple substance Cd can be obtained at a low price of about 1/10 compared to an organic Cd compound having the same purity.

In still another example, a CdTe film formed on a Si substrate using the CdTe epitaxial growth method according to the embodiment can be used as a buffer layer. That is, after a CdTe epitaxial film is grown on the single crystal Si substrate by the method according to the embodiment, another semiconductor crystal layer is grown on the CdTe epitaxial film. A target bulk semiconductor crystal or semiconductor device is manufactured from this other semiconductor crystal layer.
Another semiconductor crystal layer here may be a semiconductor having a composition different from that of CdTe, such as HgCdTe, or may be CdTe grown using a method different from the present invention.

From the HgCdTe crystal grown using the CdTe crystal film grown by the method according to the embodiment as a buffer layer, a semiconductor device such as an infrared detector can be manufactured. A semiconductor device such as a radiation detector or a solar cell can be manufactured from a CdTe crystal grown using the CdTe crystal film grown by the method according to the embodiment as a buffer layer.

Further, by using the CdTe epitaxial growth method according to the embodiment, CdTe crystal layers having various thicknesses can be grown on a single crystal CdTe substrate or a single crystal substrate other than CdTe.
In another example, a semiconductor device such as a radiation detector or a solar cell can be configured using the CdTe crystal layer grown by the method according to the embodiment.
In the above application, using the method according to the embodiment for growing a CdTe crystal is advantageous in terms of cost compared to a method of growing a CdTe crystal using an organic Cd compound as a Cd source. This is because simple Cd is used as a raw material as it is without going through the synthesis process of the organic Cd compound. High-purity simple substance Cd can be obtained at a low price of about 1/10 compared to an organic Cd compound having the same purity.

In yet another example, after CdTe is grown on a plurality of different substrates, semiconductor crystal layers having different structures are grown on the epitaxial crystals using the present invention. A target bulk semiconductor crystal or semiconductor device is manufactured from this other semiconductor crystal layer.

5). Experimental result A
CdTe deposition on a (211) Si substrate was attempted using a vapor deposition apparatus having the same basic configuration as the vapor deposition apparatus shown in FIG. Diisopropyl tellurium (DiPTe) was used as the organic Te compound. The reactor of the vapor deposition apparatus was manufactured using a quartz tube. The exhaust port of the reactor was connected to a scrubber equipped with an exhaust fan.

5.1. Experiment A1
A commercially available (211) Si substrate was subjected to chemical oxidation treatment in accordance with the procedure used in the Ishizaka-Shiragi method. The chemically oxidized (211) Si substrate was set in a reactor of a vapor deposition apparatus, and then H ₂ was introduced into the reactor through a carrier gas pipe and a barrier gas pipe. The flow rate was 4460 sccm.
After the inside of the reactor was replaced with H ₂ , the substrate was baked under the conditions of a baking temperature of 1050 ° C. and a baking time of 30 minutes. The total pressure in the reactor was 1 atm (the same applies to the subsequent steps).

After baking, the heater output was controlled with H ₂ flowing in the reactor to lower the substrate temperature to a predetermined deposition temperature. At the same time, the metal Cd in the reservoir installed in the reactor was heated to 455 ° C. higher than the melting point.
When the substrate and the metal Cd reached the target temperature, the flow rates of the carrier gas and the barrier gas flowing into the reactor were adjusted to predetermined values. Supply of the carrier gas (bubble gas) to the bubbler was started at this timing. The bubbling temperature was 29 ° C.
There were five deposition temperatures of 500 ° C., 550 ° C., 600 ° C., 650 ° C. and 700 ° C.

The carrier gas and barrier gas supplied into the reactor were all H ₂ and the total flow rate was set to 4420 sccm.
The DiPTe partial pressure in the reactor was set to 1.2 × 10 ⁻⁴ atm, and the Cd partial pressure was set to 2.3 × 10 ⁻³ atm. The gas partial pressure referred to here is a value calculated by multiplying the total pressure by the ratio of the flow rate of the gas to the sum of the flow rates of all the gases flowing in the reactor.
The DiPTe flow rate was calculated from the vapor pressure of DiPTe at the bubbling temperature and the flow rate of the bubbling gas under the assumption that the internal pressure of the bubbler was 800 Torr (slightly pressurized state).
The flow rate of Cd vapor was calculated from the vapor pressure of Cd at 455 ° C. and the flow rate of the carrier gas supplied to transport the Cd vapor.
When the predetermined deposition time had elapsed, the supply of bubbling gas to the bubbler was stopped, whereby the supply of DiPTe into the reactor was stopped and the heating of the reactor was stopped.

After the temperature in the reactor dropped to room temperature, the (211) Si substrate was taken out of the reactor, and SEM observation and XRD analysis of the CdTe film deposited on the substrate were performed.
5A to 5E show bird's-eye SEM images of five types of CdTe films deposited at different temperatures, respectively.

As shown in FIGS. 5A and 5B, the CdTe film deposited at 500 ° C. and 550 ° C. was an aggregate of fine crystal particles having a size of less than 1 μm.
In the CdTe films deposited at 600 ° C. and 650 ° C. shown in FIGS. 5C and 5D, it was confirmed from the cross-sectional SEM images measured separately that the crystals were two-dimensionally grown. 6A and 6B are cross-sectional SEM images of CdTe films deposited at 600 ° C. and 650 ° C., respectively, and (211) a CdTe crystal layer that seamlessly covers the surface of the Si substrate is formed. I understand that.
As shown in FIG. 5E, the CdTe films deposited at 700 ° C. were aggregates of coarse crystal grains each having a size on the order of 10 μm.

In the XRD analysis, X-rays were incident on the surface of the CdTe film deposited on the surface of the (211) Si substrate and 2θ / ω scan was performed as shown in FIG.
<XRD analysis>
Analyzer: Philips X'Pert
X-ray source: CuKα (45 kV, 40 mA)
Incident side optical system: Hybrid 2 bounce monochromator Divergence slit (incident): 1/2 degree Light receiving side optical system: Flat plate collimator (0.27 mm)
FIGS. 8A to 8E show XRD patterns (ray source: CuKα) of the five types of CdTe films obtained from the 2θ / ω scan.
As shown in FIGS. 8 (a) and (b), no specific peak having a significantly higher intensity than the other peaks was observed in the XRD pattern of the CdTe film deposited at 500 ° C. and 550 ° C.
In contrast, as shown in FIGS. 8C to 8E, in the CdTe film having a deposition temperature of 600 ° C. or higher, the intensity of the CdTe (422) peak is significantly higher than the other peaks, and at least some of the crystals It turns out that it is growing epitaxially.

In particular, as shown in FIG. 8C, the peak of the XRD pattern of the CdTe film deposited at 600 ° C. was only the CdTe (422) peak. When a ω-scan X-ray rocking curve (source: CuKα) of (422) reflection was measured in this CdTe film, a single peak was obtained as shown in FIG.
(422) When the reflection ω-scan X-ray rocking curve was measured, the CdTe film deposited at 650 ° C. had the narrowest half width. However, as shown in FIG. 8D, a (331) peak was also observed in the XRD pattern of this CdTe film.

From the SEM observation, the thicknesses of the CdTe films deposited at 600 ° C. and 650 ° C. were both 2.5 μm. The deposition rate calculated from the time from the start of supply of DiPTe to the reactor to the stop of supply as the deposition time was 10 μm / h.

5.2. Experiment A2
The intentional chemical oxidation treatment of the substrate was not performed, the substrate baking conditions before CdTe deposition were a baking temperature of 800 ° C., a baking time of 5 minutes, and the deposition temperature was 420 ° C., 550 ° C., 600 ° C. Attempts were made to deposit CdTe on a (211) Si substrate in the same manner as in Experiment A1, except that the temperature was 650 ° C, 700 ° C, and 750 ° C.

As a result, when the deposition temperature was 420 to 700 ° C., a CdTe film was formed on the substrate. When the deposition temperature was 750 ° C., no deposits observable by SEM were found on the substrate, suggesting that etching was dominant over deposition.
Although the CdTe film deposited at 420 ° C. contained Cd and Te as component elements, no diffraction peak peculiar to the CdTe crystal was observed in the XRD analysis, so it was considered amorphous.

The CdTe film deposited at 550 to 700 ° C. was confirmed to contain CdTe crystals by XRD analysis.
However, a plurality of peaks were observed in the XRD pattern, and the intensity ratio between the plurality of peaks was in good agreement with that in the powder XRD pattern of CdTe. From this, it was found that the orientation of the CdTe crystal constituting the film was random and epitaxial growth did not occur.
One reason why the epitaxial growth did not occur in the experiment A2 is that the (211) natural oxide film on the surface of the Si substrate could not be removed under the baking conditions used in the experiment A2. Guess.

5.3. Experiment A3
As substrate A, a commercially available (211) Si substrate prepared by chemical oxidation treatment according to the procedure used in the Ishizaka-Shiraki method was prepared as in Experiment A1.
As the substrate B, a substrate A was immersed in IPA (isopropanol) heated to 100 ° C. and washed for 10 minutes, then immersed in a 1% HF aqueous solution for 30 seconds, and then washed with pure water. The surface of the substrate B was hydrophobic and repelled water well.
As substrate C, a commercially available (211) Si substrate was immersed in IPA (isopropanol) heated to 100 ° C. and washed for 10 minutes, then immersed in a 1% HF aqueous solution for 30 seconds, and then washed with pure water. Got ready. The surface of the substrate C was hydrophobic and repelled water well.

CdTe was deposited at 600 ° C. on each of the substrates A to C. The procedure and conditions were the same as in Experiment A1, except that the substrate before CdTe deposition was not baked or was performed using any of baking conditions 1 to 3 shown in Table 1. In any of baking conditions 1 to 3, the baking gas was only H ₂ and the flow rate was the same as in Experiment A1.

The results are shown in Table 2.

In Table 2, “polycrystalline growth” indicates that the CdTe film deposited on the (211) Si substrate is a polycrystalline film, and “epitaxial growth” indicates that the CdTe film is an epitaxially grown film.
As shown in Table 2, when the substrate was not baked before CdTe deposition, the CdTe films deposited on the substrates A to C were all polycrystalline films. The same was true when the substrate was baked under baking conditions 1.
On the other hand, when the substrate was baked under baking condition 3 before CdTe deposition, epitaxial growth of CdTe crystals occurred on any of the substrates A to C.

When substrate baking before CdTe deposition was performed under baking conditions 2, that is, a baking temperature of 900 ° C. and a baking time of 30 minutes, different results were produced between the substrate A and the other substrates. That is, as shown in Table 2, the CdTe film deposited on the substrate A was a polycrystalline film, whereas the CdTe films grown on the substrate B and the substrate C were epitaxially grown films.
FIGS. 10A to 10C show XRD patterns (radiation source: CuKα) obtained from the 2θ / ω scan of the CdTe films grown on the substrates A to C, respectively.

6). Experimental result B
Using a vapor deposition apparatus having the same basic configuration as the vapor deposition apparatus shown in FIG. 1, CdTe deposition on a {211} CdTe substrate was attempted. Diisopropyl tellurium (DiPTe) was used as the organic Te compound. The reactor of the vapor deposition apparatus was manufactured using a quartz tube. The exhaust port of the reactor was connected to a scrubber equipped with an exhaust fan.

6.1. Experiment B1 Preparation of (211) CdTe Substrate A commercially available (211) Si substrate was subjected to a chemical oxidation treatment according to the procedure used in the Ishizaka-Shiragi method. The chemically oxidized (211) Si substrate was set in a reactor of a vapor deposition apparatus, and then H ₂ was introduced into the reactor through a carrier gas pipe and a barrier gas pipe. The flow rate was 4460 sccm.
After the inside of the reactor was replaced with H ₂ , the substrate was baked under the conditions of a baking temperature of 1000 ° C. and a baking time of 30 minutes. The total pressure in the reactor was 1 atm (the same applies to the subsequent steps).

After baking, the heater output was controlled with H ₂ flowing in the reactor to lower the substrate temperature to a predetermined deposition temperature. At the same time, the metal Cd in the reservoir installed in the reactor was heated to 455 ° C. higher than the melting point.
When the substrate and the metal Cd reached the target temperature, the flow rates of the carrier gas and the barrier gas flowing into the reactor were adjusted to predetermined values. Supply of the carrier gas (bubble gas) to the bubbler was started at this timing. The bubbling temperature was 29 ° C.
The deposition temperature was 625 ° C.

The carrier gas and barrier gas supplied into the reactor were all H ₂ and the total flow rate was set to 4420 sccm.
The DiPTe partial pressure in the reactor was set to 1.2 × 10 ⁻⁴ atm, and the Cd partial pressure was set to 2.3 × 10 ⁻³ atm. The gas partial pressure referred to here is a value calculated by multiplying the total pressure by the ratio of the flow rate of the gas to the sum of the flow rates of all the gases flowing in the reactor.
The DiPTe flow rate was calculated from the vapor pressure of DiPTe at the bubbling temperature and the flow rate of the bubbling gas under the assumption that the internal pressure of the bubbler was 800 Torr (slightly pressurized state).
The flow rate of Cd vapor was calculated from the vapor pressure of Cd at 455 ° C. and the flow rate of the carrier gas supplied to transport the Cd vapor.
After the deposition for 1 hour, the supply of DiPTe into the reactor was stopped and the heating of the reactor was stopped by stopping the supply of the bubbling gas to the bubbler.

After the temperature in the reactor dropped to room temperature, the (211) Si substrate on which CdTe was deposited was taken out of the reactor, and SEM observation and XRD analysis of the CdTe film deposited on the substrate were performed.
FIG. 11 shows a bird's-eye view and a cross-sectional SEM image of the deposited CdTe film.

From the cross-sectional SEM image, it was confirmed that the crystal was grown two-dimensionally, and the CdTe deposition film thickness was 15.3 μm. The deposition rate calculated from the time from the start of supply of DiPTe to the reactor to the stop of supply as the deposition time was 15.3 μm / h.

In the XRD analysis, X-rays were incident on the surface of the CdTe film deposited on the surface of the (211) Si substrate and 2θ / ω scan was performed as shown in FIG.
<XRD analysis>
Analyzer: Philips X'Pert
X-ray source: CuKα (45 kV, 40 mA)
Incident side optical system: Hybrid 2 bounce monochromator Divergence slit (incident): 1/2 degree Light receiving side optical system: Flat plate collimator (0.27 mm)
The XRD pattern (source: CuKα) and the ω-scan X-ray rocking curve of the CdTe film obtained from the 2θ / ω scan are shown in FIGS.
As shown in FIG. 13, only the CdTe (422) peak was detected, and no reflection from other plane orientations was observed. This result shows that (211) CdTe crystal is epitaxially grown on (211) Si.
In addition, the half width of the (422) reflection ω-scan X-ray rocking curve was 603 seconds.

6.2. Experiment B2 (211) CdTe Deposition on CdTe Substrate Using the (211) CdTe substrate obtained in Experiment B1 as the substrate, CdTe was deposited on the (211) CdTe substrate.

The (211) CdTe substrate obtained in Experiment B1 was set in the reactor of the vapor deposition apparatus, and then H ₂ was introduced into the reactor through the carrier gas pipe and the barrier gas pipe. The flow rate was 4460 sccm.
Next, the heater output was controlled to raise the substrate temperature to a predetermined deposition temperature. At the same time, the metal Cd in the reservoir installed in the reactor was heated to 455 ° C. higher than the melting point.
When the substrate and the metal Cd reached the target temperature, the flow rates of the carrier gas and the barrier gas flowing into the reactor were adjusted to predetermined values. Supply of the carrier gas (bubble gas) to the bubbler was started at this timing. The bubbling temperature was 29 ° C.
The deposition temperature was 625 ° C.

The carrier gas and barrier gas supplied into the reactor were all H ₂ and the total flow rate was set to 4420 sccm.
The DiPTe partial pressure in the reactor was set to 1.2 × 10 ⁻⁴ atm, and the Cd partial pressure was set to 2.3 × 10 ⁻³ atm. The gas partial pressure referred to here is a value calculated by multiplying the total pressure by the ratio of the flow rate of the gas to the sum of the flow rates of all the gases flowing in the reactor.
The DiPTe flow rate was calculated from the vapor pressure of DiPTe at the bubbling temperature and the flow rate of the bubbling gas under the assumption that the internal pressure of the bubbler was 800 Torr (slightly pressurized state).
The flow rate of Cd vapor was calculated from the vapor pressure of Cd at 455 ° C. and the flow rate of the carrier gas supplied to transport the Cd vapor.
After the deposition for 1 hour, the supply of DiPTe into the reactor was stopped and the heating of the reactor was stopped by stopping the supply of the bubbling gas to the bubbler.

After the temperature in the reactor dropped to room temperature, the (211) CdTe substrate was taken out of the reactor, and SEM observation and XRD analysis of the CdTe film deposited on the substrate were performed.
FIG. 15 shows a bird's eye view and a cross-sectional SEM image of the deposited CdTe film.

From the cross-sectional SEM image, it was confirmed that the crystal was grown two-dimensionally, and the CdTe deposited film thickness deposited on the (211) CdTe substrate was 14.3 μm. The deposition rate calculated from the time from the start of supply of DiPTe to the reactor to the stop of supply as the deposition time was 14.3 μm / h.

FIGS. 16 and 17 show the XRD pattern (source: CuKα) and the ω-scan X-ray rocking curve of the CdTe film obtained from the 2θ / ω scan, respectively.
As shown in FIG. 16, only the CdTe (211) peak was detected, and no reflection from other plane orientations was observed. This result indicates that CdTe is epitaxially grown on the (211) CdTe substrate.
In addition, the half width of the (422) reflection ω-scan X-ray rocking curve was 596 seconds, and the CdTe layer deposited in Experiment B2 showed a half width of almost the same as (211) CdTe used as the substrate. It was shown that the crystallinity was not deteriorated.

6.3. Experiment B3
In Experiment B1, a (211) CdTe substrate was obtained in the same manner as in Experiment B1, except that the deposition time was 30 minutes.
FIG. 18 shows a bird's-eye view and a cross-sectional SEM image of the deposited CdTe film.

From the cross-sectional SEM image, it was confirmed that the crystal was two-dimensionally grown, and the CdTe deposition film thickness was 7.9 μm. The deposition rate calculated from the time from the start of supply of DiPTe to the reactor to the stop of supply as the deposition time was 15.8 μm / h.

FIGS. 19 and 20 show the XRD pattern (source: CuKα) and the ω-scan X-ray rocking curve of the CdTe film obtained from the 2θ / ω scan, respectively.
As shown in FIG. 19, only the CdTe (422) peak was detected, and no reflection from other plane orientations was observed. This result shows that CdTe crystals are epitaxially grown on (211) Si.
In addition, the half width of the (422) reflection ω-scan X-ray rocking curve was 605 seconds.

6.4. Experiment B4
CdTe was deposited on the (211) CdTe substrate obtained in Experiment B3 by the same method as in Experiment B2.
FIG. 21 shows a bird's-eye view and a cross-sectional SEM image of the deposited CdTe film.

From the cross-sectional SEM image, it was confirmed that the crystal was two-dimensionally grown, and the CdTe deposited film thickness deposited on the (211) CdTe substrate was 11.5 μm. The deposition rate calculated from the time from the start of supply of DiPTe to the reactor to the stop of supply as the deposition time was 11.5 μm / h.

FIGS. 22 and 23 show the XRD pattern (source: CuKα) and the ω-scan X-ray rocking curve of the CdTe film obtained from the 2θ / ω scan, respectively.
As shown in FIG. 22, only the CdTe (211) peak was detected, and no reflection from other plane orientations was observed. This result indicates that CdTe is epitaxially grown on the (211) CdTe substrate.
In addition, the (422) reflection ω-scan X-ray rocking curve had a full width at half maximum of 460 seconds, and the CdTe layer deposited in Experiment B4 showed a half width smaller than (211) CdTe used as the substrate. It was shown that the sex did not deteriorate.

6.5. Experiment B5
In the vapor deposition apparatus to be used, the distance between the Te source supply pipe and the substrate is 5 mm away from Experiment B1, and in Experiment B1, the deposition time is set to 30 minutes (211). A CdTe substrate was obtained.
FIG. 24 shows a bird's-eye view and a cross-sectional SEM image of the deposited CdTe film.

From the cross-sectional SEM image, it was confirmed that the crystal was two-dimensionally grown, and the CdTe deposition film thickness was 7.9 μm. The deposition rate calculated from the time from the start of supply of DiPTe to the reactor to the stop of supply as the deposition time was 15.8 μm / h.

The XRD pattern (source: CuKα) and the ω-scan X-ray rocking curve of the CdTe film obtained from the 2θ / ω scan are shown in FIGS. 25 and 26, respectively.
As shown in FIG. 25, only the CdTe (422) peak was detected, and no reflection from other plane orientations was observed. This result shows that CdTe crystals are epitaxially grown on (211) Si.
In addition, the half width of the (422) reflection ω-scan X-ray rocking curve was 693 seconds.

6.6. Experiment B6
CdTe was deposited on the (211) CdTe substrate obtained in Experiment B5 by the same method as in Experiment B2.
FIG. 27 shows a bird's-eye view and a cross-sectional SEM image of the deposited CdTe film.

From the cross-sectional SEM image, it was confirmed that the crystal was grown two-dimensionally, and the CdTe deposited film thickness deposited on the (211) CdTe substrate was 12.8 μm. The deposition rate calculated from the time from the start of supply of DiPTe to the reactor to the stop of supply as the deposition time was 12.8 μm / h.

FIGS. 28 and 29 show the XRD pattern (source: CuKα) and the ω-scan X-ray rocking curve of the CdTe film obtained from the 2θ / ω scan, respectively.
As shown in FIG. 28, only the CdTe (211) peak was detected, and no reflection from other plane orientations was observed. This result indicates that CdTe is epitaxially grown on the (211) CdTe substrate.
In addition, the half width of the (422) reflection ω-scan X-ray rocking curve was 378 seconds, and the CdTe layer deposited in Experiment B6 showed a half width that was much smaller than (211) CdTe used as the substrate. It was shown that the crystallinity was improved.

100, 200 Vapor deposition apparatus 111, 211 Reactor 112, 212 Susceptor 113, 213 First heater 114, 231 Cd reservoir 115, 232 Second heater 116 First carrier gas supply pipe 117, 217 Te source gas supply pipe 118, 218 Barrier gas supply pipes 119, 219 Exhaust ports 120, 220 Bubblers 121, 221 Third carrier gas supply pipe 233 Cd source supply pipe 234 Carrier gas supply pipe

Claims (25)

1. A method of epitaxially growing CdTe on a single crystal Si substrate, wherein CdTe is deposited from the vapor phase on the surface of the single crystal Si substrate using single Cd and single Te or an organic Te compound as a Cd source and a Te source, respectively. A growth step.
2. The method according to claim 1, comprising a preparation step of preparing a single crystal Si substrate, and a baking step of baking the prepared single crystal Si substrate in a reducing gas or an inert gas.
3. The method of claim 2, wherein the baking step is performed without depositing other components on the surface of the single crystal Si substrate.
4. The method of claim 2, wherein the baking step cleans a surface of the single crystal Si substrate.
5. The method according to claim 2, wherein the single crystal Si substrate prepared in the preparation step has a surface oxide film.
6. The method according to claim 1, wherein the single crystal Si substrate is a {211} Si substrate.
7. The method according to claim 2, wherein the gas used in the baking step is a gas containing H ₂ .
8. The method according to claim 1, wherein the Te source is an organic Te compound.
9. The method according to claim 1, wherein a CdTe deposition temperature in the growth step is 570 ° C. or higher.
10. The method according to any one of claims 1 to 9, wherein the CdTe crystal obtained in the growth step has a CdTe {422} peak as a strongest peak in an XRD pattern obtained from a 2θ / ω scan.
11. The method according to any one of claims 1 to 10, wherein the single crystal Si substrate and the CdTe crystal obtained in the growth step have the same crystal plane.
12. A method for producing a semiconductor for a radiation detector, comprising a step of epitaxially growing CdTe on a single crystal Si substrate by the method according to any one of claims 1 to 11.
13. A vapor deposition apparatus for depositing CdTe on a substrate,
    A hot wall reactor,
    A susceptor disposed in the reactor to support a substrate;
    A first heater disposed outside the reactor to heat a substrate supported by the susceptor;
    A Cd reservoir disposed in the reactor;
    A second heater disposed outside the reactor to heat the metal Cd contained in the Cd reservoir;
    A vapor deposition apparatus comprising: a bubbler disposed outside the reactor for vaporizing an organic Te compound supplied into the reactor through a pipe.
14. A method of epitaxially growing CdTe on a single-crystal CdTe substrate, wherein CdTe is deposited from the vapor phase on the surface of the single-crystal CdTe substrate by using simple Cd and simple Te or an organic Te compound as a Cd source and a Te source, respectively. A growth step.
15. The method according to claim 14, comprising a preparation step of preparing a single crystal CdTe substrate, and a baking step of baking the prepared single crystal CdTe substrate in a reducing gas or an inert gas.
16. The method of claim 15, wherein the baking step is performed without depositing other components on the surface of the single crystal CdTe substrate.
17. The method of claim 15, wherein the baking step cleans a surface of the single crystal CdTe substrate.
18. The method according to claim 15, wherein the single crystal CdTe substrate prepared in the preparation step has a surface oxide film.
19. 19. The method according to any one of claims 14 to 18, wherein the single crystal CdTe substrate is a {211} CdTe substrate.
20. The method according to claim 15, wherein the gas used in the baking step is a gas containing H ₂ .
21. 21. A method according to any one of claims 14 to 20, wherein the Te source is an organic Te compound.
22. The method according to any one of claims 14 to 21, wherein a CdTe deposition temperature in the growth step is 570 ° C or higher.
23. The method according to any one of claims 14 to 22, wherein the strongest peak of the CdTe crystal obtained in the growth step is a CdTe {422} peak in an XRD pattern obtained from a 2θ / ω scan.
24. The method according to any one of claims 14 to 23, wherein the single crystal CdTe substrate and the CdTe crystal obtained in the growth step have the same crystal plane.
25. A method for manufacturing a semiconductor for a radiation detector, comprising the step of epitaxially growing CdTe on a single crystal CdTe substrate by the method according to any one of claims 14 to 24.

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