Layered semiconductor, method for manufacturing layered semiconductor

Abstract

The present invention provides a layered semiconductor having a novel composition that exhibits high electron mobility and can be formed in layers, and a method for manufacturing a layered semiconductor. [Solution] M 1-x A2H 2x A layered semiconductor consisting of a film in which atoms bonded in the composition formula are connected in a planar manner. However, 0

Description

Technical Field

[0001] The present invention relates to a layered semiconductor and a method for manufacturing the layered semiconductor.

Background Art

[0002] Conventionally, as a layered semiconductor, graphene in which carbon spreads in layers with a thickness of 1 atom is known. Also known are layered semiconductors such as silicene made of silicon and germanene made of germanium having the same structure as graphene.

[0003] The present invention relates to a layered semiconductor and a method for manufacturing the layered semiconductor. However, in the exfoliation method, which is a common method for forming graphene, it has been difficult to form it on a large area applicable to semiconductor elements. Also, silicene and germanene are difficult to form on an insulator substrate, their physical properties are unknown, and they have not been used as layered semiconductors having stable characteristics.

[0004] On the other hand, it has also been considered to form GeH in which germanium and hydrogen are bonded and SiH in which silicon and hydrogen are bonded in layers and use them as layered semiconductors (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the SiH disclosed in Patent Document 1 and the GeH disclosed in Patent Document 2 do not necessarily exhibit higher electron mobility when used as semiconductors compared to Si thin films and Ge thin films, and their physical properties cannot be controlled by controlling their composition. There was a need for a novel layered semiconductor with higher electron mobility and a composition that can be formed in layers.

[0007] This invention was proposed in view of the above problems, and aims to provide a layered semiconductor having a novel composition that has high electron mobility, a controllable composition, and can be formed in layers, and a method for manufacturing a layered semiconductor. [Means for solving the problem]

[0008] The inventors have discovered a novel layered semiconductor in which only a portion of the divalent metal element is replaced with hydrogen contained in HCl by reacting a reaction material containing HCl with a hydrogen-substituted material, and controlling the concentration of HCl and the reaction time during this reaction.

[0009] To solve the above problems, the following means are proposed in the layered semiconductor and method for manufacturing the layered semiconductor according to one embodiment of the present invention. (1) The layered semiconductor of embodiment 1 of the present invention is M 1-x A2H 2x It consists of a membrane in which atoms bonded together in the chemical formula are connected in a planar manner. However, 0 <x<1 A is Si or Ge M is a metallic element with a valence of 2. H stands for hydrogen.

[0010] (2) Embodiment 2 of the present invention is a layered semiconductor according to Embodiment 1, wherein M in the composition formula includes at least one of Eu, Ca, Sr, and Mg.

[0011] (3) Embodiment 3 of the present invention is the layered semiconductor of Embodiment 2, wherein M in the composition formula is Eu.

[0012] (4) Embodiment 4 of the present invention is a layered semiconductor according to any one of embodiments 1 to 3, wherein the range of x in the composition formula is 0.1 ≤ x ≤ 0.9.

[0013] (5) Embodiment 5 of the present invention is the layered semiconductor of Embodiment 4, wherein the range of x in the composition formula is 0.15 ≤ x ≤ 0.6.

[0014] (6) Embodiment 6 of the present invention is a layered semiconductor according to any one of embodiments 1 to 5, wherein two or more layers of the film are stacked.

[0015] (7) A method for manufacturing a layered semiconductor according to embodiment 7 of the present invention is a method for manufacturing a layered semiconductor according to any one of embodiments 1 to 6, comprising a substitution reaction step in which a hydrogen substitution material containing HCl is reacted with a reaction material having composition formula M1A2 to substitute only a portion of M with H, wherein the substitution reaction step is performed by maintaining the reaction temperature at -50°C or higher and 25°C or lower, and by varying at least one of the HCl concentration contained in the hydrogen substitution material or the reaction time to arbitrarily control the proportion of M that is substituted with H.

[0016] (8) The method for manufacturing a layered semiconductor according to embodiment 8 of the present invention is the method for manufacturing a layered semiconductor according to embodiment 7, wherein the value of x is changed in increments of at least 0.05. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a layered semiconductor having a novel composition that has high electron mobility, a controllable composition, and can be formed in layers, and a method for manufacturing a layered semiconductor. [Brief explanation of the drawing]

[0018] [Figure 1] This graph shows the results of Verification Example 1 in the embodiments of the present invention. [Figure 2] This graph shows the results of Verification Example 2 in the embodiment of the present invention. [Figure 3] This graph shows the results of Verification Example 3 in the embodiment of the present invention. [Figure 4] This is a graph showing the results of Verification Example 4 in an embodiment of the present invention.

Mode for Carrying Out the Invention

[0019] Hereinafter, a layered semiconductor according to an embodiment of the present invention and a method for manufacturing the layered semiconductor will be described. The following embodiments are specifically described to better understand the gist of the invention, and do not limit the present invention unless otherwise specified.

[0020] [Layered Semiconductor] The layered semiconductor according to an embodiment of the present invention has a composition formula M 1-x A2H 2x (0 < x < 1, A is Si or Ge, M is a divalent metal element, H is hydrogen), and is composed of a layered two-dimensional Si / Ge layer-containing material, and the atoms bonded by such a composition formula are connected in a planar manner to form a film. Also, two or more layers of this film may be stacked. Although there is no particular upper limit to the number of stacked layers, for example, about 100 layers or 1000 layers may be stacked.

[0021] The composition formula M 1-x A2H 2x As the divalent metal element represented by M constituting the formula, any one of Eu, Ca, Sr, Mg, or a metal containing two or more of these may be used as long as it is stable in the M 1-x A2H 2x structure and desorbs by reaction with HCl. In the present embodiment, Eu is used as the metal element represented by M constituting the composition formula M 1-x A2H 2x .

[0022] The range of x indicating the composition ratio of M and H in the composition formula M 1-x A2H 2x may be 0.1 ≦ x ≦ 0.9 in which a part of the divalent metal element is significantly substituted by H and the divalent metal element remains significantly. A more preferable range of x is 0.15 ≦ x ≦ 0.6.

[0023] Specific compositional formulas of the layered semiconductor of the present embodiment as described above include Eu 1-x Si2H 2x , Eu 1-x Ge2H 2x , Ca 1-x Si2H 2x , Ca 1-x Ge2H 2x , Sr 1-x Si2H 2x , Sr 1-x Ge2H 2x , Mg 1-x Si2H 2x , Mg 1-x Ge2H 2x (all 0 < x < 1). In the present embodiment, Eu 1-x Ge2H 2x was used.

[0024] If such a layered semiconductor is formed on, for example, a Si substrate (silicon wafer) or a Ge substrate, it is easy to form a circuit by the manufacturing process of existing semiconductor elements. Thereby, a high-mobility transistor having an electron mobility equivalent to or higher than that of a Si single crystal or a Ge single crystal can be formed. In particular, if the range of x in the compositional formula M 1-x A2H 2x is set to 0.15 ≤ x ≤ 0.6, a high-performance transistor having an electron mobility one digit or more higher than that of a Si single crystal, a Ge single crystal, GeH, etc. can be formed. Also, if such a layered semiconductor is used, the compatibility with the manufacturing process of existing semiconductor elements is high, and a low-resistance contact electrode and a thin-film semiconductor element having a high electron mobility can be realized using such existing processes.

[0025] [Manufacturing Method of Layered Semiconductor] The layered semiconductor of the present embodiment described above can be manufactured by a substitution reaction step of reacting a hydrogen substitution material containing HCl (hydrogen chloride) with a reaction raw material having a compositional formula of M1A2 (A is Si or Ge, and M is a divalent metal element), and substituting only a part of M in the compositional formula of M1A2 with H of HCl.

[0026] In such a substitution reaction process, the reaction temperature for hydrogen substitution is maintained at -50°C or higher and 25°C or lower, and at least either the HCl concentration contained in the hydrogen substitution material or the reaction time is arbitrarily changed to control the ratio of substituting M with H (the range of x in the composition formula M 1-x A2H 2x ), and by arbitrarily controlling this, a layered semiconductor represented by the composition formula M 1-x A2H 2x is formed.

[0027] As a specific example, for instance, when manufacturing a layered semiconductor represented by the composition formula Eu 1-x Ge2H 2x (0 < x < 1), first, a EuGe2 thin film is prepared. The EuGe2 thin film can be formed, for example, by supplying Eu on a Ge substrate and epitaxially growing EuGe2 on this Ge substrate.

[0028] ] The EuGe2 thus obtained, for example, formed on a Ge substrate, is reacted with HCl in an environment of, for example, -40°C. As the hydrogen substitution material containing HCl,' concentrated hydrochloric acid (HCl: 30 wt%) can be used, for example. When such concentrated hydrochloric acid is used, if the reaction temperature is around room temperature, the entire amount of Eu will be substituted with H and become GeH within 1 to several seconds. Therefore, by setting the reaction temperature to about -40°C to reduce the reaction rate, the ratio of Eu being substituted with H can be easily controlled.

[0029] More specifically, for example, inside a refrigeration facility maintained at -40°C, a Ge substrate on which a EuGe2 thin film is formed is inserted into a container containing concentrated hydrochloric acid, and the substitution reaction is allowed to proceed with a treatment time of about 10 to 25 minutes. For example, to make the range of x in the composition formula M 1-x A2H 2x be 0.15 ≦ x ≦ 0.6, when using concentrated hydrochloric acid in the above-mentioned -40°C environment, the substitution reaction may be carried out within the range of 10 to 20 minutes.

[0030] When such a substitution reaction between Eu and H is carried out using concentrated hydrochloric acid at a certain concentration at a certain reaction temperature, the substitution ratio of Eu and H changes linearly according to the reaction time. Therefore, if the change in the substitution ratio of Eu and H with respect to the reaction time is measured in advance, the composition formula Eu 1-x Ge2H 2x (0 < x < 1) can be accurately controlled at least in steps of about 0.05. As a result, a layered semiconductor represented by the composition formula Eu 1-x Ge2H 2x can be obtained.

[0031] As described above, in the method for manufacturing a layered semiconductor according to the present embodiment, in the substitution reaction step of reacting a hydrogen substitution material containing HCl with a reaction raw material having a composition formula of M1A2 (A is Si or Ge, and M is a divalent metal element), the reaction temperature is maintained at -50°C or higher and 25°C or lower, and at least one of the HCl concentration contained in the hydrogen substitution material or the reaction time is varied, whereby the ratio of substituting M with H can be arbitrarily controlled. As a result, a layered semiconductor represented by the composition formula M 1-x A2H 2x (0 < x < 1, A is Si or Ge, M is a divalent metal element, and H is hydrogen) can be manufactured.

[0032] As described above, one embodiment of the present invention has been described. However, such an embodiment is presented as an example and is not intended to limit the scope of the invention. Such an embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Example

[0033] A layered semiconductor according to one embodiment of the present invention was verified. In the verification, like the manufacturing method of the layered semiconductor described above, the EuGe2 thin film formed on a Ge substrate as a reaction raw material and concentrated hydrochloric acid (HCl: 30 wt%) as a hydrogen substitution material were each used to substitute Eu of EuGe2 with H of HCl at a reaction temperature of -40°C, and a layered semiconductor represented by the composition formula Eu 1-x Ge2H 2x (0 < x < 1) was manufactured.

[0034] (Verification Example 1) In FIG. 1, the relationship between the reaction time with respect to HCl and the value of x in the composition formula Eu 1-x Ge2H 2x is shown in a graph. In FIG. 1, among the measurement results, for representative data points, the substitution amount is clearly shown. According to the graph shown in this FIG. 1, at a reaction temperature of -40°C, it can be seen that the value of x in the composition formula Eu 1-x Ge2H 2x changes linearly with respect to the reaction time with respect to HCl.

[0035] For example, at a reaction time of 15 minutes, x = 0.51, and a layered semiconductor containing Eu, Ge, and H such as Eu 0.49 Ge2H 2·0.51 can be formed. Also, for example, at a reaction time of 20 minutes, x = 0.75, and a layered semiconductor containing Eu, Ge, and H such as Eu 0.25 Ge2H 2·0.75 can be formed. And when the reaction time exceeds 30 minutes, all Eu is substituted with H, and it becomes GeH.

[0036] From the results shown in FIG. 1 like this, it was confirmed that at a certain reaction temperature, by selecting the reaction time, a layered semiconductor with an arbitrarily changed value of x in the composition formula Eu 1-x Ge2H 2x can be manufactured.

[0037] (Verification Example 2) Next, the composition formula Eu 1-x Ge2H 2xX-ray diffraction was performed on samples with the x value in set to 0, 0.11, 0.27, 0.51, 0.75, and 0.99. The results are shown in Figure 2. In this case, when x = 0, the sample is in the state of EuGe2, and when x = 0.99, the sample is almost in the state of GeH. As the substitution amount of H increases, the diffraction intensities of the 001 plane and 002 plane derived from EuGa2 decrease, and a broad peak that is considered to reflect the change in the interlayer spacing appears at the location indicated by the instruction mark in Figure 2.

[0038] According to the results shown in Figure 2, for samples of each composition with different substitution ratios of H obtained by adjusting the treatment time with HCl, the peak angles of X-ray diffraction change systematically. That is, it was confirmed that the crystal structure has changed. The composition formula Eu 1-x Ge2H 2x (0 < x < 1) of the novel layered semiconductor obtained was confirmed to have different crystal structures, that is, different semiconductor characteristics, by varying the substitution ratio of H.

[0039] (Verification Example 3) The resistance values of each sample obtained by gradually changing the x value in the composition formula Eu 1-x Ge2H 2x were measured. The measurement results are shown graphically in Figure 3.

[0040] According to the results shown in Figure 3, it was confirmed that as the x value of the composition formula Eu 1-x Ge2H 2x increases, that is, as the substitution amount of Eu with H increases, the resistance value increases. EuGe2 with x = 0 has high conductivity almost as a metal, so it was confirmed that by increasing the substitution amount of Eu with H, the resistance value can be increased to obtain characteristics as a semiconductor.

[0041] (Verification Example 4) The electron mobilities of each sample obtained by gradually changing the x value in the composition formula Eu 1-x Ge2H 2x were measured. The measurement results are shown graphically in Figure 4.

[0042] According to the results shown in Figure 4, the composition formula Eu 1-x Ge2H 2x Samples in which the value of x was set to the range of 0.2 to 0.5 showed superior characteristics, with electron mobility being an order of magnitude higher compared to GeH (x=1), confirming that high-mobility layered semiconductors can be realized.

[0043] This suggests that, compared to layered semiconductors of Si or Ge where all divalent metal elements represented by the chemical formula A2H2 or AH are replaced by hydrogen, the significant remaining M in MA2 may also contribute to conduction through its electron orbitals. The layered semiconductor of one embodiment of the present invention allows for control of the composition of the remaining divalent metal elements, thereby yielding a novel material exhibiting unprecedented physical properties. [Industrial applicability]

[0044] The layered semiconductor and method for manufacturing the layered semiconductor of the present invention make it possible to realize a layered semiconductor with semiconductor properties having electron mobility equivalent to or greater than that of Si thin films, Ge thin films, etc. Using such a layered semiconductor, it is possible to realize a thin-film semiconductor device with excellent properties of high electron mobility. Therefore, it has industrial applicability.

Claims

1. M １－ｘ A ２ H ２ｘ A layered semiconductor consisting of a film in which atoms bonded in the chemical formula are connected in a planar manner. However, 0 < x < 1 A is Si or Ge M is a metallic element with a valence of 2. H stands for hydrogen.

2. The layered semiconductor according to claim 1, wherein M in the compositional formula comprises at least one of Eu, Ca, Sr, and Mg.

3. The layered semiconductor according to claim 2, wherein M in the composition formula is Eu.

4. The layered semiconductor according to any one of claims 1 to 3, wherein the range of x in the composition formula is 0.1 ≤ x ≤ 0.

9.

5. The layered semiconductor according to claim 4, wherein the range of x in the composition formula is 0.15 ≤ x ≤ 0.

6.

6. The layered semiconductor according to any one of claims 1 to 3, wherein two or more layers of the aforementioned film are stacked.

7. A method for manufacturing a layered semiconductor according to any one of claims 1 to 3, The chemical formula is M １ A ２ The reaction process involves reacting the reaction raw materials with a hydrogen-substituted material containing HCl to replace only a portion of M with H. A method for manufacturing a layered semiconductor, wherein in the substitution reaction step, the reaction temperature is maintained at -50°C or higher and 25°C or lower, and the proportion of M to H substitution is arbitrarily controlled by varying at least one of the HCl concentration contained in the hydrogen substitution material or the reaction time.

8. The method for manufacturing a layered semiconductor according to claim 7, wherein the value of x is varied in increments of at least 0.05.

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