Electromagnetic wave detector

Abstract

The electromagnetic wave detector includes a graphene layer 80, a two-dimensional semiconductor layer 50, and a first insulating film 60. The graphene layer 80 and the two-dimensional semiconductor layer 50 are electrically connected in series and are disposed opposite each other with the first insulating film 60 interposed therebetween.

Description

[Technical Field]

[0001] The present disclosure relates to electromagnetic wave detectors. [Background technology]

[0002] For example, US Patent Application Publication No. 2015 / 0243826 (Patent Document 1) describes an electromagnetic wave detector. The electromagnetic wave detector described in Patent Document 1 includes a semiconductor layer, a first dielectric layer, a second dielectric layer, a first electrode, a second electrode, and a graphene layer.

[0003] The semiconductor layer has an n-type conductivity. The first and second dielectric layers are disposed on the semiconductor layer so as to be spaced apart from each other. The first and second electrodes are disposed on the first and second dielectric layers, respectively. The graphene layer is disposed on the semiconductor layer between the first and second dielectric layers and is electrically connected to the first and second electrodes.

[0004] In the electromagnetic wave detector described in Patent Document 1, a voltage is applied to the graphene layer via a first electrode and a second electrode. When electromagnetic waves are incident on the semiconductor layer located between the first dielectric layer and the second dielectric layer, photocarriers are generated by photoelectric conversion. The generated photocarriers are amplified by the voltage applied to the graphene layer. In this way, the electromagnetic wave detector described in Patent Document 1 has improved detection sensitivity for electromagnetic waves. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US Patent Application Publication No. 2015 / 0243826 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, the detection sensitivity for electromagnetic waves depends on the quantum efficiency of the semiconductor layer. However, the quantum efficiency of the semiconductor layer for electromagnetic waves may be insufficient. The present disclosure has been made in consideration of such problems in the prior art. The present disclosure provides an electromagnetic wave detector with improved detection sensitivity. [Means for solving the problem]

[0007] The electromagnetic wave detector of the present disclosure includes a graphene layer, a two-dimensional semiconductor layer, and a first insulating film, where the graphene layer and the two-dimensional semiconductor layer are electrically connected in series and disposed opposite each other with the first insulating film interposed therebetween. [Effects of the Invention]

[0008] According to the electromagnetic wave detector of the present disclosure, it is possible to improve the detection accuracy of electromagnetic waves. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a plan view of the electromagnetic wave detector 100A. [Figure 2] FIG. 2 is a cross-sectional view of the electromagnetic wave detector 100A taken along line II-II in FIG. [Figure 3] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100A according to a first modification. [Figure 4] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100A according to a second modification. [Figure 5] FIG. 2 is a cross-sectional view of an electromagnetic wave detector 100B. [Figure 6] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100B according to a first modification. [Figure 7] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100B according to a second modification. [Figure 8] FIG. 2 is a cross-sectional view of an electromagnetic wave detector 100C. [Figure 9] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100C according to a modified example. [Figure 10] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100D. [Figure 11]FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100D according to a modified example. [Figure 12] FIG. 2 is a cross-sectional view of an electromagnetic wave detector 100E. [Figure 13] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100E according to a modified example. [Figure 14] FIG. 2 is a cross-sectional view of an electromagnetic wave detector 100F. [Figure 15] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100F according to a first modification. [Figure 16] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100F according to a second modification. [Figure 17] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100F according to a third modification. [Figure 18] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100F according to a fourth modification. [Figure 19] FIG. 2 is a cross-sectional view of an electromagnetic wave detector 100G. [Figure 20] FIG. 1 is a cross-sectional view of an electromagnetic wave detector 100H. [Figure 21] FIG. 2 is a cross-sectional view of a laminate 120A. [Figure 22] FIG. 10 is a cross-sectional view of a laminate 120B. [Figure 23] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100H according to a first modification. [Figure 24] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100H according to a second modification. [Figure 25] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100H according to a third modification. [Figure 26] FIG. 10 is a cross-sectional view of a laminate 120A in an electromagnetic wave detector 100H according to a third modification. [Figure 27] FIG. 10 is a cross-sectional view of a laminate 120B in an electromagnetic wave detector 100H according to a third modification. DETAILED DESCRIPTION OF THE INVENTION

[0010] The details of the embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant descriptions will not be repeated.

[0011] In the embodiments described below, the drawings are schematic and are intended to conceptually explain functions or structures. Furthermore, the present disclosure is not limited to the embodiments described below. Unless otherwise specified, the basic configuration of the electromagnetic wave detector is common to all embodiments. Furthermore, components with the same reference numerals are the same or equivalent as described above. This is common throughout the entire specification.

[0012] In the embodiments described below, the configuration of an electromagnetic wave detector for detecting visible light or infrared light is described, but the light detected by the electromagnetic wave detector of the present disclosure is not limited to visible light and infrared light. The embodiments described below are also effective as detectors for detecting radio waves such as X-rays, ultraviolet light, near-infrared light, terahertz (THz) waves, and microwaves in addition to visible light and infrared light. In the embodiments of the present disclosure, these lights and radio waves are collectively referred to as electromagnetic waves.

[0013] In the following embodiments, the terms p-type graphene and n-type graphene may be used for graphene. In the following embodiments, graphene having more holes than intrinsic graphene is called p-type graphene, and graphene having more electrons than intrinsic graphene is called n-type graphene. That is, n-type materials are electron-donating materials, and p-type materials are electron-withdrawing materials.

[0014] Furthermore, when there is a bias in the charge throughout the molecule, a material in which electrons are dominant may be referred to as n-type. When there is a bias in the charge throughout the molecule, a material in which holes are dominant may be referred to as p-type. The material of the member in contact with graphene, which is an example of a two-dimensional material layer, may be either an organic material or an inorganic material, or a mixture of an organic material and an inorganic material.

[0015] Furthermore, plasmon resonance phenomena such as surface plasmon resonance, which is an interaction between a metal surface and light, a phenomenon called pseudo-surface plasmon resonance, which means resonance on a metal surface outside the visible light and near-infrared light regions, and a phenomenon called metamaterial or plasmonic metamaterial, which means manipulating wavelengths using a structure with dimensions smaller than the wavelength, are treated as equivalent in terms of the effects of the phenomena without being particularly distinguished by name. Here, these resonances are referred to as surface plasmon resonance, plasmon resonance, or simply resonance.

[0016] In the embodiments, what is referred to as an insulating film is an insulating film having a thickness that does not generate a tunnel current unless otherwise specified.

[0017] Embodiment 1 A description will be given of an electromagnetic wave detector according to embodiment 1. The electromagnetic wave detector according to embodiment 1 is designated as an electromagnetic wave detector 100A.

[0018] (Configuration of the electromagnetic wave detector 100A) The configuration of the electromagnetic wave detector 100A will be described below.

[0019] Fig. 1 is a plan view of the electromagnetic wave detector 100A. Fig. 2 is a cross-sectional view of the electromagnetic wave detector 100A taken along line II-II in Fig. 1. As shown in Figs. 1 and 2, the electromagnetic wave detector 100A includes a substrate 10, an insulating film 20, an electrode 30, an electrode 40, a two-dimensional semiconductor layer 50, an insulating film 60, an electrode 70, and a graphene layer 80.

[0020] The constituent material of the substrate 10 is, for example, an electrically insulating material. Specific examples of electrically insulating materials that constitute the substrate 10 include glass, quartz, sapphire, alumina, silicon nitride, aluminum nitride, polyimide, polyester, etc. The constituent material of the substrate 10 may be a semiconductor material. Specific examples of semiconductor materials that constitute the substrate 10 include silicon, germanium, compound semiconductors such as III-V semiconductors and II-V semiconductors, cadmium mercury telluride, iridium antimonide, lead selenium, lead sulfur, cadmium sulfur, silicon carbide, gallium nitride, gallium phosphide, indium gallium arsenide, indium arsenide, gallium antimonide, and indium gallium arsenide. The substrate 10 may be a substrate including quantum wells or quantum dots. The constituent material of the substrate 10 may be a Type II superlattice. The constituent material of the substrate 10 may be any of the above materials alone or a combination of the above materials. The substrate 10 has a front surface 10a and a back surface 10b. The rear surface 10b is the surface opposite to the front surface 10a. The front surface 10a and the rear surface 10b are both end surfaces of the substrate 10 in the thickness direction.

[0021] The insulating film 20 is made of an electrically insulating material such as an oxide. Specific examples of materials that can be used to make the insulating film 20 include silicon oxide, tetraethyl orthosilicate, silicon nitride, hafnium oxide, nickel oxide, boron nitride, and siloxane-based polymers. The insulating film 20 has a thickness that prevents tunneling current from flowing. The insulating film 20 is disposed on the substrate 10. The insulating film 20 has a surface 20a. The surface 20a faces away from the substrate 10.

[0022] The electrode 30 may be made of any conductive material. The material may include, for example, at least one of aluminum, gold, silver, copper, nickel, chromium, and palladium. The electrode 30 is disposed on the substrate 10. The electrode 30 has a surface 30a. The surface 30a faces away from the substrate 10. The electrode 30 may be disposed so that the surface 30a is connected to the surface 20a to form a flat surface. The electrode 40 may be made of any conductive material. The material may include, for example, at least one of aluminum, gold, silver, copper, nickel, chromium, and palladium. The electrode 40 is disposed on the insulating film 20 (surface 20a). An adhesive layer (not shown) may be provided between the electrode 30 and the substrate 10 or between the electrode 40 and the insulating film 20. The adhesive layer is configured to enhance adhesion. The adhesive layer may include, for example, a metal material such as chromium, nickel, or titanium.

[0023] The constituent material of the two-dimensional semiconductor layer 50 is a two-dimensional semiconductor material. Examples of the two-dimensional semiconductor material include transition metal dichalcogenides, borophene, silicene, black phosphorus, AsP, germanene, PbS, GaSe, In2Se3, ZrS2, ZrSe2, TaS, TaAs, and Weyl semimetals. Examples of the transition metal dichalcogenides include MoS2, MoSe2, MoTe2, WS2, WSe2, WTe2, HfS2, SnS2, SnSe2, ReS2, and ReSe2.

[0024] The two-dimensional semiconductor layer 50 may be made of monolayer graphene. Monolayer graphene is a single atomic layer of two-dimensional carbon crystals. Graphene has multiple carbon atoms arranged in multiple hexagonal chains. Graphene has low absorption. More specifically, the absorption rate of graphene is 2.3 percent. However, monolayer graphene has linear band dispersion, resulting in sensitivity over a broad wavelength range. Alternatively, the two-dimensional semiconductor layer 50 may be made of multilayer graphene, in which multiple graphene layers are stacked. The orientations of the hexagonal lattice vectors of the graphene in the multilayer graphene may be the same or different. The orientations of the hexagonal lattice vectors of the graphene in the multilayer graphene may be completely aligned. Alternatively, the two-dimensional semiconductor layer 50 may be made of graphene doped with p-type or n-type impurities.

[0025] For example, a band gap is formed in the two-dimensional semiconductor layer 50 by stacking two or more graphene layers. That is, the size of the band gap can be adjusted by changing the number of stacked graphene layers. This allows the two-dimensional semiconductor layer 50 to have a wavelength selection effect for selecting an electromagnetic wave (detection wavelength) that is the target of photoelectric conversion. Furthermore, for example, as the number of graphene layers in the multilayer graphene increases, the mobility in the channel region decreases. On the other hand, as the number of graphene layers in the multilayer graphene increases, the influence of photocarrier scattering from the substrate is suppressed, thereby reducing noise in the electromagnetic wave detector 100A. Therefore, in the electromagnetic wave detector 100A having the two-dimensional semiconductor layer 50 using multilayer graphene, optical absorption is increased, thereby improving the detection sensitivity of electromagnetic waves.

[0026] The multilayer graphene may be turbostratic-stacked graphene, in which stacking orientation angles are randomly arranged. Turbostratic-stacked graphene is formed by stacking multiple graphene layers in a lattice-mismatched state. Turbostratic-stacked graphene has weak interlayer interactions between graphene, resulting in mobility comparable to that of monolayer graphene. Furthermore, because electrical disturbances in the graphene substrate are suppressed, the mobility is maintained higher than that of conventional monolayer graphene. Furthermore, turbostratic-stacked graphene has linear band dispersion despite being multilayer graphene, enabling broadband light absorption similar to that of monolayer graphene, thereby broadening the detection wavelength range of the electromagnetic wave detector 100A. The stacking angle of the graphene layers in turbostratic-stacked graphene may be an angle that generates moiré. In this case, a flat band is formed, allowing coupling with incident light over a wide wavelength range, thereby improving the detection efficiency of the electromagnetic wave detector 100A. Furthermore, by forming a moiré potential using the above stacking angle, the electromagnetic wave detector 100A can selectively detect a specific wavelength range.

[0027] Nanoribbon-shaped graphene (graphene nanoribbon) may be used as the two-dimensional semiconductor layer 50. The two-dimensional semiconductor layer 50 may be a single graphene nanoribbon. The two-dimensional semiconductor layer 50 may have a structure in which multiple graphene nanoribbons are stacked. The two-dimensional semiconductor layer 50 may have a structure in which graphene nanoribbons are periodically arranged on a plane. When the two-dimensional semiconductor layer 50 has a structure in which graphene nanoribbons are periodically arranged, plasmon resonance occurs in the graphene nanoribbons, improving the sensitivity of the electromagnetic wave detector 100A. A structure in which graphene nanoribbons are periodically arranged is sometimes called a graphene metamaterial. In other words, the electromagnetic wave detector 100A using a graphene metamaterial as the two-dimensional semiconductor layer 50 can achieve the above-mentioned effects. Furthermore, periodic holes may be formed in the graphene. In this case, plasmon resonance occurs depending on the size and period of the holes, increasing absorption at specific wavelengths and improving the sensitivity of the electromagnetic wave detector 100A. The shape of the holes may be a perfect circle, ellipse, square, rectangle, or the like. The period may be one-dimensional, two-dimensional, double-periodic, or asymmetric.

[0028] The end of the two-dimensional semiconductor layer 50 may be a graphene nanoribbon. In this case, since the graphene nanoribbon has a band gap, a Schottky junction is formed in the junction region with the graphene nanoribbon.

[0029] The two-dimensional semiconductor layer 50 is disposed on the insulating film 20, the electrode 30, and the electrode 40 so as to be electrically connected to the electrode 30 and the electrode 40. More specifically, one end of the two-dimensional semiconductor layer 50 (the end on the left side in the drawing) is on the electrode 30, and the other end of the two-dimensional semiconductor layer 50 (the end on the right side in the drawing) is on the electrode 40. The two-dimensional semiconductor layer 50 may form a Schottky junction with the electrode 30 and the electrode 40. The constituent material of the two-dimensional semiconductor layer 50 may have a band gap.

[0030] The insulating film 60 is made of an electrically insulating material. Specific examples of materials for the insulating film 60 include aluminum oxide, hafnium oxide, boron nitride, and siloxane-based polymers. The insulating film 60 is disposed on the electrodes 30, 40, and the two-dimensional semiconductor layer 50. However, a portion of the electrode 40 is exposed from the insulating film 60. The insulating film 60 has a thickness that prevents tunneling current from flowing, and it is preferable that the thickness of the insulating film 60 be as small as possible. The electrode 70 is made of a conductive material. The material for the electrode 70 may include at least one of aluminum, gold, silver, copper, nickel, chromium, and palladium, for example. The electrode 70 is disposed on the insulating film 60.

[0031] The graphene layer 80 is a layer of single-layer graphene or multi-layer graphene. The graphene layer 80 is disposed on the insulating film 60 so as to be electrically connected to the electrode 40 and the electrode 70. More specifically, one end of the graphene layer 80 (the end on the left side in the figure) is on the electrode 70, and the other end of the graphene layer 80 (the end on the right side in the figure) is on the electrode 40. In this manner, the graphene layer 80 is disposed opposite the two-dimensional semiconductor layer 50 with the insulating film 60 interposed therebetween, and is electrically connected in series with the two-dimensional semiconductor layer 50. The multi-layer graphene may be turbostratic-stacked graphene in which stacking orientation angles are randomly arranged. As described above, turbostratic-stacked graphene is formed by stacking multiple graphene layers in a lattice-mismatched state. In turbostratic-stacked graphene, the mobility is comparable to that of single-layer graphene due to weak interlayer interaction of graphene, and the mobility is maintained higher than that of single-layer graphene due to suppressed electrical disturbance of the graphene substrate.

[0032] A bias voltage is applied to the electromagnetic wave detector 100A from a power supply 110. More specifically, the power supply 110 is electrically connected to the electrode 30 and the electrode 70, and applies a bias voltage so that the potential at the electrode 30 is higher than the potential at the electrode 70. Although not shown, an ammeter is connected to the electromagnetic wave detector 100A in order to measure the current flowing through the graphene layer 80. A voltmeter may be used instead of this ammeter.

[0033] (Method of manufacturing the electromagnetic wave detector 100A) A method for manufacturing the electromagnetic wave detector 100A will be described below.

[0034] The manufacturing method of the electromagnetic wave detector 100A includes a preparation step, a first insulating film forming step, a first electrode forming step, a second electrode forming step, a two-dimensional semiconductor layer forming step, a second insulating film forming step, a third electrode forming step, and a graphene layer forming step.

[0035] In the preparation step, a substrate 10 is prepared. The first insulating film forming step is performed after the preparation step. In the preparation step, an insulating film 20 is formed on the substrate 10. In the first insulating film forming step, first, a constituent material of the insulating film 20 is formed by, for example, a CVD (Chemical Vapor Deposition) method. Secondly, the constituent material of the insulating film 20 that has been formed is patterned. By this patterning, openings for forming the electrodes 30 are formed. This patterning is performed, for example, by etching using a resist pattern formed on the constituent material of the insulating film 20 that has been formed as a mask.

[0036] The first electrode forming step is performed after the first insulating film forming step. In the first electrode forming step, an electrode 30 is formed on the substrate 10 in an opening in the insulating film 20. The second electrode forming step is performed after the first electrode forming step. In the second electrode forming step, an electrode 40 is formed on the insulating film 20. The electrode 30 and the electrode 40 may be formed by, for example, a lift-off method. The constituent material of the electrode 30 (electrode 40) formed by sputtering or the like may be formed by etching using a resist pattern as a mask. The second electrode forming step may be performed after the first electrode forming step.

[0037] The two-dimensional semiconductor layer forming step is performed after the second electrode forming step. In the two-dimensional semiconductor layer forming step, the two-dimensional semiconductor layer 50 is formed by transferring a two-dimensional semiconductor layer 50 that has been formed in advance by, for example, a CVD method. The two-dimensional semiconductor layer 50 may be patterned by etching using a resist pattern as a mask. The second insulating film forming step is performed after the two-dimensional semiconductor layer forming step. In the second insulating film forming step, the insulating film 60 is formed by a film formation method that causes less damage to the two-dimensional semiconductor layer 50, such as a vacuum deposition method or an ALD (Atomic Layer Deposition) method.

[0038] The third electrode forming step is performed after the second insulating film forming step. In the third electrode forming step, the electrode 70 is formed on the insulating film 60 by the same method as in the first electrode forming step and the second electrode forming step. The graphene layer forming step is performed after the third electrode forming step. In the graphene layer forming step, the graphene layer 80 is formed by transferring the graphene layer 80 that has been formed in advance by, for example, a CVD method. Through the steps described above, the structure of the electromagnetic wave detector 100A shown in FIGS. 1 and 2 is obtained.

[0039] (Operating principle of the electromagnetic wave detector 100A) The operating principle of the electromagnetic wave detector 100A will be described below.

[0040] 2, a power supply circuit that applies a voltage V is electrically connected between the electrode 30 and the electrode 70. In this case, a current I flows through the graphene layer 80 that is part of the current path between the electrode 70 and the electrode 30. An ammeter (not shown) is installed in the power supply circuit, and the current I is monitored by the ammeter.

[0041] Next, electromagnetic waves are irradiated onto the two-dimensional semiconductor layer 50. As a result, photoelectric conversion occurs in the two-dimensional semiconductor layer 50, and a photocurrent flows in the graphene layer 80. Furthermore, the two-dimensional semiconductor layer 50 applies an electric field change to the graphene layer 80 via the insulating film 60. As a result, a state in which a pseudo gate voltage is applied to the graphene layer 80 occurs, and the resistance value in the graphene layer 80 changes. This is called the optical gate effect.

[0042] Furthermore, when photoelectric conversion occurs in the two-dimensional semiconductor layer 50, the resistance value of the two-dimensional semiconductor layer 50 changes, and therefore, a change in the bias voltage applied to the graphene layer 80 also changes the electrical resistance value of the graphene layer 80. This is called the photobias effect.

[0043] These changes in resistance value result in a change in the current I, which is a photocurrent flowing through the graphene layer 80. By detecting the change in the current I, it is possible to detect the electromagnetic waves irradiated to the electromagnetic wave detector 100A.

[0044] Furthermore, for example, when the two-dimensional semiconductor layer 50 is made of a material having a band gap or when the two-dimensional semiconductor layer 50 forms a Schottky junction with the electrode 40 or the electrode 30, the current I can be made zero by adjusting the voltage V to perform reverse bias operation on the two-dimensional semiconductor layer 50. That is, the electromagnetic wave detector according to this embodiment is capable of off operation. In this case, the current I flows through the two-dimensional semiconductor layer 50 only when light is irradiated, and therefore the current I can be detected only when light is irradiated.

[0045] Here, the electromagnetic wave detector 100A according to this embodiment is not limited to the configuration for detecting a change in current in the graphene layer 80 as described above, and may, for example, flow a constant current between the electrode 70 and the electrode 30 and detect a change in the voltage V between the electrode 70 and the electrode 30 (i.e., a change in the voltage value in the graphene layer 80).

[0046] Alternatively, two or more identical electromagnetic wave detectors 100A may be used to detect electromagnetic waves. For example, two or more identical electromagnetic wave detectors 100A may be prepared. One electromagnetic wave detector 100A may be placed in a shielded space where electromagnetic waves are not irradiated, and the other electromagnetic wave detector 100A may be placed in a space where the electromagnetic waves to be measured are irradiated. Then, the difference between the current I or voltage V of the other electromagnetic wave detector 100A irradiated with electromagnetic waves and the current I or voltage V of the electromagnetic wave detector 100A placed in the shielded space is detected. Electromagnetic waves may be detected in this manner.

[0047] (Operation of the electromagnetic wave detector 100A) The specific operation of the electromagnetic wave detector 100A shown in FIGS. 1 and 2 will be described below.

[0048] The range of main detection wavelengths of the electromagnetic wave detector 100A is determined depending on the constituent material of the two-dimensional semiconductor layer 50. When electromagnetic waves of the detection wavelength are incident on the two-dimensional semiconductor layer 50, electron-hole pairs are generated in the two-dimensional semiconductor layer 50. The generated electron-hole pairs (photocarriers) are extracted as photocurrent from the electrodes 70 and 30. At this time, photocarriers generated in the region directly below the insulating film 60 cause an electric field change in the graphene layer 80 via the insulating film 60. This is the optical gate effect described above.

[0049] As described above, the graphene constituting the graphene layer 80 has high mobility, and a large displacement current can be obtained in response to a slight change in electric field. Therefore, the photocurrent extracted from the electrode 70 via the graphene layer 80 due to photoelectric conversion in the two-dimensional semiconductor layer 50 is greatly amplified by the optical gating effect. Therefore, the electromagnetic wave detector 100A can achieve high sensitivity exceeding the quantum efficiency of the material constituting the two-dimensional semiconductor layer 50.

[0050] In this case, a high-speed response can be obtained by designing the two-dimensional semiconductor layer 50 to have a short carrier diffusion length. A shorter carrier diffusion length shortens the carrier lifetime of photocarriers in the two-dimensional semiconductor layer 50. As a result, the delay in amplification due to the optical gating effect is eliminated, and the photocarriers generated by photoelectric conversion in the two-dimensional semiconductor layer 50 can be separated from the amplification due to the optical gating effect, enabling a high-speed response of the electromagnetic wave detector 100A.

[0051] (Effect of Electromagnetic Wave Detector 100A) The effects of the electromagnetic wave detector 100A will be described below.

[0052] In the electromagnetic wave detector 100A, the two-dimensional semiconductor layer 50 is disposed opposite the graphene layer 80 with the insulating film 60 interposed therebetween, and therefore, due to a potential difference between the two-dimensional semiconductor layer 50 and the graphene layer 80, Fermi level modulation occurs in the graphene layer 80. When an electromagnetic wave is incident on the two-dimensional semiconductor layer 50, photocarriers are generated in the two-dimensional semiconductor layer 50 by photoelectric conversion. As a result of the generation of photocarriers changing the electrical resistance value of the two-dimensional semiconductor layer 50, the Fermi level of the graphene layer 80 also changes, and the electrical resistance value of the graphene layer 80 also changes (photogating effect). Furthermore, as a result of the change in the electrical resistance value of the two-dimensional semiconductor layer 50 due to the generation of photocarriers, a change in the bias voltage applied to the graphene layer 80 also changes the electrical resistance value of the graphene layer 80 (photobias effect).

[0053] In particular, since the thickness of the single-layer graphene constituting the graphene layer 80 is only the thickness of one atom, the Fermi level and the electrical resistance value of the graphene layer 80 change significantly when photocarriers are generated in the two-dimensional semiconductor layer 50. Furthermore, the single-layer graphene constituting the graphene layer 80 has high electron mobility. Therefore, due to the optical gate effect and the optical bias effect, the change in current in the graphene layer 80 caused by the incidence of electromagnetic waves on the two-dimensional semiconductor layer 50 becomes extremely large.

[0054] As described above, the electromagnetic wave detector 100A can improve the detection sensitivity to electromagnetic waves.

[0055] In the electromagnetic wave detector 100A, when the surface 20a and the surface 30a are flat surfaces, the two-dimensional semiconductor layer 50 is disposed on the flat surfaces. Therefore, the two-dimensional semiconductor layer 50 is also formed flat, and the mobility of electrons in the two-dimensional semiconductor layer 50 is improved.

[0056] In the electromagnetic wave detector 100A, when the two-dimensional semiconductor layer 50 and the electrodes 30 and 40 form a Schottky junction, or when the material of the two-dimensional semiconductor layer 50 has a band gap, a current flows through the graphene layer 80 when a forward bias is applied, but no current flows through the graphene layer 80 when a reverse bias is applied. Therefore, in these cases, it is possible to prevent a dark current from flowing through the graphene layer 80, that is, it is possible to turn off the electromagnetic wave detector 100A.

[0057] When the base material 10 of the electromagnetic wave detector 100A is a semiconductor material, it is possible to form an external circuit, such as a readout circuit, connected to the electromagnetic wave detector 100A on the base material 10. When the two-dimensional semiconductor layer 50 of the electromagnetic wave detector 100A is made of turbostratic stacked graphene, turbostratic stacked graphene has a linear dispersion band despite being multilayer graphene, and therefore can absorb a wide wavelength band of electromagnetic waves. Furthermore, the absorption rate of electromagnetic waves increases with the number of stacked layers of graphene. Therefore, when the two-dimensional semiconductor layer 50 of the electromagnetic wave detector 100A is turbostratic stacked graphene, the detection sensitivity for electromagnetic waves is further improved. When different types of electrode materials are used for the electrodes 30, 40, and 70 of the electromagnetic wave detector 100A, a work function difference occurs between the electrodes, thereby improving the carrier extraction efficiency.

[0058] <Modification 1 and Modification 2> FIG. 3 is a cross-sectional view of an electromagnetic wave detector 100A according to Modification 1. FIG. 4 is a cross-sectional view of an electromagnetic wave detector 100A according to Modification 2. FIGS. 3 and 4 show cross sections taken along the same line as II-II in FIG. 1 . As shown in FIGS. 3 and 4 , the electromagnetic wave detector 100A does not necessarily have an electrode 40. In this case, the other end of the two-dimensional semiconductor layer 50 and the other end of the graphene layer 80 are electrically connected without the electrode 40. The connection between the other end of the two-dimensional semiconductor layer 50 and the other end of the graphene layer 80 is a van der Waals heterojunction. More specifically, a van der Waals heterojunction is formed between the surface at the other end of the two-dimensional semiconductor layer 50 and the surface at the other end of the graphene layer 80. In both of the configurations shown in FIGS. 3 and 4 , the electrode 40 is not formed, which reduces process damage associated with the formation of the electrode 40.

[0059] 3, the other end of the graphene layer 80 may be aligned with the other end of the two-dimensional semiconductor layer 50. At the connection between the two-dimensional semiconductor layer 50 and the graphene layer 80, an optical switching effect occurs in which the Fermi level of the graphene layer 80 changes due to photocarriers generated in the two-dimensional semiconductor layer 50. Because the optical switching effect changes the barrier between the two-dimensional semiconductor layer 50 and the graphene layer 80, a large current flows when an electromagnetic wave is incident on the two-dimensional semiconductor layer 50, thereby increasing the detection sensitivity for the electromagnetic wave.

[0060] 4, the other end of the graphene layer 80 may cover the other end of the two-dimensional semiconductor layer 50. In this case, the injection efficiency of photocarriers from the two-dimensional semiconductor layer 50 to the graphene layer 80 is improved, thereby increasing the detection sensitivity to electromagnetic waves.

[0061] Embodiment 2 An electromagnetic wave detector according to embodiment 2 will be described. The electromagnetic wave detector according to embodiment 2 is designated as electromagnetic wave detector 100B. Here, differences from electromagnetic wave detector 100A will be mainly described, and overlapping descriptions will not be repeated.

[0062] (Configuration of electromagnetic wave detector 100B) The configuration of the electromagnetic wave detector 100B will be described below.

[0063] Fig. 5 is a cross-sectional view of the electromagnetic wave detector 100B. Fig. 5 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 5, the electromagnetic wave detector 100A includes a substrate 10, an insulating film 20, an electrode 30, an electrode 40, a two-dimensional semiconductor layer 50, an insulating film 60, an electrode 70, and a graphene layer 80. In this respect, the configuration of the electromagnetic wave detector 100B is common to the configuration of the electromagnetic wave detector 100A.

[0064] The two-dimensional semiconductor layer 50 has a side surface 50a and a side surface 50b. The side surface 50b is the surface opposite to the side surface 50a. The side surfaces 50a and 50b are located at one end and the other end of the two-dimensional semiconductor layer 50, respectively. In the electromagnetic wave detector 100B, the side surfaces 50a and 50b are electrically connected to the electrodes 30 and 40, respectively. From another perspective, the two-dimensional semiconductor layer 50 is in edge contact with the electrodes 30 and 40. From yet another perspective, the surfaces 20a and 30a are not flat, and there is a step between the surfaces 20a and 30a, with the surface 20a being lower. In these respects, the configuration of the electromagnetic wave detector 100B differs from the configuration of the electromagnetic wave detector 100A.

[0065] (Effect of Electromagnetic Wave Detector 100B) The effects of the electromagnetic wave detector 100B will be described below.

[0066] The electrical resistance value in the thickness direction of the two-dimensional semiconductor layer 50 is larger than the cell resistance value in the in-plane direction. Therefore, in the electromagnetic wave detector 100B, by making the two-dimensional semiconductor layer 50 come into edge contact with the electrodes 30 and 40 (electrically connecting the side surfaces 50a and 50b to the electrodes 30 and 40, respectively), it becomes possible to more efficiently extract photocarriers generated in the two-dimensional semiconductor layer 50 when an electromagnetic wave is incident thereon.

[0067] <Variation 1> FIG. 6 is a cross-sectional view of an electromagnetic wave detector 100B according to Modification 1. FIG. 6 shows a cross section taken along the same line as II-II in FIG. 1. As shown in FIG. 6, the graphene layer 80 has a side surface 80a and a side surface 80b. The side surface 80b is opposite the side surface 80a. The side surfaces 80a and 80b are located at one end and the other end of the graphene layer 80, respectively. The side surfaces 80a and 80b are electrically connected to the electrode 70 and the electrode 40, respectively. That is, the graphene layer 80 is in edge contact with the electrode 70 and the electrode 40. The insulating film 60 has a side surface 60a. The side surface 60a is in contact with the electrode 40. The positions of the side surfaces 50b, 60a, and 80b are aligned.

[0068] The graphene layer 80 has a larger electrical resistance in the thickness direction than the cell resistance in the in-plane direction. Therefore, by making the graphene layer 80 edge-contact with the electrode 70 and the electrode 40, the extraction efficiency of photocarriers is further improved. In addition, because the positions of the side surfaces 50b, 60a, and 80b are aligned, the electrode 40 can be embedded and formed after etching the two-dimensional semiconductor layer 50, the insulating film 60, and the graphene layer 80. This simplifies the process and reduces process damage to the two-dimensional semiconductor layer 50 and the graphene layer 80.

[0069] <Variation 2> FIG. 7 is a cross-sectional view of an electromagnetic wave detector 100B according to Modification 2. FIG. 7 shows a cross section taken along the same line as II-II in FIG. 1. As shown in FIG. 7, the insulating film 20 has a side surface 20b. The side surface 20b is in contact with the electrode 30. The side surfaces 50a and 50b are inclined with respect to the thickness direction of the two-dimensional semiconductor layer 50 so that the distance between the side surfaces 50a and 50b increases toward the insulating film 20. The side surfaces 80a and 80b are inclined with respect to the thickness direction of the graphene layer 80 so that the distance between the side surfaces 80a and 80b increases toward the insulating film 60. The side surfaces 50a and 20b are connected to each other to form a first inclined surface. The side surfaces 50b, 60a, and 80b are connected to each other to form a second inclined surface. From another perspective, the side surfaces of electrode 30 in contact with side surfaces 50a and 20b are inclined so that the upper end protrudes more than the lower end, the side surfaces of electrode 40 in contact with side surfaces 50b, 60a, and 80b are inclined so that the upper end protrudes more than the lower end, and the side surface of electrode 70 in contact with side surface 80a is inclined so that the upper end protrudes more than the lower end.

[0070] The first inclined surface is formed by etching the two-dimensional semiconductor layer 50 formed on the insulating film 20. Thereafter, the electrode 30 is formed by vacuum deposition or the like, and since the first inclined surface serves as a film formation surface during this process, it is possible to ensure good contact between the electrode 30 and the side surface 50a, which is the first inclined surface, without performing film formation in an inclined state. Similarly, the two-dimensional semiconductor layer 50, the insulating film 60, and the graphene layer 80 are etched to form a second inclined surface, and the electrode 40 is formed using the second inclined surface as a film formation surface, so it is possible to ensure good contact between the side surface 50b and the side surface 80b and the electrode 40.

[0071] Embodiment 3 An electromagnetic wave detector according to embodiment 3 will be described. The electromagnetic wave detector according to embodiment 3 is designated as electromagnetic wave detector 100C. Here, differences from electromagnetic wave detector 100A will be mainly described, and overlapping descriptions will not be repeated.

[0072] (Configuration of electromagnetic wave detector 100C) The configuration of the electromagnetic wave detector 100C will be described below.

[0073] Fig. 8 is a cross-sectional view of the electromagnetic wave detector 100C. Fig. 8 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 8, the electromagnetic wave detector 100C includes a substrate 10, an insulating film 20, an electrode 30, an electrode 40, a two-dimensional semiconductor layer 50, an insulating film 60, an electrode 70, and a graphene layer 80. In this respect, the configuration of the electromagnetic wave detector 100C is common to the configuration of the electromagnetic wave detector 100A.

[0074] In the electromagnetic wave detector 100C, the graphene layer 80 is disposed on the insulating film 20 and the electrode 30 so as to be electrically connected to the electrode 30 and the electrode 40. In the electromagnetic wave detector 100C, the two-dimensional semiconductor layer 50 is disposed on the insulating film 60 so as to be electrically connected to the electrode 40 and the electrode 70. In these respects, the configuration of the electromagnetic wave detector 100C differs from the configuration of the electromagnetic wave detector 100A.

[0075] <Modification> FIG. 9 is a cross-sectional view of an electromagnetic wave detector 100C according to a modified example. FIG. 9 shows a cross section taken along the same line as II-II in FIG. 1. As shown in FIG. 9, the electromagnetic wave detector 100C does not necessarily have the electrode 30. In this case, the graphene layer 80 is electrically connected to the substrate 10. In addition, in this case, the constituent material of the substrate 10 is a semiconductor material. Therefore, the graphene layer 80 and the substrate 10 form a Schottky junction.

[0076] (Effect of Electromagnetic Wave Detector 100C) The effects of the electromagnetic wave detector 100C will be described below.

[0077] In the electromagnetic wave detector 100C, too, photocarriers are generated when electromagnetic waves are incident on the two-dimensional semiconductor layer 50, and the photocarriers cause an optical gate effect and an optical bias effect. In the electromagnetic wave detector 100C, the two-dimensional semiconductor layer 50 is disposed on the insulating film 60, so that the electromagnetic waves do not need to pass through the insulating film 60 before reaching the two-dimensional semiconductor layer 50, and deactivation of the incident electromagnetic waves is suppressed. As a result, the electromagnetic wave detector 100C further enhances the detection sensitivity for electromagnetic waves.

[0078] When the electromagnetic wave detector 100C does not have the electrode 30, the manufacturing process can be simplified because the step of forming the electrode 30 can be omitted. In this case, the base material 10 and the graphene layer 80 form a Schottky junction, so that it is possible to suppress the flow of dark current in the graphene layer 80.

[0079] Embodiment 4 An electromagnetic wave detector according to embodiment 4 will be described. The electromagnetic wave detector according to embodiment 4 is designated as electromagnetic wave detector 100D. Here, differences from electromagnetic wave detector 100A will be mainly described, and overlapping descriptions will not be repeated.

[0080] (Configuration of the electromagnetic wave detector 100D) The configuration of the electromagnetic wave detector 100D will be described below.

[0081] Fig. 10 is a cross-sectional view of the electromagnetic wave detector 100D. Fig. 10 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 10, the electromagnetic wave detector 100D includes a substrate 10, an insulating film 20, an electrode 30, an electrode 40, a two-dimensional semiconductor layer 50, an insulating film 60, an electrode 70, and a graphene layer 80. In this respect, the configuration of the electromagnetic wave detector 100D is common to the configuration of the electromagnetic wave detector 100A.

[0082] In the electromagnetic wave detector 100D, the two-dimensional semiconductor layer 50 has a first layer 51 and a second layer 52. The second layer 52 is disposed on the first layer 51. The first layer 51 is in contact with the electrodes 30 and 40, but the second layer 52 is not in contact with the electrodes 30 and 40. The first layer 51 and the second layer 52 are two-dimensional semiconductor layers. The constituent material of the first layer 51 is different from the constituent material of the second layer 52. In this respect, the configuration of the electromagnetic wave detector 100D differs from the configuration of the electromagnetic wave detector 100A.

[0083] <Modification> Fig. 11 is a cross-sectional view of an electromagnetic wave detector 100D according to a modified example. Fig. 11 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 11, not only the first layer 51 but also the second layer 52 may be in contact with the electrode 30 and the electrode 40.

[0084] (Effect of the 100D electromagnetic wave detector) The effects of the electromagnetic wave detector 100D will be described below.

[0085] In the electromagnetic wave detector 100D, the first layer 51 and the second layer 52 are bonded together on the same plane at the interface between them, and different bandgaps are formed in the first layer 51 and the second layer 52 at the interface between them. Therefore, the electromagnetic wave detector 100D makes it possible to control the absorption wavelength of electromagnetic waves in the two-dimensional semiconductor layer 50. When not only the first layer 51 but also the second layer 52 are in contact with the electrode 30 and the electrode 40, photocarriers generated in each of the first layer 51 and the second layer 52 can be extracted, making it possible to detect electromagnetic waves of multiple wavelengths in the two-dimensional semiconductor layer 50.

[0086] Embodiment 5. An electromagnetic wave detector according to embodiment 5 will be described. The electromagnetic wave detector according to embodiment 5 is designated as electromagnetic wave detector 100E. Here, differences from electromagnetic wave detector 100A will be mainly described, and overlapping descriptions will not be repeated.

[0087] (Configuration of the electromagnetic wave detector 100E) The configuration of the electromagnetic wave detector 100E will be described below.

[0088] Fig. 12 is a cross-sectional view of the electromagnetic wave detector 100E. Fig. 12 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 12, the electromagnetic wave detector 100E includes a substrate 10, an insulating film 20, an electrode 30, an electrode 40, a two-dimensional semiconductor layer 50, an insulating film 60, an electrode 70, and a graphene layer 80. In this respect, the configuration of the electromagnetic wave detector 100E is common to the configuration of the electromagnetic wave detector 100A.

[0089] The two-dimensional semiconductor layer 50 has a first portion 53 and a second portion 54. The first portion 53 and the second portion 54 are electrically connected in series. The first portion 53 and the second portion 54 form a van der Waals heterojunction. The constituent materials of the first portion 53 and the second portion 54 are both two-dimensional semiconductor materials but are different from each other. Note that the first portion 53 and the second portion 54 are formed, for example, by sequentially transferring two-dimensional semiconductor materials that have been fabricated separately.

[0090] <Modification> FIG. 13 is a cross-sectional view of an electromagnetic wave detector 100E according to a modified example. FIG. 13 shows a cross section taken along the same line as II-II in FIG. 1. As shown in FIG. 13, the first portion 53 has a side surface 53a, and the second portion 54 has a side surface 54a. The first portion 53 may be connected to the second portion 54 by contacting the side surface 53a with the side surface 54a. The first portion 53 and the second portion 54 may be pn-junctioned. That is, the conductivity type of the material constituting the first portion 53 may be different from the conductivity type of the material constituting the second portion 54. The first portion 53 and the second portion 54 can be formed separately by introducing a dopant or another material into only one of the first portion 53 and the second portion 54 during formation by, for example, CVD.

[0091] (Effect of the Electromagnetic Wave Detector 100E) The effects of the electromagnetic wave detector 100E will be described below.

[0092] In the electromagnetic wave detector 100E, the first portion 53 and the second portion 54 are joined, so it is possible to control the absorption wavelength of electromagnetic waves at the junction interface between the first portion 53 and the second portion 54. When the first portion 53 and the second portion 54 are joined by a pn junction, it is possible to efficiently extract photocarriers through light absorption. In this case, the off-state current is reduced, and dark current can be further suppressed. In the electromagnetic wave detector 100E according to the modified example, no impurities are present at the junction interface between the first portion 53 and the second portion 54, and a good junction interface is obtained, so deactivation of photocarriers that occurs at a pn junction or the like is suppressed, resulting in high sensitivity.

[0093] Embodiment 6 An electromagnetic wave detector according to embodiment 6 will be described. The electromagnetic wave detector according to embodiment 6 is designated as electromagnetic wave detector 100F. Here, differences from electromagnetic wave detector 100A will be mainly described, and overlapping descriptions will not be repeated.

[0094] (Configuration of the electromagnetic wave detector 100F) The configuration of the electromagnetic wave detector 100F will be described below.

[0095] Fig. 14 is a cross-sectional view of the electromagnetic wave detector 100F. Fig. 14 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 14, the electromagnetic wave detector 100F includes a substrate 10, an insulating film 20, an electrode 30, an electrode 40, a two-dimensional semiconductor layer 50, an insulating film 60, an electrode 70, and a graphene layer 80. In this respect, the configuration of the electromagnetic wave detector 100F is common to the configuration of the electromagnetic wave detector 100A.

[0096] In the electromagnetic wave detector 100F, the insulating film 60 is a two-dimensional insulating film. The insulating film 60 is made of, for example, hexagonal boron nitride (h-BN). In the electromagnetic wave detector 100F, the thickness of the insulating film 60 may be such that a tunneling current flows between the two-dimensional semiconductor layer 50 and the graphene layer 80, or may be such that a tunneling current does not flow between the two-dimensional semiconductor layer 50 and the graphene layer 80. In these respects, the configuration of the electromagnetic wave detector 100F differs from the configuration of the electromagnetic wave detector 100A. Note that in the electromagnetic wave detector 100F, the two-dimensional semiconductor layer 50 and the graphene layer 80 are in edge contact with the electrode 40, and the positions of the side surfaces 50b, 60a, and 80b are aligned.

[0097] <Variation 1> Fig. 15 is a cross-sectional view of an electromagnetic wave detector 100F according to Modification 1. Fig. 15 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 15, the side surface 50b may be in contact with the electrode 40, while the side surface 50a may not be in contact with the electrode 30. The two-dimensional semiconductor layer 50 is disposed on the electrode 30.

[0098] <Modification 2 and Modification 3> FIG. 16 is a cross-sectional view of an electromagnetic wave detector 100F according to Modification 2. FIG. 16 shows a cross section taken along the same line as II-II in FIG. 1. As shown in FIG. 16, the other end of the two-dimensional semiconductor layer 50 may be disposed on the electrode 40. Furthermore, one end of the graphene layer 80 may be disposed on the electrode 70. Furthermore, the side surfaces 60a and 50b may be covered with the graphene layer 80, and the other end of the graphene layer 80 may be disposed on the electrode 40. FIG. 17 is a cross-sectional view of an electromagnetic wave detector 100F according to Modification 3. FIG. 17 shows a cross-sectional view taken along the same line as II-II in FIG. 1. As shown in FIG. 17, the electrode 70 may be disposed on the insulating film 20 instead of on the insulating film 60.

[0099] <Variation 4> FIG. 18 is a cross-sectional view of an electromagnetic wave detector 100F according to Modification 4. FIG. 18 shows a cross section taken along the same line as II-II in FIG. 1. As shown in FIG. 18, the electromagnetic wave detector 100F may further include an insulating film 90 and an insulating film 91. The insulating film 90 and the insulating film 91 are two-dimensional insulating films. The insulating film 90 and the insulating film 91 are made of, for example, hexagonal boron nitride. The insulating film 90 is interposed between the two-dimensional semiconductor layer 50 and the insulating film 20. The insulating film 91 covers the graphene layer 80. In this example, the electrode 70 is also disposed on the insulating film 20, not on the insulating film 60.

[0100] (Effect of Electromagnetic Wave Detector 100F) The effects of the electromagnetic wave detector 100F will be described below.

[0101] In the electromagnetic wave detector 100F, the insulating film 60 is a two-dimensional insulating film, and therefore the insulating film 60 and the graphene layer 80 disposed on the insulating film 60 are lattice-matched. This improves the carrier mobility in the graphene layer 80. Furthermore, since the insulating film 60 is a two-dimensional insulating film, the insulating film 60 can be formed thin, which further strengthens the optical gating effect and further improves the detection sensitivity for electromagnetic waves. Note that, when the thickness of the two-dimensional insulating film forming the insulating film 60 is such that a tunneling current flows, in addition to the optical gating effect, a change in the Fermi level of the graphene layer 80 occurs due to photocarriers generated in the two-dimensional semiconductor layer 50 being injected into the graphene layer 80 via the insulating film 60.

[0102] When the two-dimensional semiconductor layer 50 is disposed on the electrode 30 and the side surface 50b and the side surface 60a are aligned, the two-dimensional semiconductor layer 50 and the insulating film 60 are formed after the electrodes 30 and 40 are formed, and therefore the electrode 70 is formed in a state where the two-dimensional semiconductor layer 50 is covered with the insulating film 60. Therefore, in this case, it is possible to reduce process damage to the two-dimensional semiconductor layer 50 that accompanies the formation of the electrode 70.

[0103] In the case where the other end of the two-dimensional semiconductor layer 50 is disposed on the electrode 30 and one end and the other end of the graphene layer 80 are disposed on the electrode 70 and the electrode 40, respectively, the two-dimensional semiconductor layer 50 and the insulating film 60 are sequentially formed after the electrodes 30 and 40 are formed, and then the electrode 70 is formed and the graphene layer 80 is formed. In other words, when the electrode 70 is formed, the two-dimensional semiconductor layer 50 is covered with the insulating film 60, and no electrode is formed after the graphene layer 80 is formed. Therefore, in this case, it is possible to reduce process damage to the two-dimensional semiconductor layer 50 and the graphene layer 80. It is also possible to transfer the two-dimensional semiconductor layer 50, the insulating film 60, and the graphene layer 80, which have been processed and stacked in advance, all at once. In this case, it is possible to reduce process damage in the transfer process of each layer.

[0104] When the electrode 70 is disposed on the insulating film 20, the electrodes 30, 40, and 70 are formed, and then the two-dimensional semiconductor layer 50, the insulating film 60, and the graphene layer 80 are formed in this order. Therefore, in this case, since other electrodes and insulating films are not formed after the two-dimensional semiconductor layer 50 and the graphene layer 80 are formed, it is possible to reduce process damage to the two-dimensional semiconductor layer 50 and the graphene layer 80.

[0105] When the insulating film 90 is interposed between the two-dimensional semiconductor layer 50 and the insulating film 20 and the graphene layer 80 is covered with the insulating film 91, the two-dimensional semiconductor layer 50 and the graphene layer 80 are encapsulated by the two-dimensional insulating film, which makes it possible to reduce the effects of moisture and oxygen in the air and residues and impurities in the process.

[0106] Embodiment 7 An electromagnetic wave detector according to embodiment 7 will be described. The electromagnetic wave detector according to embodiment 7 is designated as electromagnetic wave detector 100G. Here, differences from electromagnetic wave detector 100A will be mainly described, and overlapping descriptions will not be repeated.

[0107] (Configuration of 100G electromagnetic wave detector) The configuration of the electromagnetic wave detector 100G will be described below.

[0108] Fig. 19 is a cross-sectional view of the electromagnetic wave detector 100G. Fig. 19 shows a cross section taken along the same line as II-II in Fig. 1. As shown in Fig. 19, the electromagnetic wave detector 100G includes a substrate 10, an insulating film 20, an electrode 30, an electrode 40, a two-dimensional semiconductor layer 50, an insulating film 60, an electrode 70, and a graphene layer 80. In this respect, the configuration of the electromagnetic wave detector 100G is common to the configuration of the electromagnetic wave detector 100A.

[0109] In the electromagnetic wave detector 100G, the two-dimensional semiconductor layer 50 faces the substrate 10 with a gap 21 interposed therebetween. That is, in the electromagnetic wave detector 100G, the insulating film 20 below the two-dimensional semiconductor layer 50 is removed by, for example, etching. In this respect, the configuration of the electromagnetic wave detector 100G differs from the configuration of the electromagnetic wave detector 100A.

[0110] (Effect of 100G electromagnetic wave detector) The effects of the electromagnetic wave detector 100G will be described below.

[0111] In the electromagnetic wave detector 100G, because of the presence of the voids 21, the insulating film 20 does not exist below the two-dimensional semiconductor layer 50. Therefore, the two-dimensional semiconductor layer 50 is not affected by carrier scattering due to the underlying insulating film 20, and the carrier mobility of the two-dimensional semiconductor layer 50 is improved, improving the extraction efficiency of photocarriers, thereby further improving the detection sensitivity to electromagnetic waves.

[0112] Embodiment 8 An electromagnetic wave detector according to embodiment 8 will be described. The electromagnetic wave detector according to embodiment 8 is designated as electromagnetic wave detector 100H. Here, differences from electromagnetic wave detector 100A will be mainly described, and overlapping descriptions will not be repeated.

[0113] (Configuration of the electromagnetic wave detector 100H) The configuration of the electromagnetic wave detector 100H will be described below.

[0114] Fig. 20 is a cross-sectional view of the electromagnetic wave detector 100H. Fig. 20 shows a cross-section taken along the same line as II-II in Fig. 1. Fig. 21 is a cross-sectional view of the laminate 120A. Fig. 22 is a cross-sectional view of the laminate 120B. As shown in Figs. 20 to 22, the electromagnetic wave detector 100H has a laminate 120A and a laminate 120B.

[0115] The laminate 120A has a base material 10, an insulating film 20, electrodes 30 and 40, a graphene layer 80, and an insulating film 60. That is, the configuration of the laminate 120A is similar to that of the electromagnetic wave detector 100A, except that the laminate 120A does not have an electrode 70, does not have the graphene layer 80 on the insulating film 60, and uses the graphene layer 80 instead of the two-dimensional semiconductor layer 50. Furthermore, the laminate 120B has a base material 10, an insulating film 20, electrodes 30 and 40, a two-dimensional semiconductor layer 50, and an insulating film 60. That is, the configuration of the laminate 120B is similar to that of the electromagnetic wave detector 100A, except that the laminate 120A does not have an electrode 70 and does not have the graphene layer 80 on the insulating film 60.

[0116] The electromagnetic wave detector 100H is formed by hybrid bonding of the laminate 120A and the laminate 120B. That is, in the electromagnetic wave detector 100H, the electrodes 40 of the laminate 120A and the electrodes 40 of the laminate 120B face each other, and the graphene layer 80 of the laminate 120A and the two-dimensional semiconductor layer 50 of the laminate 120B face each other with the insulating film 60 of the laminate 120A and the insulating film 60 of the laminate 120B interposed therebetween. The bond between the electrode 40 of the laminate 120A and the electrode 40 of the laminate 120B is preferably a bond between the same metal materials. For example, the electrode 40 of the laminate 120A and the electrode 40 of the laminate 120B are made of copper, and the bond between the electrode 40 of the laminate 120A and the electrode 40 of the laminate 120B is a Cu-Cu bond.

[0117] In the electromagnetic wave detector 100H, a power supply 110 is connected to the electrode 30 of the laminate 120A and the electrode 30 of the laminate 120B, thereby reading out a signal. Note that, if the electrical resistance of the base material 10 is small, the power supply 110 may be connected to the base material 10 of the laminate 120A and the base material 10 of the laminate 120B, thereby reading out a signal.

[0118] <Modification 1 and Modification 2> FIG. 23 is a cross-sectional view of an electromagnetic wave detector 100H according to Modification 1. FIG. 24 is a cross-sectional view of an electromagnetic wave detector 100H according to Modification 2. As shown in FIG. 23, the base material 10 of the laminate 120B may be made thinner than the base material 10 of the laminate 120A, for example, by being ground. Also, as shown in FIG. 24, the base material 10 of the laminate 120B may be removed, for example, by being ground. Note that the base material 10 of the laminate 120B is ground after hybrid bonding is performed between the laminate 120A and the laminate 120B, for example.

[0119] <Variation 3> FIG. 25 is a cross-sectional view of an electromagnetic wave detector 100H according to Modification 3. FIG. 26 is a cross-sectional view of a stack 120A in the electromagnetic wave detector 100H according to Modification 3. FIG. 27 is a cross-sectional view of a stack 120B in the electromagnetic wave detector 100H according to Modification 3. As shown in FIGS. 25 to 27, in the stack 120A, the graphene layer 80 may be in edge contact with the electrode 40, and in the stack 120B, the two-dimensional semiconductor layer 50 may be in edge contact with the electrode 40. In this case, first, the graphene layer 80 (two-dimensional semiconductor layer 50) is formed. Second, a protective film is formed on the graphene layer 80 (two-dimensional semiconductor layer 50). Third, the graphene layer 80 (two-dimensional semiconductor layer 50) is etched using the protective film as a mask to form an opening. Fourth, the electrode 40 is formed in the opening, thereby achieving edge contact between the graphene layer 80 (two-dimensional semiconductor layer 50) and the electrode 40.

[0120] (Effect of Electromagnetic Wave Detector 100H) The effects of the electromagnetic wave detector 100H will be described below.

[0121] In the electromagnetic wave detector 100H, the stack 120A has the graphene layer 80, and the stack 120B has the two-dimensional semiconductor layer 50, so that the graphene layer 80 and the two-dimensional semiconductor layer 50 can be formed on separate substrates 10. This eliminates the need to sequentially transfer and form these layers on the same substrate 10, and makes it possible to prevent damage to previously formed layers when forming the layers that will be formed later. That is, in the electromagnetic wave detector 100H, it is possible to reduce the heat resistance temperature of the process and damage to previously formed layers.

[0122] When the substrate 10 of the laminate 120B is thinned or removed by grinding, it is possible to prevent the substrate 10 of the laminate 120B from interfering with the incidence of electromagnetic waves on the two-dimensional semiconductor layer 50. When the two-dimensional semiconductor layer 50 and the graphene layer 80 are in edge contact with the electrode 40, the contact resistance between the electrode 40 and the two-dimensional semiconductor layer 50 and the graphene layer 80 is reduced, improving the current extraction efficiency. Furthermore, in this case, the bonding area of ​​the electrode 40 is increased, thereby improving the accuracy of the hybrid bonding.

[0123] [Note] Aspects of the present disclosure are summarized in the appendix.

[0124] <Appendix 1> a graphene layer; a two-dimensional semiconductor layer; a first insulating film; The graphene layer and the two-dimensional semiconductor layer are electrically connected in series and are disposed opposite each other with the first insulating film interposed therebetween.

[0125] <Appendix 2> A second insulating film; Further comprising a first electrode; 2. The electromagnetic wave detector according to claim 1, wherein the two-dimensional semiconductor layer is disposed on the second insulating film and the first electrode so as to be electrically connected to the first electrode.

[0126] <Appendix 3> the second insulating film and the first electrode have a first surface and a second surface, respectively; 3. The electromagnetic wave detector according to claim 2, wherein the second insulating film and the first electrode are arranged so that the first surface and the second surface are connected to each other to form a flat surface.

[0127] <Appendix 4> Further comprising a second electrode; the second electrode is disposed on the second surface; The electromagnetic wave detector of Appendix 3, wherein the two-dimensional semiconductor layer has a first side and a second side opposite the first side and electrically connected to the second electrode.

[0128] <Appendix 5> the first insulating film is disposed on the two-dimensional semiconductor layer; The electromagnetic wave detector described in Appendix 4, wherein the graphene layer has a third side surface and a fourth side surface opposite to the third side surface, and is arranged on the first insulating film so that the fourth side surface is electrically connected to the second electrode.

[0129] <Appendix 6> the first insulating film has a fifth side surface and a sixth side surface that is opposite to the fifth side surface and in contact with the second electrode; 6. The electromagnetic wave detector of claim 5, wherein the second side surface, the fourth side surface, and the sixth side surface are aligned with each other.

[0130] <Appendix 7> A second insulating film; A first electrode; a second electrode; the two-dimensional semiconductor layer is disposed on the second insulating film, the two-dimensional semiconductor layer has a first side surface and a second side surface opposite to the first side surface, 2. The electromagnetic wave detector according to claim 1, wherein the first electrode and the second electrode are arranged so as to be electrically connected to the first side surface and the second side surface, respectively.

[0131] <Appendix 8> the first insulating film is disposed on the first electrode and the two-dimensional semiconductor layer; 8. The electromagnetic wave detector of claim 7, wherein the graphene layer has a third side surface and a fourth side surface opposite the third side surface, and is disposed on the first insulating film so that the fourth side surface is electrically connected to the second electrode.

[0132] <Appendix 9> the first insulating film has a fifth side surface and a sixth side surface that is opposite to the fifth side surface and in contact with the second electrode; 9. The electromagnetic wave detector according to claim 8, wherein the second side surface, the fourth side surface, and the sixth side surface are aligned with each other.

[0133] <Appendix 10> Further comprising a third electrode; the third side surface is electrically connected to the third electrode; the first insulating film has a fifth side surface; the second insulating film has a sixth side surface, the fifth side surface and the sixth side surface are in contact with the first electrode and the second electrode, respectively; a side surface of the first electrode in contact with the first side surface and the sixth side surface is inclined so that an upper end thereof protrudes more than a lower end thereof; the side surfaces of the second electrode in contact with the second side surface, the fourth side surface, and the fifth side surface are inclined so that the upper ends thereof protrude more than the lower ends thereof; 9. The electromagnetic wave detector according to claim 8, wherein a side surface of the third electrode in contact with the third side surface is inclined so that an upper end protrudes more than a lower end.

[0134] <Appendix 11> Further comprising a second insulating film; the graphene layer is disposed on the second insulating film; the first insulating film is disposed on the graphene layer; 2. The electromagnetic wave detector according to claim 1, wherein the two-dimensional semiconductor layer is disposed on the first insulating film.

[0135] <Appendix 12> the two-dimensional semiconductor layer includes a first layer and a second layer disposed on the first layer; 2. The electromagnetic wave detector according to claim 1, wherein the first layer is made of a material different from the second layer.

[0136] <Appendix 13> A first electrode; a second electrode; 13. The electromagnetic wave detector of claim 12, wherein the first layer and the second layer are electrically connected to the first electrode and the second electrode, respectively.

[0137] <Appendix 14> the two-dimensional semiconductor layer has a first portion and a second portion connected in series to the first portion; 2. The electromagnetic wave detector of claim 1, wherein the first portion is made of a material different from the second portion.

[0138] <Appendix 15> 15. The electromagnetic wave detector of claim 14, wherein the first portion and the second portion are pn-junctioned with each other.

[0139] <Appendix 16> Further comprising a substrate; 16. The electromagnetic wave detector according to any one of claims 1 to 15, wherein the two-dimensional semiconductor layer is disposed opposite the substrate with a gap therebetween.

[0140] <Appendix 17> 17. The electromagnetic wave detector according to claim 1, wherein the first insulating film is a two-dimensional insulating film.

[0141] <Appendix 18> 18. The electromagnetic wave detector according to any one of claims 1 to 17, wherein the two-dimensional semiconductor layer is a turbostratic stacked graphene layer.

[0142] <Appendix 19> A first laminate; a second laminate, each of the first stacked body and the second stacked body includes a second electrode and the first insulating film; one of the first stack and the second stack has the graphene layer electrically connected to the second electrode; the other of the first stack and the second stack has the two-dimensional semiconductor layer electrically connected to the second electrode; The electromagnetic wave detector described in Appendix 1, wherein the first stack and the second stack are stacked so that the second electrode of the first stack and the second electrode of the second stack face each other and face each other with the first insulating film of the first stack and the first insulating film of the second stack interposed therebetween.

[0143] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0144] 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H Electromagnetic wave detector, 110 power supply, 120A, 120B laminate, 10 substrate, 10a front surface, 10b rear surface, 20 insulating film, 20a front surface, 20b side surface, 21 gap, 30 electrode, 30a front surface, 40 electrode, 50 two-dimensional semiconductor layer, 50a, 50b side surface, 51 first layer, 52 second layer, 53 first portion, 54 second portion, 53a, 54a side surface, 60 Insulating film, 60a side, 70 electrode, 80 graphene layer, 80a side, 80b side, 90 insulating film, 91 insulating film.

Claims

1. a graphene layer; a two-dimensional semiconductor layer; a first insulating film; the graphene layer has a first end and a second end opposite the first end; the two-dimensional semiconductor layer has a third end and a fourth end opposite the third end; the graphene layer has the second end electrically connected to the third end and is disposed opposite the two-dimensional semiconductor layer with the first insulating film interposed therebetween; the first insulating film has a thickness that prevents a tunneling current from flowing between the graphene layer and the two-dimensional semiconductor layer.

2. A second insulating film; Further comprising a first electrode; The electromagnetic wave detector according to claim 1 , wherein the two-dimensional semiconductor layer is disposed on the second insulating film and the first electrode so as to be electrically connected to the first electrode.

3. the second insulating film has a first surface; the first electrode has a second surface; The electromagnetic wave detector according to claim 2 , wherein the second insulating film and the first electrode are arranged so that the first surface and the second surface are connected to each other to form a flat surface.

4. A graphene layer; a two-dimensional semiconductor layer; a first insulating film; the graphene layer has a first end and a second end opposite the first end; the two-dimensional semiconductor layer has a third end and a fourth end opposite the third end; the graphene layer has the second end electrically connected to the third end and is disposed opposite the two-dimensional semiconductor layer with the first insulating film interposed therebetween; A second insulating film; Further comprising a first electrode; the two-dimensional semiconductor layer is disposed on the second insulating film and the first electrode so as to be electrically connected to the first electrode; the second insulating film has a first surface; the first electrode has a second surface; the second insulating film and the first electrode are arranged such that the first surface and the second surface are connected to each other to form a flat surface; Further comprising a second electrode; the second electrode is disposed on the first surface; The two-dimensional semiconductor layer has a first side and a second side opposite to the first side and electrically connected to the second electrode.

5. the first insulating film is disposed on the two-dimensional semiconductor layer; 5. The electromagnetic wave detector according to claim 4, wherein the graphene layer has a third side surface and a fourth side surface that is an opposite surface to the third side surface, and is disposed on the first insulating film so that the fourth side surface is electrically connected to the second electrode.

6. the first insulating film has a fifth side surface and a sixth side surface opposite to the fifth side surface and in contact with the second electrode; The electromagnetic wave detector according to claim 5 , wherein the second side surface, the fourth side surface, and the sixth side surface are aligned with each other.

7. A graphene layer; a two-dimensional semiconductor layer; a first insulating film; the graphene layer has a first end and a second end opposite the first end; the two-dimensional semiconductor layer has a third end and a fourth end opposite the third end; the graphene layer has the second end electrically connected to the third end and is disposed opposite the two-dimensional semiconductor layer with the first insulating film interposed therebetween; A second insulating film; A first electrode; a second electrode; the two-dimensional semiconductor layer is disposed on the second insulating film, the two-dimensional semiconductor layer has a first side surface and a second side surface opposite to the first side surface, An electromagnetic wave detector, wherein the first electrode and the second electrode are arranged such that the first electrode is electrically connected to the first side surface and the second electrode is electrically connected to the second side surface.

8. the first insulating film is disposed on the first electrode and the two-dimensional semiconductor layer, 8. The electromagnetic wave detector according to claim 7, wherein the graphene layer has a third side surface and a fourth side surface that is an opposite surface to the third side surface, and is disposed on the first insulating film so that the fourth side surface is electrically connected to the second electrode.

9. the first insulating film has a fifth side surface and a sixth side surface opposite to the fifth side surface and in contact with the second electrode; The electromagnetic wave detector according to claim 8 , wherein the second side surface, the fourth side surface, and the sixth side surface are aligned with each other.

10. Further comprising a third electrode; the third side surface is electrically connected to the third electrode; the first insulating film has a fifth side surface; the second insulating film has a sixth side surface, the fifth side surface is in contact with the second electrode; the sixth side surface is in contact with the first electrode; a side surface of the first electrode in contact with the first side surface and the sixth side surface is inclined so that an upper end thereof protrudes more than a lower end thereof; side surfaces of the second electrode in contact with the second side surface, the fourth side surface, and the fifth side surface are inclined so that an upper end thereof protrudes more than a lower end thereof, The electromagnetic wave detector according to claim 8 , wherein a side surface of the third electrode in contact with the third side surface is inclined so that an upper end thereof protrudes more than a lower end thereof.

11. Further comprising a second insulating film; the graphene layer is disposed on the second insulating film; the first insulating film is disposed on the graphene layer; The electromagnetic wave detector according to claim 1 , wherein the two-dimensional semiconductor layer is disposed on the first insulating film.

12. the two-dimensional semiconductor layer includes a first layer and a second layer disposed on the first layer; 2. The electromagnetic wave detector according to claim 1, wherein the first layer is made of a material different from the second layer.

13. A first electrode; a second electrode; The electromagnetic wave detector according to claim 12 , wherein the first layer and the second layer are electrically connected to the first electrode and the second electrode, respectively.

14. the two-dimensional semiconductor layer has a first portion and a second portion connected in series to the first portion; 2. The electromagnetic wave detector of claim 1, wherein the first portion is made of a material different from the second portion.

15. The electromagnetic wave detector according to claim 14 , wherein the first portion and the second portion are pn-junctioned with each other.

16. Further comprising a substrate; The electromagnetic wave detector according to claim 1 , wherein the two-dimensional semiconductor layer is disposed opposite the base material with a gap therebetween.

17. The electromagnetic wave detector according to claim 1 , wherein the first insulating film is a two-dimensional insulating film.

18. The electromagnetic wave detector according to claim 1 , wherein the two-dimensional semiconductor layer is a turbostratic stacked graphene layer.

19. A first laminate; a second laminate, each of the first stacked body and the second stacked body includes a second electrode and the first insulating film; one of the first stacked body and the second stacked body includes the graphene layer electrically connected to the second electrode; the other of the first stack and the second stack has the two-dimensional semiconductor layer electrically connected to the second electrode; 2. The electromagnetic wave detector according to claim 1, wherein the first stack and the second stack are stacked such that the second electrode of the first stack and the second electrode of the second stack face each other and face each other with the first insulating film of the first stack and the first insulating film of the second stack interposed therebetween.

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