Electromagnetic wave detector

Abstract

The electromagnetic wave detector includes a graphene layer 40, a thermoelectric material layer 70, and a semiconductor layer 11. The graphene layer 40, the thermoelectric material layer 70, and the semiconductor layer 11 are electrically connected in series. A Schottky junction is formed between the graphene layer 40 and the semiconductor layer 11.

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 thermoelectric material layer, and a semiconductor layer, the graphene layer, the thermoelectric material layer, and the semiconductor layer being electrically connected in series, and a Schottky junction being present between the graphene layer and the semiconductor layer. [Effects of the Invention]

[0008] According to the radio 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. 10 is a cross-sectional view of an electromagnetic wave detector 100A according to a third modification. [Figure 6] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100A according to a fourth modification. [Figure 7] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100A according to a fifth modification. [Figure 8] 1 is a cross section of an electromagnetic wave detector 100B. [Figure 9] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100B according to a first modification. [Figure 10] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100B according to a second modification. [Figure 11] 1 is a cross section of an electromagnetic wave detector 100C. [Figure 12] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100C according to a first modification. [Figure 13] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100C according to a second modification. [Figure 14] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100C according to a third modification. [Figure 15] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100C according to a fourth modification. [Figure 16] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100D. [Figure 17] FIG. 2 is a cross-sectional view of a laminate 120A. [Figure 18] FIG. 10 is a cross-sectional view of a laminate 120B. [Figure 19] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100D according to a first modification. [Figure 20] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100D according to a second modification. [Figure 21] FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100D according to a third modification. [Figure 22] 10 is a cross-sectional view of a laminate 120A in an electromagnetic wave detector 100D according to a third modification. FIG. [Figure 23] 10 is a cross-sectional view of a laminate 120B in an electromagnetic wave detector 100D according to a third modification. FIG. 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, a graphene layer 40, an insulating film 50, an electrode 60, and a thermoelectric material layer 70.

[0020] The substrate 10 is made of a semiconductor material. That is, the substrate 10 forms a semiconductor layer 11. Specific examples of semiconductor materials that can be used for 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 containing quantum wells or quantum dots. The material of the substrate 10 may be a Type II superlattice. The 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 back surface 10b is the surface opposite the front surface 10a. The front surface 10a and the back 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 for 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. The electrode 30 may be made of any conductive material. The electrode 30 may be made of at least one of aluminum, gold, silver, copper, nickel, chromium, and palladium. The electrode 30 is disposed on the insulating film 20. An adhesion layer (not shown) may be provided between the electrode 30 and the insulating film 20. The adhesion layer is configured to enhance adhesion. The adhesion layer may include a metal material such as chromium, nickel, or titanium.

[0022] The graphene layer 40 is a layer of single-layer graphene or multi-layer graphene. Single-layer graphene is a layer of two-dimensional carbon crystals. Graphene has multiple carbon atoms arranged in multiple chains arranged in a hexagonal shape. Multi-layer graphene has multiple layers of graphene stacked together. In the multi-layer graphene, the lattice vectors of the hexagonal lattices of the graphene may be aligned or different. Furthermore, the lattice vectors of the hexagonal lattices of the graphene may be aligned completely. The multi-layer graphene may be turbostratic stacked graphene, in which the stacking orientation angles are randomly arranged. 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 the graphene, and the mobility is higher than that of single-layer graphene due to suppressed electrical disturbance of the graphene substrate.

[0023] The graphene layer 40 is disposed on the insulating film 20 such that one end (the end on the left side in the figure) and the other end (the end on the right side in the figure) are connected to the substrate 10 and the electrode 30, respectively. More specifically, one end of the graphene layer 40 is in contact with the surface 10a, and the other end of the graphene layer 40 is disposed on the electrode 30. The interface between the graphene layer 40 and the substrate 10 forms a Schottky junction. That is, a Schottky junction exists between the graphene layer 40 and the substrate 10 (semiconductor layer 11).

[0024] The insulating film 50 is made of an electrically insulating material such as an oxide. Specific examples of the insulating film 50 include aluminum oxide, hafnium oxide, boron nitride, and siloxane-based polymers. The insulating film 50 has a thickness that prevents tunneling current from flowing. The insulating film 50 covers the graphene layer 40. The upper portion of the electrode 30 protrudes from the insulating film 50. The electrode 60 may be made of any conductive material. The electrode 60 may be made of at least one of aluminum, gold, silver, copper, nickel, chromium, and palladium. The electrode 60 is disposed on the insulating film 50.

[0025] The thermoelectric material layer 70 is a layer made of a material that generates heat and carriers when irradiated with electromagnetic waves. The material of the thermoelectric material layer 70 is, for example, multilayer graphene. The thermoelectric material layer 70 may generate carriers when electromagnetic waves are incident on it. The material of the thermoelectric material layer 70 may be graphite or turbostratic stacked graphene. The graphene that makes up the thermoelectric material layer 70 may be doped with p-type or n-type impurities.

[0026] For example, a band gap is formed in the thermoelectric material layer 70 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 thermoelectric material layer 70 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 carrier scattering from the substrate is suppressed, thereby reducing noise in the electromagnetic wave detector 100A. Therefore, in the electromagnetic wave detector 100A having a thermoelectric material layer 70 using multilayer graphene, light absorption is increased, thereby improving the electromagnetic wave detection sensitivity.

[0027] The multilayer 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. Because the interlayer interactions of graphene in turbostratic-stacked graphene are weak, the mobility is comparable to that of monolayer graphene, and electrical disturbances in the graphene substrate are suppressed, resulting in higher mobility than in conventional monolayer graphene. Furthermore, turbostratic-stacked graphene, despite being multilayer graphene, has linear band dispersion, 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 flood 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 stacking angle, the electromagnetic wave detector 100A can selectively detect a specific wavelength range.

[0028] The thermoelectric material layer 70 may be made of nanoribbon-shaped graphene (graphene nanoribbon). The thermoelectric material layer 70 may be made of a single graphene nanoribbon. The thermoelectric material layer 70 may have a structure in which multiple graphene nanoribbons are stacked. The thermoelectric material layer 70 may have a structure in which graphene nanoribbons are periodically arranged on a plane. When the thermoelectric material layer 70 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 thermoelectric material layer 70 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.

[0029] The end of the thermoelectric material layer 70 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.

[0030] The constituent material of the thermoelectric material layer 70 may include at least one of p-type bismuth telluride, n-type bismuth telluride, bismuth-tellurium-based thermoelectric semiconductor material, telluride-based thermoelectric semiconductor material, antimony-tellurium-based thermoelectric semiconductor material, antimony-zinc-based thermoelectric semiconductor material, silicon-germanium-based thermoelectric semiconductor material, selenide-based thermoelectric semiconductor material, silicide-based thermoelectric semiconductor material, oxide-based thermoelectric semiconductor material, Heusler material, oxide material, sulfide material, skutterudite-based material, chalcogenide-based material, etc. The constituent material of the thermoelectric material layer 70 is not limited to the above and may be a material that generates a potential difference due to a temperature difference between substances or that generates a temperature difference between substances due to the flow of current.

[0031] Bismuth-tellurium-based thermoelectric semiconductor materials include, for example, Bi2Te3 and the like. Telluride-based thermoelectric semiconductor materials include, for example, GeTe, MgTe, PbTe and the like. Antimony-tellurium-based thermoelectric semiconductor materials include, for example, Sb2Te3 and the like. Zinc-antimony-based thermoelectric semiconductor materials include, for example, ZnSb, Zn3Sb2, Zn4Sb3 and the like. Silicon-germanium-based thermoelectric semiconductor materials include, for example, SiGe and the like. Selenide-based thermoelectric semiconductor materials include, for example, Bi2Se3, Cu2Se, SnSe and the like. Silicide-based thermoelectric semiconductor materials include, for example, β-FeSi2, CrSi2, MnSi 1.73 , Mg2Si and the like. Heusler materials include, for example, FeVAl, FeVAlSi, FeVTiAl and the like. Oxide-based thermoelectric semiconductor materials include, for example, BiCuSeO, Co:BiCuSeO and the like.

[0032] The constituent material of the thermoelectric material layer 70 is preferably any one of p-type bismuth telluride, n-type bismuth telluride, bismuth-tellurium-based thermoelectric semiconductor material and silicide-based thermoelectric semiconductor material. Preferably, the carrier of p-type bismuth telluride is a hole, the Seebeck coefficient of p-type bismuth telluride is a positive value, and the composition of p-type bismuth telluride is Bi X Te3Sb2-X (0 < X ≤ 0.6). Preferably, the carrier of n-type bismuth telluride is an electron, the Seebeck coefficient of n-type bismuth telluride is a negative value, and the composition of n-type bismuth telluride is Bi2Te3-YSe Y (0 < Y ≤ 3). A plurality of pairs of p-type bismuth telluride and n-type bismuth telluride connected in series with each other may be used in the thermoelectric material layer 70. The constituent material of the thermoelectric material layer 70 may be added with impurities to control the p-type or n-type polarity and conductivity, and the crystal grain size may also be controlled.

[0033] The thermoelectric material layer 70 may be made of a two-dimensional material. Specific examples of materials for the thermoelectric material layer 70 include Bi2Te3, BiTeBr, Cu2Se, SnSe, MoS2, SrTiO3, and WSe2. Other specific examples of materials for the thermoelectric material layer 70 include TiS2, fullerenes, carbon nanotubes, and nanosheets using PEDOT:PSS. For example, when the thermoelectric material layer 70 is made of iron selenide, using an ultrathin two-dimensional material dramatically improves the thermoelectric effect, thereby improving detection sensitivity compared to when a bulk material is used for the thermoelectric material layer 70. Alternatively, tin selenide or tin selenide doped with Te may be used as the material for the thermoelectric material layer 70. Doping tin selenide with Te can achieve high electrical conductivity and thermoelectric power. Furthermore, strontium titanate can also be made into an ultrathin film of several nanometers, thereby improving thermoelectric efficiency compared to bulk strontium titanate. Alternatively, a bulk material may be thinned and used as a two-dimensional material for the thermoelectric material layer 70 .

[0034] The thermoelectric material layer 70 is disposed on the insulating film 50 so that one end (the end on the left side in the figure) and the other end (the end on the right side in the figure) are connected to the electrode 60 and the electrode 30, respectively. As a result, the thermoelectric material layer 70 is electrically connected in series with the graphene layer 40 and the substrate 10 (semiconductor layer 11). The thermoelectric material layer 70 has a side surface 70a at one end and a side surface 70b at the other end. The side surface 70a and the side surface 70b are in contact with the electrode 60 and the electrode 30, respectively. From another perspective, the thermoelectric material layer 70 is in edge contact with the electrode 60 and the electrode 30.

[0035] As described above, the thermoelectric material layer 70 is disposed on the insulating film 50, and the insulating film 50 covers the graphene layer 40, so that the thermoelectric material layer 70 and the graphene layer 40 are disposed opposite each other with the insulating film 50 interposed therebetween.

[0036] 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 substrate 10 (semiconductor layer 11) and the electrode 60, and applies a bias voltage so that the potential at the substrate 10 is higher than the potential at the electrode 60. Although not shown, an ammeter is connected to the electromagnetic wave detector 100A for detecting the current flowing through the substrate 10, the graphene layer 40, and the thermoelectric material layer 70. A voltmeter may be connected instead of this ammeter.

[0037] (Method of manufacturing the electromagnetic wave detector 100A) A method for manufacturing the electromagnetic wave detector 100A will be described below.

[0038] 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 graphene layer forming step, a second insulating film forming step, a second electrode forming step, and a thermoelectric material layer forming step.

[0039] 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 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 film as a mask.

[0040] 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 insulating film 20. The second electrode forming step is performed after the first electrode forming step. The electrode 30 may be formed by, for example, a lift-off method, or may be formed by etching the constituent material of the electrode 30 that has been deposited by sputtering or the like using a resist pattern as a mask. The second electrode forming step may be performed after the first electrode forming step.

[0041] The graphene layer forming step is performed after the first electrode forming step. In the graphene layer forming step, the graphene layer 40 is formed by transferring a graphene layer 40 that has been formed in advance by, for example, a CVD method. The graphene layer 40 may be patterned by etching using a resist pattern as a mask. The second insulating film forming step is performed after the graphene layer forming step. In the second insulating film forming step, an insulating film is formed by a film forming method that causes less damage to the graphene layer 40, such as an ALD (Atomic Layer Deposition) method or a vacuum deposition method. A veneer 50 is formed.

[0042] The second electrode forming step is performed after the second insulating film forming step. In the second electrode forming step, the electrode 60 is formed on the insulating film 50 by the same method as in the first electrode forming step. The thermoelectric material layer forming step is performed after the second electrode forming step. In the thermoelectric material layer forming step, the thermoelectric material layer 70 is formed by transferring the thermoelectric material layer 70 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.

[0043] (Operating principle of the electromagnetic wave detector 100A) The operating principle of the electromagnetic wave detector 100A will be described below.

[0044] 2, a power supply circuit that applies a voltage V is electrically connected between the substrate 10 and the electrode 60. In this case, a current I flows through the graphene layer 40, which is part of the current path between the electrode 60 and the substrate 10. An ammeter (not shown) is installed in the power supply circuit, and the current I is monitored by the ammeter.

[0045] Next, electromagnetic waves are irradiated onto the thermoelectric material layer 70. This causes thermoelectric conversion in the thermoelectric material layer 70, causing a current to flow through the graphene layer 40. The thermoelectric material layer 70 also applies a change in the electric field to the graphene layer 40 via the insulating film 50. As a result, a state in which a pseudo-gate voltage is applied to the graphene layer 40 occurs, causing a change in the resistance value within the graphene layer 40. This is called the optical gate effect.

[0046] Furthermore, when thermoelectric conversion occurs in the thermoelectric material layer 70, the resistance value of the thermoelectric material layer 70 changes, and therefore, a change in the bias voltage applied to the graphene layer 40 also changes the electrical resistance value of the graphene layer 40. This is called the optical bias effect.

[0047] Furthermore, the thermoelectric material layer 70 generates heat when irradiated with electromagnetic waves. The heat generated in the thermoelectric material layer 70 is transferred to the diode, changing the diode characteristics of the diode. As a result, the current flowing through the electromagnetic wave detector 100A changes. This is called the thermal gate effect. The heat generated in the thermoelectric material layer 70 when irradiated with electromagnetic waves has little dependency on the wavelength of the incident electromagnetic waves. Therefore, the electromagnetic wave detector 100A can improve the detection accuracy of electromagnetic waves.

[0048] These changes in resistance value result in a change in the current I flowing through the graphene layer 40, and by detecting the change in the current I, the electromagnetic wave irradiated to the electromagnetic wave detector 100A can be detected.

[0049] Furthermore, when the graphene layer 40 forms a Schottky junction with the substrate 10, the current I can be set to zero by adjusting the voltage V to perform reverse bias operation. That is, the electromagnetic wave detector according to this embodiment is capable of off operation. In this case, the current I flows through the Schottky junction between the graphene layer 40 and the substrate 10 only when light is irradiated, and therefore the current I can be detected only when light is irradiated.

[0050] 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 40 as described above, and may, for example, flow a constant current between the electrode 60 and the substrate 10 and detect a change in the voltage V between the electrode 60 and the substrate 10 (i.e., a change in the voltage value in the graphene layer 40).

[0051] 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.

[0052] (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.

[0053] The range of main detection wavelengths of the electromagnetic wave detector 100A is determined depending on the constituent material of the thermoelectric material layer 70. When electromagnetic waves of the detection wavelength are incident on the thermoelectric material layer 70, carriers are generated in the thermoelectric material layer 70 by thermoelectric conversion. The generated carriers are extracted as photocurrent from the electrode 60 and the substrate 10. At this time, the carriers generated in the region directly below the insulating film 50 cause an electric field change in the graphene layer 40 via the insulating film 50. This is the optical gating effect described above. Furthermore, a change in the resistance value of the thermoelectric material layer 70 causes a change in the bias voltage applied to the graphene layer 40, which changes the electrical resistance value of the graphene layer 40. This is the optical bias effect described above. Furthermore, since the thermoelectric material layer 70 generates heat when irradiated with electromagnetic waves, the heat generated in the thermoelectric material layer 70 is transferred to the diode composed of the graphene layer 40 and the substrate 10, changing the diode characteristics of the diode. This is the thermal gating effect described above. The combination of these resistance changes changes the resistance value of the graphene layer 40, the thermoelectric material layer 70, and the diode composed of the graphene layer 40 and the substrate 10, and by detecting this change as an electrical signal, the electromagnetic wave detector 100A can be operated.

[0054] As described above, graphene constituting the graphene layer 40 has high mobility, and a large displacement current can be obtained in response to a slight change in resistance. Therefore, the current extracted from the electrode 60 via the graphene layer 40 due to the thermoelectric conversion of the thermoelectric material layer 70 is greatly amplified by the optical gate effect, the optical bias effect, and the thermal gate effect. Therefore, the electromagnetic wave detector 100A can achieve high sensitivity that significantly exceeds the efficiency of thermoelectric conversion of the thermoelectric material layer 70.

[0055] (Effect of Electromagnetic Wave Detector 100A) The effects of the electromagnetic wave detector 100A will be described below.

[0056] In the electromagnetic wave detector 100A, there is a Schottky junction between the substrate 10 (semiconductor layer 11) and the graphene layer 40. That is, in the electromagnetic wave detector 100A, a diode exists between the substrate 10 and the graphene layer 40. Therefore, in the electromagnetic wave detector 100A, a current flows when the substrate 10 is biased, but no current flows when the substrate 10 is reverse biased. That is, the electromagnetic wave detector 100A can be in an off state.

[0057] The thermoelectric material layer 70 generates heat when irradiated with electromagnetic waves. The heat generated in the thermoelectric material layer 70 is transferred to the diode, causing a change in the diode characteristics of the diode. As a result, the current flowing through the electromagnetic wave detector 100A changes (thermal gate effect). The heat generated by the thermoelectric material layer 70 when irradiated with electromagnetic waves has little dependency on the wavelength of the incident electromagnetic waves. Therefore, the electromagnetic wave detector 100A can improve the detection accuracy of electromagnetic waves.

[0058] Furthermore, carriers are generated in the thermoelectric material layer 70 when irradiated with electromagnetic waves. Because the graphene layer 40 is disposed opposite the thermoelectric material layer 70 with the insulating film 50 interposed therebetween, the Fermi level in the graphene layer 40 changes due to a potential difference between the thermoelectric material layer 70 and the graphene layer 40 caused by the generation of carriers, and the electrical resistance value of the graphene layer 40 changes (photo-gating effect). Furthermore, the electrical resistance value of the graphene layer 40 also changes due to a change in the bias voltage applied to the graphene layer 40 caused by the generation of photocarriers (photo-bias effect).

[0059] Because the thickness of the single-layer graphene constituting the graphene layer 40 is only the thickness of one atom, the generation of carriers in the thermoelectric material layer 70 significantly changes the Fermi level and electrical resistance value of the graphene layer 40. The single-layer graphene constituting the graphene layer 40 has high electron mobility. Therefore, due to the optical gate effect and optical bias effect, the change in current accompanying the incidence of electromagnetic waves on the thermoelectric material layer 70 becomes extremely large. From this perspective, the electromagnetic wave detector 100A can also improve the detection accuracy of electromagnetic waves.

[0060] When the thermoelectric material layer 70 is made of a layered material such as multilayer graphene, the electrical resistance in the thickness direction is higher than the cell resistance in the in-plane direction. In the electromagnetic wave detector 100A, the thermoelectric material layer 70 is in edge contact with the electrodes 60 and 30 (the side surfaces 70a and 70b are connected to the electrodes 60 and 30, respectively), improving the extraction efficiency of carriers generated when electromagnetic waves are incident on the thermoelectric material layer 70. When the thermoelectric material layer 70 is made of multilayer graphene, the band exhibits linear dispersion, resulting in a wide wavelength range of electromagnetic waves that can be absorbed. Furthermore, the absorption rate of electromagnetic waves increases with the number of stacked layers of multilayer graphene. Therefore, in the electromagnetic wave detector 100A, using multilayer graphene as the material for the thermoelectric material layer 70 further improves the detection sensitivity to electromagnetic waves. Note that when the thermoelectric material layer 70 is made of a thin layered material consisting of several layers or a bulk material, edge contacts are not necessarily required.

[0061] In the electromagnetic wave detector 100A, since the constituent material of the substrate 10 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 substrate 10. When different types of electrode materials are used for the electrodes 30 and 60 in the electromagnetic wave detector 100A, a difference in work function occurs between the electrodes, thereby improving the efficiency of extracting carriers.

[0062] (Variation 1) FIG. 3 is a cross-sectional view of an electromagnetic wave detector 100A according to Modification 1. FIG. 3 shows a cross section taken along a line II-II in FIG. 1. As shown in FIG. 3, the electromagnetic wave detector 100A may further include a buffer layer 12. The buffer layer 12 is made of an electrically insulating material. Specific examples of materials for the buffer layer 12 include metal oxides such as alumina and hafnium oxide, oxides of semiconductor materials such as silicon oxide and silicon nitride, and boron nitride. The buffer layer 12 is formed by an ALD method, a vacuum deposition method, a sputtering method, or the like. The buffer layer 12 may be formed by oxidizing or nitriding the surface 10a, or a native oxide film present on the surface 10a may be used as the buffer layer 12.

[0063] The buffer layer 12 is disposed on the surface 10a exposed through the opening in the insulating film 20, and one end of the graphene layer 40 is in contact with the surface 10a via the buffer layer 12. The buffer layer 12 has a thickness that allows a tunneling current to flow (for example, a thickness of 1 nm or more and 10 nm or less). Therefore, even with the buffer layer 12 interposed, the graphene layer 40 and the substrate 10 are electrically connected, and a Schottky junction exists between them.

[0064] When the buffer layer 12 is interposed between the graphene layer 40 and the substrate 10 as described above, the insulating performance between the graphene layer 40 and the substrate 10 is improved, and the dark current can be reduced (noise can be reduced).

[0065] (Modification 2 and Modification 3) Fig. 4 is a cross-sectional view of an electromagnetic wave detector 100A according to Modification 2. Fig. 5 is a cross-sectional view of an electromagnetic wave detector 100A according to Modification 3. Figs. 4 and 5 show cross sections taken along a line corresponding to II-II in Fig. 1. As shown in Figs. 4 and 5, the graphene layer 40 has a side surface 40a at the other end thereof in contact with the electrode 30. The insulating film 50 has a side surface 50a in contact with the electrode 30.

[0066] 4, the positions of the side surfaces 40a, 50a, and 70b may be aligned with one another. In this case, the electrode 30 can be formed so as to be embedded after etching the ends of the graphene layer 40 and the thermoelectric material layer 70, which facilitates the manufacturing process. In addition, in this case, the number of times that the electrodes are formed is reduced, which reduces process damage to the graphene layer 40 and the thermoelectric material layer 70.

[0067] As shown in FIG. 5 , the side surfaces 70a and 70b may be inclined such that the distance between them increases toward the insulating film 50. From another perspective, the side surfaces 40a, 50a, and 70b may form inclined flat surfaces. From yet another perspective, the side surfaces of the electrode 30 in contact with the side surfaces 40a, 50a, and 70b may be inclined so that their upper ends protrude beyond their lower ends, and the side surfaces of the electrode 60 in contact with the side surface 70a may be inclined so that their upper ends protrude beyond their lower ends. The inclined flat surfaces are formed by etching the graphene layer 40, the insulating film 50, and the thermoelectric material layer 70 after they have been formed. The electrode 30 is then formed by vacuum deposition or the like. During this process, the inclined flat surfaces serve as the film formation surfaces, ensuring good contact between the electrode 30 and the inclined flat surfaces without forming the film in an inclined state. Similarly, since the side surface 70a is inclined and the electrode 60 is formed using the side surface 70a as a film formation surface, good contact between the side surface 70a and the electrode 60 can be ensured.

[0068] (Modification 4 and Modification 5) FIG. 6 is a cross-sectional view of an electromagnetic wave detector 100A according to Modification 4. FIG. 7 is a cross-sectional view of an electromagnetic wave detector 100A according to Modification 5. FIGS. 6 and 7 show cross sections taken along a line corresponding to II-II in FIG. 1. As shown in FIGS. 6 and 7, the electromagnetic wave detector 100A may further include an electrode 80. The electrode 80 is disposed on the surface 10a. The electrode 80 has a surface 80a. The surface 80a faces away from the substrate 10. The surface 80a and the surface 20a may be flat. The electrode 80 may be made of any conductive material. The material of the electrode 80 may include at least one of aluminum, gold, silver, copper, nickel, chromium, and palladium, for example.

[0069] One end of the graphene layer 40 is disposed on the electrode 80 (surface 80a). The electrode 80 and the substrate 10 are connected by a Schottky junction. Therefore, in this case as well, a Schottky junction exists between the graphene layer 40 and the substrate 10. In this case, the contact resistance between the graphene layer 40 and the substrate 10 can be reduced compared to when there is no electrode 80. Furthermore, in this case, the graphene layer 40 becomes flat, and therefore the carrier mobility in the graphene layer 40 is improved.

[0070] 7, the graphene layer 40 may face the substrate 10 with a gap 21 interposed therebetween. That is, the insulating film 20 below the graphene layer 40 may be removed by, for example, etching. In this case, carriers flowing through the graphene layer 40 are not scattered by the underlying insulating film 20, and the carrier mobility and extraction efficiency are improved, thereby further improving the detection sensitivity for electromagnetic waves.

[0071] 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.

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

[0073] Fig. 8 is a cross-section of the electromagnetic wave detector 100B. Note that Fig. 8 shows a cross-section at a position corresponding to II-II in Fig. 1. As shown in Fig. 8, the electromagnetic wave detector 100B has a substrate 10, an insulating film 20, an electrode 30, a graphene layer 40, an insulating film 50, an electrode 60, and a thermoelectric material layer 70. In this respect, the configuration of the electromagnetic wave detector 100B is common to the configuration of the electromagnetic wave detector 100A.

[0074] The electromagnetic wave detector 100B further includes an electrode 80. In the electromagnetic wave detector 100B, the semiconductor layer 11 is configured separately from the substrate 10. In the electromagnetic wave detector 100B, the semiconductor layer 11 is disposed on an insulating film 20. In the electromagnetic wave detector 100B, one end of the graphene layer 40 is disposed on the electrode 80 (surface 80a), and the other end of the graphene layer 40 is disposed on the semiconductor layer 11. The graphene layer 40 is Schottky-junctioned to the semiconductor layer 11. In the electromagnetic wave detector 100B, the electrode 30 is disposed on the semiconductor layer 11 so as to protrude from the insulating film 50. In the electromagnetic wave detector 100B, a power supply 110 is connected between the electrode 60 and the electrode 80. In these respects, the configuration of the electromagnetic wave detector 100B differs from the configuration of the electromagnetic wave detector 100A.

[0075] (Effect of Electromagnetic Wave Detector 100B) The effects of the electromagnetic wave detector 100B will be described below.

[0076] In the electromagnetic wave detector 100B, the Schottky junction between the semiconductor layer 11 and the graphene layer 40 is closer to the thermoelectric material layer 70 than in the electromagnetic wave detector 100A. Therefore, heat generated in the thermoelectric material layer 70 is more easily transferred to the vicinity of the Schottky junction, making it easier to generate a thermal gate effect, thereby further improving the detection sensitivity to electromagnetic waves. Furthermore, different materials can be used for the substrate 10 and the semiconductor layer 11, making it possible to use a substrate 10 made of any material.

[0077] (Modification 1 and Modification 2) FIG. 9 is a cross-sectional view of an electromagnetic wave detector 100B according to Modification 1. FIG. 10 is a cross-sectional view of an electromagnetic wave detector 100B according to Modification 2. FIGS. 9 and 10 show cross sections taken along the line II-II in FIG. 1 . As shown in FIGS. 9 and 10 , the electrode 80 is disposed on the insulating film 20. The semiconductor layer 11 is disposed on the electrode 30, and the electrode 30 is disposed on the insulating film 20. The thermoelectric material layer 70 is disposed on the insulating film 20 such that its side surfaces 70a and 70b are connected to the electrode 80 and the electrode 30, respectively. The graphene layer 40 is disposed on the insulating film 50 such that it is connected to the electrode 60 and the semiconductor layer 11. In this case, the graphene layer 40 is formed after the semiconductor layer 11 and the electrode 60 are formed, thereby reducing process damage to the graphene layer 40.

[0078] 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.

[0079] (Configuration of electromagnetic wave detector 100C) The configuration of the electromagnetic wave detector 100C will be described below.

[0080] Fig. 11 is a cross-section of the electromagnetic wave detector 100C. Note that Fig. 11 shows a cross-section at a position corresponding to II-II in Fig. 1. As shown in Fig. 11, the electromagnetic wave detector 100C has a substrate 10, an insulating film 20, an electrode 30, a graphene layer 40, an insulating film 50, an electrode 60, and a thermoelectric material layer 70. In this respect, the configuration of the electromagnetic wave detector 100C is common to the configuration of the electromagnetic wave detector 100A.

[0081] In the electromagnetic wave detector 100C, the substrate 10 has a protrusion 10c on a surface 10a. The top surface of the protrusion 10c and the surface 20a may be flat. In the electromagnetic wave detector 100C, one end of the graphene layer 40 is on the protrusion 10c (connected to the protrusion 10c), and the other end of the graphene layer 40 is connected to the electrode 30. More specifically, the side surface 40a is connected to the electrode 30.

[0082] In the electromagnetic wave detector 100C, the insulating film 50 is a two-dimensional insulating film. The insulating film 50 is made of, for example, hexagonal boron nitride (h-BN). In the electromagnetic wave detector 100C, the insulating film 50 may have a thickness that allows a tunneling current to flow between the graphene layer 40 and the thermoelectric material layer 70, or may have a thickness that prevents a tunneling current from flowing between the graphene layer 40 and the thermoelectric material layer 70. The positions of the side surfaces 40a, 50a, and 70b may be aligned with one another. In these respects, the configuration of the electromagnetic wave detector 100C differs from the configuration of the electromagnetic wave detector 100A.

[0083] (Effect of Electromagnetic Wave Detector 100C) The effects of the electromagnetic wave detector 100C will be described below.

[0084] In the electromagnetic wave detector 100C, the insulating film 50 is a two-dimensional insulating film, and therefore the insulating film 50 and the graphene layer 40 are lattice-matched. This improves the carrier mobility in the graphene layer 40. Furthermore, since the insulating film 50 is a two-dimensional insulating film, it is possible to form the insulating film 50 thin, which further strengthens the optical gate effect and the thermal gate effect, thereby further improving the detection sensitivity for electromagnetic waves. Note that, when the thickness of the two-dimensional insulating film forming the insulating film 50 is such that a tunneling current flows, carriers generated in the thermoelectric material layer 70 are tunnel-injected into the graphene layer 40 via the insulating film 50, which also changes the Fermi level of the graphene layer 40.

[0085] When the positions of the side surfaces 40a and 50a are aligned, the graphene layer 40 and the insulating film 50 can be transferred in a stacked state after the electrode 30 is formed, which reduces process damage and makes it easy to obtain edge contact between the graphene layer 40 and the electrode 30.

[0086] (Variation 1) Fig. 12 is a cross-sectional view of an electromagnetic wave detector 100C according to Modification 1. Note that Fig. 12 shows a cross section at a position corresponding to II-II in Fig. 1. As shown in Fig. 12, the other end of the graphene layer 40 may be disposed on the electrode 30. Furthermore, the thermoelectric material layer 70 is disposed on the insulating film 50 so that one end is disposed on the electrode 60 and the other end is disposed on the electrode 30.

[0087] In this case, the graphene layer 40 and the insulating film 50 are transferred after the electrode 30 is formed, and then the electrode 60 is formed and the thermoelectric material layer 70 is transferred. As a result, the graphene layer 40 is covered with the insulating film 50 when the electrode 60 is formed, and no step for forming the electrode is performed after the thermoelectric material layer 70 is transferred. Therefore, in this case, process damage to the graphene layer 40 and the thermoelectric material layer 70 can be reduced.

[0088] (Variation 2) 13 is a cross-sectional view of an electromagnetic wave detector 100C according to Modification 2. Note that Fig. 13 shows a cross section taken along a line corresponding to II-II in Fig. 1. As shown in Fig. 13, the electromagnetic wave detector 100C does not necessarily have the electrode 30. In this case, the thermoelectric material layer 70 is disposed on the insulating film 50 such that the other end of the thermoelectric material layer 70 is disposed on the other end of the graphene layer 40.

[0089] In this case, the other end of the thermoelectric material layer 70 forms a Vendel-Waals heterojunction with the other end of the graphene layer 40, causing an optical switch effect in which the Fermi level of the graphene layer 40 is modulated, changing the barrier between the graphene layer 40 and the thermoelectric material layer 70 and generating a large current. In addition, in this case, the graphene layer 40 is covered with the insulating film 50 when the electrode 60 is formed, and therefore no step for forming an electrode is performed after the thermoelectric material layer 70 is transferred, thereby reducing process damage to the graphene layer 40 and the thermoelectric material layer 70.

[0090] (Variation 3) FIG. 14 is a cross-sectional view of an electromagnetic wave detector 100C according to Modification 3. Note that FIG. 14 shows a cross section at a position corresponding to II-II in FIG. 1. As shown in FIG. 14, the electrode 60 may be disposed on the insulating film 20. Alternatively, the positions of the side surfaces 40a, 50a, and 70b may be aligned with one another, and the side surfaces 40a, 50a, and 70b may be in contact with the electrode 30. Furthermore, the side surface 70a may be in contact with the electrode 60. In this case, the stacked graphene layer 40, insulating film 50, and thermoelectric material layer 70 are transferred collectively. This reduces process damage caused by the transfer process of each layer.

[0091] (Variation 4) FIG. 15 is a cross-sectional view of an electromagnetic wave detector 100C according to Modification 4. Note that FIG. 15 shows a cross section taken along a line II-II in FIG. 1. As shown in FIG. 15, the electromagnetic wave detector 100C may have 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 graphene layer 40 and the insulating film 20. The insulating film 91 covers the thermoelectric material layer 70. In this example, the electrode 60 may also be disposed on the insulating film 20.

[0092] In this case, when the insulating film 90 is interposed between the graphene layer 40 and the insulating film 20 and the thermoelectric material layer 70 is covered with the insulating film 91, the graphene layer 40 and the thermoelectric material layer 70 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. Furthermore, in this case, after the electrodes 30 and 60 are formed, the laminated insulating film 90, graphene layer 40, insulating film 50, thermoelectric material layer 70, and insulating film 91 are transferred all at once, eliminating the need for a step of forming electrodes after this transfer, and reducing process damage.

[0093] (Variation 5) Although the example in which the insulating film 50 is a two-dimensional insulating film has been described above, the insulating film 50 may be an insulating film other than a two-dimensional insulating film. Furthermore, although the example in which the protrusions 10c are formed on the substrate 10 has been described above, the protrusions 10c may not be formed on the substrate 10. In this case, the graphene layer 40 is electrically connected to the substrate 10 by an appropriate method.

[0094] 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 and electromagnetic wave detector 100B will be mainly described, and overlapping descriptions will not be repeated.

[0095] (Configuration of the electromagnetic wave detector 100D) The configuration of the electromagnetic wave detector 100D will be described below.

[0096] Fig. 16 is a cross-sectional view of the electromagnetic wave detector 100D. Fig. 16 shows a cross-section taken along the same line as II-II in Fig. 1. Fig. 17 is a cross-sectional view of the laminate 120A. Fig. 18 is a cross-sectional view of the laminate 120B. As shown in Figs. 16 to 18, the electromagnetic wave detector 100D has a laminate 120A and a laminate 120B.

[0097] The laminate 120A has a base material 10 (semiconductor layer 11), an insulating film 20, an electrode 30, a graphene layer 40, and an insulating film 50. That is, the configuration of the laminate 120A is similar to the configuration of the electromagnetic wave detector 100A, except that the laminate 120A does not have the electrode 60 and does not have the thermoelectric material layer 70. Furthermore, the laminate 120B has a base material 10, an insulating film 20, an electrode 30, an insulating film 50, a thermoelectric material layer 70, and an electrode 80. In the laminate 120B, the electrode 80 is disposed on the base material 10. That is, the configuration of the laminate 120B is similar to the configuration of the electromagnetic wave detector 100B (see FIG. 9 ) according to Modification 1, except that the laminate 120B does not have the electrode 60, does not have the graphene layer 40, and the electrode 80 is disposed on the base material 10.

[0098] The electromagnetic wave detector 100D is formed by hybrid bonding of the laminate 120A and the laminate 120B. That is, in the electromagnetic wave detector 100D, the electrodes 30 of the laminate 120A and the electrodes 30 of the laminate 120B face each other, and the graphene layer 40 of the laminate 120A and the thermoelectric material layer 70 of the laminate 120B face each other with the insulating film 50 of the laminate 120A and the insulating film 50 of the laminate 120B interposed therebetween. The bond between the electrode 30 of the laminate 120A and the electrode 30 of the laminate 120B is preferably a bond between the same metal materials. For example, the electrode 30 of the laminate 120A and the electrode 30 of the laminate 120B are made of copper, and the bond between the electrode 30 of the laminate 120A and the electrode 30 of the laminate 120B is a Cu-Cu bond.

[0099] In the electromagnetic wave detector 100D, a power supply 110 is connected to the base material 10 (semiconductor layer 11) of the laminate 120A and the electrode 80 of the laminate 120B, thereby reading out a signal.

[0100] (Modification 1 and Modification 2) FIG. 19 is a cross-sectional view of an electromagnetic wave detector 100D according to Modification 1. FIG. 20 is a cross-sectional view of an electromagnetic wave detector 100D according to Modification 2. As shown in FIG. 19, the substrate 10 of the laminate 120B may be made thinner than the substrate 10 of the laminate 120A, for example, by being ground. Also, as shown in FIG. 20, the substrate 10 of the laminate 120B may be removed, for example, by being ground. Note that the substrate 10 of the laminate 120B is ground after hybrid bonding is performed between the laminate 120A and the laminate 120B, for example.

[0101] (Variation 3) FIG. 21 is a cross-sectional view of an electromagnetic wave detector 100D according to Modification 3. FIG. 22 is a cross-sectional view of a laminate 120A in the electromagnetic wave detector 100D according to Modification 3. FIG. 23 is a cross-sectional view of a laminate 120B in the electromagnetic wave detector 100D according to Modification 3. As shown in FIGS. 21 to 23, in the laminate 120A, the graphene layer 40 may be in edge contact with the electrode 30, and in the laminate 120B, the thermoelectric material layer 70 may be in edge contact with the electrode 30. In this case, first, the graphene layer 40 (thermoelectric material layer 70) is formed. Second, a protective film is formed on the graphene layer 40 (thermoelectric material layer 70). Third, an opening is formed by etching the graphene layer 40 (thermoelectric material layer 70) using the protective film as a mask. Fourth, an electrode 30 is formed in the opening, thereby achieving edge contact between the graphene layer 40 (thermoelectric material layer 70) and the electrode 30.

[0102] (Effect of the 100D electromagnetic wave detector) The effects of the electromagnetic wave detector 100D will be described below.

[0103] In the electromagnetic wave detector 100D, the laminate 120A has the graphene layer 40, and the laminate 120B has the thermoelectric material layer 70, so that the graphene layer 40 and the thermoelectric material layer 70 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 100D, it is possible to reduce the heat resistance temperature of the process and damage to previously formed layers.

[0104] 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 thermoelectric material layer 70. Furthermore, when the graphene layer 40 and the thermoelectric material layer 70 are in edge contact with the electrode 30, the contact resistance between the electrode 30 and the graphene layer 40 and the thermoelectric material layer 70 is reduced, improving the current extraction efficiency. Furthermore, in this case, the bonding area of ​​the electrode 30 is increased, thereby improving the precision of the hybrid bonding.

[0105] [Note] Aspects of the present disclosure are summarized in the appendix.

[0106] <Appendix 1> a graphene layer; a thermoelectric material layer; a semiconductor layer; the graphene layer, the thermoelectric material layer, and the semiconductor layer are electrically connected in series; an electromagnetic wave detector, wherein a Schottky junction is present between the graphene layer and the semiconductor layer;

[0107] <Appendix 2> 2. The electromagnetic wave detector of claim 1, wherein the thermoelectric material layer is a multilayer graphene layer.

[0108] <Appendix 3> Further comprising a first insulating film; 3. The electromagnetic wave detector according to claim 2, wherein the thermoelectric material layer and the graphene layer are disposed opposite each other with the first insulating film interposed therebetween.

[0109] <Appendix 4> a substrate forming the semiconductor layer; a second insulating film; the second insulating film is disposed on the substrate; the graphene layer is disposed on the second insulating film; the graphene layer has a first end and a second end; the first end contacts the substrate; the second end is electrically connected to the thermoelectric material layer; the first insulating film covers the graphene layer; 4. The electromagnetic wave detector according to claim 3, wherein the thermoelectric material layer is disposed on the first insulating film.

[0110] <Appendix 5> Further comprising a first electrode; the first electrode is disposed on the second insulating film, 5. The electromagnetic wave detector according to claim 4, wherein the second end and the thermoelectric material layer are connected with the first electrode interposed therebetween.

[0111] <Appendix 6> the graphene layer has a first side at the second end; the thermoelectric material layer has a third end and a fourth end; the thermoelectric material layer has a second side at the fourth end; 6. The electromagnetic wave detector of claim 5, wherein the first side surface and the second side surface are in contact with the first electrode.

[0112] <Appendix 7> Further comprising a second electrode; the second electrode is disposed on the first insulating film, the thermoelectric material layer has a third side at the third end; 7. The electromagnetic wave detector of claim 6, wherein the third side surface is in contact with the second electrode.

[0113] <Appendix 8> the first insulating film has a fourth side surface in contact with the first electrode; 8. The electromagnetic wave detector according to claim 7, wherein the first side surface, the second side surface, and the fourth side surface form a single flat surface.

[0114] <Appendix 9> a side surface of the first electrode in contact with the second side surface is inclined so that an upper end thereof protrudes more than a lower end thereof; 9. The electromagnetic wave detector according to claim 8, wherein a side surface of the second electrode in contact with the third side surface is inclined so that an upper end protrudes more than a lower end.

[0115] <Appendix 10> a substrate forming the semiconductor layer; A second insulating film; a buffer layer; the second insulating film is disposed on the substrate; the graphene layer is disposed on the second insulating film; the graphene layer has a first end and a second end; the first end is in contact with the substrate with the buffer layer interposed therebetween; a tunneling current flows between the first end and the substrate; the second end is connected to the thermoelectric material layer; the first insulating film covers the graphene layer; 4. The electromagnetic wave detector according to claim 3, wherein the thermoelectric material layer is disposed on the first insulating film.

[0116] <Appendix 11> a substrate forming the semiconductor layer; A second insulating film; a third electrode; the second insulating film and the third electrode are disposed on the substrate; the graphene layer has a first end and a second end; the first end is connected to the third electrode; the second end is connected to the thermoelectric material layer; the first insulating film covers the graphene layer; 4. The electromagnetic wave detector according to claim 3, wherein the thermoelectric material layer is disposed on the first insulating film.

[0117] <Appendix 12> 12. The electromagnetic wave detector according to claim 11, wherein the graphene layer is disposed opposite the substrate with a gap therebetween.

[0118] <Appendix 13> A substrate; A second insulating film; A first electrode; a third electrode; the second insulating film and the third electrode are disposed on the substrate; the semiconductor layer is disposed on the second insulating film, the graphene layer has a first end and a second end, and is disposed on the second insulating film such that the first end and the second end are connected to the third electrode and the semiconductor layer, respectively; the first electrode is disposed on the semiconductor layer; the first insulating film covers the graphene layer; 4. The electromagnetic wave detector according to claim 3, wherein the thermoelectric material layer is disposed on the first insulating film and connected to the first electrode.

[0119] <Appendix 14> A second insulating film; A first electrode; a third electrode; the first electrode and the third electrode are disposed on the second insulating film; the thermoelectric material layer has a third end and a fourth end, and is disposed on the second insulating film such that the third end and the fourth end are connected to the third electrode and the first electrode, respectively; the semiconductor layer is disposed on the first electrode; the first insulating film covers the thermoelectric material layer; 4. The electromagnetic wave detector according to claim 3, wherein the graphene layer is disposed on the first insulating film and connected to the semiconductor layer.

[0120] <Appendix 15> 4. The electromagnetic wave detector according to claim 3, wherein the first insulating film is a two-dimensional insulating film.

[0121] <Appendix 16> a substrate forming the semiconductor layer; a second insulating film; the substrate has a surface; the substrate has protrusions on the surface; the second insulating film is disposed on the surface; the graphene layer is disposed on the protrusion and the second insulating film; the graphene layer has a first end and a second end; the first end is connected to the protrusion; the second end is electrically connected to the thermoelectric material layer; 16. The electromagnetic wave detector according to claim 3 or 15, wherein the first insulating film covers the graphene layer.

[0122] <Appendix 17> Further comprising a first electrode; the first electrode is disposed on the second insulating film, 17. The electromagnetic wave detector of claim 16, wherein the second end is connected to the thermoelectric material layer with the first electrode interposed therebetween.

[0123] <Appendix 18> the graphene layer has a first side at the second end; the thermoelectric material layer has a third end and a fourth end; the thermoelectric material layer has a second side at the fourth end; 18. The electromagnetic wave detector of claim 17, wherein the first side surface and the second side surface are in contact with the first electrode.

[0124] <Appendix 19> the first insulating film has a fourth side surface in contact with the first electrode; 19. The electromagnetic wave detector according to claim 18, wherein the first side surface, the second side surface, and the fourth side surface form a single flat surface.

[0125] <Appendix 20> Further comprising a second electrode; the thermoelectric material layer has a third side at the third end; 19. The electromagnetic wave detector of claim 18, wherein the third side surface is in contact with the second electrode.

[0126] <Appendix 21> 21. The electromagnetic wave detector according to claim 20, wherein the second electrode is disposed on the first insulating film or the second insulating film.

[0127] <Appendix 22> A second electrode; A third insulating film; a fourth insulating film; the second electrode is disposed on the first insulating film, the third insulating film is interposed between the graphene layer and the protrusion and between the graphene layer and the second insulating film; 18. The electromagnetic wave detector according to claim 17, wherein the fourth insulating film covers the thermoelectric material layer, the first electrode, and the second electrode.

[0128] <Appendix 23> A first laminate; a second laminate, each of the first stacked body and the second stacked body has a first electrode; the first stacked body includes the semiconductor layer and the graphene layer electrically connected to the first electrode, the second stack has the thermoelectric material layer electrically connected to the first electrode; An electromagnetic wave detector as described in Appendix 1, wherein the first stack and the second stack are stacked so that the first electrode of the first stack and the first electrode of the second stack face each other.

[0129] 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]

[0130] 10 substrate, 10a front surface, 10b rear surface, 10c protrusion, 11 semiconductor layer, 12 buffer layer, 20 insulating film, 20a front surface, 21 void, 30 electrode, 40 graphene layer, 40a side surface, 50 insulating film, 50a side surface, 60 electrode, 70 thermoelectric material layer, 70a, 70b side surface, 80 electrode, 80a front surface, 90, 91 insulating film, 100A, 100B, 100C electromagnetic wave detector, 110 power supply, 120A, 120B laminate.

Claims

1. a graphene layer; a thermoelectric material layer; a semiconductor layer; the graphene layer, the thermoelectric material layer, and the semiconductor layer are electrically connected in series; a Schottky junction between the graphene layer and the semiconductor layer; The thermoelectric material layer and the graphene layer are disposed opposite each other.

2. Further comprising a first insulating film; The electromagnetic wave detector according to claim 1 , wherein the thermoelectric material layer and the graphene layer are disposed opposite to each other with the first insulating film interposed therebetween.

3. The electromagnetic wave detector according to claim 1 , wherein the thermoelectric material layer is a multi-layer graphene layer.

4. a substrate forming the semiconductor layer; a second insulating film; the second insulating film is disposed on the substrate; the graphene layer is disposed on the second insulating film; the graphene layer has a first end and a second end; the first end contacts the substrate; the second end is electrically connected to the thermoelectric material layer; the first insulating film covers the graphene layer; The electromagnetic wave detector according to claim 2 , wherein the thermoelectric material layer is disposed on the first insulating film.

5. Further comprising a first electrode; the first electrode is disposed on the second insulating film, The electromagnetic wave detector according to claim 4 , wherein the second end and the thermoelectric material layer are connected with the first electrode interposed therebetween.

6. the graphene layer has a first side at the second end; the thermoelectric material layer has a third end and a fourth end; the thermoelectric material layer has a second side at the fourth end; The electromagnetic wave detector according to claim 5 , wherein the first side surface and the second side surface are in contact with the first electrode.

7. Further comprising a second electrode; the second electrode is disposed on the first insulating film, the thermoelectric material layer has a third side at the third end; The electromagnetic wave detector according to claim 6 , wherein the third side surface is in contact with the second electrode.

8. the first insulating film has a fourth side surface in contact with the first electrode; The electromagnetic wave detector according to claim 7 , wherein the first side surface, the second side surface, and the fourth side surface form a single flat surface.

9. a side surface of the first electrode in contact with the second side surface is inclined so that an upper end thereof protrudes more than a lower end thereof; The electromagnetic wave detector according to claim 8 , wherein the side surface of the second electrode in contact with the third side surface is inclined so that an upper end thereof protrudes more than a lower end thereof.

10. a substrate forming the semiconductor layer; A second insulating film; a buffer layer; the second insulating film is disposed on the substrate; the graphene layer is disposed on the second insulating film; the graphene layer has a first end and a second end; the first end is in contact with the substrate with the buffer layer interposed therebetween; a tunneling current flows between the first end and the substrate; the second end is connected to the thermoelectric material layer; the first insulating film covers the graphene layer; The electromagnetic wave detector according to claim 2 , wherein the thermoelectric material layer is disposed on the first insulating film.

11. a substrate forming the semiconductor layer; A second insulating film; a third electrode; the second insulating film and the third electrode are disposed on the substrate; the graphene layer has a first end and a second end; the first end is connected to the third electrode; the second end is connected to the thermoelectric material layer; the first insulating film covers the graphene layer; The electromagnetic wave detector according to claim 2 , wherein the thermoelectric material layer is disposed on the first insulating film.

12. The electromagnetic wave detector according to claim 11 , wherein the graphene layer is disposed opposite the substrate with a gap therebetween.

13. A substrate; A second insulating film; A first electrode; a third electrode; the second insulating film and the third electrode are disposed on the substrate; the semiconductor layer is disposed on the second insulating film, the graphene layer has a first end and a second end, and is disposed on the second insulating film such that the first end and the second end are connected to the third electrode and the semiconductor layer, respectively; the first electrode is disposed on the semiconductor layer; the first insulating film covers the graphene layer; The electromagnetic wave detector according to claim 2 , wherein the thermoelectric material layer is disposed on the first insulating film and connected to the first electrode.

14. A second insulating film; A first electrode; a third electrode; the first electrode and the third electrode are disposed on the second insulating film; the thermoelectric material layer has a third end and a fourth end, and is disposed on the second insulating film such that the third end and the fourth end are connected to the third electrode and the first electrode, respectively; the semiconductor layer is disposed on the first electrode; the first insulating film covers the thermoelectric material layer; The electromagnetic wave detector according to claim 2 , wherein the graphene layer is disposed on the first insulating film and connected to the semiconductor layer.

15. The electromagnetic wave detector according to claim 2 , wherein the first insulating film is a two-dimensional insulating film.

16. a substrate forming the semiconductor layer; a second insulating film; the substrate has a surface; the substrate has protrusions on the surface; the second insulating film is disposed on the surface; the graphene layer is disposed on the protrusion and the second insulating film; the graphene layer has a first end and a second end; the first end is connected to the protrusion; the second end is electrically connected to the thermoelectric material layer; The electromagnetic wave detector according to claim 2 or 15, wherein the first insulating film covers the graphene layer.

17. Further comprising a first electrode; the first electrode is disposed on the second insulating film, The electromagnetic wave detector according to claim 16 , wherein the second end is connected to the thermoelectric material layer with the first electrode interposed therebetween.

18. the graphene layer has a first side at the second end; the thermoelectric material layer has a third end and a fourth end; the thermoelectric material layer has a second side at the fourth end; The electromagnetic wave detector according to claim 17 , wherein the first side surface and the second side surface are in contact with the first electrode.

19. the first insulating film has a fourth side surface in contact with the first electrode; The electromagnetic wave detector according to claim 18 , wherein the first side surface, the second side surface, and the fourth side surface form a single flat surface.

20. Further comprising a second electrode; the thermoelectric material layer has a third side at the third end; The electromagnetic wave detector of claim 18 , wherein the third side surface is in contact with the second electrode.

21. The electromagnetic wave detector according to claim 20 , wherein the second electrode is disposed on the first insulating film or the second insulating film.

22. A second electrode; A third insulating film; a fourth insulating film; the second electrode is disposed on the first insulating film, the third insulating film is interposed between the graphene layer and the protrusion and between the graphene layer and the second insulating film; The electromagnetic wave detector according to claim 17 , wherein the fourth insulating film covers the thermoelectric material layer, the first electrode, and the second electrode.

23. A first laminate; a second laminate, each of the first stacked body and the second stacked body includes a first electrode; the first stacked body includes the semiconductor layer and the graphene layer electrically connected to the first electrode, the second stack has the thermoelectric material layer electrically connected to the first electrode; The electromagnetic wave detector according to claim 1 , wherein the first stack and the second stack are stacked such that the first electrode of the first stack and the first electrode of the second stack face each other.

Images