Electromagnetic wave detector and electromagnetic wave detector array

Abstract

An electromagnetic wave detector (100) comprises a light-receiving element (40). The light-receiving element has a first semiconductor layer (41) and a second semiconductor layer (42). A third surface (41B) of the first semiconductor layer and a fourth surface (42B) of the second semiconductor layer are laminated so as to overlap each other. The electromagnetic wave detector also comprises: a first two-dimensional material layer (11) that extends from above a first opening (31A) to above a first insulating layer (31); a first electrode (21) that is electrically connected to the first two-dimensional material layer without the first semiconductor layer being interposed therebetween; a second two-dimensional material layer (12) that extends from above a second opening (32A) to above a second insulating layer (32); and a second electrode (22) that is electrically connected to the second two-dimensional material layer without the second semiconductor layer being interposed therebetween.

Description

Electromagnetic wave detector and electromagnetic wave detector array

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to electromagnetic wave detectors and electromagnetic wave detector arrays.

[0002] Graphene, an example of a two-dimensional material layer with extremely high mobility, has been known as a material for the electromagnetic wave detection layer used in next-generation electromagnetic wave detectors. The absorption rate of graphene is low, at 2.3%. Therefore, methods for increasing the sensitivity of graphene-based electromagnetic wave detectors have been proposed. For example, U.S. Patent Application Publication No. 2015 / 0243826 (Patent Document 1) proposes a detector with the following structure. Specifically, the detector in Patent Document 1 includes two or more dielectric layers on an n-type semiconductor layer. A graphene layer is formed on the two dielectric layers and on a surface portion of the n-type semiconductor layer located between the two dielectric layers. The graphene layer and the n-type semiconductor layer form a Schottky junction. Source and drain electrodes connected to both ends of the graphene layer are disposed on the dielectric layer. The gate electrode is connected to the n-type semiconductor layer. When a voltage is applied between the gate electrode and the source or drain electrode, the Schottky junction enables OFF operation.

[0003] US Patent Application Publication No. 2015 / 0243826

[0004] However, when a voltage is applied between the gate electrode and the source or drain electrode, the sensitivity of the detector depends on the quantum efficiency of the semiconductor layer, which prevents sufficient amplification of photocarriers, making it difficult to increase the sensitivity of the detector.

[0005] In the present disclosure, a technique is proposed that increases the detection sensitivity compared to the above detector.

[0006] an insulating layer disposed on the first surface and having a first opening formed therein; a first two-dimensional material layer electrically connected to the first semiconductor layer at the first opening and extending from above the first opening onto the first insulating layer; a first electrode electrically connected to the first two-dimensional material layer without an intervening first semiconductor layer; a second semiconductor layer having a third surface and a fourth surface opposite the third surface; a second insulating layer disposed on the third surface and having a second opening formed therein; a second two-dimensional material layer electrically connected to the second semiconductor layer at the second opening and extending from above the second opening onto the second insulating layer; and a second electrode electrically connected to the second two-dimensional material layer without an intervening second semiconductor layer. The first semiconductor layer and the second semiconductor layer are stacked such that the second surface and the fourth surface overlap each other.

[0007] According to the present disclosure, detection sensitivity can be increased compared to the above detector.

[0008] 1 is a schematic cross-sectional view of an electromagnetic wave detector 100 according to a first embodiment. FIG. 2 is a schematic plan view of the electromagnetic wave detector 100 according to the first embodiment. FIG. 3 is a schematic bottom view of the electromagnetic wave detector 100 according to the first embodiment. FIG. 4 is a flowchart for explaining a method for manufacturing the electromagnetic wave detector according to the first embodiment. FIG. 5 is a schematic cross-sectional view of an electromagnetic wave detector 101 according to a second embodiment. FIG. 6 is a schematic cross-sectional view of an electromagnetic wave detector 102 according to a third embodiment. FIG. 7 is a schematic cross-sectional view of an electromagnetic wave detector 103 according to a fourth embodiment. FIG. 8 is a schematic cross-sectional view of an electromagnetic wave detector 104 according to a fifth embodiment. FIG. 9 is a schematic cross-sectional view of an electromagnetic wave detector 104 according to the fifth embodiment. FIG. 10 is a schematic cross-sectional view of a modified example of the electromagnetic wave detector 104 according to the fifth embodiment. FIG. 11 is a schematic cross-sectional view of an electromagnetic wave detector 105 according to a sixth embodiment. FIG. 12 is a schematic cross-sectional view of the electromagnetic wave detector 105 according to the sixth embodiment. FIG. 13 is a schematic plan view of an electromagnetic wave detector 106 according to a seventh embodiment. FIG. 14 is a schematic bottom view of the electromagnetic wave detector 106 according to the seventh embodiment. Fig. 10 is a schematic cross-sectional view of an electromagnetic wave detector 106 according to embodiment 7. Fig. 11 is a schematic cross-sectional view of an electromagnetic wave detector 107 according to embodiment 8. Fig. 12 is a schematic plan view for explaining an electromagnetic wave detector array according to embodiment 9. Fig. 13 is a schematic plan view showing a modified example of the electromagnetic wave detector array according to embodiment 9.

[0009] Hereinafter, embodiments will be described with reference to the drawings. In the following, the same or corresponding parts will be denoted by the same reference numerals, and overlapping descriptions will not be repeated.

[0010] 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 applies throughout the entire specification.

[0011] In the embodiments described below, the configuration of an electromagnetic wave detector that detects visible light or infrared light as electromagnetic waves is described, but the electromagnetic waves detected by the electromagnetic wave detector of the present disclosure are not limited to visible light and infrared light. The embodiments described below are also effective as detectors that detect 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 described below, these lights and radio waves are collectively referred to as electromagnetic waves.

[0012] In the following description, graphene is used as an example of the material of the two-dimensional material layer, but the material constituting the two-dimensional material layer is not limited to graphene. For example, transition metal dichalcogenides (TMDs), black phosphorus, silicene (a two-dimensional honeycomb structure of silicon atoms), germanene (a two-dimensional honeycomb structure of germanium atoms), and the like can be used as the material of the two-dimensional material layer. Examples of transition metal dichalcogenides include MoS, WS, and WSe.

[0013] These materials have a structure similar to that of graphene, and are capable of arranging atoms in a single layer in a two-dimensional plane. Therefore, when these materials are applied to a two-dimensional material layer, the same effects can be obtained as when graphene is applied to a two-dimensional material layer.

[0014] The two-dimensional material layer may be composed of two-dimensional materials arranged in a single layer (e.g., single-layer graphene). The two-dimensional material layer may be composed of two-dimensional materials arranged in multiple layers (e.g., multi-layer graphene). The latter two-dimensional material layer increases the photoelectric conversion efficiency and the sensitivity of the electromagnetic wave detector. Furthermore, a band gap is formed in the latter two-dimensional material layer. As a result, the latter two-dimensional material layer can be configured so that photoelectric conversion occurs in the two-dimensional material layer only when electromagnetic waves in a predetermined wavelength range are incident on the two-dimensional material layer. Furthermore, as the number of layers of secondary raw materials contained in the two-dimensional material layer increases, the carrier mobility in the channel region decreases, but the two-dimensional material layer becomes less susceptible to carrier scattering from underlying structures such as a substrate, resulting in a lower noise level. Therefore, an electromagnetic wave detector including a two-dimensional material layer including two-dimensional materials arranged in multiple layers can improve the detection sensitivity of electromagnetic waves. Among the multiple graphenes stacked on top of each other in the two-dimensional material layer, the directions of the hexagonal lattice vectors between any two layers of graphene may or may not be aligned with each other.

[0015] When the two-dimensional material layer is composed of multilayer graphene, the stacking orientation angle may be turbostratic rather than the AB stacking seen in natural graphite. Turbostratic stacking is also called random stacking or turbostratic graphene. The method for producing the turbostratic structure portion may be determined as appropriate. For example, a turbostratic structure portion may be formed by multiple transfers of single-layer graphene produced by CVD and stacking multilayer graphene. Alternatively, a turbostratic structure portion may be formed by disposing ethanol or methane as a carbon source on graphene and growing graphene by CVD. The stacking orientation angle may also 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 photodetector efficiency. Furthermore, a moiré potential can be formed depending on the stacking orientation angle, allowing selective detection of a specific wavelength range.

[0016] In the following, the terms p-type and n-type may be used for two-dimensional material layers. In the following embodiments, a two-dimensional material layer having more holes than a two-dimensional material layer in an intrinsic state is called p-type, and a two-dimensional material layer having more electrons than a two-dimensional material layer in an intrinsic state is called n-type. The two-dimensional material layer may be intrinsic, not doped with impurities, or may have p-type or n-type conductivity.

[0017] In the following, the terms n-type and p-type may be used to refer to materials of components in contact with the two-dimensional material layer. Here, for example, n-type materials refer to materials with electron-donating properties, and p-type materials refer to materials with electron-withdrawing properties. Furthermore, a material in which there is a bias in the charge throughout the molecule, with electrons predominating, may be referred to as n-type, and a material in which holes predominate may be referred to as p-type. These materials may be either organic or inorganic, or a mixture thereof.

[0018] Furthermore, when the two-dimensional material layer is in contact with an electrode, carriers are doped from the electrode into the two-dimensional material layer. For example, when gold (Au) is used as the electrode material, holes are doped into the two-dimensional material layer near the electrode due to the difference in work function between the two-dimensional material layer and Au. When the electromagnetic wave detector is operated in an electron conduction state in this state, the influence of the holes doped from the electrode into the two-dimensional material layer reduces the mobility of electrons flowing into the channel region of the two-dimensional material layer, increasing the contact resistance between the two-dimensional material layer and the electrode. This increase in contact resistance may reduce the mobility of electrons (carriers) due to the field effect in the electromagnetic wave detector, resulting in a deterioration in the performance of the electromagnetic wave detector. In particular, when the two-dimensional material layer is made of single-layer graphene, the amount of doped carriers injected from the electrode is greater than when the two-dimensional material layer is made of multilayer graphene. Therefore, the decrease in electron mobility in the electromagnetic wave detector is particularly significant when single-layer graphene is used as the two-dimensional material layer. Therefore, if the entire two-dimensional material layer is made of single-layer graphene, the performance of the electromagnetic wave detector may be degraded. Therefore, at least the contact area of ​​the secondary raw material layer with the electrode may be made of multi-layer graphene. Compared to single-layer graphene, multi-layer graphene reduces carrier doping from the electrode. Therefore, an increase in contact resistance between the two-dimensional material layer and the electrode can be suppressed. As a result, the aforementioned decrease in electron mobility in the electromagnetic wave detector can be suppressed, improving the performance of the electromagnetic wave detector.

[0019] The two-dimensional material layer may also include nanoribbon-shaped graphene (hereinafter also referred to as graphene nanoribbons). The two-dimensional material layer may be, for example, a single graphene nanoribbon, a composite in which multiple graphene nanoribbons are stacked, or a structure in which graphene nanoribbons are periodically arranged on a plane (e.g., a graphene metamaterial). In a two-dimensional material layer configured as a structure in which graphene nanoribbons are periodically arranged on a plane, plasmon resonance may occur. As a result, the sensitivity of the electromagnetic wave detector can be improved.

[0020] In this specification, the following plasmon resonance phenomena, such as surface plasmon resonance, which is an interaction between a metal surface and light, the phenomenon called pseudo-surface plasmon resonance, which means resonance on a metal surface outside the visible light and near-infrared light regions, and the phenomenon called metamaterial or plasmonic metamaterial, which means manipulating specific wavelengths using a structure with dimensions smaller than the wavelength, are not particularly distinguished by name, but are treated as equivalent in terms of the effects of the phenomena. In this specification, these resonances are referred to as surface plasmon resonance, plasmon resonance, or simply resonance.

[0021] In this specification, what is referred to as an insulating layer is an insulating film layer having a thickness that does not generate a tunnel current.

[0022] Embodiment 1 Fig. 1 is a cross-sectional schematic view of an electromagnetic wave detector 100 according to embodiment 1. Typical electrical connections of the electromagnetic wave detector 100 are also shown in Fig. 1. Fig. 2 is a plan schematic view of the electromagnetic wave detector 100 shown in Fig. 1. Fig. 3 is a bottom schematic view of the electromagnetic wave detector 100 shown in Fig. 1.

[0023] As shown in Figures 1 to 3, the electromagnetic wave detector 100 mainly comprises a first two-dimensional material layer 11, a first electrode 21, a second electrode 22, a first insulating layer 31, a second insulating layer 32, and a light receiving element 40.

[0024] The light-receiving element 40 has a first surface 41A and a second surface 42A located on the opposite side to the first surface 41A. The light-receiving element 40 includes a first semiconductor layer 41 having the first surface 41A and a second semiconductor layer 42 having the second surface 42A.

[0025] The first semiconductor layer 41 further has a third surface 41B located on the opposite side to the first surface 41A. The first two-dimensional material layer 11, the first electrode 21, and the first insulating layer 31 are disposed on the first surface 41A. Hereinafter, for each of the first two-dimensional material layer 11, the first electrode 21, and the first insulating layer 31, a portion located on the opposite side from the first semiconductor layer 41 will be referred to as an upper portion, and a portion located on the first semiconductor layer 41 side will be referred to as a lower portion. A viewpoint viewing the first surface 41A from a direction perpendicular to the first surface 41A or a viewpoint viewing the second surface 42A from a direction perpendicular to the second surface 42A will be referred to as a planar view.

[0026] The second semiconductor layer 42 further has a fourth surface 42B located on the opposite side to the second surface 42A. The second two-dimensional material layer 12, the second electrode 22, and the second insulating layer 32 are disposed on the second surface 42A. Hereinafter, for each of the second two-dimensional material layer 12, the second electrode 22, and the second insulating layer 32, a portion located on the opposite side from the second semiconductor layer 42 will be referred to as an upper portion, and a portion located on the second semiconductor layer 42 side will be referred to as a lower portion.

[0027] The first semiconductor layer 41 and the second semiconductor layer 42 are stacked such that the third surface 41B and the fourth surface 42B overlap each other. The third surface 41B faces the fourth surface 42B. For example, the entire surface of the third surface 41B overlaps the entire surface of the fourth surface 42B. It is sufficient that the third surface 41B overlaps at least a portion of the fourth surface 42B.

[0028] The light receiving element 40 is an element that is sensitive to electromagnetic waves of the detection wavelength of the electromagnetic wave detector 100 and performs photoelectric conversion when irradiated with electromagnetic waves of the detection wavelength.

[0029] The light receiving element 40 of the electromagnetic wave detector 100 includes a pn junction photodiode. The fourth surface 42B of the second semiconductor layer 42 is in contact with the third surface 41B of the first semiconductor layer 41. The first semiconductor layer 41 has a first conductivity type. The second semiconductor layer 42 has a second conductivity type different from the first conductivity type. For example, the first conductivity type of the first semiconductor layer 41 may be p-type, and the second conductivity type of the second semiconductor layer 42 may be n-type. The first conductivity type of the first semiconductor layer 41 may be n-type, and the second conductivity type of the second semiconductor layer 42 may be p-type. A pn ​​junction is formed at the interface between the third surface 41B of the first semiconductor layer 41 and the fourth surface 42B of the second semiconductor layer 42.

[0030] The light receiving element 40 may include a pin photodiode, a Schottky photodiode, an avalanche photodiode, or a phototransistor.

[0031] The materials constituting the first semiconductor layer 41 and the second semiconductor layer 42 can be selected arbitrarily depending on the detection wavelength of the electromagnetic wave detector 100. The material constituting the first semiconductor layer 41 may be the same as the material constituting the second semiconductor layer 42. The material constituting the first semiconductor layer 41 may be different from the material constituting the second semiconductor layer 42. In the latter case, the electromagnetic wave detector 100 can detect multiple wavelengths.

[0032] The material constituting the first semiconductor layer 41 and the second semiconductor layer 42 is, for example, Si, germanium (Ge), a compound semiconductor such as a III-V group or II-V group semiconductor, mercury cadmium telluride (HgCdTe), indium antimony (InSb), lead selenium (PbSe), lead sulfur (PbS), cadmium sulfur (CdS), gallium nitride (GaN), silicon carbide (SiC), gallium phosphide (GaP), indium gallium arsenide (InGaAs), indium arsenide (InAs), a substrate including a quantum well or quantum dots, a Type II superlattice, or a material selected from a group consisting of a single material or a combination thereof.

[0033] When the detection wavelength range of the electromagnetic wave detector 100 is 0.1 μm or more and 0.6 μm or less, the material constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 may contain GaP. When the detection wavelength range of the electromagnetic wave detector 100 is 0.2 μm or more and 1.1 μm or less, the material constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 may contain Si. When the detection wavelength range of the electromagnetic wave detector 100 is 0.8 μm or more and 1.8 μm or less, the material constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 may contain Ge. When the detection wavelength range of the electromagnetic wave detector 100 is 0.7 μm or more and 2.55 μm or less, the material constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 may contain InGaAs. When the detection wavelength range of the electromagnetic wave detector 100 is 1.0 μm or more and 3.1 μm or less, the material constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 may contain InAs. When the detection wavelength range of the electromagnetic wave detector 100 is 1.0 μm or more and 5.5 μm or less, the material constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 may contain InSb. When the detection wavelength range of the electromagnetic wave detector 100 is 2.0 μm or more and 16.0 μm or less, the material constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 may contain HgCdTe.

[0034] Preferably, the first semiconductor layer 41 and the second semiconductor layer 42 are each doped with impurities so that the electrical resistivity of each of the first semiconductor layer 41 and the second semiconductor layer 42 is 100 Ω cm or less. By doping each of the first semiconductor layer 41 and the second semiconductor layer 42 to a high concentration, the carrier movement speed (readout speed) in each of the first semiconductor layer 41 and the second semiconductor layer 42 increases. As a result, the response speed of the electromagnetic wave detector 100 improves.

[0035] The thickness of each of the first semiconductor layer 41 and the second semiconductor layer 42 is preferably 10 μm or less. By reducing the thickness of each of the first semiconductor layer 41 and the second semiconductor layer 42, the distance between the pn junction interface and the first two-dimensional material layer 11 and the second two-dimensional material layer 12 is shortened, and deactivation of photocarriers generated at the pn junction interface is reduced. As a result, the sensitivity of the electromagnetic wave detector can be increased.

[0036] The first insulating layer 31 is disposed on the first surface 41A of the first semiconductor layer 41. The lower surface of the first insulating layer 31 is in contact with the first surface 41A of the first semiconductor layer 41. The upper surface of the first insulating layer 31 is in contact with, for example, a third portion 11c of the first two-dimensional material layer 11 described below and the lower surface of each of the first electrodes 21. A first opening 31A is formed in the first insulating layer 31. The first opening 31A exposes a portion of the first surface 41A.

[0037] The second insulating layer 32 is disposed on the second surface 42A of the second semiconductor layer 42. The lower surface of the second insulating layer 32 is in contact with the second surface 42A of the second semiconductor layer 42. The upper surface of the second insulating layer 32 is in contact with, for example, a sixth portion 12c of the second two-dimensional material layer 12 described below and the lower surfaces of the second electrodes 22. A second opening 32A is formed in the second insulating layer 32. The second opening 32A exposes a portion of the second surface 42A.

[0038] The material constituting the first insulating layer 31 and the second insulating layer 32 may be any material having electrical insulation properties, including, for example, silicon oxide (SiO). The material constituting the first insulating layer 31 may include, for example, at least one selected from the group consisting of SiO, tetraethyl orthosilicate (Si(OCH)), silicon nitride (SiN), hafnium oxide (HfO), aluminum oxide (AlO), nickel oxide (NiO), boron nitride (BN) (boron nitride), and siloxane-based polymer materials. For example, the atomic arrangement of boron nitride is similar to that of graphene, so even when boron nitride comes into contact with a two-dimensional material layer made of graphene, it does not adversely affect charge mobility. Therefore, boron nitride is suitable as the material constituting the first insulating layer 31 and the second insulating layer 32 from the viewpoint of preventing the first insulating layer 31 and the second insulating layer 32 from impairing the performance of the first two-dimensional material layer 11 and the second two-dimensional material layer 12, such as electron mobility.

[0039] The thickness of the first insulating layer 31 is not particularly limited as long as no tunnel current is generated in the region of the first two-dimensional material layer 11 located on the first insulating layer 31 (a second portion 11b and a third portion 11c described later) and between the first electrode 21 and the first semiconductor layer 41. From the viewpoint of enhancing the optical gate effect described later and increasing the degree of electric field change generated in the first two-dimensional material layer 11, it is preferable that the thickness of the first insulating layer 31 be as thin as possible.

[0040] The thickness of the second insulating layer 32 is not particularly limited as long as no tunnel current is generated in the regions of the second two-dimensional material layer 12 located on the second insulating layer 32 (a fifth portion 12b and a sixth portion 12c described later) and between the second electrode 22 and the second semiconductor layer 42. From the viewpoint of enhancing the optical gate effect described later and increasing the degree of electric field change generated in the second two-dimensional material layer 12, it is preferable that the thickness of the second insulating layer 32 be as thin as possible.

[0041] The first electrode 21 is disposed on the upper surface of the first insulating layer 31. The first electrode 21 is formed, for example, in the lower part of the first two-dimensional material layer 11. The second electrode 22 is disposed on the upper surface of the second insulating layer 32. The second electrode 22 is formed, for example, in the lower part of the second two-dimensional material layer 12. The first electrode 21 may be formed on the upper part of the first two-dimensional material layer 11. The second electrode 22 may be formed on the upper part of the second two-dimensional material layer 12. The first electrode 21 is disposed so as to overlap with the second electrode 22 in, for example, a direction perpendicular to the first surface 41A. The first electrode 21 may be disposed so as not to overlap with the second electrode 22 in the direction perpendicular to the first surface 41A.

[0042] The material constituting the first electrode 21 and the second electrode 22 may be any conductive material, for example, at least one selected from the group consisting of gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), chromium (Cr), and palladium (Pd). Furthermore, an adhesion layer (not shown) may be formed between the first electrode 21 and the first insulating layer 31 and / or between the second electrode 22 and the second insulating layer 32 to enhance adhesion therebetween. The material constituting the adhesion layer is not particularly limited, but may include, for example, at least one of chromium (Cr) and titanium (Ti).

[0043] 2, the area of ​​the first electrode 21 is equal to or larger than, for example, the area of ​​the first opening 31A in a plan view. As shown in Fig. 3, the area of ​​the second electrode 22 is equal to or larger than, for example, the area of ​​the second opening 32A in a plan view.

[0044] 1 , a power supply circuit for applying a bias voltage V to the first two-dimensional material layer 11 and the second two-dimensional material layer 12 is electrically connected between the first electrode 21 and the second electrode 22 of the first set. The power supply circuit includes a voltage source PW and an ammeter IM. The voltage source PW applies the bias voltage V between the first electrode 21 and the second electrode 22. The ammeter IM detects a current I that flows when the bias voltage V is applied between the first electrode 21 and the second electrode 22.

[0045] The first two-dimensional material layer 11 is electrically connected to the first semiconductor layer 41 in the first opening 31A. The first two-dimensional material layer 11 extends from above the first opening 31A onto the first insulating layer 31.

[0046] The second two-dimensional material layer 12 is electrically connected to the second semiconductor layer 42 in the second opening 32A. The second two-dimensional material layer 12 extends from above the second opening 32A onto the second insulating layer 32.

[0047] The first two-dimensional material layer 11 has a first portion 11a electrically connected to the first semiconductor layer 41, a second portion 11b electrically connected to the first electrode 21, and a third portion 11c electrically connecting the first portion 11a and the second portion 11b. The second portion 11b and the third portion 11c are disposed on the first insulating layer 31. The third portion 11c is in contact with, for example, the upper surface of the first insulating layer 31. In the first two-dimensional material layer 11, the third portion 11c acts as a channel of the field-effect transistor. In the first two-dimensional material layer 11, the first portion 11a and the second portion 11b act as a source and a drain of the field-effect transistor. The upper surface of the first two-dimensional material layer 11 has unevenness due to, for example, the first electrode 21 and the first insulating layer 31.

[0048] The first portion 11a includes, for example, one end of the first two-dimensional material layer 11. The second portion 11b includes, for example, the other end of the first two-dimensional material layer 11. The one end of the first two-dimensional material layer 11 is in contact with, for example, an inner circumferential surface of the first opening 31A of the first insulating layer 31. Note that the first two-dimensional material layer 11 may further have a portion that is located on the opposite side of the first portion 11a from the third portion 11c, is disposed on the first insulating layer 31, and includes the one end of the first two-dimensional material layer 11.

[0049] The second two-dimensional material layer 12 has a fourth portion 12a electrically connected to the second semiconductor layer 42, a fifth portion 12b electrically connected to the second electrode 22, and a sixth portion 12c electrically connecting the fourth portion 12a and the fifth portion 12b. The second portion 11b and the third portion 11c of the first two-dimensional material layer 11 are disposed on the first insulating layer 31. The third portion 11c is in contact with, for example, the upper surface of the first insulating layer 31. In the second two-dimensional material layer 12, the sixth portion 12c acts as a channel of the field-effect transistor. In the second two-dimensional material layer 12, the fourth portion 12a and the fifth portion 12b act as a source and a drain of the field-effect transistor. The upper surface of the second two-dimensional material layer 12 has unevenness due to, for example, the second electrode 22 and the second insulating layer 32.

[0050] The fourth portion 12a includes, for example, one end of the second 2D material layer 12. The fifth portion 12b includes, for example, the other end of the second 2D material layer 12. The one end of the second 2D material layer 12 is in contact with, for example, the inner circumferential surface of the second opening 32A of the second insulating layer 32. Note that the second 2D material layer 12 may further have a portion that is located on the opposite side of the sixth portion 12c with respect to the fourth portion 12a, is disposed on the second insulating layer 32, and includes the one end of the second 2D material layer 12.

[0051] Each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 has sensitivity to electromagnetic waves of the detection wavelength and is configured to perform photoelectric conversion when electromagnetic waves of the detection wavelength are incident. At least one of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 may be configured to perform photoelectric conversion only when electromagnetic waves of the detection wavelength are incident.

[0052] The thicknesses of the first portion 11a, the second portion 11b, and the third portion 11c of the first two-dimensional material layer 11 are, for example, equal to each other. The thicknesses of the fourth portion 12a, the fifth portion 12b, and the sixth portion 12c of the second two-dimensional material layer 12 are, for example, equal to each other. The thicknesses of the first portion 11a, the second portion 11b, and the third portion 11c of the first two-dimensional material layer 11 are, for example, equal to the thicknesses of the fourth portion 12a, the fifth portion 12b, and the sixth portion 12c of the second two-dimensional material layer 12. The thicknesses of the first portion 11a, the second portion 11b, and the third portion 11c of the first two-dimensional material layer 11 may be different from each other. The thicknesses of the fourth portion 12a, the fifth portion 12b, and the sixth portion 12c of the second two-dimensional material layer 12 may be different from each other. The thickness of each of the first portion 11a, the second portion 11b, and the third portion 11c of the first two-dimensional material layer 11 may be different from the thickness of each of the fourth portion 12a, the fifth portion 12b, and the sixth portion 12c of the second two-dimensional material layer 12.

[0053] The electromagnetic wave detector 100 has symmetry with respect to, for example, the interface between the third surface 41B and the fourth surface 42B as the mirror plane. A portion located on the first semiconductor layer 41 side of the interface has a mirror-symmetric relationship with a portion located on the second semiconductor layer 42 side of the interface. In a plan view, the first portion 11a, the second portion 11b, and the third portion 11c of the first two-dimensional material layer 11 are arranged to overlap, for example, the fourth portion 12a, the fifth portion 12b, and the sixth portion 12c of the second two-dimensional material layer 12, respectively. In a plan view, the first opening 31A is arranged to overlap, for example, the second opening 32A. In a plan view, the first electrode 21 is arranged to overlap, for example, the second electrode 22.

[0054] Each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 has a conductivity type of, for example, p-type or n-type. The conductivity type of the first two-dimensional material layer 11 is different from the conductivity type of the first semiconductor layer 41, for example. If the conductivity type of the first semiconductor layer 41 is n-type, the conductivity type of the first two-dimensional material layer 11 is, for example, p-type. If the conductivity type of the first semiconductor layer 41 is p-type, the conductivity type of the first two-dimensional material layer 11 is, for example, n-type. Note that the conductivity type of the first two-dimensional material layer 11 may be the same as the conductivity type of the first semiconductor layer 41, for example. If the conductivity type of the first semiconductor layer 41 is n-type, the conductivity type of the first two-dimensional material layer 11 may be n-type. If the conductivity type of the first semiconductor layer 41 is p-type, the conductivity type of the first two-dimensional material layer 11 may be p-type. The conductivity type of the second two-dimensional material layer 12 may also be different from or the same as the conductivity type of the second semiconductor layer 42.

[0055] The conductivity type of the first 2D material layer 11 is, for example, the same as the conductivity type of the second 2D material layer 12. Note that the conductivity type of the first 2D material layer 11 may be different from the conductivity type of the second 2D material layer 12, for example.

[0056] The two-dimensional surface of the first two-dimensional material layer 11 is aligned with the top surface of the first two-dimensional material layer 11. The absolute value of the angle that the two-dimensional surface of the first two-dimensional material layer 11 forms with respect to the top surface of the first two-dimensional material layer 11 is equal to or greater than 0° and equal to or less than 10°. The two-dimensional surface of the first two-dimensional material layer 11 is, for example, parallel to the top surface of the first two-dimensional material layer 11.

[0057] The two-dimensional surface of the second two-dimensional material layer 12 is aligned with the top surface of the second two-dimensional material layer 12. The absolute value of the angle that the two-dimensional surface of the second two-dimensional material layer 12 forms with respect to the top surface of the second two-dimensional material layer 12 is equal to or greater than 0° and equal to or less than 10°. The two-dimensional surface of the second two-dimensional material layer 12 is, for example, parallel to the top surface of the second two-dimensional material layer 12.

[0058] The two-dimensional surface of the second two-dimensional material layer 12 extends along the two-dimensional surface of the first two-dimensional material layer 11. The two-dimensional surface of the second two-dimensional material layer 12 is, for example, parallel to the two-dimensional surface of the first two-dimensional material layer 11.

[0059] As described above, each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 may be composed of single-layer graphene or multi-layer graphene. At least one of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 may include a turbostratic structure portion.

[0060] <Method of Manufacturing Electromagnetic Wave Detector 100> Fig. 4 is a flowchart for explaining an example of a method of manufacturing the electromagnetic wave detector 100 according to embodiment 1. With reference to Fig. 4, an example of a method of manufacturing the electromagnetic wave detector 100 shown in Figs.

[0061] First, a step (S1) of preparing a second semiconductor layer 42 is performed. In this step (S1), the second semiconductor layer 42 is prepared as a flat substrate made of, for example, Si. A protective film may be formed on the surface of the second semiconductor layer 42.

[0062] Second, a step (S2) of forming a first semiconductor layer 41 is performed. In this step (S2), the first semiconductor layer 41 is formed on the second semiconductor layer 42. If a protective film is formed on the surface of the second semiconductor layer 42, the protective film is removed before the first semiconductor layer 41 is formed. The first semiconductor layer 41 may be formed by, for example, epitaxial growth. In this case, the first semiconductor layer 41 is formed on the fourth surface 42B of the second semiconductor layer 42. The first semiconductor layer 41 may be formed by doping impurities into the second semiconductor layer 42 by ion implantation or the like.

[0063] Third, a step (S3) of forming a first insulating layer 31 is performed. In this step (S3), the first insulating layer 31 is formed on the first semiconductor layer 41. The first insulating layer 31 may be formed by, for example, at least one of a chemical vapor deposition (CVD) method and a sputtering method. When the material constituting the first semiconductor layer 41 is Si, the first insulating layer 31 may be silicon oxide (SiO) formed by, for example, partially thermally oxidizing the first surface 41A of the first semiconductor layer 41.

[0064] Fourth, a step (S4) of forming a first electrode 21 is performed. In this step (S4), the first electrode 21 is formed on the first insulating layer 31. The material for forming the first electrode 21 is, for example, a metal such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), or chromium (Cr). At this time, in order to improve the adhesion between the first electrode 21 and the first insulating layer 31, an adhesion layer may be formed between the first insulating layer 31 and the first electrode 21. The material for forming the adhesion layer may be, for example, chromium (Cr) or titanium (Ti).

[0065] The first electrode 21 can be formed, for example, by the following process. First, a resist mask is formed on the surface of the first insulating layer 31 using photolithography, EB lithography, or the like. An opening is formed in the resist mask in the area where the first electrode 21 is to be formed. Then, a film of metal or the like that will become the first electrode 21 is formed on the resist mask. The film can be formed by evaporation, sputtering, or the like. At this time, the film is formed so as to extend from the inside of the opening in the resist mask to the upper surface of the resist mask. Then, the resist mask is removed together with a portion of the film, so that the other portion of the film that was located in the opening in the resist mask remains on the surface of the first insulating layer 31 and becomes the first electrode 21. The above-described method is generally called lift-off.

[0066] Other methods may be used to form the first electrode 21. For example, a film, such as a metal film, to become the first electrode 21 is first formed on the surface of the first insulating layer 31. Then, a resist mask is formed on the film by photolithography. The resist mask is formed so as to cover the region where the first electrode 21 is to be formed, while not being formed in regions other than the region where the first electrode 21 is to be formed. Then, the film is partially removed by wet etching or dry etching using the resist mask as a mask. As a result, a portion of the film remains under the resist mask. This portion of the film becomes the first electrode 21. Then, the resist mask is removed. In this manner, the first electrode 21 may be formed.

[0067] Fifth, a step (S5) of forming first openings 31A is performed. In this step (S5), first openings 31A are formed in first insulating layer 31. Specifically, a resist mask is formed on first insulating layer 31 using photolithography, EB lithography, or the like. An opening is formed in the resist mask in a region where first openings 31A in first insulating layer 31 are to be formed. Thereafter, first insulating layer 31 is partially removed by wet etching or dry etching using the resist mask as a mask, thereby forming first openings 31A. Next, the resist mask is removed. Note that step (S5) may be performed before step (S4).

[0068] Sixth, a step (S6) of forming a first two-dimensional material layer 11 is performed. In this step (S6), the first two-dimensional material layer 11 is formed so as to cover the entire portions of the first electrode 21, the first insulating layer 31, and the first semiconductor layer 41 exposed in the first opening 31A. The first two-dimensional material layer 11 may be formed by any method. For example, the first two-dimensional material layer 11 may be formed by epitaxial growth, or the first two-dimensional material layer 11 formed in advance using a CVD method may be transferred and attached onto portions of the first electrode 21, the first insulating layer 31, and the first semiconductor layer 41. Alternatively, the first two-dimensional material layer 11 may be formed using screen printing or the like. Alternatively, the first two-dimensional material layer 11 may be peeled off by mechanical peeling or the like and transferred onto the above-mentioned first electrode 21, etc. Next, a resist mask is formed on the first two-dimensional material layer 11 using photolithography or the like. The resist mask is formed so as to cover the areas where the first two-dimensional material layer 11 is to remain, while not being formed in the areas where the first two-dimensional material layer 11 is not to remain. Then, using the resist mask as a mask, the first two-dimensional material layer 11 is partially removed by etching with oxygen plasma. This removes unnecessary parts of the two-dimensional material layer, and forms the first two-dimensional material layer 11 as shown in FIGS. 1 to 3. Then, the resist mask is removed.

[0069] Seventh, a step (S7) of forming a second insulating layer 32 is performed. In this step (S7), the second insulating layer 32 is formed on the second semiconductor layer 42. The second insulating layer 32 may be formed by, for example, at least one of a CVD method and a sputtering method. When the material constituting the second semiconductor layer 42 is Si, the second insulating layer 32 may be, for example, SiO formed by partially thermally oxidizing the second surface 42A of the second semiconductor layer 42.

[0070] Eighth, a step (S8) of forming a second electrode 22 is performed. In this step (S8), the second electrode 22 is formed on the second insulating layer 32. The material constituting the first electrode 21 is, for example, a metal such as gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), or chromium (Cr). At this time, to improve adhesion between the first electrode 21 and the first insulating layer 31, an adhesion layer may be formed between the first insulating layer 31 and the first electrode 21. The material constituting the adhesion layer may be, for example, chromium (Cr) or titanium (Ti). The method of forming the second electrode 22 may be selected in the same manner as the method of forming the first electrode 21 described above.

[0071] Ninth, a step (S9) of forming a second opening 32A is performed. In this step (S9), the second opening 32A is formed in the second insulating layer 32. Specifically, a resist mask is formed on the second insulating layer 32 using photolithography, EB lithography, or the like. An opening is formed in the resist mask in a region where the second opening 32A in the second insulating layer 32 is to be formed. Thereafter, the second insulating layer 32 is partially removed by wet etching or dry etching using the resist mask as a mask, thereby forming the second opening 32A. Next, the resist mask is removed. Note that the above step (S9) may be performed before step (S8).

[0072] Tenth, a step (S10) of forming a second two-dimensional material layer 12 is performed. In this step (S10), the second two-dimensional material layer 12 is formed to cover the entire portions of the second electrode 22, the second insulating layer 32, and the second semiconductor layer 42 that are exposed in the second opening 32A. The second two-dimensional material layer 12 may be formed by any method. For example, the second two-dimensional material layer 12 may be formed by epitaxial growth, or the second two-dimensional material layer 12 that has been formed in advance using a CVD method may be transferred and attached onto portions of the second electrode 22, the second insulating layer 32, and the second semiconductor layer 42. Alternatively, the second two-dimensional material layer 12 may be formed using screen printing or the like. Alternatively, the second two-dimensional material layer 12 may be peeled off by mechanical peeling or the like and transferred onto the above-mentioned second electrode 22 or the like. Next, a resist mask is formed on the second two-dimensional material layer 12 using photolithography or the like. The resist mask is formed to cover the areas where the second two-dimensional material layer 12 is to remain, while not being formed in the areas where the second two-dimensional material layer 12 is not to remain. Then, using the resist mask as a mask, the second two-dimensional material layer 12 is partially removed by etching with oxygen plasma. This removes the unnecessary parts of the two-dimensional material layer, forming the second two-dimensional material layer 12 as shown in Figures 1 and 2. Then, the resist mask is removed.

[0073] The electromagnetic wave detector 100 shown in FIGS. 1 to 3 is obtained through the above steps (S1 to S10). In the above-described manufacturing method, the first two-dimensional material layer 11 is formed on the first electrode 21. However, the first two-dimensional material layer 11 may be formed in advance on the first insulating layer 31, and the first electrode 21 may be formed to overlap a portion of the first two-dimensional material layer 11. However, when using this structure, care must be taken not to cause process damage to the first two-dimensional material layer 11 when forming the first electrode 21. For example, it is possible to form the first electrode 21 after previously covering the first two-dimensional material layer 11 with a protective film or the like, except for the area where the first electrode 21 will be formed. The same applies to the second two-dimensional material layer.

[0074] <Operation Principle of Electromagnetic Wave Detector> Next, the operation principle of the electromagnetic wave detector according to this embodiment will be described.

[0075] 1 , a power supply circuit that applies a bias voltage V is electrically connected between the first electrode 21 and the second electrode 22. When the voltage V is applied between the first electrode 21 and the second electrode 22, a current I flows through the first two-dimensional material layer 11 and the second two-dimensional material layer 12. An ammeter IM included in the power supply circuit monitors the current I that flows through the first two-dimensional material layer 11 and the second two-dimensional material layer 12.

[0076] In the above state, when electromagnetic waves are irradiated onto the light-receiving element 40 consisting of the first semiconductor layer 41 and the second semiconductor layer 42, photoelectric conversion occurs at the pn junction of the light-receiving element 40, and a photocurrent flows through the first two-dimensional material layer 11 and the second two-dimensional material layer 12.

[0077] Furthermore, the light receiving element 40 applies an electric field change to the first two-dimensional material layer 11 via the first insulating layer 31, and further applies an electric field change to the second two-dimensional material layer 12 via the second insulating layer 32. As a result, a pseudo-gate voltage is applied to each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12, and the resistance values ​​of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 change. This is called the optical gating effect. The change in the resistance values ​​of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 changes the current I flowing through the first two-dimensional material layer 11 and the second two-dimensional material layer 12. By detecting this change in current I, the electromagnetic wave irradiated to the electromagnetic wave detector 100 can be detected.

[0078] Furthermore, for example, if the first semiconductor layer 41 constituting the light receiving element 40 is made of an n-type material and the second semiconductor layer 42 is made of a p-type material, the current I can be made zero by adjusting the voltage V and operating the light receiving element 40 in reverse bias. In other words, the electromagnetic wave detector 100 can be turned off. In this case, a current flows through the light receiving element 40 only when light is irradiated, and therefore the current I can be detected only when light is irradiated.

[0079] Here, the electromagnetic wave detector 100 is not limited to a configuration for detecting changes in current in the first two-dimensional material layer 11 and the second two-dimensional material layer 12 as described above, but may, for example, pass a constant current between the first electrode 21 and the second electrode 22 and detect changes in the voltage V between the first electrode 21 and the second electrode 22 (i.e., changes in the voltage value in the two-dimensional material layer).

[0080] Furthermore, two or more identical electromagnetic wave detectors may be used to detect electromagnetic waves. For example, two or more identical electromagnetic wave detectors are prepared. One electromagnetic wave detector is placed in a shielded space where electromagnetic waves are not irradiated. Another electromagnetic wave detector is 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 irradiated with the electromagnetic waves and the current I or voltage V of the electromagnetic wave detector placed in the shielded space is detected. Electromagnetic waves may be detected in this manner.

[0081] <Operation of Electromagnetic Wave Detector 100> Next, a specific operation of the electromagnetic wave detector 100 will be described. Here, a case where p-type silicon is used as the second semiconductor layer 42 and n-type silicon is used as the first semiconductor layer 41 will be described.

[0082] 1, when a reverse bias voltage is applied to the light receiving element 40, a depletion layer is formed near the junction interface between the first semiconductor layer 41 and the second semiconductor layer 42. The range of detection wavelengths of the electromagnetic wave detector is determined depending on the constituent material of the light receiving element 40. The detection wavelength of an electromagnetic wave detector having the light receiving element 40 configured as described above is 0.2 μm or more and 1.1 μm or less.

[0083] When an electromagnetic wave of the detection wavelength is incident on the light receiving element 40, electron-hole pairs are generated in the depletion layer. The generated electron-hole pairs (photocarriers) are extracted as a photocurrent from the first electrode 21 and the second electrode 22.

[0084] At this time, photocarriers generated in the region directly below the first insulating layer 31 cause an electric field change in the first two-dimensional material layer 11 via the first insulating layer 31. Furthermore, photocarriers generated in the region directly below the second insulating layer 32 cause an electric field change in the second two-dimensional material layer 12 via the second insulating layer 32. This is the optical gating effect described above. As described above, the two-dimensional material (e.g., graphene) constituting the first two-dimensional material layer 11 and the second two-dimensional material layer 12 has high mobility, allowing a large displacement current to be obtained in response to a slight electric field change. Therefore, the photocurrent extracted from the first electrode 21 via the first two-dimensional material layer 11 and the second two-dimensional material layer 12 by photoelectric conversion in the light-receiving element 40 is greatly amplified by the optical gating effect. This enables the electromagnetic wave detector 100 to achieve high sensitivity exceeding the quantum efficiency of silicon.

[0085] In this case, it is preferable to design the light-receiving element 40 so that the carrier diffusion length is short. A shorter carrier diffusion length shortens the carrier lifetime of photocarriers in the light-receiving element 40. As a result, the delay in amplification due to the optical gating effect is eliminated, and the photocarriers generated by photoelectric conversion in the light-receiving element 40 can be separated from the amplification due to the optical gating effect, enabling the electromagnetic wave detector 100 to achieve a high-speed response.

[0086] <Effects of the Electromagnetic Wave Detector 100> As described above, according to the electromagnetic wave detector 100, when electromagnetic waves of a detection wavelength are incident on the light receiving element 40, the optical gating effect can significantly amplify the current flowing through each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12. Specifically, photocarriers generated in the region directly below the first insulating layer 31 cause an electric field change in the first two-dimensional material layer 11, significantly amplifying the current flowing through the first two-dimensional material layer 11, and photocarriers generated in the region directly below the second insulating layer 32 cause an electric field change in the second two-dimensional material layer 12, significantly amplifying the current flowing through the second two-dimensional material layer 12. Therefore, the detection sensitivity of the electromagnetic wave detector 100 is improved compared to conventional semiconductor electromagnetic wave detectors or graphene electromagnetic wave detectors that do not apply the optical gating effect, and is also improved compared to electromagnetic wave detectors that do not include the second two-dimensional material layer 12 and the second semiconductor layer 42.

[0087] By utilizing the optical gating effect, the extraction efficiency of the detection current in the first two-dimensional material layer 11 and the second two-dimensional material layer 12 is significantly improved. The optical gating effect does not directly enhance the quantum efficiency of the photoelectric conversion material in the light-receiving element 40, but rather amplifies the current change (differential current) associated with the incidence of electromagnetic waves. Therefore, the quantum efficiency calculated from the current change associated with the incidence of electromagnetic waves can equivalently exceed 100%. Therefore, the electromagnetic wave detector 100 can detect electromagnetic waves with higher sensitivity than conventional semiconductor electromagnetic wave detectors or graphene electromagnetic wave detectors that do not apply the optical gating effect.

[0088] In the electromagnetic wave detector 100, the third surface 41B of the first semiconductor layer 41 is in contact with the fourth surface 42B of the second semiconductor layer 42, and the conductivity type of the second semiconductor layer 42 is different from the conductivity type of the first semiconductor layer 41. In other words, the first semiconductor layer 41 and the second semiconductor layer 42 form a pn junction. Therefore, by adjusting the voltage V to perform reverse bias operation on the light receiving element 40, the current I can be made zero when no electromagnetic waves to be detected are irradiated. In other words, the electromagnetic wave detector 100 is capable of OFF operation, and the current I is detected only when electromagnetic waves to be detected are irradiated.

[0089] In the electromagnetic wave detector 100, when an electromagnetic wave to be detected is incident, in addition to the above-described current generated in the light-receiving element 40, a photocurrent may also be generated due to the photoelectric conversion efficiency of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12. Therefore, in the electromagnetic wave detector 100, when an electromagnetic wave is incident, in addition to the current generated in the light-receiving element 40 described above and the amplified current due to the optical gate effect, the photocurrent due to the photoelectric conversion efficiency of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 can also be detected.

[0090] As described above, the electromagnetic wave detector 100 can have a quantum efficiency of 100% or more and a sensitivity 100 times or more higher than normal.

[0091] In the electromagnetic wave detector 100, the conductivity type of the first two-dimensional material layer 11 may be different from the conductivity type of the second two-dimensional material layer 12. In this case, it is possible to optimize the change in the resistance value of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 caused by the optical gating effect.

[0092] When at least one of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 includes a turbostratic portion, the carrier mobility in the turbostratic portion increases, thereby improving detection sensitivity.

[0093] Embodiment 2. Unless otherwise specified, the electromagnetic wave detector according to embodiment 2 has the same configuration, operating principle, and effects as those of the above-described embodiment 1. Therefore, the same components as those of the above-described embodiment 1 are denoted by the same reference numerals, and description thereof will not be repeated.

[0094] <Configuration of Electromagnetic Wave Detector 101> Fig. 5 is a cross-sectional schematic diagram of the electromagnetic wave detector 101 according to the second embodiment. As shown in Fig. 5, the electromagnetic wave detector 101 further includes a barrier layer 50. The barrier layer 50 is sandwiched between the first semiconductor layer 41 and the second semiconductor layer 42, and is in contact with each of the third surface 41B and the fourth surface 42B. The barrier layer 50 is electrically connected to each of the first semiconductor layer 41 and the second semiconductor layer 42. Each of the first semiconductor layer 41 and the second semiconductor layer 42 functions, for example, as a contact layer for applying a bias to the light receiving element 40 and also functions as a light absorbing layer for absorbing the electromagnetic waves to be detected.

[0095] The conductivity type of the first semiconductor layer 41 is, for example, the same as the conductivity type of the second semiconductor layer 42. The conductivity type of each of the first semiconductor layer 41 and the second semiconductor layer 42 is, for example, p-type. Note that the conductivity type of each of the first semiconductor layer 41 and the second semiconductor layer 42 may also be n-type.

[0096] The barrier layer 50 has physical properties that do not prevent minority carriers of the first semiconductor layer 41 (e.g., electrons if the conductivity type of the first semiconductor layer 41 is p-type) from flowing from the first semiconductor layer 41 into the second semiconductor layer 42 among photocarriers (electron-hole pairs) generated in the first semiconductor layer 41 when electromagnetic waves of the detection wavelength are incident on the light-receiving element 40, and prevent majority carriers of the first semiconductor layer 41 (e.g., holes if the conductivity type of the first semiconductor layer 41 is p-type) generated by thermal excitation in the second semiconductor layer 42 from flowing from the second semiconductor layer 42 into the first semiconductor layer 41.

[0097] The material constituting the barrier layer 50 and the thickness of the barrier layer 50 are selected so that the barrier layer 50 has the above physical properties.

[0098] When the conductivity type of the first semiconductor layer 41 is p-type, the material constituting the barrier layer 50 has a larger electron affinity, a larger ionization potential, and a larger band gap than the material constituting the first semiconductor layer 41. The material constituting the barrier layer 50 includes, for example, at least one of tin oxide (SnO), zinc oxide (ZnO), and titanium oxide (TiO).

[0099] When the conductivity type of the first semiconductor layer 41 is n-type, the material constituting the barrier layer 50 has a smaller electron affinity and ionization potential and a larger band gap than the material constituting the first semiconductor layer 41. The material constituting the barrier layer 50 includes, for example, at least one of nickel oxide (NiO) and manganese oxide (MnO).

[0100] The barrier layer 50 is preferably thinner than each of the first insulating layer 31 and the second insulating layer 32. The thickness of the barrier layer 50 is, for example, not less than 1 nm and not more than 100 nm.

[0101] The electromagnetic wave detector 101 further includes, for example, a third electrode 23 electrically connected to the first semiconductor layer 41 without the first two-dimensional material layer 11 therebetween, and a fourth electrode 24 electrically connected to the second semiconductor layer 42 without the second two-dimensional material layer 12 therebetween. The third electrode 23 is in ohmic contact with the first semiconductor layer 41. The fourth electrode 24 is in ohmic contact with the second semiconductor layer 42.

[0102] In the manufacturing method of the electromagnetic wave detector 101, a step of forming a barrier layer 50 on the fourth surface 42B of the second semiconductor layer 42 may be carried out before the step of forming the first semiconductor layer 41 in the manufacturing method of the electromagnetic wave detector 100.

[0103] <Operation of Electromagnetic Wave Detector 101> In the electromagnetic wave detector 101, a power supply circuit is electrically connected between the first electrode 21 and the second semiconductor layer 42. The power supply circuit is connected, for example, between the first electrode 21 and the fourth electrode 24. The power supply circuit includes a power supply that applies a voltage V between the first electrode 21 and the second semiconductor layer 42, and an ammeter that measures a current I flowing through the power supply circuit. Furthermore, in the electromagnetic wave detector 101, the first semiconductor layer 41 and the second electrode 22 are electrically connected. For example, the third electrode 23 and the second electrode 22 are electrically connected.

[0104] The positive and negative polarities of the voltage V are selected according to the conductivity type (doping type) of the first semiconductor layer 41 so that a reverse bias is applied to the junction between the barrier layer 50 and the first semiconductor layer 41 .

[0105] If the conductivity type of the first semiconductor layer 41 is p-type, a voltage is applied so that the potential of the first electrode 21 is lower than the potential of the second semiconductor layer 42, as shown in FIG. 5 . This puts the electromagnetic wave detector 101 in a state where it can detect electromagnetic waves of the detection wavelength. In this case, the barrier layer 50 does not prevent electrons generated in the first semiconductor layer 41 from flowing into the second semiconductor layer 42. On the other hand, the barrier layer 50 prevents holes generated by thermal excitation in the second semiconductor layer 42 from flowing into the first semiconductor layer 41. In other words, the barrier layer 50 can act as a hole barrier layer.

[0106] Specifically, in a state where electromagnetic waves of the detection wavelength are not irradiated (dark state), the barrier layer 50 prevents thermally excited holes in the second semiconductor layer 42 from flowing into the first semiconductor layer 41. In a state where electromagnetic waves of the detection wavelength are irradiated, the barrier layer 50 does not prevent electrons of electron-hole pairs (photocarriers) generated in the first semiconductor layer 41 from flowing into the second semiconductor layer 42. In a state where electromagnetic waves of the detection wavelength are irradiated, the electrons of the electron-hole pairs generated in the first semiconductor layer 41 are attracted toward the second semiconductor layer 42. The energy of the bottom of the conduction band of the barrier layer 50 is lower than the energy of the bottom of the conduction band of the first semiconductor layer 41, and the energy of the bottom of the conduction band of the second semiconductor layer 42 is lower than the energy of the bottom of the conduction band of the barrier layer 50. Therefore, electrons generated in the first semiconductor layer 41 are injected into the second semiconductor layer 42 without being hindered by the barrier layer 50. The electrons injected from the first semiconductor layer 41 to the second semiconductor layer 42 are extracted as a photocurrent together with the electrons of the electron-hole pairs generated in the second semiconductor layer 42. The photocurrent is detected as a change in the current I.

[0107] The energy of the top of the valence band of the barrier layer 50 is lower than the energy of the top of the valence band of each of the first semiconductor layer 41 and the second semiconductor layer 42. Therefore, the holes of the electron-hole pairs generated in the second semiconductor layer 42 flow into the first semiconductor layer 41 through the second two-dimensional material layer 12 and the second electrode 22, and are discharged to the outside through the first two-dimensional material layer 11 together with the holes of the electron-hole pairs generated in the first semiconductor layer 41.

[0108] Furthermore, if the conductivity type of the first semiconductor layer 41 is n-type, a voltage is applied so that the potential of the first electrode 21 is higher than the potential of the second semiconductor layer 42. This puts the electromagnetic wave detector 101 in a state where it can detect electromagnetic waves of the detection wavelength. In this case, the barrier layer 50 does not prevent holes generated in the first semiconductor layer 41 from flowing into the second semiconductor layer 42. On the other hand, the barrier layer 50 prevents electrons generated by thermal excitation in the second semiconductor layer 42 from flowing into the first semiconductor layer 41. In other words, the barrier layer 50 can act as an electron barrier layer.

[0109] <Modifications> In the electromagnetic wave detector 101, the conductivity type of the first semiconductor layer 41 may be different from the conductivity type of the second semiconductor layer 42. The conductivity type of the first semiconductor layer 41 may be p-type, and the conductivity type of the second semiconductor layer 42 may be n-type. In this case, too, the barrier layer 50 can function as a hole barrier layer. The conductivity type of the first semiconductor layer 41 may be n-type, and the conductivity type of the second semiconductor layer 42 may be p-type. In this case, too, the barrier layer 50 can function as an electron barrier layer.

[0110] In the electromagnetic wave detector 101, the barrier layer 50 may have physical properties that do not prevent minority carriers of the second semiconductor layer 42 (e.g., electrons if the conductivity type of the second semiconductor layer 42 is p-type) from flowing from the second semiconductor layer 42 into the first semiconductor layer 41 among photocarriers (electron-hole pairs) generated in the second semiconductor layer 42 when electromagnetic waves of the detection wavelength are incident on the light receiving element 40, but prevent majority carriers of the second semiconductor layer 42 (e.g., holes if the conductivity type of the second semiconductor layer 42 is p-type) generated by thermal excitation in the first semiconductor layer 41 from flowing from the first semiconductor layer 41 into the second semiconductor layer 42.

[0111] The configuration of the electromagnetic wave detector according to this embodiment can also be applied to other embodiments.

[0112] <Effects of the Electromagnetic Wave Detector 101> According to the electromagnetic wave detector 101, the barrier layer 50 acts as a hole barrier layer or an electron barrier layer regardless of the combination of the conductivity types of the first semiconductor layer 41 and the second semiconductor layer 42, and therefore, photocarriers can be efficiently extracted while suppressing dark current.

[0113] Embodiment 3 Unless otherwise specified, the electromagnetic wave detector according to embodiment 3 has the same configuration, operating principle, and effects as those of the above-described embodiment 1. Therefore, the same components as those of the above-described embodiment 1 are denoted by the same reference numerals, and description thereof will not be repeated.

[0114] <Configuration of Electromagnetic Wave Detector 102> Fig. 6 is a cross-sectional schematic diagram of the electromagnetic wave detector 102 according to embodiment 3. As shown in Fig. 6, the electromagnetic wave detector 102 further includes a first tunnel insulating layer 61 and a second tunnel insulating layer 62. The first tunnel insulating layer 61 is sandwiched between the first two-dimensional material layer 11 and the first semiconductor layer 41. The second tunnel insulating layer 62 is sandwiched between the second two-dimensional material layer 12 and the second semiconductor layer 42.

[0115] The first tunnel insulating layer 61 is disposed inside the first opening 31A of the first insulating layer 31. The second tunnel insulating layer 62 is disposed inside the second opening 32A of the second insulating layer 32. The thicknesses of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 are set so that, when electromagnetic waves to be detected are incident on the electromagnetic wave detector 102, tunnel currents are generated between the first two-dimensional material layer 11 and the first semiconductor layer 41 and between the second two-dimensional material layer 12 and the second semiconductor layer 42. The thickness of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 is, for example, not less than 1 nm and not more than 10 nm.

[0116] The material constituting each of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 may be any electrically insulating material, for example, at least one selected from the group consisting of metal oxides such as alumina and hafnium oxide, oxides containing semiconductors such as silicon oxide and silicon nitride, and nitrides such as boron nitride. Any method can be used to fabricate each of the first tunnel insulating layer 61 and the second tunnel insulating layer 62. For example, each of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 can be fabricated using an atomic layer deposition (ALD) method, a vacuum evaporation method, a sputtering method, or the like. Each of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 can also be formed by oxidizing or nitriding the first surface 41A of the first semiconductor layer 41 or the second surface 42A of the second semiconductor layer 42. Each of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 may be a native oxide film.

[0117] The electromagnetic wave detector 102 may further include at least one of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 .

[0118] The configuration of the electromagnetic wave detector according to this embodiment can also be applied to other embodiments.

[0119] <Effects of the Electromagnetic Wave Detector 102> The electromagnetic wave detector 102 includes the first tunnel insulating layer 61 disposed between the first two-dimensional material layer 11 and the first semiconductor layer 41, which can suppress leakage current and reduce dark current at the junction interface between the first semiconductor layer 41 and the first two-dimensional material layer 11. Furthermore, the electromagnetic wave detector 102 further includes the second tunnel insulating layer 62 disposed between the second two-dimensional material layer 12 and the second semiconductor layer 42, which can suppress leakage current and reduce dark current at the junction interface between the second semiconductor layer 42 and the second two-dimensional material layer 12.

[0120] The thickness of each of the first tunnel insulating layer 61 and the second tunnel insulating layer 62 is set so that, when electromagnetic waves to be detected are incident on the electromagnetic wave detector 102, tunnel currents are generated between the first two-dimensional material layer 11 and the first semiconductor layer 41 and between the second two-dimensional material layer 12 and the second semiconductor layer 42. In this way, when electromagnetic waves to be detected are incident on the electromagnetic wave detector 102, relatively large photocurrents can flow between the first semiconductor layer 41 and the first two-dimensional material layer 11 and between the second semiconductor layer 42 and the second two-dimensional material layer 12, thereby increasing the sensitivity of the electromagnetic wave detector 102.

[0121] Embodiment 4 Unless otherwise specified, the electromagnetic wave detector according to embodiment 4 has the same configuration, operating principle, and effects as those of the above-described embodiment 1. Therefore, the same components as those of the above-described embodiment 1 are denoted by the same reference numerals, and description thereof will not be repeated.

[0122] <Configuration of Electromagnetic Wave Detector 102> Fig. 7 is a cross-sectional schematic diagram of an electromagnetic wave detector 103 according to embodiment 4. As shown in Fig. 7, the electromagnetic wave detector 103 further includes a first connecting conductor 71 and a second connecting conductor 72. The first connecting conductor 71 electrically connects the first two-dimensional material layer 11 and the first semiconductor layer 41. The second connecting conductor 72 electrically connects the second two-dimensional material layer 12 and the second semiconductor layer 42.

[0123] Preferably, the first connecting conductor 71 forms a Schottky junction with the first semiconductor layer 41. Preferably, the second connecting conductor 72 forms a Schottky junction with the second semiconductor layer .

[0124] <Modification> The thickness of the first connecting conductor 71 may be equal to the thickness of the first insulating layer 31. In this case, the first two-dimensional material layer 11 extends in a planar manner from the upper surface of the first insulating layer 31 to above the upper surface of the first connecting conductor 71 without bending. Similarly, the thickness of the second connecting conductor 72 may be equal to the thickness of the second insulating layer 32. In this case, the second two-dimensional material layer 12 extends in a planar manner from the upper surface of the second insulating layer 32 to above the upper surface of the second connecting conductor 72 without bending.

[0125] The configuration of the electromagnetic wave detector according to this embodiment can also be applied to other embodiments.

[0126] <Effects of the electromagnetic wave detector 103> In the electromagnetic wave detector 103, the first semiconductor layer 41 and the first two-dimensional material layer 11 are electrically connected via the first connecting conductor 71, and therefore the contact resistance between the first two-dimensional material layer 11 and the first semiconductor layer 41 can be reduced compared to when the first connecting conductor 71 is not provided.

[0127] Furthermore, if the first connecting conductor 71 forms a Schottky junction with the first semiconductor layer 41, the dark current can be reduced.

[0128] If the thickness of the first connecting conductor 71 is equivalent to the thickness of the first insulating layer 31, the two-dimensional surfaces of the first portion 11 a and the third portion 11 c of the first two-dimensional material layer 11 extend in the same direction, thereby improving the mobility of carriers in the first two-dimensional material layer 11. The optical gating effect on the first two-dimensional material layer 11 is proportional to the mobility of carriers in the first two-dimensional material layer 11. Therefore, the detection sensitivity of the electromagnetic wave detector 103 can be improved compared to the electromagnetic wave detector 100.

[0129] Embodiment 5 Unless otherwise specified, the electromagnetic wave detector according to embodiment 5 has the same configuration, operating principle, and effects as those of the above-described embodiment 1. Therefore, the same components as those of the above-described embodiment 1 are denoted by the same reference numerals, and description thereof will not be repeated.

[0130] <Configuration of Electromagnetic Wave Detector 104> Fig. 8 is a schematic plan view of the electromagnetic wave detector 104 according to embodiment 5. Fig. 9 is a schematic cross-sectional view taken along the arrow IX-IX in Fig. 8. As shown in Figs. 8 and 9, the electromagnetic wave detector 104 has a plurality of concave-convex portions 81, 82 formed on the surface of each of the first electrode 21 and the second electrode 22. Each of the plurality of concave-convex portions 81, 82 forms a pattern in which surface plasmons are resonantly excited when electromagnetic waves to be detected are incident thereon. In other words, a pattern in which surface plasmons are resonantly excited when electromagnetic waves to be detected are incident thereon is provided on the surface of each of the first electrode 21 and the second electrode 22.

[0131] The plurality of uneven portions 81 formed on the surface of the first electrode 21 are formed, for example, by the first electrode 21 and a plurality of conductors arranged at intervals on the upper surface of the first electrode 21. The plurality of uneven portions 82 formed on the surface of the second electrode 22 are formed, for example, by the second electrode 22 and a plurality of conductors arranged at intervals on the upper surface of the second electrode 22. The material constituting the conductor is a material that generates surface plasmon resonance. The material constituting the conductor includes at least one selected from the group consisting of gold (Au), silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), chromium (Cr), and palladium (Pd).

[0132] The method for forming the plurality of concave and convex portions 81 and 82 is not particularly limited, but may be formed in the same manner as the first electrode 21 and the second electrode 22, for example.

[0133] The plurality of concave and convex portions 81, 82 may be formed by partially removing the first electrode 21 or the second electrode 22 by dry etching, wet etching, or the like.

[0134] The plurality of concave and convex portions 81 and 82 are formed as a pattern 80 on the surface of each of the first electrode 21 and the second electrode 22, in which surface plasmon resonance occurs.

[0135] The multiple concave-convex portions 81, 82 have, for example, a one-dimensional periodic structure or a two-dimensional periodic structure. The one-dimensional periodic structure or the two-dimensional periodic structure of the multiple concave-convex portions 81, 82 is a periodic structure along the two-dimensional surface of the first two-dimensional material layer 11 or the second two-dimensional material layer 12. The multiple concave-convex portions 81, 82 having a one-dimensional periodic structure are, for example, periodically arranged in any one direction along the two-dimensional surface of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12. The multiple concave-convex portions 81, 82 having a two-dimensional periodic structure are, for example, arranged at positions corresponding to lattice points of a square lattice, a triangular lattice, or the like in a planar view.

[0136] The plurality of concave-convex portions 81, 82 may have a non-periodic structure. The arrangement of the plurality of concave-convex portions 81, 82 in plan view may be asymmetric.

[0137] In plan view, the planar shape of the convex portions of the plurality of concave-convex portions 81, 82 may be any shape such as a circle, a triangle, a rectangle, a polygon, or an ellipse.

[0138] <Modifications> In the electromagnetic wave detector 104, a pattern that resonantly excites surface plasmons when electromagnetic waves to be detected are incident on at least one of the surfaces of the first electrode 21, the first two-dimensional material layer 11, the second electrode 22, and the second two-dimensional material layer 12 may be provided. A plurality of concave-convex portions may be provided on the surface of at least one of the first electrode 21, the first two-dimensional material layer 11, the second electrode 22, and the second two-dimensional material layer 12. In plan view, the plurality of concave-convex portions may have a periodic structure or a non-periodic structure.

[0139] 10 and 11 , in the electromagnetic wave detector 104, a plurality of concave-convex portions 91, 92 may be formed on the surface of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12. Each of the plurality of concave-convex portions 91, 92 constitutes a pattern in which surface plasmons are resonantly excited when electromagnetic waves to be detected are incident thereon. In other words, a pattern in which surface plasmons are resonantly excited when electromagnetic waves to be detected are incident thereon is provided on the surface of each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12.

[0140] The plurality of uneven portions 91 are formed, for example, by the first two-dimensional material layer 11 and a plurality of conductors arranged at intervals from one another on the upper surface of the first two-dimensional material layer 11. The plurality of uneven portions 92 are formed, for example, by the second two-dimensional material layer 12 and a plurality of conductors arranged at intervals from one another on the upper surface of the second two-dimensional material layer 12. Each of the plurality of conductors is in contact with the upper surface of the first two-dimensional material layer 11 or the second two-dimensional material layer 12. Each of the plurality of conductors is in contact, for example, with the third portion 11c of the first two-dimensional material layer 11 or the sixth portion 12c of the second two-dimensional material layer 12.

[0141] At least one of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 may have a plurality of recesses or protrusions, and the plurality of recesses or protrusions may form a plurality of uneven portions 91, 92. Because the first two-dimensional material layer 11 and the second two-dimensional material layer 12 each have high electrical conductivity, surface plasmon resonance may occur in each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12. Therefore, similar to the plurality of uneven portions 81, 82 and the plurality of uneven portions 91, 92 formed from conductors described above, surface plasmon resonance may also occur in each of the first two-dimensional material layer 11 and the second two-dimensional material layer 12 due to the plurality of uneven portions 91, 92 formed from a plurality of recesses or protrusions.

[0142] In the electromagnetic wave detector 104, a plurality of concave-convex portions may be formed on the surface of each of the first electrode 21, the first two-dimensional material layer 11, the second electrode 22, and the second two-dimensional material layer 12. In other words, in the electromagnetic wave detector 104, a plurality of concave-convex portions 81, 82 and a plurality of concave-convex portions 91, 92 may be formed simultaneously.

[0143] The configuration of the electromagnetic wave detector according to this embodiment can also be applied to other embodiments.

[0144] <Effects of Electromagnetic Wave Detector 104> In the electromagnetic wave detector 104, a pattern that resonantly excites surface plasmons when electromagnetic waves to be detected are incident on at least one surface of the first electrode 21, the first two-dimensional material layer 11, the second electrode 22, and the second two-dimensional material layer 12 is provided. Therefore, in the electromagnetic wave detector 104, only the electromagnetic waves to be detected are incident on the light receiving element 40, thereby increasing the detection sensitivity for the electromagnetic waves to be detected.

[0145] For example, if the multiple concave-convex portions 81, 82, 91, and 92 have a one-dimensional periodic structure, only electromagnetic waves having a polarization that generates surface plasmon resonance can be detected, thereby increasing the detection sensitivity for the electromagnetic waves. If the multiple concave-convex portions 81, 82, 91, and 92 have a two-dimensional periodic structure, only electromagnetic waves having a wavelength that generates surface plasmon resonance can be detected, thereby increasing the detection sensitivity for the electromagnetic waves. Even if the multiple concave-convex portions 81, 82, 91, and 92 have a non-periodic structure, polarization dependence occurs in the multiple concave-convex portions 81, 82, 91, and 92 depending on the irradiated electromagnetic waves, and only electromagnetic waves having a specific polarization can be detected, just as in the case where the multiple concave-convex portions 81, 82, 91, and 92 have a one-dimensional periodic structure.

[0146] Embodiment 6 Unless otherwise specified, the electromagnetic wave detector according to embodiment 6 has the same configuration, operating principle, and effects as those of the above-described embodiment 1. Therefore, the same components as those of the above-described embodiment 1 are denoted by the same reference numerals, and description thereof will not be repeated.

[0147] <Configuration of Electromagnetic Wave Detector 105> FIG. 12 is a schematic plan view of the electromagnetic wave detector 105 according to embodiment 6. FIG. 13 is a schematic cross-sectional view taken along arrow XIII-XIII in FIG. 12. As shown in FIGS. 12 and 13, in the electromagnetic wave detector 105, the area of ​​the first electrode 21 is smaller than the area of ​​the first opening 31A in a plan view. The ratio of the area of ​​the first electrode 21 to the area of ​​the first surface 41A is, for example, 0.3 or less. Preferably, the ratio of the area of ​​the first electrode 21 to the area of ​​the first surface 41A is, for example, 0.1 or less.

[0148] In a plan view, the area of ​​the second electrode 22 is smaller than the area of ​​the second opening 32A. The ratio of the area of ​​the second electrode 22 to the area of ​​the second surface 42A is, for example, 0.3 or less. Preferably, the ratio of the area of ​​the second electrode 22 to the area of ​​the second surface 42A is, for example, 0.1 or less.

[0149] The configuration of the electromagnetic wave detector according to this embodiment can also be applied to other embodiments.

[0150] <Effects of Electromagnetic Wave Detector 105> In the electromagnetic wave detector 105, the area of ​​the first electrode 21 is smaller than the area of ​​the first opening 31A. Therefore, compared to when the area of ​​the first electrode 21 is equal to or greater than the area of ​​the first opening 31A, the amount of light that passes through the first surface 41A and reaches the second surface 42A increases, resulting in an increased output.

[0151] Embodiment 7 Unless otherwise specified, the electromagnetic wave detector according to embodiment 7 has the same configuration, operating principle, and effects as those of the above-described embodiment 1. Therefore, the same components as those of the above-described embodiment 1 are denoted by the same reference numerals, and description thereof will not be repeated.

[0152] <Configuration of Electromagnetic Wave Detector 106> FIG. 14 is a schematic plan view of the electromagnetic wave detector 106 according to the seventh embodiment. FIG. 15 is a schematic bottom view of the electromagnetic wave detector 106 according to the seventh embodiment. FIG. 16 is a schematic cross-sectional view taken along arrows XVI-XVI in FIGS. 14 and 15 . As shown in FIGS. 14 to 16 , in the electromagnetic wave detector 106, the area of ​​the second electrode 22 is larger than the area of ​​the first electrode 21 in a plan view. In a plan view, the area of ​​the second electrode 22 is, for example, two or more times the area of ​​the first electrode 21. The area of ​​the first electrode 21 is smaller than the area of ​​the first opening 31A, for example. The area of ​​the second electrode 22 is equal to or larger than the area of ​​the second opening 32A, for example.

[0153] The configuration of the electromagnetic wave detector according to this embodiment can also be applied to other embodiments.

[0154] <Effects of Electromagnetic Wave Detector 106> In the electromagnetic wave detector 106, the area of ​​the second electrode 22 is larger than the area of ​​the first electrode 21, so that electromagnetic waves that are incident on the light-receiving element 40 from the first surface 41A side and transmitted through the light-receiving element 40 are reflected by the second electrode 22. The electromagnetic waves reflected by the second electrode 22 are incident on the light-receiving element 40 again from the second surface 42A side. Therefore, electromagnetic waves are incident on the light-receiving element 40 from both the first surface 41A and the second surface 42A sides. This increases the electromagnetic wave absorption rate of the light-receiving element 40, and therefore increases the output.

[0155] Embodiment 8 Unless otherwise specified, the electromagnetic wave detector according to embodiment 8 has the same configuration, operating principle, and effects as those of the above-described embodiment 1. Therefore, the same components as those of the above-described embodiment 1 are denoted by the same reference numerals, and description thereof will not be repeated.

[0156] <Configuration of Electromagnetic Wave Detector 107> FIG. 17 is a schematic plan view of the electromagnetic wave detector 107 according to the eighth embodiment. As shown in FIG. 17, the electromagnetic wave detector 107 does not have symmetry with respect to the interface between the third surface 41B and the fourth surface 42B as a mirror plane. The portion located on the first semiconductor layer 41 side of the interface does not have a mirror-symmetric relationship with the portion located on the second semiconductor layer 42 side of the interface. In a plan view, the first portion 11a of the first two-dimensional material layer 11 is arranged so as not to overlap with the fourth portion 12a of the second two-dimensional material layer 12. In a plan view, the first opening 31A is arranged so as not to overlap with the second opening 32A. In a plan view, the first electrode 21 is arranged so as not to overlap with the second electrode 22.

[0157] The configuration of the electromagnetic wave detector according to this embodiment can also be applied to other embodiments.

[0158] Ninth Embodiment Fig. 18 is a schematic plan view of an electromagnetic wave detector array according to a ninth embodiment. Fig. 19 is a schematic plan view showing a modified example of the electromagnetic wave detector according to the ninth embodiment.

[0159] The electromagnetic wave detector array 200 shown in Fig. 18 is an electromagnetic wave detector assembly and includes a plurality of electromagnetic wave detectors 300 as detection elements. Each of the plurality of electromagnetic wave detectors 300 is any one of the electromagnetic wave detectors 100 to 107 according to the first to eighth embodiments. For example, each electromagnetic wave detector 300 may be the electromagnetic wave detector 100. In the electromagnetic wave detector array 200 shown in Fig. 18, each of the plurality of electromagnetic wave detectors 300 is arranged in an array in a two-dimensional direction. Note that each of the plurality of electromagnetic wave detectors 300 may also be arranged so as to be aligned in a one-dimensional direction.

[0160] 18 , the electromagnetic wave detector array 200 includes four electromagnetic wave detectors 300, which are arranged in a 2×2 array. However, the electromagnetic wave detector array 200 may include any number of electromagnetic wave detectors 300, and may include, for example, nine or more electromagnetic wave detectors 300. The multiple electromagnetic wave detectors 100 may also be arranged in a 3 or more×3 or more array.

[0161] Furthermore, in the electromagnetic wave detector array 200, the plurality of electromagnetic wave detectors 300 may be arranged non-periodically.

[0162] Furthermore, in the electromagnetic wave detector array 200, as long as each of the plurality of electromagnetic wave detectors 300 can function as a single detection element, the components of the electromagnetic wave detectors 300 may be common.

[0163] Each of the plurality of electromagnetic wave detectors 300 forms, for example, one pixel in the electromagnetic wave detector array 200. In this case, the electromagnetic wave detector array 200 can be used, for example, as an image sensor in which each of the plurality of electromagnetic wave detectors 300 forms one pixel.

[0164] Each of the plurality of electromagnetic wave detectors 300 may be an electromagnetic wave detector according to another embodiment other than the electromagnetic wave detector 100 according to the first embodiment.

[0165] 19 has basically the same configuration as the electromagnetic wave detector array 200 shown in FIG. 18 and can achieve the same effects, but differs from the electromagnetic wave detector array 200 in that it includes a plurality of electromagnetic wave detectors 300, 301, 302, and 303 having mutually different configurations. Each of the plurality of electromagnetic wave detectors 300, 301, 302, and 303 is any one of the electromagnetic wave detectors 100 to 107 according to the first to eighth embodiments. For example, the electromagnetic wave detector 300 may be the electromagnetic wave detector 100, the electromagnetic wave detector 301 may be the electromagnetic wave detector 101, the electromagnetic wave detector 302 may be the electromagnetic wave detector 102, and the electromagnetic wave detector 303 may be the electromagnetic wave detector 103.

[0166] 19, the electromagnetic wave detector array 201 has a plurality of different types of electromagnetic wave detectors 300, 301, 302, and 303 arranged in a one-dimensional or two-dimensional array, thereby providing the array with the functionality of an image sensor. For example, the electromagnetic wave detectors 300, 301, 302, and 303 may each have a different detection wavelength. Specifically, electromagnetic wave detectors having different detection wavelength selectivities may be prepared from the electromagnetic wave detectors according to any one of the first to eighth embodiments and arranged in an array. In this case, the electromagnetic wave detector array 201 can detect electromagnetic waves of at least two or more different wavelengths.

[0167] By arranging the electromagnetic wave detectors 300, 301, 302, and 303 having different detection wavelengths in an array, it is possible to distinguish the wavelength of electromagnetic waves in any wavelength range, such as ultraviolet light, infrared light, terahertz waves, radio wave wavelength ranges, etc. As a result, it is possible to obtain a color image in which differences in wavelength are displayed as differences in color, for example.

[0168] The materials constituting at least one of the first semiconductor layer 41 and the second semiconductor layer 42 of each of the multiple types of electromagnetic wave detectors 300, 301, 302, and 303 may be materials sensitive to different wavelength ranges. For example, the material constituting the first semiconductor layer 41 of the electromagnetic wave detector 300 may be a semiconductor material whose detection wavelength is that of visible light, and the material constituting the first semiconductor layer 41 of the electromagnetic wave detector 301 may be a semiconductor material whose detection wavelength is that of infrared light. Such an electromagnetic wave detector array 201 is suitable for, for example, an in-vehicle sensor. Such an electromagnetic wave detector array 201 can function as an image sensor for a visible light camera during the day and as an image sensor for an infrared camera at night. Therefore, a camera equipped with the above-described electromagnetic wave detector array 201 as an image sensor does not need to be selectively used depending on the detection wavelength.

[0169] The electromagnetic wave detector array 201, which includes multiple electromagnetic wave detectors 300, 301, 302, and 303 having different detection wavelengths, can be used as an image sensor capable of detecting multiple electromagnetic waves having different wavelengths. This makes it possible to detect multiple electromagnetic waves having different wavelengths without using color filters, which have conventionally been required in CMOS (Complementary MOS) sensors and the like. Furthermore, it is possible to obtain a colored image in which differences in the wavelengths of the electromagnetic waves are displayed as different colors.

[0170] Furthermore, a polarization-discriminating image sensor can be formed by arraying electromagnetic wave detectors 300, 301, 302, and 303 that detect different polarizations. For example, polarization imaging can be achieved by arranging multiple electromagnetic wave detectors, each of which consists of four pixels that detect polarization angles of 0°, 90°, 45°, and 135°. A polarization-discriminating image sensor can, for example, distinguish between artificial and natural objects, distinguish between materials, distinguish between objects at the same temperature in the infrared wavelength range, distinguish between boundaries between objects, or provide equivalent resolution improvement.

[0171] 19, there is no particular limitation on the arrangement of the plurality of electromagnetic wave detectors 300, 301, 302, and 303. The plurality of electromagnetic wave detectors 300, 301, 302, and 303 may be arranged periodically or non-periodically.

[0172] As described above, the electromagnetic wave detector assembly according to this embodiment configured as described above can detect electromagnetic waves in a wide wavelength range. In addition, the electromagnetic wave detector assembly according to this embodiment can detect electromagnetic waves of different wavelengths.

[0173] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0174] 11 First two-dimensional material layer, 11a First portion, 11b Second portion, 11c Third portion, 12 Second two-dimensional material layer, 12a Fourth portion, 12b Fifth portion, 12c Sixth portion, 21 First electrode, 22 Second electrode, 23 Third electrode, 24 Fourth electrode, 31 First insulating layer, 31A First opening, 32 Second insulating layer, 32A Second opening, 40 Light receiving element, 41 First semiconductor layer, 41A First surface, 41B Third surface, 42 Second semiconductor layer, 42A Second surface, 42B Fourth surface, 50 Barrier layer, 61 First tunnel insulating layer, 62 Second tunnel insulating layer, 71 First connecting conductor, 72 Second connecting conductor, 80 Pattern, 81, 82, 91, 92 Concave and convex portions, 100, 101, 102, 103, 104, 105, 106, 107, 300, 301, 302, 303: electromagnetic wave detectors, 200, 201: electromagnetic wave detector arrays.

Claims

1. A light-receiving element having a first surface and a second surface located on the opposite side of the first surface, the light-receiving element having a first semiconductor layer having the first surface and a second semiconductor layer having the second surface, a first insulating layer disposed on the first surface and having a first opening formed therein, a first two-dimensional material layer electrically connected to the first semiconductor layer at the first opening and extending from above the first opening to above the first insulating layer, a first electrode electrically connected to the first two-dimensional material layer without passing through the first semiconductor layer, a second insulating layer disposed on the second surface and having a second opening formed therein, a second two-dimensional material layer electrically connected to the second semiconductor layer at the second opening and extending from above the second opening to above the second insulating layer, and a second electrode electrically connected to the second two-dimensional material layer without passing through the second semiconductor layer, the first semiconductor layer further having a third surface located on the opposite side of the first surface, the second semiconductor layer further having a fourth surface located on the opposite side of the second surface, and an electromagnetic wave detector in which the third surface and the fourth surface are laminated so as to overlap each other.

2. The third surface is in contact with the fourth surface, the first semiconductor layer has a first conductivity type, and the second semiconductor layer has a second conductivity type different from the first conductivity type. The electromagnetic wave detector according to claim 1.

3. Further comprising a barrier layer sandwiched between the first semiconductor layer and the second semiconductor layer and electrically connected to each of the first semiconductor layer and the second semiconductor layer, the barrier layer having a physical property that does not prevent minority carriers of the first semiconductor layer from flowing from the first semiconductor layer into the second semiconductor layer, but prevents majority carriers of the first semiconductor layer from flowing from the first semiconductor layer into the second semiconductor layer. The electromagnetic wave detector according to claim 1.

4. The second semiconductor layer has a conductivity type different from that of the first semiconductor layer. The electromagnetic wave detector according to claim 3.

5. The first semiconductor layer and the second semiconductor layer have the same conductivity type as each other. The electromagnetic wave detector according to claim 3.

6. The second two-dimensional material layer has a conductivity type different from that of the first two-dimensional material layer. The electromagnetic wave detector according to any one of claims 1 to 5.

7. The electromagnetic wave detector according to any one of claims 1 to 6, further comprising at least one of a first tunnel insulating layer sandwiched between the first two-dimensional material layer and the first semiconductor layer and a second tunnel insulating layer sandwiched between the second two-dimensional material layer and the second semiconductor layer.

8. The electromagnetic wave detector according to any one of claims 1 to 7, further comprising at least one of a first connection conductor that electrically connects between the first semiconductor layer and the first two-dimensional material layer and a second connection conductor that electrically connects between the second semiconductor layer and the second two-dimensional material layer.

9. The electromagnetic wave detector according to any one of claims 1 to 8, wherein a pattern is provided on at least one of the surfaces of the first electrode, the first two-dimensional material layer, the second electrode, and the second two-dimensional material layer, in which surface plasmons are resonantly excited when an electromagnetic wave to be detected is incident.

10. The electromagnetic wave detector according to any one of claims 1 to 9, wherein in a plan view, the area of the first electrode is smaller than the area of the first opening.

11. The electromagnetic wave detector according to any one of claims 1 to 10, wherein in a plan view, the area of the second electrode is larger than the area of the first electrode.

12. The electromagnetic wave detector according to any one of claims 1 to 11, wherein at least one of the first two-dimensional material layer and the second two-dimensional material layer includes a turbostratic structure portion.

13. The electromagnetic wave detector according to any one of claims 1 to 12, wherein the first two-dimensional material layer and the second two-dimensional material layer include any material selected from the group consisting of transition metal dichalcogenides, graphene, black phosphorus, silicene, germanene, Weyl semimetals, graphene nanoribbons, and borophene.

14. An electromagnetic wave detector array comprising a plurality of electromagnetic wave detectors according to any one of claims 1 to 13, wherein the plurality of electromagnetic wave detectors are arranged side by side in a direction along the first surface.

Images