Infrared sensor

Abstract

To provide an infrared sensor that can attain a high optical absorption efficiency and a high thermoelectric conversion efficiency.SOLUTION: The infrared sensor includes: a first graphene layer for absorbing infrared rays by using plasmon resonance; a second graphene layer having a connection unit connected to the first graphene layer; a first electrode and a second electrode connected to the second graphene layer, with the connection unit in between; and a control electrode for controlling the distribution of Fermi energy of the second graphene layer between the first and second electrodes, asymmetrically.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to infrared sensors. [Background technology]

[0002] Materials emit thermal radiation according to their temperature. The wavelength of thermal radiation emitted by materials at room temperature is the strongest in the infrared wavelength range. For this reason, infrared sensors that detect thermal radiation are widely used in night vision and thermography.

[0003] In recent years, a method for infrared detection using graphene has been proposed. Graphene is a two-dimensional material in which carbon atoms are arranged in a two-dimensional honeycomb pattern. Graphene has a unique energy band structure, allowing it to absorb light over a wide wavelength range, from the ultraviolet to the terahertz band.

[0004] One example of a graphene-based infrared sensor is a detection method using the photothermoelectric effect of graphene. The photothermoelectric effect is a thermoelectric effect caused by heating due to light absorption. In this detection method, when light is incident on the graphene that makes up the infrared sensor, electrons in the graphene absorb the light and gain energy. The energy gained by the electrons through light absorption is then shared with other electrons through scattering between electrons, converting it into heat. Because the time it takes for energy to thermalize between electrons differs from the time it takes for energy to be shared with lattice atoms, the thermalization between electrons is faster. Therefore, after light absorption, the electron temperature becomes higher than the lattice temperature. At the metal electrodes connected to the edge of the graphene, the electron temperature is similar to the lattice temperature, and thermal diffusion forms an electron temperature distribution within the graphene.

[0005] Furthermore, by applying different gate voltages in the plane, a potential distribution can be created within the graphene. Since the Seebeck coefficient varies depending on the potential of the graphene, the Seebeck coefficient distribution is created by the potential distribution within the graphene layer. When the electron temperature distribution and the Seebeck coefficient distribution exist simultaneously, an electromotive force is generated by the Seebeck effect.

[0006] The light absorption efficiency of graphene is typically on the order of a few percent, which is small compared to common materials used in optical sensors. Recently, a method has been proposed to improve the light absorption efficiency of graphene by utilizing plasmon resonance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 173347 [Patent Document 2] Japanese Patent Application Publication No. 2018-37617 [Non-patent literature]

[0008] [Non-Patent Document 1] K. Kinoshita et al., Photo-thermoelectric detection of cyclotron resonance in asymmetrically carrier-doped graphene two-terminal device, Applied Physics Letter 113, 103102 (2018) [Non-patent document 2] X. Cai et al., Sensitive room-temperature terahertz detection via the photothermoelectric effect in graphene, Nature Nanotechnology 9, 814 (2014) [Non-patent document 3] A. Safaei et al., Dynamically tunable extraordinary light absorption in monolayer graphene, Physical Review B 96, 165431 (2017) [Non-patent document 4] A. Safaei et al., Dirac plasmon-assisted asymmetric hot carrier generation for room-temperature infrared detection, Nature Communications 10, 3498 (2019) Summary of the Invention [Problem to be solved by the invention]

[0009] However, controlling the potential distribution of graphene to obtain good thermoelectric conversion efficiency reduces the effect of plasmon resonance. Conversely, increasing the effect of plasmon resonance reduces the thermoelectric conversion efficiency. In other words, conventional infrared sensors cannot obtain good thermoelectric conversion efficiency while obtaining high light absorption efficiency through plasmon resonance.

[0010] An object of the present disclosure is to provide an infrared sensor that can achieve both high light absorption efficiency and high thermoelectric conversion efficiency. [Means for solving the problem]

[0011] According to one embodiment of the present disclosure, there is provided a semiconductor device comprising: a first graphene layer that absorbs infrared light by utilizing plasmon resonance; a second graphene layer having a connecting portion continuous to the first graphene layer; a first electrode and a second electrode connected to the second graphene layer with the connecting portion sandwiched therebetween; and a control electrode that controls a distribution of Fermi energy of the second graphene layer, wherein the control electrode comprises a third electrode disposed between the first electrode and the second electrode in a planar view, and a fourth electrode disposed between the third electrode and the second electrode in a planar view, and voltages having polarities opposite to each other are applied to the third electrode and the fourth electrode, the third electrode and the fourth electrode control the Fermi energy of the second graphene layer to a range in which an electromotive force due to the Seebeck effect in the second graphene layer is large; The second graphene layer serves as a thermoelectric conversion region to provide an infrared sensor. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to achieve both high light absorption efficiency and high thermoelectric conversion efficiency. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a plan view showing an infrared sensor according to a first embodiment. [Figure 2] FIG. 1 is a cross-sectional view (part 1) showing the infrared sensor according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view (part 2) showing the infrared sensor according to the first embodiment. [Figure 4] FIG. 1 is a diagram showing the relationship between the Fermi energy and the Seebeck coefficient of graphene. [Figure 5] FIG. 10 is a top view showing an infrared sensor according to a second embodiment. [Figure 6] FIG. 10 is a cross-sectional view showing an infrared sensor according to a second embodiment. [Figure 7] 10A and 10B are diagrams illustrating an example of a current path in an infrared sensor according to a second embodiment. [Figure 8] 10 is a diagram showing another example of a current path in the infrared sensor according to the second embodiment. FIG. [Figure 9] FIG. 10 is a top view showing an infrared sensor according to a third embodiment. [Figure 10] 10A and 10B are diagrams illustrating an example of a current path in an infrared sensor according to a third embodiment. [Figure 11] FIG. 10 is a top view showing an infrared sensor according to a fourth embodiment. [Figure 12] 10A and 10B are diagrams illustrating an example of a current path in an infrared sensor according to a fourth embodiment. [Figure 13] FIG. 10 is a cross-sectional view showing an infrared sensor according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that in this specification and drawings, components having substantially the same functional configurations may be denoted by the same reference numerals to avoid redundant description. In this specification and drawings, the X1-X2 direction, the Y1-Y2 direction, and the Z1-Z2 direction are defined as mutually orthogonal directions. The plane including the X1-X2 direction and the Y1-Y2 direction is defined as the XY plane, the plane including the Y1-Y2 direction and the Z1-Z2 direction is defined as the YZ plane, and the plane including the Z1-Z2 direction and the X1-X2 direction is defined as the ZX plane. For convenience, the Z1 direction is defined as the upward direction, and the Z2 direction is defined as the downward direction. Furthermore, in this disclosure, a planar view refers to viewing an object from the Z1 side.

[0015] (First embodiment) First, a first embodiment will be described. The first embodiment relates to an infrared sensor using graphene. FIG. 1 is a plan view showing the infrared sensor according to the first embodiment. FIGS. 2 and 3 are cross-sectional views showing the infrared sensor according to the first embodiment. FIG. 2 corresponds to a cross-sectional view taken along line II-II in FIG. 1. FIG. 3 corresponds to a cross-sectional view taken along line III-III in FIG. 1.

[0016] As shown in Figures 1 to 3, the infrared sensor 1 according to the first embodiment mainly includes a substrate 11, an insulating layer 12, an insulating layer 13, a graphene layer 20, a control electrode 40, a first electrode 31, a second electrode 32, and a fifth electrode 55.

[0017] The substrate 11 has an insulating surface on the Z1 side. The substrate 11 may be, for example, an insulating substrate or a Si substrate with a thermal oxide film. A control electrode 40 is provided on the substrate 11. The control electrode 40 includes a third electrode 43 and a fourth electrode 44. The third electrode 43 and the fourth electrode 44 are electrically insulated from each other. The third electrode 43 and the fourth electrode 44 extend parallel to the X1-X2 direction. The fourth electrode 44 is disposed closer to the Y1 side than the third electrode 43, and the third electrode 43 is disposed closer to the Y2 side than the fourth electrode 44. An insulating layer 12 is provided on the substrate 11 so as to cover the third electrode 43 and the fourth electrode 44. The insulating layer 12 is, for example, a silicon oxide layer.

[0018] A graphene layer 20 is provided on the insulating layer 12. The graphene layer 20 includes one or more graphenes stacked on top of each other. When the graphene layer 20 includes more than one graphene, the more than one graphene is preferably randomly (rotatedly) stacked. This is because the randomly (rotatedly) stacked graphene provides a relatively high carrier mobility. The graphene layer 20 includes a first graphene layer 21 and a second graphene layer 22. The first graphene layer 21 and the second graphene layer 22 are connected to each other. The first graphene layer 21 functions as a light absorption region, and the second graphene layer 22 functions as a thermoelectric conversion region.

[0019] The second graphene layer 22 is disposed above the third electrode 43 and the fourth electrode 44 and overlaps with the third electrode 43 and the fourth electrode 44 in a planar view. As will be described in detail later, the Fermi energy of the second graphene layer 22 is controlled by the third electrode 43 and the fourth electrode 44. The first graphene layer 21 is disposed on the X2 side of the second graphene layer 22, and the second graphene layer 22 is disposed on the X1 side of the first graphene layer 21. In a planar view, the first graphene layer 21 and the second graphene layer 22 have a rectangular shape. The dimension of the first graphene layer 21 in the Y1-Y2 direction is smaller than the dimension of the second graphene layer 22 in the Y1-Y2 direction. Of the two sides of the first graphene layer 21 parallel to the X1-X2 direction, the side located on the Y1 side is closer to the Y2 side than the side of the second graphene layer 22 parallel to the X1-X2 direction that is located on the Y1 side. Of the two sides of the first graphene layer 21 parallel to the X1-X2 direction, the side located on the Y2 side is closer to the Y1 side than of the two sides of the second graphene layer 22 parallel to the X1-X2 direction, the side located on the Y2 side. The second graphene layer 22 has a connecting portion 22A continuing to the first graphene layer 21. For example, the connecting portion 22A overlaps with the third electrode 43 and the fourth electrode 44 in a planar view.

[0020] The first graphene layer 21 absorbs infrared rays by utilizing plasmon resonance. For example, a plurality of openings 23 are periodically formed in the first graphene layer 21. For example, the planar shape of the openings 23 is a circle with a diameter of 400 nm, and the plurality of openings 23 are arranged in a regular hexagonal lattice pattern at a pitch of 600 nm. On the other hand, no openings 23 are formed in the second graphene layer 22. The second graphene layer 22 may also absorb infrared rays, but the density of carriers photoexcited in the second graphene layer 22 by absorption of infrared rays is lower than the density of carriers photoexcited in the first graphene layer 21 by absorption of infrared rays.

[0021] An insulating layer 13 is provided on the insulating layer 12 so as to cover the graphene layer 20. The insulating layer 13 is, for example, an aluminum oxide layer with a thickness of approximately 10 nm. The insulating layer 13 has an opening 13A exposing an end of the second graphene layer 22 on the Y2 side and an opening 13B exposing an end of the second graphene layer 22 on the Y1 side. A first electrode 31 is provided inside the opening 13A. The first electrode 31 contacts the second graphene layer 22. A second electrode 32 is provided inside the opening 13B. The second electrode 32 contacts the second graphene layer 22. In a plan view, the third electrode 43 and the fourth electrode 44 are arranged between the first electrode 31 and the second electrode 32, the third electrode 43 is arranged between the first electrode 31 and the fourth electrode 44, and the fourth electrode 44 is arranged between the second electrode 32 and the third electrode 43. The first electrode 31 and the second electrode 32 are connected to the second graphene layer 22 with the connecting portion 22A sandwiched therebetween. The material of the first electrode 31 and the second electrode 32 is not particularly limited, and may be, for example, Au, Pd, Ni, Cr, or Ti. The first electrode 31 and the second electrode 32 may include a laminate of these metals. For example, the first electrode 31 and the second electrode 32 may include a laminate of a Ti film and an Au film formed on the Ti film, or a laminate of a Cr film and an Au film formed on the Cr film. The first electrode 31 and the second electrode 32 may be made of the same material or different materials.

[0022] For example, based on the center line C between the first electrode 31 and the second electrode 32 of the second graphene layer 22, the third electrode 43 is arranged on the first electrode 31 side, i.e., the Y2 side, and the fourth electrode 44 is arranged on the second electrode 32 side, i.e., the Y1 side.

[0023] A fifth electrode 55 is provided on the insulating layer 13. The fifth electrode 55 is made of a material that transmits infrared rays. The fifth electrode 55 is a transparent conductive film such as an indium tin oxide (ITO) film. The fifth electrode 55 is disposed above the first graphene layer 21 and overlaps with the first graphene layer 21 in a planar view. The Fermi energy of the first graphene layer 21 is controlled by the fifth electrode 55, as will be described in detail later.

[0024] Here, the operation of the infrared sensor 1 according to the first embodiment will be described.

[0025] The fifth electrode 55 controls the Fermi energy of the first graphene layer 21 to a range in which light absorption due to plasmon resonance is likely to occur in the first graphene layer 21. For example, the Fermi energy of the first graphene layer 21 is controlled to about +0.5 eV to +1.0 eV.

[0026] Furthermore, the third electrode 43 and the fourth electrode 44 control the Fermi energy of the second graphene layer 22 to a range in which the electromotive force due to the Seebeck effect in the second graphene layer 22 is likely to be large. FIG. 4 is a diagram showing the relationship between the Fermi energy and the Seebeck coefficient of graphene. As shown in FIG. 4, the Seebeck coefficient of graphene reaches a maximum when the Fermi energy is approximately 0.05 eV and a minimum when the Fermi energy is approximately −0.05 eV. Therefore, for example, the Fermi energy of the portion of the second graphene layer 22 overlapping with the third electrode 43 is controlled to approximately +0.05 eV or −0.05 eV, and the Fermi energy of the portion of the second graphene layer 22 overlapping with the fourth electrode 44 is controlled to approximately −0.05 eV or +0.05 eV, which is the opposite polarity.

[0027] The Seebeck coefficient S of graphene can be expressed by the following Mott approximation formula (formula (1)) and a phenomenological formula for the electrical conductivity σ of graphene (formula (2)). In formulas (1) and (2), e is the elementary charge, and k B is the Boltzmann constant, T is the absolute temperature, and ε F is the Fermi energy, and σ min and Δ is a phenomenological parameter.

[0028]

number

[0029]

number

[0030] According to equations (1) and (2), the absolute value of the Seebeck coefficient S of graphene is ε F = ±Δ, and in the region where the Fermi energy is higher, it monotonically decreases with respect to the Fermi energy. The relationship shown in Figure 4 is derived in this way. As shown in Figure 4, if the phenomenological parameter Δ is typically set to 100 meV, the Seebeck coefficient S of graphene is approximately 1 / 4 to 1 / 2 of the maximum value at Fermi energies of approximately 0.5 eV to 1.0 eV, which is suitable for plasmon resonance.

[0031] Infrared rays incident on the infrared sensor 1 are transmitted through the fifth electrode 55 and absorbed by the first graphene layer 21 (light absorption region). At this time, the Fermi energy of the first graphene layer 21 is controlled within a range in which light absorption due to plasmon resonance is likely to occur, so carriers in the first graphene layer 21 are heated with high efficiency. The heated and heated carriers flow out to the second graphene layer 22 (thermoelectric conversion region) adjacent to the first graphene layer 21 by thermal diffusion.

[0032] Since the Fermi energy of the second graphene layer 22 is controlled within a range in which the electromotive force due to the Seebeck effect is likely to be large, the carriers that have flowed into the second graphene layer 22 further flow by thermal diffusion to the first electrode 31 or the second electrode 32 depending on the polarity of the voltages applied to the third electrode 43 and the fourth electrode 44. In this way, an output responsive to infrared light is formed.

[0033] As described above, the range of Fermi energy in which light absorption due to plasmon resonance is likely to occur differs from the range of Fermi energy in which the electromotive force due to the Seebeck effect is likely to increase. In this embodiment, the Fermi energy of the first graphene layer 21 and the Fermi energy of the second graphene layer 22 can be controlled separately. This makes it possible to obtain high light absorption efficiency in the first graphene layer 21, which functions as a light absorption region, and high thermoelectric conversion efficiency in the second graphene layer 22, which functions as a thermoelectric conversion region. Therefore, this embodiment can achieve both high light absorption efficiency and high thermoelectric conversion efficiency.

[0034] The distance between the fifth electrode 55 and the first graphene layer 21 is preferably smaller than the distance between the control electrode 40 (the third electrode 43 and the fourth electrode 44) and the second graphene layer 22. This is to make it easier to apply, from the fifth electrode 55 to the first graphene layer 21, a voltage whose absolute value is higher than the absolute value of the voltage applied from the control electrode 40 to the second graphene layer 22.

[0035] (Second embodiment) Next, a second embodiment will be described. Fig. 5 is a top view showing an infrared sensor according to the second embodiment. Fig. 6 is a cross-sectional view showing the infrared sensor according to the second embodiment. FIG. 6 corresponds to a cross-sectional view taken along line VI-VI in FIG.

[0036] 5 and 6, in the infrared sensor 2 according to the second embodiment, an opening 13C is formed in the insulating layer 13, through which an end portion of the first graphene layer 21 on the Y2 side is exposed. A sixth electrode 56 is provided inside the opening 13C. The sixth electrode 56 is in contact with the first graphene layer 21. The sixth electrode 56 is made of, for example, the same material as the first electrode 31 and the second electrode 32. The first electrode 31 and the sixth electrode 56 are electrically connected.

[0037] The other configurations are the same as those in the first embodiment.

[0038] In the infrared sensor 2 according to the second embodiment, the polarity of the voltage applied to the fifth electrode 55 and the polarity of the voltage applied to the third electrode 43 are the same, and the polarity of the voltage applied to the fourth electrode 44 is opposite. For example, the polarities of the voltage applied to the fifth electrode 55 and the voltage applied to the third electrode 43 are positive, and the polarity of the voltage applied to the fourth electrode 44 is negative. Conversely, the polarities of the voltage applied to the fifth electrode 55 and the voltage applied to the third electrode 43 may be negative, and the polarity of the voltage applied to the fourth electrode 44 may be positive.

[0039] When the polarities of the voltages applied to the fifth electrode 55 and the third electrode 43 are positive and the polarity of the voltage applied to the fourth electrode 44 is negative, the conductivity type of the first graphene layer 21 becomes n-type, the conductivity type of the portion of the second graphene layer 22 closer to the first electrode 31 than the center line C becomes n-type, and the conductivity type of the portion closer to the second electrode 32 becomes p-type. In this case, electrons serving as carriers are heated in the first graphene layer 21, a current flows in response to the thermal diffusion of the electrons, and an output responsive to infrared rays is generated.

[0040] Furthermore, when the polarities of the voltages applied to the fifth electrode 55 and the third electrode 43 are negative and the polarity of the voltage applied to the fourth electrode 44 is positive, the conductivity type of the first graphene layer 21 becomes p-type, the conductivity type of the portion of the second graphene layer 22 closer to the first electrode 31 than the center line C becomes p-type, and the conductivity type of the portion closer to the second electrode 32 becomes n-type. In this case, holes serving as carriers are heated in the first graphene layer 21, a current flows in response to the thermal diffusion of the holes, and an output responsive to infrared light is generated.

[0041] In the first embodiment, when infrared light is irradiated intermittently, carriers that migrate from the first graphene layer 21 to the second graphene layer 22 while the infrared light is on can return to the first graphene layer 21 while the infrared light is off. In contrast, when infrared light is irradiated continuously, carriers continue to migrate from the first graphene layer 21 to the second graphene layer 22, causing carriers to accumulate in the second graphene layer 22 and generating an electric field between the first graphene layer 21 and the second graphene layer 22 in a direction that hinders carrier movement. When such an electric field is generated, there is a risk of a decrease in sensitivity.

[0042] In the second embodiment, carriers that have moved from the first graphene layer 21 to the second graphene layer 22 move to the first graphene layer 21 through the first electrode 31 and the sixth electrode 56. This prevents carriers from accumulating in the second graphene layer 22, and allows good sensitivity to be maintained even when infrared rays are continuously irradiated.

[0043] When the polarities of the voltages applied to the fifth electrode 55 and the third electrode 43 are positive and the polarity of the voltage applied to the fourth electrode 44 is negative, a current I1 flows from the sixth electrode 56 to the first electrode 31 outside the graphene layer 20, as shown in Fig. 7. When the polarities of the voltages applied to the fifth electrode 55 and the third electrode 43 are negative and the polarity of the voltage applied to the fourth electrode 44 is positive, a current I2 flows from the first electrode 31 to the sixth electrode 56 outside the graphene layer 20, as shown in Fig. 8.

[0044] (Third embodiment) Next, a third embodiment will be described below. Fig. 9 is a top view showing an infrared sensor according to the third embodiment.

[0045] 9, in the infrared sensor 3 according to the third embodiment, a DC power supply 61 is connected between the first electrode 31 and the sixth electrode 56. The positive electrode of the DC power supply 61 is connected to the first electrode 31, and the negative electrode is connected to the sixth electrode 56.

[0046] The other configurations are the same as those in the second embodiment.

[0047] In the infrared sensor 2 according to the second embodiment, the polarity of the voltage applied to the fifth electrode 55 is negative. The polarities of the voltages applied to the third electrode 43 and the fourth electrode 44 may be positive as long as they are opposite to each other. When the polarity of the voltage applied to the fifth electrode 55 is positive, the conductivity type of the first graphene layer 21 is n-type. When the polarity of the voltage applied to the third electrode 43 is positive and the polarity of the voltage applied to the third electrode 43 is negative, the conductivity type of the portion of the second graphene layer 22 closer to the first electrode 31 than the center line C is n-type, and the conductivity type of the portion of the second graphene layer 22 closer to the second electrode 32 than the center line C is p-type. On the other hand, when the polarity of the voltage applied to the third electrode 43 is negative and the polarity of the voltage applied to the third electrode 43 is positive, the conductivity type of the portion of the second graphene layer 22 closer to the first electrode 31 than the center line C is p-type, and the conductivity type of the portion of the second graphene layer 22 closer to the second electrode 32 than the center line C is n-type.

[0048] If the polarity of the voltage applied to the fifth electrode 55 is negative and the polarities of the voltages applied to the third electrode 43 and the fourth electrode 44 are opposite to each other, then, as shown in FIG. 10, a current I3 flows from the sixth electrode 56 to the first electrode 31 outside the graphene layer 20 via the DC power supply 61.

[0049] The third embodiment also provides the same effects as the second embodiment. In the third embodiment, the DC power supply 61 further promotes the diffusion of carriers.

[0050] (Fourth embodiment) Next, a fourth embodiment will be described below. Fig. 11 is a top view showing an infrared sensor according to the fourth embodiment.

[0051] 11, in the infrared sensor 4 according to the fourth embodiment, a DC power supply 62 is connected between the first electrode 31 and the sixth electrode 56. The positive electrode of the DC power supply 62 is connected to the sixth electrode 56, and the negative electrode is connected to the first electrode 31.

[0052] The other configurations are the same as those in the second embodiment.

[0053] In the infrared sensor 2 according to the second embodiment, the polarity of the voltage applied to the fifth electrode 55 is positive. The polarities of the voltages applied to the third electrode 43 and the fourth electrode 44 may be positive as long as they are opposite to each other. When the polarity of the voltage applied to the fifth electrode 55 is negative, the conductivity type of the first graphene layer 21 becomes p-type. When the polarity of the voltage applied to the third electrode 43 is positive and the polarity of the voltage applied to the third electrode 43 is negative, the conductivity type of the portion of the second graphene layer 22 closer to the first electrode 31 than the center line C becomes n-type, and the conductivity type of the portion of the second graphene layer 22 closer to the second electrode 32 than the center line C becomes p-type. On the other hand, when the polarity of the voltage applied to the third electrode 43 is negative and the polarity of the voltage applied to the third electrode 43 is positive, the conductivity type of the portion of the second graphene layer 22 closer to the first electrode 31 than the center line C becomes p-type, and the conductivity type of the portion of the second graphene layer 22 closer to the second electrode 32 than the center line C becomes n-type.

[0054] If the polarity of the voltage applied to the fifth electrode 55 is positive and the polarities of the voltages applied to the third electrode 43 and the fourth electrode 44 are opposite to each other, then, as shown in FIG. 12, outside the graphene layer 20, a current I4 flows from the first electrode 31 to the sixth electrode 56 via the DC power supply 61.

[0055] The fourth embodiment also provides the same effects as the second embodiment. In the fourth embodiment, the DC power supply 62 further promotes the diffusion of carriers.

[0056] (Fifth embodiment) Next, a fifth embodiment will be described. Fig. 13 is a cross-sectional view showing an infrared sensor according to the fifth embodiment. Fig. 13, like Fig. 2, corresponds to a cross-sectional view taken along line II-II in Fig. 1.

[0057] 13, the infrared sensor 5 according to the fifth embodiment has a reflective layer 57 that reflects infrared light that has passed through the first graphene layer 21 toward the first graphene layer 21. The reflective layer 57 is provided on, for example, the substrate 11 and is surrounded by an insulating layer 12. The reflective layer 57 overlaps with the first graphene layer 21 in a planar view. The reflective layer 57 is, for example, an Au layer.

[0058] The other configurations are the same as those in the first embodiment.

[0059] The fifth embodiment also provides the same effects as the first embodiment. Furthermore, since the infrared rays reflected by the reflective layer 57 are incident on the first graphene layer 21, the sensitivity can be improved.

[0060] In the second to fourth embodiments, a reflective layer 57 may be provided, as in the fifth embodiment.

[0061] The above describes in detail preferred embodiments, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0062] Various aspects of the present disclosure are summarized below as appendices.

[0063] (Appendix 1) a first graphene layer that absorbs infrared light using plasmon resonance; a second graphene layer having a connecting portion connected to the first graphene layer; a first electrode and a second electrode connected to the second graphene layer with the connecting portion sandwiched therebetween; a control electrode that controls a distribution of Fermi energy of the second graphene layer asymmetrically between the first electrode and the second electrode; An infrared sensor comprising: (Appendix 2) The control electrode is a third electrode disposed between the first electrode and the second electrode in a plan view; a fourth electrode disposed between the third electrode and the second electrode in a plan view; 2. The infrared sensor according to claim 1, comprising: (Appendix 3) With respect to a center line between the first electrode and the second electrode of the second graphene layer as a reference, the third electrode is disposed on the first electrode side, 3. The infrared sensor according to claim 2, wherein the fourth electrode is disposed on the second electrode side. (Appendix 4) 4. The infrared sensor according to claim 1, further comprising a fifth electrode for controlling the Fermi energy of the first graphene layer. (Appendix 5) 5. The infrared sensor of claim 4, wherein the distance between the fifth electrode and the first graphene layer is smaller than the distance between the control electrode and the second graphene layer. (Appendix 6) a sixth electrode connected to the first graphene layer; 6. The infrared sensor according to claim 1, wherein the first electrode and the sixth electrode are electrically connected. (Appendix 7) a sixth electrode connected to the first graphene layer; a DC power supply electrically connected between the first electrode and the sixth electrode; 6. The infrared sensor according to any one of claims 1 to 5, comprising: (Appendix 8) 8. The infrared sensor according to claim 1, wherein the first graphene layer has a plurality of openings formed periodically. (Appendix 9) 9. The infrared sensor according to claim 1, further comprising a reflective layer that reflects infrared light transmitted through the first graphene layer toward the first graphene layer. [Explanation of symbols]

[0064] 1, 2, 3, 4, 5: Infrared sensors 21: First graphene layer 22: Second graphene layer 22A: Connection part 31: 1st electrode 32:Second electrode 40: Control electrode 43:Third electrode 44: 4th electrode 55: 5th electrode 56: 6th electrode 57: Reflective layer 61, 62: DC power supply

Claims

1. a first graphene layer that absorbs infrared light using plasmon resonance; a second graphene layer having a connecting portion connected to the first graphene layer; a first electrode and a second electrode connected to the second graphene layer with the connecting portion interposed therebetween; a control electrode that controls a distribution of Fermi energy of the second graphene layer; and The control electrode is a third electrode disposed between the first electrode and the second electrode in a plan view; a fourth electrode disposed between the third electrode and the second electrode in a plan view; and Voltages having polarities opposite to each other are applied to the third electrode and the fourth electrode, the Fermi energy of the second graphene layer is controlled by the third electrode and the fourth electrode to be within a range in which an electromotive force due to the Seebeck effect in the second graphene layer is large; The infrared sensor is characterized in that the second graphene layer functions as a thermoelectric conversion region.

2. An infrared sensor as described in claim 1, characterized in that the Fermi energy of the portion of the second graphene layer overlapping with the third electrode is controlled to +0.05 eV or -0.05 eV by the third electrode and the fourth electrode, and the Fermi energy of the portion of the second graphene layer overlapping with the fourth electrode is controlled to the opposite polarity of -0.05 eV or +0.

05.

3. 2. The infrared sensor according to claim 1, further comprising a fifth electrode that controls the Fermi energy of the first graphene layer to a range in which light absorption due to plasmon resonance is likely to occur in the first graphene layer.

4. An infrared sensor as described in Claim 3, wherein the Fermi energy of the first graphene layer is controlled to +0.5 eV to +1.0 eV by the fifth electrode.

5. a sixth electrode connected to the first graphene layer; 5. The infrared sensor according to claim 1, wherein the first electrode and the sixth electrode are electrically connected to each other.

6. a sixth electrode connected to the first graphene layer; a DC power supply electrically connected between the first electrode and the sixth electrode; 5. The infrared sensor according to claim 1, further comprising:

7. The infrared sensor according to claim 1 , wherein a plurality of openings are periodically formed in the first graphene layer.

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