A MIM-enhanced and tunable mid-infrared photodetector

Abstract

The invention provides a MIM enhanced controllable mid-infrared photoelectric detector, wherein the upper surface of the substrate is separated into source / drain electrodes on both sides and a metal back reflection layer in the middle by a hexagonal boron nitride layer, the source / drain electrodes are titanium-gold metal composite electrodes, the lower layer is titanium as an adhesion layer, and the upper layer is gold; the metal back reflection layer is completely covered by the hexagonal boron nitride layer; a molybdenum disulfide layer and a black arsenic phosphide layer form a b‑AsP / MoS2 heterojunction, the overlapping part of the two layers is on the metal back reflection layer, and the molybdenum disulfide layer and the black arsenic phosphide layer respectively form ohmic contacts with the metal composite electrode on one side, and a MIM grating is integrated on the b‑AsP / MoS2 heterojunction junction region, and a transverse resonance mode is formed between the metal back reflection layer and the periodic metal grating, so that the light absorption of the b‑AsP / MoS2 heterojunction is significantly increased in the mid-wave band range after 4μm in the mid-wave infrared, thereby enhancing absorption control.

Description

Technical Field

[0001] The invention belongs to the technical field of mid-infrared detection, and in particular relates to a MIM-enhanced and controllable mid-infrared photoelectric detector. Background Art

[0002] Mid-wave infrared (MWIR), 3-5 μm photodetectors have been applied in a wide range of fields, including infrared astronomy and environmental monitoring. Black phosphorus (BP) is a new mid-infrared photodetector material with a moderate direct band gap of 0.3 eV / 4.1 μm and a high carrier mobility of -1000 cm 2 V -1 s -1 Black arsenic phosphorus (b-AsP) is a complex of black phosphorus and arsenic atoms in the form of As x P 1-x The alloy is formed in the form of arsenic, and its band gap changes from 0.3eV to 0.15eV accordingly as the composition x of arsenic changes. This energy range indicates that b-AsP may interact with light with a wavelength of up to 8.5μm. The extended detection range not only completely covers the first atmospheric window of mid-wavelength infrared 3~5μm, but also extends to the second atmospheric window of long-wave infrared 8~14μm, making b-AsP an extremely attractive material for ultra-wideband light detection and energy conversion.

[0003] Photodetectors based on b-AsP have the problem of large dark current, which will directly affect the performance of the detector.

[0004] For photodetectors based on b-AsP, the material's light absorption decreases when the infrared light wavelength exceeds 4μm, and the detector's detection performance decreases significantly.

[0005] In response to these problems, in the existing technology, Professor Miao Feng's research group at the School of Physics of Nanjing University and the scientific research cooperation team used b-AsP and MoS2 van der Waals heterojunctions to successfully achieve high-sensitivity mid-wave infrared photodetection at room temperature with performance exceeding that of existing commercial technologies. However, for this type of mid-wave infrared photodetector, these attractive material properties can usually only be observed at a smaller film thickness, which reduces the absorption and performance of the photodetector. Its detection performance still decreases significantly after the infrared light wavelength exceeds 4 μm.

[0006] On October 26, 2022, the 22nd issue of Nano Express, “Resonant Grating Enhanced Black Phosphorus Mid-Wave Infrared Photodetector”, disclosed an absorption-enhanced resonant metal-insulator-metal (MIM) metasurface grating integrated with a thin-film BP photodetector. When integrated with a thin-film BP photodetector, the MIM structure increases the room temperature responsivity from 12 mA·W to 1.5 mA·W at a wavelength of 3.37 μm. –1 Increased to 77 mA·W –1The MIM structure simultaneously increases the mid-wave infrared absorption and responsivity of the thin-film BP photodetector, achieving enhanced light absorption in the band less than 4 μm, but it cannot achieve enhanced detection of room-temperature mid-wave infrared above 4 μm.

[0007] The article "Black phosphorus molybdenum sulfide mid-wave infrared photodiode with broadband absorption enhanced metasurface" in Volume 23, Issue 21 of Nano Express, published on October 26, 2023, disclosed how the metasurface grating increases the absorption of BP-MoS2 heterojunction photodiodes in the MWIR wide wavelength range, but it also cannot achieve detection enhancement of room temperature mid-wave infrared above 4μm.

[0008] In addition, mature devices for broadband absorption enhancement and regulation of room temperature mid-wave infrared light beyond 4μm have not yet appeared. Therefore, how to solve the problem of light absorption enhancement and regulation of room temperature mid-wave infrared light beyond 4μm, and to provide a room temperature mid-wave infrared photoelectric detection device with enhanced and adjustable light absorption peak above 4μm is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0009] The purpose of the present invention is to provide a MIM-enhanced and controllable mid-infrared photodetector in view of the problems in the prior art.

[0010] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0011] A MIM-enhanced adjustable mid-infrared photodetector, characterized in that: the device comprises, from bottom to top, a substrate, a source / drain electrode and a metal back reflection layer, a hexagonal boron nitride layer, a molybdenum disulfide layer, a black arsenic phosphide layer and a MIM grating in sequence; the upper surface of the substrate is separated into source / drain electrodes on both sides and a metal back reflection layer in the middle by a hexagonal boron nitride layer; the source / drain electrode is a titanium-gold metal composite electrode, wherein the lower layer is titanium as an adhesion layer and the upper layer is gold; the metal back reflection layer is completely covered by the hexagonal boron nitride layer; the molybdenum disulfide layer and the black arsenic phosphide layer form a b-AsP / MoS2 heterojunction, the overlapping part of the two layers is on the metal back reflection layer, and the molybdenum disulfide layer and the black arsenic phosphide layer respectively form ohmic contacts with the metal composite electrode on one side;

[0012] The thicknesses of the hexagonal boron nitride layer, the molybdenum disulfide layer, and the black arsenic phosphorus layer are as follows:

[0013]

[0014] Wherein, n1, n2, n3 are the refractive indices of black arsenic phosphide, molybdenum disulfide, and hexagonal boron nitride, respectively; d1, d2, d3 are the thicknesses of the black arsenic phosphide layer, molybdenum disulfide layer, and hexagonal boron nitride layer, respectively; λ is the wavelength of the incident light; and m is an integer;

[0015] The MIM grating is integrated on the b-AsP / MoS2 heterojunction junction area. By forming a lateral resonance mode between the metal back reflection layer and the periodic metal grating, the light absorption of the b-AsP / MoS2 heterojunction in the medium-wave infrared band after 4μm is significantly increased. The duty cycle and period of the MIM grating are adjusted to enhance the absorption of infrared light of specific wavelengths in the medium-wave band after 4μm, thereby improving the light absorption rate of the device and changing the absorption peak position.

[0016] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0017] As a preferred technical solution of the present invention: the thickness of the hexagonal boron nitride layer is 60-200 nm;

[0018] The thickness of the MoS2 layer is 20 nm;

[0019] The thickness of the black arsenic phosphorus layer is 80 nm;

[0020] The thickness of the metal film in the MIM grating is 50nm, the grating period P=3μm-4μm, and the grating duty cycle d=0.5-0.9.

[0021] As a preferred technical solution of the present invention: when the period of the MIM grating is 3.5 μm, the duty cycle increases from 0.5 to 0.9, and the peak position of the light absorption spectrum red-shifts from 4 μm to 5.5 μm.

[0022] As a preferred technical solution of the present invention: the duty cycle of the MIM grating is 0.65, the period increases from 3μm to 4μm, and the peak position of the light absorption spectrum red-shifts from 4μm to 5μm; there is a second absorption peak near 6μm, and the surface plasmon resonance coupling enhanced by the MIM grating enhances the absorption here, which will also red-shift when the duty cycle or period increases, and the resonance intensity is enhanced, the absorption rate increases, and its peak position varies between 6μm-6.3μm.

[0023] As a preferred technical solution of the present invention: the direction of the grating lines of the MIM grating is perpendicular to the high absorption axis of b-AsP.

[0024] As a preferred technical solution of the present invention: the metal in the MIM grating is gold, the length is 40 μm, and there are 8 periods.

[0025] As a preferred technical solution of the present invention: the metal back reflection layer is gold.

[0026] As a preferred technical solution of the present invention: two hexagonal boron nitride layers are provided, and the stacked portion of the two hexagonal boron nitride layers completely covers the metal back reflection layer.

[0027] As a preferred technical solution of the present invention: in the substrate, the thickness of the single crystal silicon is 500 μm, and the thickness of the SiO2 insulating layer on its surface is 285 nm;

[0028] The thickness of titanium is 5 nm;

[0029] The thickness of gold is 95nm;

[0030] The thickness of the hexagonal boron nitride layer is 60-200 nm;

[0031] The thickness of the MoS2 layer is 20 nm;

[0032] The thickness of the black arsenic phosphorus layer is 80 nm.

[0033] As a preferred technical solution of the present invention: in the black arsenic phosphorus layer, the number of As atoms in the b-AsP crystal accounts for 90%.

[0034] Compared with the prior art, the MIM-enhanced adjustable mid-infrared photodetector of the present invention has the following beneficial effects: by utilizing the metal back reflection layer, the MIM grating, and the dielectric layer arranged therebetween, a transverse resonance mode is formed between the metal back reflection layer and the metal grating in the MIM grating, so that the response wavelength becomes larger and red-shifts, thereby solving the problem that the MIM grating cannot form an effective and stable resonance in the medium-wave band after 4 μm. Through the transverse resonance, the incident light undergoes multiple reflections and propagations, which significantly enhances the absorption of light in the black arsenic phosphorus layer, so that the detector of the present invention has high absorption efficiency in the room temperature medium-wave wavelength range after 4 μm.

[0035] In the present invention, the diffraction behavior of the MIM grating is utilized, and the period and duty cycle of the grating are adjusted to move the absorption peak toward the medium-wave band after 4 μm.

[0036] In the present invention, the light absorption rate of the b-AsP / MoS2 heterojunction enhanced by the MIM grating in the medium-wave band after 4μm at room temperature is increased by 3 to 5 times, and the response rate is at least doubled, which solves the problem of insufficient light absorption of room-temperature medium-wave detectors after 4μm and the inability to control the enhanced light absorption of the device, making the detector of the present invention extremely promising in the field of room-temperature medium-wave infrared, especially 4-6μm band infrared photoelectric detection.

[0037] In the present invention, the dielectric layer is composed of a b-AsP / MoS2 heterojunction and a hexagonal boron nitride layer, so that a transverse resonance mode is formed in the dielectric layer by incident light, and the light is reflected and propagated multiple times in the dielectric layer, which increases the interaction time between the light and the medium, and the b-AsP fully absorbs the light and forms a heterojunction with MoS2 to generate a response. The surface plasmons propagating along the metal surface formed by the MIM grating structure and the metal back reflection layer cooperate with the detection enhancement of the b-AsP / MoS2 heterojunction, which solves the problem that the b-AsP / MoS2 detector in the prior art cannot realize the detection of mid-wave infrared photoelectric detection devices after 4μm at room temperature, realizes the enhancement of light absorption and response rate in this band, can efficiently utilize light energy, and improve the performance of photoelectric devices, so that the detector of the present invention has great application prospects in the field of mid-infrared photoelectric detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of the MIM-enhanced and controllable mid-infrared photodetector of the present invention;

[0039] Figure 2 A schematic diagram of the three-dimensional structure of the MIM-enhanced and controllable mid-infrared photodetector of the present invention;

[0040] Figure 3 The light absorption rate and peak position of b-AsP / MoS2 heterojunction with and without MIM grating when the MIM grating size is period P=3.5 μm and duty cycle d=0.65;

[0041] Figure 4 The light absorption rate and peak position of b-AsP / MoS2 heterojunction with and without MIM grating when the period of MIM grating is P=3.5 μm and the duty cycle is d=0.70;

[0042] Figure 5 The light absorption rate and peak position of b-AsP / MoS2 heterojunction with and without MIM grating when the period of MIM grating is P=3.5 μm and the duty cycle is d=0.83;

[0043] Figure 6 The two-dimensional field diagram of the light absorption rate of the b-AsP / MoS2 heterojunction with respect to the MIM grating duty cycle and the infrared light wavelength when the period of the MIM grating is P = 3.5μm;

[0044] In the figure, there is a MIM grating 1 , a black arsenic phosphide layer 2 , a molybdenum disulfide layer 3 , a hexagonal boron nitride layer 4 , gold 5 , titanium 6 , a silicon dioxide layer 7 , and a silicon layer 8 . DETAILED DESCRIPTION

[0045] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. Example 1

[0046] like Figure 1-Figure 2 As shown, a MIM-enhanced adjustable mid-infrared photodetector of the present invention comprises, from bottom to top, a substrate, a source / drain electrode and a metal back reflection layer, a hexagonal boron nitride layer 4, a molybdenum disulfide layer 3, a black arsenic phosphorus layer 2 and a MIM grating 1 in sequence, the upper surface of the substrate is separated into source / drain electrodes on both sides and a metal back reflection layer in the middle by a hexagonal boron nitride layer, the source / drain electrode is a titanium-gold metal composite electrode, wherein the lower layer is titanium 6 as an adhesion layer and the upper layer is gold 5; the metal back reflection layer is completely covered by the hexagonal boron nitride layer; the molybdenum disulfide layer 3 and the black arsenic phosphorus layer 2 form a b-AsP / MoS2 heterojunction, the overlapping part of the two layers is on the metal back reflection layer, and the molybdenum disulfide layer and the black arsenic phosphorus layer respectively form ohmic contacts with the metal composite electrode on one side;

[0047] The MIM grating is integrated on the junction area of ​​the b-AsP / MoS2 heterojunction, which significantly increases the light absorption of the b-AsP / MoS2 heterojunction in a specific mid-wave infrared region, thereby enhancing the performance of the photodetector. The MIM grating duty cycle is adjusted to directionally control infrared light in the 4-6μm band.

[0048] The direction of the grating lines of the grating is perpendicular to the high absorption axis of b-AsP, the thickness of the metal film in the MIM grating is 50nm, the grating period P=3.5μm, and the grating duty cycle d=0.5~0.9.

[0049] The metal in MIM grating 1 is gold, 40 μm long, and has 8 periods in total.

[0050] The metal back reflector is gold 5.

[0051] There are two hexagonal boron nitride layers, and the stacked portion of the two hexagonal boron nitride layers completely covers the metal back reflection layer.

[0052] In the substrate, the thickness of the single crystal silicon layer 8 is 500 μm, and the thickness of the insulating silicon dioxide layer 7 on its surface is 285 nm;

[0053] The thickness of titanium 6 is 5 nm;

[0054] The thickness of gold 5 is 95 nm;

[0055] The thickness of the hexagonal boron nitride layer 4 is 110 nm;

[0056] The thickness of the molybdenum disulfide layer 3 is 20 nm;

[0057] The thickness of the black arsenic phosphorus layer 2 is 80 nm.

[0058] In theory, stacking b-AsP and MoS2 into a vertical van der Waals heterojunction can produce optoelectronic devices with relatively excellent performance. While ensuring the carrier collection efficiency, MoS2 can also reduce the dark current by forming a potential barrier with b-AsP.

[0059] The MIM grating is integrated on the b-AsP / MoS2 heterojunction junction area. By forming a lateral resonance mode between the metal back reflection layer and the periodic metal grating, the light absorption of the b-AsP / MoS2 heterojunction in the medium-wave infrared band after 4μm is significantly increased. The duty cycle and period of the MIM grating are adjusted to enhance the absorption of infrared light of specific wavelengths in the medium-wave band after 4μm, thereby improving the light absorption rate of the device and changing the absorption peak position.

[0060] In the present invention, the source and drain electrodes form ohmic contacts with the molybdenum disulfide layer and the black arsenic phosphorus layer respectively, and the formed photocurrent loop realizes efficient photoelectric conversion and transmission; hBN is a good dielectric layer, which provides sufficient thickness for the MIM grating. The metal back reflection layer can reflect the transmitted incident light back, so that the incident light and the reflected light are constructive. The metal grating and the metal back reflector wrap the b-AsP layer and the MoS2 layer to support the MIM mode. In the generated localized mode, the grid width is the main factor determining the peak position, and its size is equal to the period * duty cycle, and its direction just corresponds to the strong absorption direction of b-AsP. At the same time, MIM enhances the surface plasmon, and these structures work together to maximize the light absorption of the AsP material. b-AsP is a p-type semiconductor and MoS2 is an n-type semiconductor, and the two form a heterojunction. A large number of photogenerated carriers generated by b-AsP are transmitted through MoS2 and collected by the metal electrode to form a photocurrent.

[0061] In the invention, by selecting different hBN thicknesses and changing the duty cycle or period, the peak position of the light absorption spectrum has changed significantly. When the MIM grating period is 3.5μm, the duty cycle increases from 0.5 to 0.9, and the peak position of the light absorption spectrum can be red-shifted from 4μm to 5.5μm; when the MIM grating duty cycle is 0.65, the period increases from 3μm to 4μm, and the peak position of the light absorption spectrum can be red-shifted from 4μm to 5μm; in the MIM localized mode here, the grating bar width is the main factor determining the peak position, and the bar width is equal to the period multiplied by the duty cycle, which plays a major role in the influence of the peak position. In addition, there is a second absorption peak near 6μm, and the MIM-enhanced surface plasmon resonance coupling enhances the absorption here, which will also be red-shifted when the duty cycle or period increases, and its peak position varies between 6μm-6.3μm.

[0062] In the MIM local mode here, the grating bar width is the main factor determining the peak position, and the grating bar width is equal to the period multiplied by the duty cycle, which plays a major role in the influence of the peak position. In the MIM grating of the present invention, there is a dielectric layer between the metal back reflection layer and the metal grating, and the dielectric layer is composed of b-AsP / MoS2 heterojunction and hBN. When the wavelength of the incident light matches the thickness and refractive index of the dielectric layer, a transverse resonance mode can be formed in the dielectric layer. The transverse resonance mode makes the light reflect and propagate multiple times in the dielectric layer, thereby increasing the interaction time between the light and the medium. As a light absorbing material, b-AsP can fully absorb light and form a heterojunction with MoS2 to produce a response.

[0063] The conditions for resonance generation are usually determined by the thickness and refractive index of the dielectric layer. When the thickness of the dielectric layer is equal to an integer multiple of the half wavelength of light in the medium, a resonance mode can be formed. For the present invention, its mathematical relationship can be expressed as:

[0064]

[0065] Among them, n1, n2, n3 are the refractive indices of b-AsP, MoS2, and hBN, respectively; d1, d2, d3 are the thicknesses of b-AsP, MoS2, and hBN, respectively; λ is the wavelength of the incident light, and m is an integer.

[0066] At the same time, the grating has diffraction behavior at sub-wavelength size. The local effect of sub-wavelength grating on infrared light can be analyzed by diffraction theory, and its diffraction efficiency and direction can be calculated by the following formula:

[0067]

[0068] I m is the intensity of the mth order diffracted light, I0 is the intensity of the incident light, d is the grating period, λ is the wavelength, and θ is the diffraction angle. The grating size can be tuned to the maximum diffraction position for a specific incident light wavelength. At the same time, although there is no direct mathematical relationship between the grating duty cycle and the diffraction angle, the duty cycle affects the diffraction efficiency of the grating, and thus affects the position and intensity of the absorption peak of light absorption. When the duty cycle increases, the width of the grating increases, which causes the wave vector mismatch of the resonant mode, thereby affecting the frequency and intensity of the resonant mode. Specifically, an increase in the duty cycle will shift the frequency of the resonant mode toward low frequencies, thereby moving the absorption peak toward the long-wave direction. In the present invention, adjusting different parameters of the structure can achieve enhanced absorption of light of a specific wavelength, and tuning the MIM grating size can achieve maximum light absorption of the most specific wavelength of light.

[0069] In the prior art, b-AsP / MoS2 can only generate light response by light transmitted through the material, and the light absorption rate in this case is often not high.

[0070] After the structure is introduced, the MIM grating forms a transverse resonance mode between the metal back reflection layer and the periodic metal grating, so that the incident light is reflected and propagated multiple times in the structure. The transverse resonance mode can significantly increase the absorption of light in the medium b-AsP. This makes the MIM structure have a high absorption efficiency in a specific wavelength range, thereby improving the performance of the photodetector.

[0071] Compared with the prior art, the MIM grating with specific absorption enhancement characteristics of the present invention is integrated with the b-AsP / MoS2 heterojunction, which improves the problem of poor light response performance of the detector caused by insufficient light absorption of the device after 4μm, making the detector of the present invention extremely promising in the field of room temperature mid-wave infrared, especially 4-6μm band infrared photoelectric detection.

[0072] like Figure 3 As shown in the figure, by integrating the MIM grating structure, the light absorption of the b-AsP / MoS2 heterojunction mid-infrared photodetector is significantly enhanced, and the absorptivity of the material at 4.6 μm is increased from 0.18 to 0.72. In the present invention, by adjusting the structural parameters of the MIM grating, the absorption enhancement at a specific wavelength or in a wide spectral range is achieved. Using different duty cycles under the same grating period, at P=3.5μm, they are d=0.65, d=0.70, and d=0.83, respectively. Figure 3 , Figure 4 and Figure 5 As shown, the peak absorption rate appears at 4.6μm, 4.83μm, and 5.25μm, and the absorption rate increases from 0.18 to 0.72, from 0.12 to 0.40, and from 0.12 to 0.40, respectively. The second absorption peak increases from 0.05 to 0.22 at 6.1μm, from 0.05 to 0.23 at 6.17μm, and from 0.05 to 0.27 at 6.3μm.

[0073] like Figure 6 As shown: When the period of the MIM grating is P=3.5μm, the light absorption rate of the b-AsP / MoS2 heterojunction for light of different wavelengths and its changes under different duty cycles are shown.

[0074] Constructing a heterojunction of MoS2 and b-AsP is an effective way to effectively suppress dark current. At the same time, the design and introduction of a metal-insulator-metal (MIM) metasurface grating integrated with a thin layer of b-AsP can improve the light absorption rate of the material and thus enhance the device performance.

[0075] The specific implementation is:

[0076] 1. Prepare the substrate:

[0077] A single crystal silicon with a thickness of 500 μm and a 285 nm thick SiO2 insulating layer on the surface was used as the substrate. Ultrasonic cleaning was performed twice using acetone and isopropanol as cleaning agents to remove surface contaminants (particles, organic matter, process residues, and mobile ions).

[0078] 2. Deposition of metal electrodes and metal reflective layers

[0079] Spin-coat the photoresist on the prepared substrate, expose it using maskless lithography, and then develop it. This step will transfer the pre-prepared pattern to the photoresist. Subsequently, electron beam evaporation is used to deposit titanium (Ti) with a thickness of 5 nm on the surface as an adhesion layer, and then gold (Au) with a thickness of 95 nm is deposited. The photoresist is stripped with an organic solvent to form source / drain electrodes distributed on both sides and a metal back reflection layer distributed in the center.

[0080] 3. Deposition of grating

[0081] Similar to the deposition of metal electrodes and metal back reflection layers, photoresist is spin-coated on the prepared substrate, exposed using maskless lithography, and then developed. This step will transfer the grating pattern to the photoresist. Subsequently, electron beam evaporation is used to deposit 50 nm thick gold (Au) on the surface. The photoresist is stripped off with an organic solvent to form a grating structure. The specific dimensions of the grating are 40 μm long, 8 periods in total, period T=3.5 μm, and duty cycle P=0.65.

[0082] 3. Stripping and transfer of hexagonal boron nitride (hBN), molybdenum disulfide (MoS2) and black arsenic phosphorus (b-AsP):

[0083] Thin layers of materials were obtained by mechanical exfoliation from bulk crystals of hBN, MoS2, and b-AsP (purchased from HQ Graphene) using tape and transferred to a clean substrate. The materials were transferred to the designated positions using a polydimethylsiloxane (PDMS) stamp. It should be noted that hBN and MoS2 can be operated in air, and b-AsP needs to be exfoliated and transferred in an argon-filled glove box to avoid oxidation of b-AsP and exposure to water vapor. The b-AsP crystals we used here have an As atomic ratio of 90%.

[0084] An atomic force microscope (AFM) is used to characterize the thickness of hBN, MoS2 and b-AsP. By observing and comparing the color characteristics of materials of different thicknesses under an optical microscope, the material with the thickness required for this implementation scheme is judged and selected.

[0085] After confirming the thickness of the material sample, first use PDMS to transfer 1~2 pieces of hBN material with a total thickness of 120-140 nm to the metal back reflector on the substrate, so that the two hBN samples are stacked and completely covered on the metal back reflector. Then use PDMS to transfer a 20 nm thick MoS2 material and an 80 nm thick b-AsP material to construct a b-AsP / MoS2 heterojunction. The overlapping part of the two materials is on the metal back reflector, and the two materials form ohmic contacts with the metal electrodes on one side respectively.

[0086] 4. Determination of the b-AsP crystal axis

[0087] b-AsP is an anisotropic material with two orthogonal axes, usually the armchair direction (AC) along the x direction and the zigzag direction (ZZ) along the y direction. The absorptivity (A) of b-AsP samples at different polarization angles was measured using a Fourier transform infrared spectrometer (FTIR) to determine the high absorption axis (AC axis) and low absorption axis (ZZ axis) of b-AsP.

[0088] 5. Transfer of MIM grating

[0089] The fabricated grating structure was transferred from the substrate to the junction area of ​​the b-AsP / MoS2 heterojunction using a PDMS stamp by dry transfer. It should be noted that in order to maximize absorption, the direction of the MIM grating lines was designed to be perpendicular to the high absorption axis (AC axis) of b-AsP.

[0090] In this application:

[0091] b-AsP is black arsenic phosphorus.

[0092] MoS2 is molybdenum disulfide.

[0093] MIM grating is metal-insulator-metal grating;

[0094] hBN is hexagonal boron nitride.

[0095] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A MIM-enhanced controllable mid-infrared photodetector, characterized in that: The device includes, from bottom to top, a substrate, a source / drain electrode and a metal back reflection layer, a hexagonal boron nitride layer, a molybdenum disulfide layer, a black arsenic phosphide layer and a MIM grating in sequence. The upper surface of the substrate is separated into source / drain electrodes on both sides and a metal back reflection layer in the middle by a hexagonal boron nitride layer. The source / drain electrode is a titanium-gold metal composite electrode, wherein the lower layer is titanium as an adhesion layer and the upper layer is gold; the metal back reflection layer is completely covered by the hexagonal boron nitride layer; the molybdenum disulfide layer and the black arsenic phosphide layer form a b-AsP / MoS2 heterojunction, and the overlapping part of the two layers is on the metal back reflection layer, and the molybdenum disulfide layer and the black arsenic phosphide layer respectively form ohmic contacts with the metal composite electrode on one side; The thicknesses of the hexagonal boron nitride layer, the molybdenum disulfide layer, and the black arsenic phosphorus layer are as follows: , where n1, n2, and n3 are the refractive indices of black arsenic phosphide, molybdenum disulfide, and hexagonal boron nitride, respectively; d1, d2, and d3 are the thicknesses of the black arsenic phosphide layer, molybdenum disulfide layer, and hexagonal boron nitride layer, respectively; λ is the wavelength of the incident light, and m is an integer.

2. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: The thickness of the hexagonal boron nitride layer is 60-200 nm; The thickness of the MoS2 layer is 20 nm; The thickness of the black arsenic phosphorus layer is 80 nm; The thickness of the metal film in the MIM grating is 50nm, the grating period P=3μm-4μm, and the grating duty cycle d=0.5-0.

9.

3. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: When the period of the MIM grating is 3.5μm, the duty cycle increases from 0.5 to 0.9, and the peak position of the light absorption spectrum red-shifts from 4μm to 5.5μm.

4. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: The duty cycle of the MIM grating is 0.65, and the period increases from 3μm to 4μm. The peak position of the light absorption spectrum red-shifts from 4μm to 5μm, and red-shifts when the duty cycle or period increases. The resonance intensity is enhanced, and the absorption rate increases. Its peak position varies from 6μm to 6.3μm, forming a second absorption peak.

5. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: The grating lines of the MIM grating are oriented perpendicular to the high absorption axis of b-AsP.

6. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: The metal in the MIM grating is gold, with a total of 8 periods and a length of 40 μm.

7. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: The metal back reflector is gold.

8. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: There are two hexagonal boron nitride layers, and the stacked portion of the two hexagonal boron nitride layers completely covers the metal back reflection layer.

9. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: In the substrate, the thickness of the single crystal silicon is 500 μm, and the thickness of the SiO2 insulating layer on its surface is 285 nm; The thickness of titanium is 5 nm; The thickness of gold is 95 nm.

10. The MIM-enhanced controllable mid-infrared photodetector according to claim 1, characterized in that: In the black arsenic phosphorus layer, the number of As atoms in the b-AsP crystal accounts for 90%.

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