Self-driven photodetector and preparation method thereof

Abstract

A self-driven photodetector and a preparation method thereof, comprising a silicon substrate sheet, the silicon substrate sheet comprising a bottom layer of silicon and a silicon dioxide layer, a graphene layer, covering the surface of the silicon dioxide layer for collecting photo-generated carriers transmitted from a light absorption layer and leading out current, a tunneling layer material being hexagonal boron nitride, covering the surface of the graphene layer and the silicon dioxide layer, a light absorption layer material being molybdenum disulfide, located on the surface of the tunneling layer for absorbing light and generating photo-generated carriers, and a metal electrode, provided with two groups and arranged on the surface of the graphene layer and the light absorption layer respectively for connecting an external circuit, by constructing a unique structure of graphene / hexagonal boron nitride / molybdenum disulfide heterojunction, the characteristics of hexagonal boron nitride with NBVN anti-site nitrogen vacancy defects are fully utilized, so that the detector can internally generate current by itself only through light in the state of no external bias, realizing photoelectric detection without external bias, and the high sensitivity of the material itself realizes rapid and stable detection.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection equipment, specifically a self-driven photoelectric detector. Background Technology

[0002] Since the discovery of graphene in 2004 ushered in a new era of research on two-dimensional materials, the application of these materials in the fields of electronics and optoelectronics has made great strides. They play an important role in fields such as transistors, photodetectors, optical modulators, supercapacitors, and solar cells. Through the clever selection of different two-dimensional materials and precise stacking techniques, we can maximize the utilization of the unique properties of each material. Photodetectors based on two-dimensional materials exhibit many advantages, such as extremely high response rates, excellent detection efficiency, wide bandwidth compatibility, and extremely short response delays.

[0003] However, these detectors often require an external bias to function, a limitation that makes them difficult to popularize in environments where wiring is not possible or continuous power supply is difficult. At the same time, due to interference from dark current, the switching ratio of these photodetectors is usually not ideal, and the response time is mostly in the millisecond range, which limits their application in optical switching.

[0004] The publication number CNCN201811181613.4 discloses a three-in-one composite self-driven photodetector and its fabrication method. It uses a perovskite solar cell, a thermoelectric generator, and a pressure generator connected in parallel as the voltage drive for the perovskite photodetector. The perovskite solar cell, thermoelectric generator, and pressure generator can each provide voltage to the perovskite photodetector individually. At the same time, the thermoelectric generator converts thermal energy into electrical energy, and the pressure generator converts external kinetic energy into electrical energy.

[0005] Although the aforementioned existing technologies can achieve photoelectric detection without external power, they still require a power system to power the detection system, and the detection device itself still requires an external bias voltage. Summary of the Invention

[0006] The purpose of this invention is to provide a self-driven photodetector to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A self-driven photodetector, comprising:

[0009] A silicon substrate comprising a bottom silicon layer and a silicon dioxide layer stacked sequentially from bottom to top, wherein the bottom silicon layer provides mechanical support and the silicon dioxide layer provides electrical isolation;

[0010] A graphene layer, which covers the surface of a silicon dioxide layer, is used to collect photogenerated carriers transmitted from the light-absorbing layer and to conduct current.

[0011] A tunneling layer, which covers the surface of the graphene layer and the silicon dioxide layer, is used to provide electrical isolation between the graphene layer and the light-absorbing layer, preventing direct contact between the graphene layer and the light-absorbing layer. The material of the tunneling layer is hexagonal boron nitride.

[0012] A light-absorbing layer is located on the surface of the tunneling layer and is used to absorb light and generate photogenerated carriers. The carriers are transported to the graphene layer through the tunneling layer. The material of the light-absorbing layer is molybdenum disulfide.

[0013] The metal electrode has two sets disposed on the surfaces of the graphene layer and the light absorption layer, respectively. One set is in ohmic contact with the graphene layer as the drain electrode, and the other set is in ohmic contact with the light absorption layer as the source electrode. It is used to connect to an external circuit to extract the photogenerated carriers generated by the light absorption layer.

[0014] Preferably, the molybdenum disulfide material in the tunneling layer has defects of NBVN anti-nitrogen vacancies.

[0015] Preferably, the light absorption layer is biased on the upper surface of one side of the tunneling layer, and the graphene layer is biased on the lower surface of the other side of the tunneling layer. The graphene layer, the tunneling layer and the light absorption layer constitute a graphene / hexagonal boron nitride / molybdenum disulfide heterojunction with the tunneling layer as a potential barrier.

[0016] Preferably, the thickness of the silicon dioxide layer on the silicon substrate ranges from 200nm to 300nm, the thickness of the graphene layer ranges from 0.34nm to 0.77nm, the thickness of the tunneling layer ranges from 10nm to 20nm, the thickness of the light absorption layer ranges from 0.65nm to 0.88nm, and the metal electrode material is a chromium-gold alloy.

[0017] The present invention also provides a method for fabricating a self-driven photodetector, the method being used to fabricate the aforementioned self-driven photodetector, the specific steps of which include:

[0018] S1. Graphene layer is obtained by mechanical exfoliation and attached to the silicon dioxide layer surface of silicon substrate. Similarly, hexagonal boron nitride tunneling layer and molybdenum disulfide light absorption layer are prepared by polymer sacrificial substrate using mechanical exfoliation.

[0019] S2. By dry transfer, the hexagonal boron nitride tunneling layer is aligned with the graphene layer and bonded together, and the molybdenum disulfide light-absorbing layer is aligned with the hexagonal boron nitride tunneling layer and bonded together, thus forming a three-layer heterostructure.

[0020] S3. Apply a uniformly thick photoresist film to the three-layer heterojunction using a spin coater.

[0021] S4. Electrode patterns are delineated by electron beam exposure, followed by development and fixing;

[0022] S5. Use a vacuum evaporation method to deposit chromium-gold alloy metal electrodes and clean them.

[0023] Preferably, the silicon substrate with a silicon dioxide layer thickness of 200nm-300nm obtained by dry oxidation is a polydimethylsiloxane.

[0024] Preferably, in a glove box under an inert gas atmosphere, a hexagonal boron nitride tunneling layer is bonded to a graphene layer, and an absorber layer of molybdenum disulfide is bonded to a hexagonal boron nitride tunneling layer. Both layers are heated to 55°C for 10 minutes to achieve a fully bonded three-layer heterostructure. After the three-layer heterostructure is stacked, it is annealed in an inert atmosphere at a temperature of 150°C, a heating rate of 5°C / min, and a time of 120 minutes.

[0025] Preferably, the photoresist used is polymethyl methacrylate, and the spin coater used is set to a low speed of 500 r / min for 5 seconds and a high speed of 4000 r / min for 60 seconds for 5 minutes at 150°C. In the developing stage, the developing solution is a 1:3 mixture of deionized water and isopropanol, and the developing time is 25 seconds. Immediately after the developing is completed, the silicon wafer is quickly placed into the fixing solution, which is an isopropanol solution, and the fixing time is 30 seconds.

[0026] Preferably, 5 nm of chromium and 50 nm of gold are deposited by electron beam evaporation at a rate of 5 A / s, followed by cleaning of the device.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] This invention utilizes the unique structure of graphene / hexagonal boron nitride / molybdenum disulfide heterojunction to fully leverage the characteristics of hexagonal boron nitride with NBVN anti-site nitrogen vacancy defects. This allows the detector to generate an internal current simply by illumination without external bias, achieving photoelectric detection without external bias. Furthermore, the high sensitivity of the material itself enables rapid and stable detection. Attached Figure Description

[0029] Figure 1 This is a schematic cross-sectional view of the structure of the present invention;

[0030] Figure 2 This is a response time curve of the present invention;

[0031] Figure 3 This is a self-driving curve diagram of the present invention;

[0032] Figure 4 This is a response diagram of the present invention to light of different wavelengths;

[0033] In the diagram: 10 Silicon substrate, 11 Bottom silicon layer, 12 Silicon dioxide layer, 20 Conductive layer, 30 Tunneling layer, 40 Light absorption layer, 50 Metal electrode. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example:

[0036] Please see Figures 1 to 4 The present invention provides a technical solution:

[0037] A self-driven photodetector, comprising:

[0038] The silicon substrate 10 includes a bottom silicon layer 11 and a silicon dioxide layer 12 stacked sequentially from bottom to top. The bottom silicon layer 11 is used to provide mechanical support to ensure the stability and durability of the entire photodetector structure. The silicon dioxide layer 12 is used for electrical isolation to prevent current leakage between the bottom silicon layer 11 and other conductive layers, thereby improving the operating efficiency and reliability of the device.

[0039] A graphene layer 20 covers the surface of the silicon dioxide layer 12 and is used to collect photogenerated carriers transported from the light-absorbing layer 40 and conduct current. Due to its excellent conductivity and ultra-high carrier mobility, graphene can quickly and efficiently conduct electrons and holes, thereby improving the response speed and sensitivity of the photodetector. Furthermore, the two-dimensional structure and high transmittance of graphene allow it to effectively collect photogenerated carriers generated by the light-absorbing layer 40 without significant light absorption.

[0040] The tunneling layer 30 covers the surfaces of the graphene layer 20 and the silicon dioxide layer 12, and is used to provide electrical isolation between the graphene layer 20 and the light-absorbing layer 40, preventing direct contact between the graphene layer 20 and the light-absorbing layer 40. The material of the tunneling layer 30 is hexagonal boron nitride, which has excellent electrical insulation properties and thermal stability. At the same time, its lattice structure matches that of graphene and molybdenum disulfide, which helps to form a high-quality interface.

[0041] The light absorption layer 40 is located on the surface of the tunneling layer 30 and is used to absorb light and generate photogenerated carriers. The material of the light absorption layer 40 is molybdenum disulfide. As a two-dimensional semiconductor material, molybdenum disulfide has a direct bandgap structure and can efficiently absorb visible light and near-infrared light. The photogenerated carriers (electron-hole pairs) generated by the light absorption layer 40 are transported to the graphene layer 20 through the tunneling layer 30, thereby forming a photocurrent and improving the photoelectric conversion efficiency of the detector.

[0042] The metal electrode 50 has two sets disposed on the surfaces of the graphene layer 20 and the light absorption layer 40, respectively. One set is in ohmic contact with the graphene layer 20 as the drain electrode, and the other set is in ohmic contact with the light absorption layer 40 as the source electrode. It is used to connect to the external circuit and to extract the photogenerated carriers generated by the light absorption layer 40 so as to realize the effective output and transmission of photoelectric signals.

[0043] As a preferred embodiment, the tunneling layer 30 molybdenum disulfide material has the defect of NBVN anti-nitrogen vacancy. This defect forms a unique mechanism in molybdenum disulfide material: nitrogen atoms mistakenly occupy the lattice positions that originally belonged to boron atoms, while the positions of the original nitrogen atoms become vacant. This atomic-scale structural rearrangement leads to a significant distortion of the hexagonal boron nitride crystal structure. This structural distortion introduces new electronic states into the band structure of hexagonal boron nitride, namely the so-called defect ground state and defect excited state.

[0044] In a preferred embodiment, the light-absorbing layer 40 is biased onto the upper surface of one side of the tunneling layer 30, and the graphene layer 20 is biased onto the lower surface of the other side of the tunneling layer 30. The graphene layer 20, the tunneling layer 30, and the light-absorbing layer 40 constitute a graphene / hexagonal boron nitride / molybdenum disulfide heterojunction with the tunneling layer 30 as a potential barrier. At the interface between the graphene layer 20 and the hexagonal boron nitride of the tunneling layer 30, when the defect states in the hexagonal boron nitride of the tunneling layer 30 are excited by external energy, its band structure undergoes a specific adjustment. This change causes the Fermi level of the graphene layer 20 to be located precisely in the band gap between the defect excited state and the defect ground state of the hexagonal boron nitride of the tunneling layer 30. Therefore, the graphene layer 20 can not only... The tunneling layer 30 (hexagonal boron nitride) serves as a conductive channel and also acts as a temporary reservoir for electrons and holes, capturing and temporarily storing charge carriers from the hexagonal boron nitride layer 30. The interface between the hexagonal boron nitride layer 30 and the molybdenum disulfide layer 40 exhibits complex and variable band alignment. This band alignment depends on whether defect states in the hexagonal boron nitride layer 30 are excited. When no defect states are excited, a type I band alignment is formed at the interface, meaning the minimum conduction band and maximum valence band of the molybdenum disulfide layer 40 are located below and above the intrinsic bands of the hexagonal boron nitride layer 30, respectively. This constitutes a "misaligned" band structure, which restricts the movement of electrons and holes between the tunneling layer 30 and the light-absorbing layer 40. When the defect states in the tunneling layer 30 (hexagonal boron nitride) are effectively excited, the band alignment between the tunneling layer 30 (hexagonal boron nitride) and the light-absorbing layer 40 (molybdenum disulfide) transforms to type II. That is, the conduction band minimum and valence band maximum of the light-absorbing layer 40 (molybdenum disulfide) are both located below the defect excited state and defect ground state of the tunneling layer 30 (hexagonal boron nitride), forming an "interleaved" band structure. This structure promotes the effective separation and transfer of photoexcited carriers between the tunneling layer 30 and the light-absorbing layer 40, because electrons and holes can be more easily transported through the interface. The defect ground state in the tunneling layer 30 (hexagonal boron nitride) acts as an intermediate state, assisting in the photoexcited hole transfer from the tunneling layer 30 to the light-absorbing layer 40. The efficient transfer of molybdenum sulfide to graphene, and the band alignment changes caused by the defect ground state play an important role in achieving a sensitive photoelectric response without external bias. In the type I alignment case, the tunneling layer 30 hexagonal boron nitride layer acts as a high barrier, preventing charge flow between the graphene layer 20 and the light-absorbing layer 40 molybdenum disulfide. This means that the photoelectric response of the device is severely limited under this alignment case. In the type II alignment case, photo-excited holes can be more easily transported through the interface and captured by the graphene layer 20. At this time, a current is spontaneously and sensitively generated inside, achieving a sensitive photoelectric response. Furthermore, the excitation of the defect state of the tunneling layer 30 hexagonal boron nitride can also be achieved by illumination.

[0045] In a preferred embodiment, the silicon dioxide layer 12 on the silicon substrate 10 has a thickness ranging from 200 nm to 300 nm, the graphene layer 20 has a thickness ranging from 0.34 nm to 0.77 nm, the tunneling layer 30 has a thickness ranging from 10 nm to 20 nm, the light-absorbing layer 40 has a thickness ranging from 0.65 nm to 0.88 nm, and the metal electrode 50 is made of a chromium-gold alloy. Chromium is used to improve the adhesion between the metal and graphene or molybdenum disulfide, while gold provides good conductivity.

[0046] As a preferred embodiment, such as Figure 2 As shown, when the light is turned on, the defect states in hexagonal boron nitride realize unidirectional charge flow. This special charge transport mechanism promotes the efficient separation of electron-hole pairs in molybdenum disulfide, thereby improving the generation efficiency of photocurrent and ensuring a fast photogenerated carrier transport interface with a rise time of 7 μs and a fall time of 7 μs, possessing excellent potential as a switching device.

[0047] As a preferred embodiment, such as Figure 3 As shown, under light excitation at a wavelength of 405 nm, the device exhibits significant self-driving behavior. This self-driving behavior manifests as the ability of the device to generate and maintain a certain photocurrent even without external electrode power supply. This phenomenon is attributed to the photogenerated carriers generated by the graphene / hexagonal boron nitride / molybdenum disulfide heterojunction under 405 nm light illumination. These carriers separate under the influence of the internal electric field and move towards the source and drain electrodes respectively, thereby forming a photocurrent. The emergence of self-driving behavior not only reduces the energy consumption of the device but also improves its practicality in fields such as photoelectric detection.

[0048] As a preferred embodiment Figure 4 The example provides a response diagram of a self-driven photodetector with ultrafast response speed to different wavelengths of light. Due to the different wavelength responsivity of hexagonal boron nitride and TMD, we can design two-dimensional heterojunction optoelectronic devices with different photoelectric response characteristics to different wavelengths from a heterostructure. It can also be seen that the on / off ratio can reach up to 105 under 405nm illumination. The excellent on / off ratio represents the high sensitivity of the device.

[0049] The present invention also provides a method for fabricating a self-driven photodetector, the method being used to fabricate the aforementioned self-driven photodetector, the specific steps of which include:

[0050] S1. The conductive layer 20 graphene is obtained by mechanical exfoliation and bonded to the silicon dioxide surface of the silicon substrate 10. The tunneling layer 30 hexagonal boron nitride and the light-absorbing layer 40 molybdenum disulfide are also prepared by mechanical exfoliation through a polymer sacrificial substrate.

[0051] S2. By means of dry transfer, the tunneling layer 30 hexagonal boron nitride is aligned with the conductive layer 20 graphene and bonded together, and the light-absorbing layer 40 molybdenum disulfide is aligned with the tunneling layer 30 hexagonal boron nitride and bonded together, thus forming a three-layer heterostructure.

[0052] S3. Apply a uniformly thick photoresist film to the three-layer heterojunction using a spin coater.

[0053] S4. Electrode patterns are delineated by electron beam exposure, followed by development and fixing;

[0054] S5. Use a vacuum evaporation method to deposit 50 chromium gold alloy metal electrodes and clean them.

[0055] In a preferred embodiment, a silicon substrate 10 with a thickness of 200nm-300nm is obtained by dry oxidation of silicon dioxide. The polymer sacrificial substrate is polydimethylsiloxane. A small amount of blocky layered graphene material is placed on a specific strong adhesive tape. By repeatedly sticking and separating the transparent tape and observing the state of the graphene material on the tape, after confirming that the graphene material has been successfully dissociated, a weaker adhesive tape is used to peel off thin graphene crystals from the strong adhesive tape. Then, silicon / silica is used to bond it, and after pressing for 10 seconds, the tape is peeled off. This method has the potential to obtain high-quality few-layer or single-layer two-dimensional graphene material. Then, a weaker adhesive tape containing hexagonal boron nitride and molybdenum disulfide crystals is prepared using the above method. A polymer sacrificial substrate polydimethylsiloxane supported by a glass slide is used to bond it, and after pressing for 10 seconds, the tape is peeled off. This method has the potential to obtain high-quality few-layer or single-layer two-dimensional hexagonal boron nitride and molybdenum disulfide material.

[0056] In a preferred embodiment, a vacuum-assisted mechanical pump is used in an argon-filled glove box to fix the silicon wafer substrate onto a triaxial stage 1. The target sample is located and centered using an optical microscope. Then, a glass slide containing polydimethylsiloxane is fixed using a triaxial stage 2. Without moving the optical path, the glass slide is moved along the x and y axes of the triaxial stage 2 until the target two-dimensional thin-layer hexagonal boron nitride material is centered in the field of view. The glass slide containing the two-dimensional thin-layer hexagonal boron nitride material is pressed down using the z-axis knob of the triaxial stage, while the x and y axes are finely adjusted to position both samples in the target position until the polydimethylsiloxane material is centered. Dimethylsiloxane and a silicon substrate are bonded together. After heating to 60°C and waiting for 10 minutes, the glass slide is lifted. By reducing the van der Waals forces between polydimethylsiloxane and the material, the two-dimensional thin-layer hexagonal boron nitride material is facilitated to detach from the polydimethylsiloxane. Similarly, after transferring a single layer of molybdenum disulfide, a three-layer heterostructure is obtained. After the three-layer heterostructure is stacked, it needs to be annealed immediately. The heterostructure is annealed using a tube furnace. The annealing temperature is 150°C, the heating rate is 5°C / min, the annealing time is 120min, and the annealing atmosphere is argon.

[0057] As a preferred embodiment, the photoresist used is polymethyl methacrylate. The silicon wafer sample is placed on a spin coater, and the photoresist is dropped on the surface of the silicon wafer for spin coating. The low rotation speed is 500 r / min, the duration is 5 seconds, the high rotation speed is 4000 r / min, and the duration is set to 60 seconds, then a uniform thin film can be deposited. The thin film sample is placed on a heating table for baking the photoresist. The temperature is 150 °C and the time is 5 min, then the residual solvent in the photoresist can be evaporated and the polymethyl methacrylate can be cured.

[0058] As a preferred embodiment, the software supporting the electron beam exposure system is used to design the electrode pattern to be exposed. The exposure parameters are set as follows: exposure dose: 160 μC / cm, beam current: 0.88 nA. The overall exposure area is a square area of 1000 μm × 1000 μm. In the exposed area, the macromolecular structure of the polymethyl methacrylate is damaged and can be dissolved in the developer, so as to achieve the effect of forming the required metal electrode channel. The developer used is a 1:3 mixture of deionized water and isopropanol, and the development time is 25 seconds. Immediately after the development ends, the silicon wafer is quickly put into the fixing solution. The fixing solution used is an isopropanol solution, and the fixing time is 30 seconds.

[0059] As a preferred embodiment, the silicon wafer sample is placed in an electron beam evaporation platform and chromium metal and gold metal are deposited in sequence at a rate of 5 A / s, and a 5-nm chromium metal layer and a 50-nm gold metal layer are obtained on the surface of the sample. The device is placed in an acetone solution and soaked for a period of time to dissolve the photoresist, then a disposable plastic dropper is used to remove the photoresist and the metal layer on the unexposed part and leave the designed metal electrode, and then the isopropanol solution is used to remove the residual acetone liquid on the surface, and finally it is dried with a high-pressure nitrogen gas gun.

[0060] The working principle of this invention: When light shines on the light-absorbing layer 40 (molybdenum disulfide), its energy is absorbed by the molybdenum disulfide layer 40. When the energy of the photon is greater than or equal to the band gap energy of molybdenum disulfide, it excites electrons to jump from the valence band to the conduction band. During the transition, free electrons and holes are generated to form charge carriers. These charge carriers become the source of photocurrent. At the interface between the tunneling layer 30 (hexagonal boron nitride) and the light-absorbing layer 40 (molybdenum disulfide) in the heterojunction, due to the different band structures of the two materials, the conventional defect states of hexagonal boron nitride are insufficient to cause these charge carriers to undergo a sufficient amount of quantum tunneling effect to form a current. This is because after the tunneling layer 30 hexagonal boron nitride absorbs light energy, the defect state is excited and transformed into a defect excited state. The band alignment between the tunneling layer 30 hexagonal boron nitride and the light-absorbing layer 40 molybdenum disulfide changes to type II, which promotes the effective separation and transfer of photoexcited carriers between the two layers. The separated electrons and holes move in different directions. Electrons are transported to the graphene layer, while holes are transported to the source. In this process, without external bias voltage, the separation and flow of electrons and holes form a closed current path, thereby generating photocurrent, thus realizing self-driven photoelectric detection.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A self-driven photodetector, characterized in that, include: A silicon substrate (10) comprising a bottom silicon layer (11) and a silicon dioxide layer (12) stacked sequentially from bottom to top, wherein the bottom silicon layer (11) provides mechanical support and the silicon dioxide layer (12) provides electrical isolation; A graphene layer (20) is placed on the surface of a silicon dioxide layer (12) to collect photogenerated carriers transmitted from the light-absorbing layer (40) and to conduct current. A tunneling layer (30) is formed on the surface of the graphene layer (20) and the silicon dioxide layer (12) to provide electrical isolation between the graphene layer (20) and the light absorption layer (40) and to prevent direct contact between the graphene layer (20) and the light absorption layer (40). The material of the tunneling layer (30) is hexagonal boron nitride. The tunneling layer (30) hexagonal boron nitride material has defects of NBVN anti-site nitrogen vacancies; A light-absorbing layer (40) is located on the surface of the tunneling layer (30) and is used to absorb light and generate photogenerated carriers. The carriers are transported to the graphene layer (20) through the tunneling layer (30). The material of the light-absorbing layer (40) is molybdenum disulfide. Metal electrode (50) is provided in two sets and is respectively disposed on the surface of graphene layer (20) and light absorption layer (40). One set is in ohmic contact with graphene layer (20) as drain electrode and the other set is in ohmic contact with light absorption layer (40) as source electrode, used to connect external circuit and export photogenerated carriers generated by light absorption layer (40).

2. The self-driven photodetector according to claim 1, characterized in that: The light absorption layer (40) is biased on the upper surface of one side of the tunneling layer (30), and the graphene layer (20) is biased on the lower surface of the other side of the tunneling layer (30). The graphene layer (20), the tunneling layer (30) and the light absorption layer (40) constitute a graphene / hexagonal boron nitride / molybdenum disulfide heterojunction with the tunneling layer (30) as a potential barrier.

3. A self-driven photodetector according to claim 2, characterized in that: The silicon dioxide layer (12) on the silicon substrate (10) has a thickness ranging from 200nm to 300nm, the graphene layer (20) has a thickness ranging from 0.34nm to 0.77nm, the tunneling layer (30) has a thickness ranging from 10nm to 20nm, the light absorption layer (40) has a thickness ranging from 0.65nm to 0.88nm, and the metal electrode (50) is made of chromium-gold alloy.

4. A method for fabricating a self-driven photodetector, characterized in that: The method is used to prepare the self-driven photodetector according to any one of claims 1-3, and the specific steps include: S1. Graphene layer (20) is obtained by mechanical exfoliation and is attached to the surface of silicon dioxide layer (12) on silicon substrate (10). Tunneling layer (30) hexagonal boron nitride and light absorption layer (40) molybdenum disulfide are prepared by mechanical exfoliation through polymer sacrificial substrate. S2. By means of dry transfer, the tunneling layer (30) hexagonal boron nitride is aligned with the graphene layer (20) and bonded together, and the light absorption layer (40) molybdenum disulfide is aligned with the tunneling layer (30) hexagonal boron nitride and bonded together, thereby forming a three-layer heterostructure. S3. Apply a uniformly thick photoresist film to the three-layer heterojunction using a spin coater. S4. Electrode patterns are delineated by electron beam exposure, followed by development and fixing; S5. Use a vacuum evaporation method to deposit metal electrodes (50) chromium-gold alloy and clean them.

5. The method for fabricating a self-driven photodetector according to claim 4, characterized in that: A silicon substrate (10) with a silicon dioxide layer (12) thickness of 200nm-300nm was obtained by dry oxygen oxidation, wherein the polymer sacrificial substrate is polydimethylsiloxane.

6. The method for fabricating a self-driven photodetector according to claim 5, characterized in that: In a glove box under an inert gas atmosphere, a tunneling layer (30) of hexagonal boron nitride was bonded to a graphene layer (20), and an absorption layer (40) of molybdenum disulfide was bonded to a tunneling layer (30) of hexagonal boron nitride. Both layers were heated to 55°C for 10 minutes to achieve a fully bonded three-layer heterostructure. After the three-layer heterostructure was stacked, it was annealed in an inert atmosphere at a temperature of 150°C, a heating rate of 5°C / min, and a time of 120 min.

7. The method for fabricating a self-driven photodetector according to claim 6, characterized in that: The photoresist used is polymethyl methacrylate. The spin coater used is set to a low speed of 500 r / min for 5 seconds and a high speed of 4000 r / min for 60 seconds for 5 minutes, and is heated at 150°C. In the development stage, the developer is a 1:3 mixture of deionized water and isopropanol, and the development time is 25 seconds. Immediately after the development is completed, the silicon wafer is quickly placed into the fixing solution, which is an isopropanol solution, and the fixing time is 30 seconds.

8. The method for fabricating a self-driven photodetector according to claim 7, characterized in that: The device is then cleaned after electron beam evaporation to deposit 5 nm of chromium and 50 nm of gold at a rate of 5 A / s.

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