A bias reconfigurable dual-mode photodetector and a driving method and a preparation method thereof

Abstract

The application relates to a bias reconfigurable dual-mode photodetector and a driving method and a preparation method thereof, and belongs to the technical field of semiconductor photodetection. The photodetector comprises an n-type gallium nitride layer, a p-type tungsten diselenide layer, a first electrode and a second electrode; the p-type tungsten diselenide layer and the n-type gallium nitride layer are stacked in a vertical direction to form a van der Waals heterojunction. When a reverse bias is applied to the first electrode and the second electrode, the cross-heterojunction transport of visible-near-infrared band photogenerated carriers in the p-type tungsten diselenide layer is inhibited, and the device presents ultraviolet selective response; when a forward bias is applied, the photogenerated carriers participate in the cross-heterojunction transport, and the device presents ultraviolet-visible-near-infrared wide-spectrum response. The dark current of the device is as low as 10 ‑12 A, the responsivity is greater than 0.5 A / W, the detection rate is greater than 10 12 Jones, the response speed is in the order of microseconds, and the device can be applied to the fields of ultraviolet leakage early warning and flame monitoring.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor photoelectric detection technology, specifically relating to a bias-reconfigurable dual-mode photodetector and its driving and fabrication methods. Background Technology

[0002] Gallium nitride (GaN), as a representative of wide bandgap semiconductor materials, possesses characteristics such as a large bandgap, high temperature resistance, radiation resistance, and excellent ultraviolet response, making it suitable for constructing ultraviolet detection units. Tungsten diselenide (WSe2), as an important member of transition metal chalcogenides (TMDCs), has strong absorption capabilities from the visible to near-infrared bands, with a bandgap of approximately 1.3 eV (monolayer). It can be heterointegrated with GaN through van der Waals forces to construct two-dimensional / three-dimensional vertical heterostructures.

[0003] In the field of heterojunction photodetectors, compared with lateral heterojunctions, vertical heterojunctions have shorter photogenerated carrier transport paths and stronger built-in electric fields at the interfaces, which are more conducive to the rapid extraction of photogenerated carriers and the reduction of recombination losses. Therefore, constructing vertical heterojunction photodetectors based on GaN and transition metal chalcogenides has become one of the research directions in this field.

[0004] However, current research on controlling the band alignment, barrier height variation, and coupling relationships between photogenerated carrier generation, separation, recombination, and transport at heterojunction interfaces through external bias voltage is insufficient. In particular, a clear technical path is lacking for achieving reversible switching between different spectral detection modes within the same photodetector. On the one hand, switching between ultraviolet selective detection and broadband detection typically requires external filters, gratings, or beam splitters, resulting in larger photodetectors and higher system complexity. On the other hand, while some solutions attempt to switch operating modes by changing the photodetector electrode configuration, this method relies on altering the external circuit topology, increasing the design difficulty of the drive circuit and limiting switching flexibility.

[0005] In summary, existing heterojunction photodetectors based on GaN and transition metal chalcogenides still struggle to achieve reconfigurable switching of the spectral response range through simple manipulation techniques using a single photodetector and the same electrode connection method. Therefore, there is an urgent need to provide a compact, well-defined, and easily integrated dual-mode photodetector and its fabrication method. Summary of the Invention

[0006] The purpose of this invention is to provide a bias-reconfigurable dual-mode photodetector and its driving and fabrication methods. The invention aims to achieve reversible switching between an ultraviolet selective detection mode and an ultraviolet-visible-near-infrared broadband detection mode in the same vertical heterojunction photodetector by changing the polarity of the applied bias voltage, thereby reconstructing the spectral response range without relying on external filters or changes in electrode configuration.

[0007] On the one hand, the present invention provides a bias-reconfigurable dual-mode photodetector, which adopts the following technical solution: A bias-reconfigurable dual-mode photodetector, comprising: n-type gallium nitride layer; p-type tungsten diselenide layer, wherein the p-type tungsten diselenide layer and the n-type gallium nitride layer are stacked in a vertical direction to form a van der Waals heterojunction; The first electrode electrically connected to the n-type gallium nitride layer; and The second electrode is electrically connected to the p-type tungsten diselenide layer; When a reverse bias voltage is applied to the first electrode and the second electrode, the transport of photogenerated carriers excited in the visible-near infrared band across the van der Waals heterojunction interface in the p-type tungsten diselenide layer is suppressed. When a forward bias is applied, photogenerated carriers excited in the visible-near-infrared band in the p-type tungsten diselenide layer participate in transport across the van der Waals heterojunction interface.

[0008] Preferably, the reverse bias voltage ranges from -3 V to 0 V; The positive bias voltage ranges from 0 V to +3 V.

[0009] Preferably, when the reverse bias voltage is applied, the response current of the photodetector to the ultraviolet band is greater than the response current to the visible and near-infrared bands. When a forward bias voltage is applied, the photodetector generates a response current in the 300 nm to 900 nm wavelength band.

[0010] Preferably, the p-type tungsten diselenide layer is a single-layer tungsten diselenide thin film or a few-layer tungsten diselenide thin film; The n-type gallium nitride layer is a self-supporting n-type gallium nitride thin film, and the thickness of the n-type gallium nitride layer is 50 nm to 100 nm.

[0011] Preferably, an interface control layer is provided between the n-type gallium nitride layer and the p-type tungsten diselenide layer; The material of the interface control layer is selected from at least one of Al2O3, SiO2, and h-BN, and the thickness of the interface control layer is 0.5 nm to 5 nm.

[0012] Preferably, the first electrode is any one of a Cr / Au electrode, a Ti / Al / Ni / Au electrode, a Ti / Al / Ti / Au electrode, and a Cr / Al electrode; The second electrode is any one of the following: graphene transparent electrode, Au electrode, Pd / Au electrode, Ni / Au electrode, and Cr / Au electrode.

[0013] On the one hand, the present invention also provides a spectral detection method for the above-mentioned bias-reconfigurable dual-mode photodetector, which adopts the following technical solution: Spectral detection methods for bias-reconfigurable dual-mode photodetectors include: Applying a reverse bias voltage to the photodetector suppresses the transvan der Waals heterojunction transport of photogenerated carriers excited in the visible-near-infrared band in the p-type tungsten diselenide layer; A forward bias is applied to the photodetector, causing photogenerated carriers excited in the visible-near-infrared band in the p-type tungsten diselenide layer to participate in transvan der Waals heterojunction transport.

[0014] Furthermore, this invention also provides a method for fabricating the aforementioned bias-reconfigurable dual-mode photodetector, employing the following technical solution: A method for fabricating a bias-reconfigurable dual-mode photodetector includes the following steps: 1) Depositing a bottom electrode on a substrate, wherein the bottom electrode serves as the first electrode; 2) The self-supporting n-type gallium nitride thin film obtained by electrochemical stripping is transferred onto the bottom electrode as the n-type gallium nitride layer; 3) The monolayer tungsten diselenide film or few-layer tungsten diselenide film obtained by mechanical peeling is stacked on the surface of the n-type gallium nitride film to form the van der Waals heterojunction, wherein the monolayer tungsten diselenide film or few-layer tungsten diselenide film serves as the p-type tungsten diselenide layer. 4) A top electrode is formed on the single-layer tungsten diselenide thin film or the few-layer tungsten diselenide thin film, and the top electrode serves as the second electrode to obtain the photodetector.

[0015] Preferably, after each transfer of the n-type gallium nitride film to the monolayer tungsten diselenide film or few-layer tungsten diselenide film, the film is vacuum annealed at 120°C for 10 minutes.

[0016] In summary, the present invention has the following beneficial technical effects: 1. This invention achieves reversible switching between an ultraviolet-selective detection mode and an ultraviolet-visible-near-infrared broadband detection mode in the same p-WSe2 / n-GaN vertical van der Waals heterojunction photodetector by changing the polarity of the applied bias voltage. Under reverse bias, the transport of photogenerated carriers excited in the visible-near-infrared band across the heterojunction in the p-WSe2 layer is suppressed, and the photodetector exhibits an ultraviolet-selective response. Under forward bias, the interface barrier is lowered, and photogenerated carriers excited in the visible-near-infrared band in the p-WSe2 layer participate in the transport across the heterojunction, and the photodetector responds to the 300 nm to 900 nm band. This bias control mechanism differs from existing technologies that require changing the electrode configuration or using external filter structures for switching; it can reconstruct the spectral response range using only electrical signals, significantly reducing system complexity.

[0017] 2. This invention employs a vertical heterojunction structure, resulting in a short transport path for photogenerated carriers, which facilitates rapid carrier separation and extraction. Simultaneously, detection mode switching can be completed on a single chip without the need for external filters, gratings, or multiple photodetectors, promoting miniaturization and high-density integration of the optoelectronic system. Furthermore, the vertical heterojunction structure, combined with the intrinsic properties of GaN's wide bandgap material, reduces the dark current of the photodetector under bias voltage to approximately 10. -12 A (picoampere level) is beneficial for improving the signal-to-noise ratio under low-light detection conditions.

[0018] 3. Under forward bias, the photodetector's effective optical response range covers 300 nm to 900 nm, encompassing the ultraviolet, visible, and near-infrared bands, achieving multi-spectral detection capability on a single chip. Simultaneously, the vertical heterojunction structure shortens the transport path of photogenerated carriers, and the built-in electric field at the interface facilitates rapid carrier extraction. The photodetector's rise and fall times are both on the order of microseconds (approximately 34 μs to 46 μs), meeting the requirements of rapid detection scenarios.

[0019] 4. This invention is based on the van der Waals heterostructure integration strategy. It achieves vertical stacking of p-WSe2 and n-GaN through mechanical exfoliation and dry transfer, without considering lattice matching constraints. Combined with the transfer process of the self-supporting GaN thin film obtained by electrochemical exfoliation and the transparent graphene top electrode, the photodetector fabrication process is compatible with mainstream semiconductor processes. It has good repeatability and large-scale fabrication prospects, and can be applied to scenarios that require detector miniaturization, low power consumption and adaptive spectral band recognition capabilities, such as intelligent vision systems, autonomous sensing, ultraviolet leakage early warning, flame monitoring and space optical communication. Attached Figure Description

[0020] Figure 1 A schematic diagram of the layered structure of the bias-reconfigurable dual-mode photodetector of the present invention; Figure 2The current-voltage characteristic curve of the bias-reconfigurable dual-mode photodetector of this invention; Figure 3 The spectral responsivity curve of the bias-reconfigurable dual-mode photodetector of this invention; Figure 4 A schematic diagram of band alignment before contact in the van der Waals heterojunction of the present invention; Figure 5 A schematic diagram of the band structure of the van der Waals heterojunction in the zero-bias equilibrium state of this invention; Figure 6 A schematic diagram of the band structure and carrier transport of the van der Waals heterojunction under reverse bias in this invention. Figure 7 A schematic diagram of the band structure and carrier transport of the van der Waals heterojunction under forward bias in this invention; Figure 8 The transient optical response curve of the bias-reconfigurable dual-mode photodetector of this invention in the ultraviolet band; Figure 9 The transient optical response curve of the bias-reconfigurable dual-mode photodetector of this invention in the visible-near-infrared band.

[0021] Explanation of reference numerals in the attached figures: 1. Substrate; 11. Silicon dioxide insulating layer; 2. First electrode; 3. n-type gallium nitride layer; 4. Interface control layer; 5. p-type tungsten diselenide layer; 6. Second electrode. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, the scope of protection of this invention is not limited to the following specific embodiments. Those skilled in the art can make several improvements and modifications without departing from the concept of this invention, and these all fall within the scope of protection of this invention.

[0023] Example Example 1 This embodiment provides a bias-reconfigurable dual-mode photodetector. (Refer to...) Figure 1 The bias-reconfigurable dual-mode photodetector is a vertically stacked layered structure, which includes, from bottom to top, a substrate 1, a first electrode 2, an n-type gallium nitride layer 3, an interface control layer 4, a p-type tungsten diselenide layer 5, and a second electrode 6; wherein the n-type gallium nitride layer 3 and the p-type tungsten diselenide layer 5 are stacked vertically and form a van der Waals heterojunction through the interface control layer.

[0024] Reference Figure 1In this embodiment, substrate 1 is a p-type silicon (p-Si) substrate, which serves as a support substrate. A silicon dioxide insulating layer 11 is grown on the surface of substrate 1 to achieve electrical insulation between substrate 1 and the functional layer above it, preventing leakage current in the photodetector, and providing a flat surface for thin film fabrication.

[0025] Reference Figure 1 The first electrode 2 is the bottom electrode and is disposed on the upper surface of the silicon dioxide insulating layer 11. In this embodiment, the first electrode 2 adopts a chromium / gold (Cr / Au) stacked structure. The upper surface of the first electrode 2 is in direct contact only with the n-type gallium nitride layer 3 to form an electrical connection, which is used to extract the electrical signal of the photodetector. The n-type gallium nitride layer 3 is the gallium nitride (GaN) functional layer, which is an n-type self-supporting gallium nitride thin film, stacked on the upper surface of the first electrode 2, with a thickness of 50 nm to 100 nm. Moreover, the n-type gallium nitride layer 3 is a wide bandgap semiconductor material with a bandgap width of about 3.4 eV. It only absorbs incident light in the ultraviolet band and is the core functional layer for the photodetector to realize ultraviolet band photodetection.

[0026] Reference Figure 1 An interface control layer 4 is disposed between an n-type gallium nitride layer 3 and a p-type tungsten diselenide layer 5. The material is selected from at least one of aluminum oxide (Al2O3), silicon dioxide (SiO2), and hexagonal boron nitride (h-BN). The thickness is 0.5 nm to 5 nm. It can be used as an insulating layer, a passivation layer, or a tunneling auxiliary layer to optimize the barrier state and carrier transport characteristics of the heterojunction interface.

[0027] Reference Figure 1 The p-type tungsten diselenide layer 5, also known as the tungsten diselenide (WSe2) functional layer, is a single-layer or few-layer tungsten diselenide thin film, stacked on the upper surface of the interface control layer 4, and has no direct contact with the first electrode 2. It is bonded to the n-type gallium nitride layer 3 through van der Waals forces, forming a vertical van der Waals heterojunction. The p-type tungsten diselenide layer 5 is a narrow bandgap semiconductor material with a bandgap of approximately 1.3 eV, capable of absorbing incident light from the visible to near-infrared bands, and is the core functional layer for achieving broadband detection in the photodetector. The second electrode 6 is the top electrode, disposed on the upper surface of the p-type tungsten diselenide layer 5; in this embodiment, the second electrode 6 is a graphene transparent electrode, which directly contacts the p-type tungsten diselenide layer 5 to form a good electrical connection, while also possessing high light transmittance, ensuring efficient transmission of incident light to the underlying semiconductor functional layer.

[0028] Example 2 The fabrication method of a bias-reconfigurable dual-mode photodetector includes the following steps: S1: Fabrication of the bottom electrode Provide a silicon dioxide / silicon (SiO2 / Si) substrate, perform standard cleaning on the substrate, and ultrasonically clean it sequentially with acetone, ethanol and deionized water for at least 10 min each, and then dry it with nitrogen. A chromium (Cr) layer and a gold (Au) layer with thicknesses of 5 nm and 30 nm, respectively, were sequentially deposited on the substrate surface using magnetron sputtering to form a Cr / Au bottom electrode, which served as the first electrode.

[0029] S2: Fabrication and Transfer of Self-Supported n-Type Gallium Nitride Thin Films The self-supporting n-type gallium nitride (GaN) thin film obtained by electrochemical stripping is transferred onto the bottom electrode as an n-type gallium nitride layer; The self-supporting n-type gallium nitride thin film was obtained by electrochemical lift-off of a GaN epitaxial structure. The GaN epitaxial structure included a nucleation layer of approximately 30 nm and a doping concentration of approximately 1 × 10⁻⁶ μm. 19 cm -3 A silicon (Si) doped GaN sacrificial layer and a target n-type gallium nitride layer located above the sacrificial layer are used. The self-supporting n-type gallium nitride film after being stripped is aligned and transferred to the bottom electrode surface using a dry transfer method. In this embodiment, the thickness of the transferred n-type gallium nitride layer is approximately 85 nm.

[0030] S3: Preparation and Transfer of p-type Tungsten Diselenide Layers Monolayer or few-layer tungsten diselenide films were obtained from bulk tungsten diselenide (WSe2) crystals using mechanical exfoliation. These films were then transferred to a target substrate using a micro-aligned dry transfer system with elastic films such as PDMS as the transfer medium.

[0031] The selected monolayer or few-layer tungsten diselenide film is stacked on the surface of the n-type GaN film obtained in step S2 using an alignment transfer method to form a van der Waals heterojunction. The monolayer or few-layer WSe2 film serves as the p-type WSe2 layer. Both mechanical exfoliation and alignment transfer methods can be implemented using conventional processes in the art.

[0032] S4: Fabrication of the top electrode A top electrode is formed on the p-type WSe2 layer obtained in step S3, and the top electrode serves as the second electrode to obtain a bias-reconfigurable dual-mode photodetector. Among them, the graphene sheet obtained by mechanical exfoliation is used as a transparent top electrode and transferred to the surface of the p-type WSe2 layer.

[0033] S5: Annealing treatment After each thin film transfer (including n-type GaN thin film transfer, monolayer / few-layer WSe2 thin film transfer and top electrode transfer), vacuum annealing was performed at 120 °C for 10 min to improve the heterojunction interface quality and electrical contact reliability.

[0034] Through the above steps, a bias-reconfigurable dual-mode photodetector is obtained.

[0035] Test case Test Example 1 Reference Figures 2 to 4 This test example verifies the ultraviolet selective detection characteristics of the photodetector under reverse bias. The first electrode on the n-type gallium nitride layer side is used as the bias application terminal, and the test bias range is set from -3 V to +3 V. Monochromatic light from 300 nm to 900 nm is used to illuminate the photodetector, with an incident light power density of 40 μW / cm². 2 The current-voltage characteristics and spectral response characteristics of the photodetector were tested.

[0036] Test results show that the reverse bias voltage ranges from -3 V to 0 V. When a reverse bias voltage is applied, the photodetector's response current in the ultraviolet band is greater than its response current in the visible and near-infrared bands. Specifically, under negative bias conditions, the photodetector only generates a significant photocurrent under 350 nm ultraviolet light illumination; the light response in the 400 nm to 900 nm band is not significant and is significantly suppressed, indicating that the photodetector operates in ultraviolet-selective detection mode. Throughout the entire test bias voltage range, the dark current of the photodetector is as low as 10. -12 A (picoampere level).

[0037] Further comparative tests showed that under 350 nm ultraviolet light irradiation, the photodetector could generate photocurrent under both forward and reverse bias conditions, and the photocurrent increased with increasing incident power. Under 400 nm visible light irradiation, the photodetector only showed significant photocurrent under forward bias conditions, while the response was basically suppressed under reverse bias conditions. This result corresponds to the suppression of the transport of photogenerated carriers excited in the visible-near-infrared band across the van der Waals heterojunction interface in the p-type tungsten diselenide layer under reverse bias, and the photodetector mainly retains the ultraviolet detection channel dominated by the n-type gallium nitride layer.

[0038] Test Example 2 Reference Figure 2 , Figure 3 and Figure 5 This test example verifies the ultraviolet-visible-near-infrared broadband detection characteristics of the photodetector under forward bias, and the test conditions are the same as those in Test Example 1.

[0039] Test results show that the forward bias voltage ranges from 0 V to +3 V. When a forward bias voltage is applied, the photodetector generates a response current in the 300 nm to 900 nm wavelength band. Specifically, under forward bias conditions, in addition to maintaining its response to the ultraviolet band, the photodetector also generates significant light responses to the visible and near-infrared bands, achieving broadband detection in the ultraviolet-visible-near-infrared spectrum. Wavelength-dependent tests show that under a +3 V forward bias voltage, the effective light response range of the photodetector covers 300 nm to 900 nm; under this condition, the photodetector has a responsivity greater than 0.5 A / W and a detectivity greater than 10 in the 300 nm to 900 nm range. 12 Jones.

[0040] This result corresponds to the fact that, under forward bias, photogenerated carriers excited in the visible-near-infrared band in the p-type tungsten diselenide layer participate in the transport across the van der Waals heterojunction interface, and work together with the ultraviolet response of the n-type gallium nitride layer to achieve broadband detection.

[0041] Test Example 3 Combination Figures 4 to 7 The mode switching mechanism of the photodetector was verified by band structure analysis and Kelvin probe force microscopy. Before contact, the electron affinities of p-type WSe2 and n-type GaN were approximately 4.0 eV and 4.1 eV, respectively, with band gaps of approximately 1.3 eV and 3.4 eV, respectively. After contact, a nearly continuous conduction band and a valence band step of approximately 2.1 eV were formed, constituting a type II band arrangement. Kelvin probe force microscopy showed a contact potential difference of approximately 52 mV, indicating a built-in electric field at the van der Waals heterojunction interface, and that the depletion region was mainly located on the n-type GaN layer side.

[0042] When a reverse bias is applied, the band bending at the heterojunction interface intensifies, and the valence band barrier rises, hindering the transfer of visible-near-infrared photogenerated holes from the p-type WSe2 layer to the n-type GaN layer. Therefore, the transport of photogenerated carriers excited in the visible-near-infrared band across the van der Waals heterojunction interface in the p-type tungsten diselenide layer is suppressed, and the photodetector exhibits an ultraviolet-selective detection mode. When a forward bias is applied, the band bending at the interface decreases, and the valence band barrier lowers. Photogenerated carriers excited in the visible-near-infrared band in the p-type tungsten diselenide layer participate in the transport across the van der Waals heterojunction interface, and the photodetector switches to a broadband detection mode.

[0043] Combination Figure 8 and Figure 9Transient photocurrent tests were performed on the photodetector to verify its response speed. The test results showed that under a +3 V bias and 350 nm wavelength illumination, the rise time of the photodetector was approximately 34 μs and the fall time was approximately 37 μs; under a +3 V bias and 400 nm wavelength illumination, the rise time was approximately 46 μs and the fall time was approximately 40 μs. These results indicate that the vertical van der Waals heterojunction structure shortens the carrier transport path, enabling the photodetector to achieve a fast photoelectric response on the order of microseconds.

[0044] The embodiments shown in this specification are only used to illustrate the technical solutions of the present invention and are intended to help those skilled in the art understand the principles and advantages of the present invention. They do not constitute a limitation on the scope of protection of the present invention. Although the present invention has been specifically described, those skilled in the art can still make any modifications, equivalent substitutions or other reasonable variations to the implementation methods without departing from the spirit and scope of the present invention. All equivalent technical solutions resulting therefrom should be considered within the scope of protection of this patent.

Claims

1. A bias-reconfigurable dual-mode photodetector, characterized in that, include: n-type gallium nitride layer (3); p-type tungsten diselenide layer (5), wherein the p-type tungsten diselenide layer (5) and the n-type gallium nitride layer (3) are stacked in a vertical direction to form a van der Waals heterojunction; The first electrode (2) is electrically connected to the n-type gallium nitride layer (3); and A second electrode (6) electrically connected to the p-type tungsten diselenide layer (5); When a reverse bias voltage is applied to the first electrode (2) and the second electrode (6), the transport of photogenerated carriers excited in the visible-near infrared band across the van der Waals heterojunction interface in the p-type tungsten diselenide layer (5) is suppressed. When a forward bias is applied, photogenerated carriers excited in the visible-near-infrared band in the p-type tungsten diselenide layer (5) participate in transport across the van der Waals heterojunction interface.

2. The bias-reconfigurable dual-mode photodetector according to claim 1, characterized in that, The reverse bias voltage ranges from -3 V to 0 V; The positive bias voltage ranges from 0 V to +3 V.

3. The bias-reconfigurable dual-mode photodetector according to claim 1, characterized in that, When the reverse bias voltage is applied, the response current of the photodetector to the ultraviolet band is greater than the response current to the visible and near-infrared bands. When a forward bias voltage is applied, the photodetector generates a response current in the 300 nm to 900 nm wavelength band.

4. A bias-reconfigurable dual-mode photodetector according to claim 1, characterized in that, The p-type tungsten diselenide layer (5) is a single-layer tungsten diselenide thin film or a few-layer tungsten diselenide thin film; The n-type gallium nitride layer (3) is a self-supporting n-type gallium nitride thin film, and the thickness of the n-type gallium nitride layer (3) is 50 nm to 100 nm.

5. A bias-reconfigurable dual-mode photodetector according to claim 1, characterized in that, An interface control layer (4) is provided between the n-type gallium nitride layer (3) and the p-type tungsten diselenide layer (5). The material of the interface control layer (4) is selected from at least one of Al2O3, SiO2, and h-BN, and the thickness of the interface control layer (4) is 0.5 nm to 5 nm.

6. A bias-reconfigurable dual-mode photodetector according to claim 1, characterized in that, The first electrode (2) is any one of Cr / Au electrode, Ti / Al / Ni / Au electrode, Ti / Al / Ti / Au electrode, and Cr / Al electrode; The second electrode (6) is any one of the following: graphene transparent electrode, Au electrode, Pd / Au electrode, Ni / Au electrode, and Cr / Au electrode.

7. A spectral detection method for a bias-reconfigurable dual-mode photodetector as described in any one of claims 1 to 6, characterized in that, include: Apply a reverse bias voltage to the photodetector to suppress transvan der Waals heterojunction transport of photogenerated carriers excited in the visible-near infrared band in the p-type tungsten diselenide layer (5); A forward bias is applied to the photodetector so that photogenerated carriers excited in the visible-near-infrared band in the p-type tungsten diselenide layer (5) participate in the transport across the van der Waals heterojunction.

8. A method for fabricating a bias-reconfigurable dual-mode photodetector as described in any one of claims 1 to 6, characterized in that, Includes the following steps: 1) A bottom electrode is deposited on a substrate (1), the bottom electrode serving as the first electrode (2). 2) The self-supporting n-type gallium nitride thin film obtained by electrochemical stripping is transferred to the bottom electrode as the n-type gallium nitride layer (3). 3) The single-layer tungsten diselenide film or few-layer tungsten diselenide film obtained by mechanical peeling is stacked on the surface of the n-type gallium nitride film (3) to form the van der Waals heterojunction, wherein the single-layer tungsten diselenide film or few-layer tungsten diselenide film serves as the p-type tungsten diselenide layer (5). 4) A top electrode is formed on the single-layer tungsten diselenide thin film or the few-layer tungsten diselenide thin film, and the top electrode serves as the second electrode (6) to obtain the photodetector.

9. The method for fabricating a bias-reconfigurable dual-mode photodetector according to claim 8, characterized in that, After each transfer of the n-type gallium nitride thin film (3) to the monolayer tungsten diselenide thin film or the few-layer tungsten diselenide thin film, vacuum annealing is performed at 120 °C for 10 min.

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