Bidirectional polarization sensitive photoelectric detector based on Van der Waals sandwich heterojunction and preparation method and application thereof

Abstract

The invention belongs to the technical field of optoelectronic devices, and discloses a bidirectional polarization sensitive photoelectric detector based on a Van der Waals sandwich heterojunction and a preparation method and application of the bidirectional polarization sensitive photoelectric detector based on the Van der Waals sandwich heterojunction. The bidirectional polarization sensitive photoelectric detector is a Van der Waals sandwich heterojunction formed by stacking ReSe2 nanosheets / graphene / WSe2 nanosheets on a SiO2 / Si substrate, electrodes are prepared on the sides of the ReSe2 nanosheets, the WSe2 nanosheets and the graphene outside the heterojunction area, the electrodes on the sides of the ReSe2 nanosheets and the WSe2 nanosheets are mutually connected to serve as drain electrodes, the electrode connected with the graphene serves as a source electrode, Si of the SiO2 / Si substrate serves as a gate electrode, and SiO2 serves as an insulating layer. According to the photoelectric detector, precise switching of bidirectional light currents can be achieved by regulating and controlling the polarity of grid voltage, the photoelectric detector has the excellent polarization sensitive characteristic, and the performance of the photoelectric detector is remarkably superior to that of an existing two-dimensional material-based polarized photoelectric detector.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic device technology, and more specifically, relates to a bidirectional polarization-sensitive photodetector based on a van der Waals heterojunction, its fabrication method, and its application. Background Technology

[0002] From a technological trend perspective: As a core component of modern information technology, photodetectors, with the development of the intelligent era, need to break through the traditional functions of light intensity, wavelength, and frequency detection, and integrate bidirectional response (dynamic switching between positive and negative photoconductivity) and polarization sensitivity (detecting the polarization angle of light, enhancing detection performance in complex environments, and improving imaging resolution). This has become an inevitable requirement for the development of intelligent optoelectronic devices. From the perspective of existing materials: Two-dimensional materials with high in-plane anisotropy (such as ReSe2, ReS2, and 1T phase MoTe2) have become ideal candidate materials for polarization-sensitive photodetectors due to their strong in-plane dichroism, atomically flat surfaces, and simplified fabrication processes that do not require polarizers. From the perspective of technological bottlenecks: There are currently two major challenges: First, the key performance indicator of two-dimensional polarization photodetectors, "polarization ratio (PR)," still needs optimization, making it difficult to achieve high polarization sensitivity; second, although van der Waals-Schottky heterojunctions can achieve bidirectional photocurrent, they cannot simultaneously integrate high polarization sensitivity and a large polarization ratio. Furthermore, the intrinsic mechanism of bidirectional response and polarization sensitivity working together, as well as suitable device design schemes, are not yet clear, which restricts the development of integrated sensing-computing vision technology. Summary of the Invention

[0003] To address the aforementioned technical problems, the primary objective of this invention is to provide a bidirectional polarization-sensitive photodetector based on a van der Waals heterojunction. This photodetector integrates bidirectional response and polarization sensitivity characteristics through the synergistic effect of the ReSe2 / graphene / WSe2 van der Waals heterojunction interface, overcoming the dual bottlenecks of functional integration and performance optimization, and possessing both bidirectional photocurrent characteristics and polarization sensitivity. This solves the technical challenge of current photodetectors being unable to efficiently integrate bidirectional photocurrent characteristics and polarization sensitivity, and thus failing to meet the requirements of polarization imaging and in-sensor computation.

[0004] Another object of the present invention is to provide a method for fabricating the above-mentioned bidirectional polarization-sensitive photodetector based on a van der Waals heterojunction.

[0005] Another objective of this invention is to provide applications for the aforementioned bidirectional polarization-sensitive photodetector based on a van der Waals heterojunction. It is primarily used in polarization imaging, in-sensor computing, intelligent optical sensing (such as medical imaging, artificial vision, and optical detection related to autonomous driving), and next-generation integrated sensing-computing vision systems. It can achieve photocurrent direction modulation and optical polarization angle detection, providing core device support for intelligent optoelectronic devices.

[0006] The objective of this invention is achieved through the following technical solution: A bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction is constructed by stacking ReSe2 nanosheets / graphene / WSe2 nanosheets on a SiO2 / Si substrate. Electrodes are fabricated on the ReSe2 nanosheet, WSe2 nanosheet, and graphene sides outside the heterojunction region. The electrodes on the ReSe2 nanosheet and WSe2 nanosheet sides are interconnected to serve as drain electrodes, the graphene-connected electrodes serve as source electrodes, the Si on the SiO2 / Si substrate serves as the gate electrode, and SiO2 serves as the insulating layer.

[0007] Furthermore, the bidirectional polarization-sensitive photodetector is obtained by transferring WSe2 nanosheets obtained through mechanical exfoliation onto a SiO2 / Si substrate, and then obtaining graphene and ReSe2 nanosheets through a polydimethylsiloxane-assisted mechanical exfoliation method. Then, the ReSe2 nanosheets are transferred to the surface of graphene and stacked on the WSe2 nanosheets using a dry transfer method. The overlapping part of the ReSe2 nanosheets, graphene and WSe2 nanosheets forms a sandwich-type van der Waals heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets. Electrodes are fabricated on the ReSe2 nanosheets, WSe2 nanosheets and graphene sides outside the above heterojunction region.

[0008] Preferably, the thickness of the WSe2 nanosheet is 1~50 nm and the lateral dimension is 5~100 μm; the thickness of the ReSe2 nanosheet is 1~50 nm and the lateral dimension is 5~100 μm; and the thickness of the graphene is 1~50 nm.

[0009] Preferably, the electrode is Au, and its thickness is 30~100 nm.

[0010] The fabrication method of the bidirectional polarization-sensitive photodetector based on the van der Waals sandwich heterojunction includes the following specific steps: S1. Multilayer WSe2 nanosheets were exfoliated from WSe2 crystals using a mechanical exfoliation method and then transferred onto a pre-prepared SiO2 / Si substrate; S2. Graphene and ReSe2 nanosheets were obtained by mechanical exfoliation assisted by polydimethylsiloxane. Then, graphene was transferred to the surface of WSe2 nanosheets by dry transfer method, and then ReSe2 nanosheets were transferred to the surface of graphene to form a heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets. S3. Photoresist is spin-coated onto a SiO2 / Si substrate with a ReSe2 nanosheet / graphene / WSe2 nanosheet heterojunction. The pattern is then lithographically patterned using maskless ultraviolet light. Electrodes are fabricated on the ReSe2 nanosheet, WSe2 nanosheet and graphene sides outside the heterojunction region by electron beam evaporation to obtain a bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction.

[0011] Preferably, the thickness of the SiO2 layer in the SiO2 / Si substrate in step S1 is 100~300 nm.

[0012] The application of the bidirectional polarization-sensitive photodetector based on the van der Waals sandwich heterojunction in the fields of photoelectric detection or artificial vision.

[0013] The core of this invention is a heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets stacked together. Graphene serves as the source electrode (S), and WSe2 nanosheets (P-type conductivity) and ReSe2 nanosheets (N-type conductivity) are interconnected as a common drain electrode (D). The bottom layer, Si, serves as the gate electrode (G), and SiO2 acts as the insulating layer. The Fermi level difference (ΔEf) between ReSe2 nanosheets / graphene and graphene / WSe2 nanosheets is 97 meV and 15 meV, respectively. After thermal equilibrium, a double-asymmetric Schottky junction with two built-in electric fields (Vbi-1 and Vbi-2) is formed, providing key structural support for photoelectric performance.

[0014] The working mechanism of this invention is that the bidirectional photocurrent characteristic originates from the band bending regulated by the gate electrode voltage at the asymmetric double Schottky junction. The photocurrent direction can be reversed by changing the polarity of the gate electrode voltage. The polarization-sensitive characteristic relies on the orthorhombic crystal structure and strong in-plane anisotropy of ReSe2, promoting efficient light-matter interaction and anisotropic carrier transport. The photocurrent varies with the angle between the incident polarized light and the b-axis of the ReSe2 nanosheet (…). θ ) exhibits periodic oscillations ( θ The minimum value is when the angle is 0° / 180°. θ =Maximum at 90° / 270°). WSe2 exhibits P-type conductivity, while ReSe2 exhibits N-type conductivity. The band gaps of ReSe2 nanosheets and WSe2 nanosheets are approximately 1.2 eV and 1.08 eV, respectively. Graphene, as an intermediate layer, acts as a barrier modulator and charge transport bridge, forming asymmetric double Schottky junctions at the ReSe2 nanosheet / graphene and graphene / WSe2 nanosheet interfaces, thus constructing a heterojunction system with synergistic functions.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The photodetector of this invention is a sandwich heterostructure of ReSe2 nanosheets / graphene / WSe2 nanosheets, wherein the graphene layer serves as the intermediate layer, forming stable interfacial contacts with both the ReSe2 and WSe2 nanosheets, thus constituting a heterojunction system with synergistic functions. This photodetector can achieve precise switching of bidirectional photocurrent by controlling the polarity of the gate voltage, providing a foundation for controllable detection of optical signals in intelligent optical sensing scenarios. Simultaneously, it possesses excellent polarization sensitivity characteristics, achieving a polarization ratio of up to 9 under incident light at a wavelength of 635 nm and up to 6 under incident light at a wavelength of 808 nm, significantly outperforming existing two-dimensional material-based polarization photodetectors.

[0016] 2. The photodetector structure of this invention is rationally designed. Through the synergistic effect of the interface of the heterogeneous structure, it achieves integrated bidirectional response and polarization sensitivity functions. In zero-bias self-driven operation mode, it exhibits excellent photodetection performance: a specific detectivity (D*) of 1.5 × 10⁻⁶. 11 Jones, photocurrent switching ratio up to 10 4 The response speed can reach the millisecond level. Breaking through the bottleneck of low functional integration efficiency of traditional photodetectors, the fabricated bidirectional polarization-sensitive photodetector has a controllable structure and stable performance. The fabrication process is scalable, laying a key component foundation for the research and application of next-generation sensing-computing integrated vision systems. It has important application value in fields such as polarization imaging, in-sensor computing modules, intelligent light control, intelligent optical sensing systems, and adaptive optical sensing.

[0017] 3. The photodetector of the present invention utilizes the inherent in-plane anisotropy of ReSe2 nanosheets to achieve polarization-sensitive photodetection with high polarization ratio (PR) in both visible and near-infrared bands. It can accurately identify the polarization information of incident light, effectively enhance the detection accuracy and imaging resolution in complex environments, and outperform most reported two-dimensional anisotropic material-based devices. Moreover, it can achieve polarization angle resolution of incident light without the need for a polarizer.

[0018] 4. This invention can reverse the direction of photocurrent by changing the polarity of the gate voltage. The essence of this bidirectional photocurrent characteristic is that at the asymmetric double Schottky heterojunction, the gate modulation effect induces a change in the energy band bending, thereby realizing the dynamic switching of the transmission direction of photogenerated carriers, providing core support for directional controllable detection in intelligent optical sensing. Attached Figure Description

[0019] Figure 1 (a) A side view of the atomic structure of a bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction, (b) a schematic diagram of the bidirectional polarization-sensitive photodetector, and (c) an optical microscope image.

[0020] Figure 2 A schematic diagram (a) of the measurement circuit of the bidirectional polarization-sensitive photodetector in Example 1, and IV characteristic curves (b) at different optical power densities; I SC and V OC Relationship with optical power density (c).

[0021] Figure 3 The graphs show the detectivity (D*) and external quantum efficiency (EQE) of the bidirectional polarization-sensitive photodetector of Example 1 as a function of optical power intensity (a), time response (b), and time-correlated optical response (c) at different gate voltages.

[0022] Figure 4 The diagram (a) shows the bidirectional polarization-sensitive photodetector of Example 1, and the inset shows the optical image of the corresponding device and the polarization-related current (b). Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0024] This specification uses spatially relative terms such as “below,” “under,” “down,” “above,” “above,” and “upper” to explain the positioning of one element relative to a second element. These terms are intended to cover different orientations of the device, except for those different from those shown in the figures.

[0025] Furthermore, the use of terms such as "first" and "second" to describe various elements, layers, regions, and sections is not intended to be restrictive. The use of terms such as "having," "containing," "including," and "comprises" are open-ended terms, indicating the presence of the stated elements or features, but not excluding additional elements or features, unless the context explicitly states otherwise.

[0026] The WSe2 crystal used in this embodiment of the invention was purchased from Taizhou SUNANO New Energy Co., Ltd., the maskless ultraviolet lithography system was purchased from Suzhou Toto Technology Co., Ltd., and the ARP-5350 positive photoresist was purchased from Taizhou SUNANO New Energy Co., Ltd.

[0027] Example 1 A bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction includes a gate electrode, a ReSe2 nanosheet / graphene / WSe2 nanosheet sandwich van der Waals heterojunction, a source electrode, and a drain electrode. The gate electrode is a heavily doped Si substrate with an approximately 300 nm thick SiO2 insulating layer on its surface. WSe2 nanosheets (10 nm thick) and ReSe2 nanosheets (10 nm thick) are connected in parallel as a conductive channel layer, graphene (10 nm thick) serves as the source electrode, and gold electrodes deposited on the WSe2 nanosheets and ReSe2 nanosheets outside the heterojunction region serve as the drain electrode.

[0028] Graphene and ReSe2 nanosheets were obtained separately using a polydimethylsiloxane (PDMS)-assisted mechanical exfoliation method. Then, a dry transfer process was used to transfer graphene onto WSe2 nanosheets, followed by the transfer of ReSe2 nanosheets onto the graphene surface, forming a sandwich-type van der Waals heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets. ARP-5350 positive photoresist was spin-coated onto the SiO2 / Si substrate with the completed heterostructure stack. Specific photoresist coating parameters were: spin-coating speed set to 4000 rpm, spin-coating time lasting 60 seconds; after coating, the substrate was baked at 100℃ for 4 minutes to enhance the adhesion between the photoresist and the substrate and remove solvent. A maskless ultraviolet lithography system was used to create a photolithographic pattern. Au electrodes, each 50 nm thick, were fabricated on one side of the ReSe2 nanosheets, WSe2 nanosheets, and graphene outside the heterojunction region using electron beam evaporation. The electrode located at the graphene end was the source electrode, and the electrodes located at the WSe2 and ReSe2 nanosheet ends were the drain electrodes. The drain electrodes formed an ohmic contact with the ReSe2 and WSe2 nanosheets, and the electrodes on the ReSe2 and WSe2 nanosheets were connected in series to form a common drain.

[0029] Figure 1 (a) A side view of the atomic structure of a bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction, (b) a schematic diagram of the bidirectional polarization-sensitive photodetector, and (c) an optical microscope image. Figure 1 It is known that the bidirectional polarization-sensitive photodetector is a sandwich-type van der Waals heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets stacked on a SiO2 / Si substrate. Electrodes are fabricated on the ReSe2 nanosheet, WSe2 nanosheet and graphene sides outside the heterojunction region. The electrodes on the ReSe2 nanosheet and WSe2 nanosheet sides are interconnected as drain electrodes (D), the graphene-connected electrodes are source electrodes (S), the Si on the SiO2 / Si substrate is used as gate electrodes, and SiO2 is used as an insulating layer. Figure 2A schematic diagram (a) of the measurement circuit of the bidirectional polarization-sensitive photodetector in Example 1; wherein, graphene is used as the source electrode (S), gold electrodes deposited on WSe2 nanosheets and ReSe2 nanosheets outside the heterojunction region are used as drain electrodes (D), and Si on the SiO2 / Si substrate is used as the gate electrode (G); IV characteristic curves at different optical power densities (b); I sc and V oc Relationship with optical power density (c). From Figure 2 As shown in (b), under illumination, due to the photovoltaic effect in the ReSe2 nanosheet / graphene / WSe2 nanosheet heterojunction, the short-circuit current (Isc) and open-circuit voltage (Voc) can be observed. Figure 2 As shown in (c), the short-circuit current I sc The value increases with increasing light intensity, indicating the photovoltaic response capability of the detection device.

[0030] Figure 3 The graphs (a) showing the detectivity (D*) and external quantum efficiency (EQE) of the bidirectional polarization-sensitive photodetector as a function of optical power intensity, the time response (b), and the time-correlated optical response (c) at different gate voltages are shown below. Figure 3 As shown in (a), D* and EQE increase as the light intensity decreases, reaching 1.6 × 10⁻⁶ respectively. 11 Jones and 12%. From Figure 3 From (b), we can see that the response speed is 15~25 ms; from Figure 3 As shown in (c), the magnitude and direction of the photocurrent can be controlled by the gate voltage to achieve a bidirectional photoelectric response. Response speed is a key performance indicator of a photodetector, used to quantify the time response characteristics of the device to incident light signals. The time response is typically characterized by two key parameters: rise time and fall time. The rise time is the time required for the photocurrent to rise from 10% to 90% of its maximum value, and the fall time is the time required for the photocurrent to decay from 90% to 10% of its maximum value.

[0031] Figure 4 This is a schematic diagram (a) of the bidirectional polarization-sensitive photodetector of Example 1, with an inset showing the optical image of the corresponding device and the polarization-dependent current (b). From Figure 4 As shown in (a), circularly polarized 635 nm light is converted into linearly polarized light by a polarizer, with a polarization angle ranging from 0 to 360 degrees. O Periodic variation. The angle between the incident polarized light and the b-axis of the ReSe2 nanosheet is... θ Because ReSe2 nanosheets possess a strongly in-plane anisotropic structure, the photocurrent and the included angle... θ They are strongly correlated. From Figure 4 As shown in (b), when the polarization angle of the incident light is changed, the photocurrent exhibits significant periodic oscillations: θ It reaches its minimum value at 0° or 180°. θ The polarization ratio reaches its maximum value at 90° or 270°. Therefore, this bidirectional polarization-sensitive photodetector exhibits excellent polarization sensitivity characteristics, achieving a polarization ratio of 9 under incident light at a wavelength of 635 nm and 6 under incident light at a wavelength of 808 nm.

[0032] Example 2 A bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction includes a gate electrode, a ReSe2 nanosheet / graphene / WSe2 nanosheet sandwich van der Waals heterojunction, a source electrode, and a drain electrode. The gate electrode is a heavily doped Si substrate with an approximately 200 nm thick SiO2 insulating layer on its surface. WSe2 nanosheets (50 nm thick) and ReSe2 nanosheets (50 nm thick) are connected in parallel to form a conductive channel, graphene (10 nm thick) serves as the source electrode, and gold electrodes are deposited on the WSe2 nanosheets and ReSe2 nanosheets outside the heterojunction region to serve as the drain electrode.

[0033] Graphene and ReSe2 nanosheets were obtained separately using a polydimethylsiloxane (PDMS)-assisted mechanical exfoliation method. Then, a dry transfer process was used to transfer graphene onto WSe2 nanosheets, followed by the transfer of ReSe2 nanosheets onto the graphene surface, forming a sandwich-type van der Waals heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets. Using a maskless ultraviolet lithography system and electron beam evaporation, Au electrodes with a thickness of 100 nm were fabricated on one side of the ReSe2 nanosheets, WSe2 nanosheets, and graphene outside the ReSe2 nanosheet / graphene / WSe2 nanosheet sandwich-type van der Waals heterojunction region. The electrode located at the graphene end served as the source electrode, while those located at the WSe2 nanosheet and ReSe2 nanosheet ends served as drain electrodes. The drain electrodes formed an ohmic contact with the ReSe2 nanosheets and WSe2 nanosheets, and the electrodes on the ReSe2 nanosheets and WSe2 nanosheets were connected in series to form a common drain electrode.

[0034] The bidirectional polarization-sensitive photodetector of the present invention has both bidirectional response and polarization sensitivity characteristics. By changing the gate voltage, it can reverse the polarity of the photocurrent and has a high polarization ratio, thereby meeting the needs of polarization imaging and in-sensor computing.

[0035] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction, characterized in that, The bidirectional polarization-sensitive photodetector is a van der Waals sandwich heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets stacked on a SiO2 / Si substrate. Electrodes are fabricated on the ReSe2 nanosheet, WSe2 nanosheet, and graphene sides outside the heterojunction region. The electrodes on the ReSe2 nanosheet and WSe2 nanosheet sides are interconnected as drain electrodes, and the electrode connected to the graphene is the source electrode. The Si on the SiO2 / Si substrate is used as the gate electrode, and SiO2 is used as the insulating layer.

2. The bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction according to claim 1, characterized in that, The bidirectional polarization-sensitive photodetector is obtained by transferring WSe2 nanosheets obtained through mechanical exfoliation onto a SiO2 / Si substrate, and then obtaining graphene and ReSe2 nanosheets through a polydimethylsiloxane-assisted mechanical exfoliation method. The ReSe2 nanosheets are then transferred to the surface of graphene using a dry transfer method and stacked onto the WSe2 nanosheets. The overlapping portion of the ReSe2 nanosheets, graphene, and WSe2 nanosheets forms a sandwich-type van der Waals heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets. Electrodes are fabricated on the ReSe2 nanosheet, WSe2 nanosheet, and graphene sides outside the heterojunction region.

3. The bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction according to claim 1, characterized in that, The WSe2 nanosheets have a thickness of 1-50 nm and a lateral dimension of 5-100 μm; the ReSe2 nanosheets have a thickness of 1-50 nm and a lateral dimension of 5-100 μm; and the graphene has a thickness of 1-50 nm.

4. The bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction according to claim 1, characterized in that, The electrode is made of Au and has a thickness of 30~100 nm.

5. The method for fabricating a bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction according to any one of claims 1-4, characterized in that, The specific steps include the following: S1. Multilayer WSe2 nanosheets were exfoliated from WSe2 crystals using a mechanical exfoliation method and then transferred onto a pre-prepared SiO2 / Si substrate; S2. Graphene and ReSe2 nanosheets were obtained by mechanical exfoliation assisted by polydimethylsiloxane. Then, graphene was transferred to the surface of WSe2 nanosheets by dry transfer method, and then ReSe2 nanosheets were transferred to the surface of graphene to form a heterojunction of ReSe2 nanosheets / graphene / WSe2 nanosheets. S3. Photoresist is spin-coated onto a SiO2 / Si substrate with a ReSe2 nanosheet / graphene / WSe2 nanosheet heterojunction. The pattern is then lithographically patterned using maskless ultraviolet light. Electrodes are fabricated on the ReSe2 nanosheet, WSe2 nanosheet and graphene sides outside the heterojunction region by electron beam evaporation to obtain a bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction.

6. The method for fabricating a bidirectional polarization-sensitive photodetector based on a van der Waals sandwich heterojunction according to claim 5, characterized in that, The thickness of the SiO2 layer in the SiO2 / Si substrate described in step S1 is 100~300 nm.

7. The application of the bidirectional polarization-sensitive photodetector based on the van der Waals sandwich heterojunction as described in any one of claims 1-4 in the fields of photoelectric detection or artificial vision.

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