A sandwich phototransistor based on two-dimensional topological insulator and preparation method and application thereof

Abstract

The application belongs to the technical field of multifunctional optoelectronic transistors, and discloses a sandwich optoelectronic transistor based on a two-dimensional topological insulator as well as a preparation method and application thereof. The optoelectronic transistor is prepared by transferring a topological insulator nanosheet to a SnSe2 nanosheet, transferring a 2H-MoTe2 nanosheet to the SnSe2 / topological insulator heterojunction, forming a SnSe2 / topological insulator / 2H-MoTe2 heterojunction without contact between the SnSe2 nanosheet and the 2H-MoTe2 nanosheet, evaporating a metal bonding layer and an Au electrode on the SnSe2 nanosheet and the 2H-MoTe2 nanosheet respectively, and annealing at 150-300 DEG C under a protective atmosphere. The topological insulator nanosheet is a Bi2Se3 or Bi2Te3 nanosheet. The optoelectronic transistor has good photoelectric response performance under an 808 nm waveband, and can be used in the fields of logic loop devices or visible-near infrared light response optoelectronic devices.

Description

Technical Field

[0001] This invention belongs to the technical field of multifunctional phototransistors, and more specifically, relates to a sandwich phototransistor based on a two-dimensional topological insulator, its fabrication method, and its application. Background Technology

[0002] The conversion of optical signals into electrical signals is of great significance in modern technology. Photodetectors are a crucial means of achieving this and a key component of modern technology, with wide applications in various fields, including military and national economy. In particular, infrared photodetectors can be applied in spectroscopy, remote sensing, imaging, security, and optical communication. Traditional photodetectors can be formed by vertically stacking two-dimensional materials. Two-dimensional materials possess excellent physical properties such as no need to consider lattice matching, thickness dependence, strong interactions, and quantum optical effects. To date, photodetectors based on two-dimensional van der Waals heterojunctions have achieved superior performance and have attracted widespread attention from researchers.

[0003] However, most current research on photodetectors focuses on double heterojunctions composed of two stacked materials. Based on the bandgap arrangement between the materials, double heterojunctions can be classified into three types: The first type has the band gap of one material entirely within the band gap of the other material; this is a straddle type, where electrons and holes are concentrated in the lower bandgap material, facilitating recombination. It is commonly used in the fabrication of light-emitting diodes (LEDs). The second type has the valence band top of one material located within the band gap of the other material; this is a staggered type, which facilitates electron and hole separation and can be used in solar cells. The third type has the conduction band bottom of one material lower than the valence band top of the other material; this is a gap-breaking type and can be used in tunneling transistors. Research on double heterojunctions composed of three stacked materials is relatively limited. Studies have shown that compared to single heterojunctions, double heterojunction photodetectors can significantly suppress dark current, improve photoresponsivity, broaden the absorption range, increase the polarization current ratio, and improve response speed. However, for two-dimensional topological insulators with high surface conductivity, internal insulation, narrow band gap, high mobility, and broad absorption, no reports have been found regarding double heterojunctions. Summary of the Invention

[0004] In order to overcome the shortcomings and disadvantages of the existing technology, the present invention aims to provide a sandwich phototransistor based on a two-dimensional topological insulator.

[0005] Another object of the present invention is to provide a method for fabricating the above-mentioned sandwich phototransistor based on a two-dimensional topological insulator.

[0006] Another object of the present invention is to provide an application of the above-described two-dimensional topological insulator sandwich phototransistor.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A two-dimensional topological insulator sandwich phototransistor is disclosed. The phototransistor is fabricated by first transferring a topological insulator nanosheet onto a SnSe2 nanosheet on a SiO2 / Si substrate to form a SnSe2 / topological insulator heterojunction, and then transferring a 2H-MoTe2 nanosheet onto the topological insulator nanosheet of the SnSe2 / topological insulator heterojunction, wherein the SnSe2 nanosheet and the 2H-MoTe2 nanosheet are not in contact, forming a SnSe2 / topological insulator / 2H-MoTe2 heterojunction. A metal bonding layer and an Au electrode are deposited on the SnSe2 nanosheet and the 2H-MoTe2 nanosheet, respectively, and the mixture is annealed at 150–300°C under a protective atmosphere. The topological insulator nanosheet is either Bi2Se3 or Bi2Te3 nanosheet.

[0009] Preferably, the thickness of the SnSe2 nanosheet is 10–70 nm; the thickness of the topological insulator nanosheet is 5–50 nm; and the thickness of the 2H-MoTe2 nanosheet is 10–70 nm.

[0010] Preferably, the SnSe2 nanosheets are N-type doped SnSe2 nanosheets, which are obtained by mechanical exfoliation on a cleaned SiO2 / Si substrate;

[0011] The topological insulator nanosheet is obtained by vapor-depositing a Cr / Au or Ti / Au layer onto a SiO2 / Si substrate and then pressing and peeling the topological insulator tape onto the Cr / Au or Ti / Au layer onto the SiO2 / Si substrate.

[0012] The 2H-MoTe2 nanosheets were obtained on PDMS films by mechanical exfoliation.

[0013] Preferably, the metal bonding layer is Cr or Ti with a thickness of 3 to 15 nm, and the Au has a thickness of 20 to 200 nm.

[0014] The fabrication method of the sandwich phototransistor with the two-dimensional topological insulator includes the following specific steps:

[0015] S1. SnSe2 nanosheets were obtained on a cleaned 300nm SiO2 / Si substrate by mechanical exfoliation. The sample surface was then soaked in acetone to remove residual adhesive and other small organic molecules. SnSe2 nanosheets of appropriate size were selected by optical metallographic microscope.

[0016] S2. Using a dry transfer process, topological insulator nanosheets are stacked onto SnSe2 nanosheets through a three-dimensional micro-region transfer platform, and then annealed at 100-150℃ under a protective gas to obtain SnSe2 / Bi2Se3 heterojunctions with clean interfaces and tight contact.

[0017] S3. Using a dry transfer process, 2H-MoTe2 nanosheets are stacked onto Bi2Se3 nanosheets through a three-dimensional micro-region transfer platform, and then annealed at 100-150℃ under a protective gas to obtain SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunctions with clean interfaces and tight contact.

[0018] S4. Electrode patterns are lithographically patterned and developed on SnSe2 nanosheets and 2H-MoTe2 nanosheets using an ultraviolet lithography machine. A metal bonding layer and Au electrodes are deposited by electron beam evaporation or thermal evaporation system. After immersion in acetone to remove the electrode patterns, the electrodes are annealed in an inert gas at 150–300 °C to obtain a phototransistor based on a SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction, which is a sandwich phototransistor based on a two-dimensional topological insulator.

[0019] Preferably, the preparation method of the topological insulator nanosheet in step S2 is mechanical exfoliation, gold-assisted exfoliation-transfer, or physical vapor deposition.

[0020] More preferably, the gold-assisted lift-transfer method specifically involves mechanically lifting a SiO2 / Si substrate coated with a Cr / Au or Ti / Au layer using a tape with a topological insulator single crystal, and then obtaining a clean and undamaged sample with a thickness of 5-50 nm on the new SiO2 / Si substrate through dry transfer and gold etching solution.

[0021] Preferably, the protective gas in step S2 is nitrogen or argon; the annealing time is 0.3 to 2 hours.

[0022] The application of the sandwich phototransistor with the two-dimensional topological insulator in the field of logic circuit components or optoelectronic devices with visible-near-infrared light response.

[0023] Preferably, the SnSe2 nanosheets are obtained by mechanical exfoliation on a cleaned SiO2 / Si substrate; the topological insulator nanosheets are obtained by evaporating Ti / Au onto the SiO2 / Si substrate; and by pressing and peeling off topological insulator tape adhered to the Ti / AuSiO2 / Si substrate.

[0024] This invention significantly improves photoelectric performance by using Bi₂Se₃ as an intermediate layer in a type III bandgap arrangement of MoTe₂ / SnSe₂. Based on theoretical reports and experimental results, the device generates two built-in electric fields in the same direction. MoTe₂, as a bipolar material, provides significant gate voltage modulation capability. At a gate voltage (V... g At 60V, the built-in electric field between MoTe2 and Bi2Se3 reverses, resulting in two back-to-back built-in electric fields. The device operates at 808nm and V...g At 60V, the maximum photoresponsivity and specific detectivity reach 492.80 mA / W and 1.8 × 10⁻⁶, respectively. 11 Jones achieves an external quantum efficiency of 76% and a response speed of 553μs / 583μs. These performance parameters far exceed those of MoTe2 / SnSe2 double heterojunction photodiodes, providing an effective strategy for constructing an ultrafast-response tunneling phototransistor.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction-based phototransistor of this invention achieves tunable gate photoresponse. Under different gate voltage applications (0V or 60V), the two built-in electric field directions of the phototransistor change from being in the same direction to being back-to-back. Results show that the back-to-back built-in electric field direction significantly improves the photoelectric performance of the phototransistor compared to the in-direction built-in electric field direction. This solves the problem in this field where the responsivity and response time of phototransistors cannot be simultaneously satisfied.

[0027] 2. This invention can change the direction of the built-in electric field formed by 2H-MoTe2 as a bipolar material and Bi2Se3 by controlling the Fermi level position of 2H-MoTe2 through gate voltage modulation.

[0028] 3. The phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction of the present invention exhibits excellent near-infrared self-driven photoelectric performance (maximum photoresponse at 808nm reaches 492.80 mA·W). -1 The external quantum efficiency reaches 76%, and the maximum specific detectivity reaches 1.8 × 10⁻⁶. 11 Jones (with a response speed of 553 μs) has an upstream level of self-driven photoelectric performance among similar photodetectors. Compared with the structure without topological insulator sandwich, the external quantum efficiency, specific detectivity and responsivity are significantly improved, and it has broad application prospects in the fields of low power consumption and near-infrared photoelectric detection. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction of the present invention.

[0030] Figure 2 This is an optical microscope image of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1.

[0031] Figure 3The phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 is shown in V ds The transfer curve at 1V.

[0032] Figure 4 The output curves of the phototransistor based on the Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 are shown at gate voltages of 0V and 40V, respectively.

[0033] Figure 5 The self-driven response I of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 under different optical power densities with 808nm laser and a gate voltage of 60V is shown. ds -V ds Line graph.

[0034] Figure 6 The graph shows the self-driven response time of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 under different optical power densities with an 808nm laser and a gate voltage of 60V.

[0035] Figure 7 The graph shows the relationship between photoresponsivity, photocurrent, and optical power density of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 under different optical power densities with 808nm laser and gate voltage of 60V.

[0036] Figure 8 The graph shows the relationship between the specific detectivity and external quantum efficiency of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 and the optical power density under different optical power densities with an 808nm laser and a gate voltage of 60V.

[0037] Figure 9 The graph shows the response speed of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 under 808nm laser and a gate voltage of 60V.

[0038] Figure 10 The graph shows a comparison of the photoresponsivity-external quantum efficiency versus optical power density between the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction and the phototransistor based on the SnSe2 / 2H-MoTe2 heterojunction in Example 1 under 808nm laser and gate voltage of 60V.

[0039] Figure 11 Optical microscope images and electrical properties of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 2. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings, but should not be construed as limiting the present invention. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; the reagents and materials described, unless otherwise specified, can be obtained from publicly available commercial sources. The present invention will now be described in further detail.

[0041] Example 1

[0042] 1. Sonicate the SiO2 / Si substrate with acetone, isopropanol, and deionized water for 10 minutes each, and then dry it with a nitrogen gun.

[0043] 2. Using SiO2 / Si as a substrate, semiconductor SnSe2 nanosheets were prepared by tape peeling method, and SnSe2 nanosheets with a thickness of 20-40 nm were selected by optical microscopy;

[0044] 3. Bi2Se3 nanosheets were prepared using a gold-assisted large-area method, and Bi2Se3 nanosheets with a thickness of 10–50 nm were selected by optical microscopy.

[0045] 4. 2H-MoTe2 nanosheets were prepared on PDMS by tape peeling method, and 2H-MoTe2 nanosheets with a thickness of 10-70 nm were selected by optical microscopy;

[0046] 5. Using a three-dimensional micro-region transfer platform, the Bi2Se3 nanosheets selected in step 3 and the SnSe2 nanosheets selected in step 2 are aligned pairwise using dry transfer. The overlapping portion of the two nanosheets forms a SnSe2 / Bi2Se3 heterojunction. The 2H-MoTe2 nanosheets selected in step 4 are then stacked with the SnSe2 / Bi2Se3 heterojunction using dry transfer again, with the 2H-MoTe2 nanosheets only in contact with the Bi2Se3 nanosheets, to construct the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction. The mixture is then annealed at 100–150 °C for 0.3–2 h under nitrogen or argon atmosphere to enhance the interfacial contact between the three materials and remove small molecule impurities from the substrate surface and the material interfaces.

[0047] 5. Using a maskless ultraviolet lithography system and evaporation process, 10 nm Cr and 50 nm Au electrodes were sequentially fabricated on SnSe2 and 2H-MoTe2 of the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction. Then, the electrodes were annealed at 150–300 °C for 0.3–1 h under nitrogen or argon atmosphere to improve the contact quality between the electrodes and the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction and reduce the contact barrier, thus obtaining a phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction, which is a sandwich phototransistor based on a two-dimensional topological insulator.

[0048] Figure 1 This is a schematic diagram of a phototransistor based on a SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction. D (anode) and S (cathode). Figure 1 As can be seen from the diagram, this phototransistor is a heterojunction phototransistor based on a SnSe2 / Bi2Se3 / 2H-MoTe2 sandwich structure. The 2H-MoTe2 is connected to the anode, and the SnSe2 is connected to the cathode. Figure 2 An optical microscope image of the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction phototransistor prepared in Example 1. Figure 2 It is known that the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction is made by transferring SnSe2 nanosheets on a SiO2 / Si substrate, then transferring Bi2Se3 nanosheets prepared with gold assistance onto the SnSe2 nanosheets. The overlapping part of the SnSe2 nanosheets and Bi2Se3 nanosheets forms the SnSe2 / Bi2Se3 heterojunction. Then, the 2H-MoTe2 nanosheets are transferred to the Bi2Se3 nanosheets in the SnSe2 / Bi2Se3 heterojunction using a dry transfer method to form the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction. The metal bonding layer Cr and Au electrode are deposited sequentially on the SnSe2 nanosheets and the 2H-MoTe2 nanosheets, respectively.

[0049] Figure 3 The phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 is shown in V ds The transfer curve at 1V. From Figure 3 It can be seen that the source-drain current can be effectively controlled under a gate voltage of -60 to 60V. Figure 4 The output curves of the phototransistor based on the Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 are shown at gate voltages of 0V and 40V, respectively. Figure 4It can be seen that when the gate voltage is 0V, the output curve shows that the positive current is greater than the negative current; when the gate voltage is 40V, the phototransistor becomes that the negative current is greater than the positive current, and the output curve shows completely different rectification characteristics, indicating that the built-in electric field has changed under the action of the gate voltage. Figure 5 The self-driven response I of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 under different optical power densities with an 808nm laser gate voltage of 60V. ds -V ds Curve. From Figure 5 It can be seen that the short-circuit current of the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction is negative, and the maximum value is 14.6nA. Figure 6 The image shows the self-driven response time curves of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 under different optical power densities with an 808nm laser gate voltage of 60V. From... Figure 6 It can be seen that as the optical power increases, the photocurrent of the device also gradually increases, and the photocurrent and I under the self-driven response time... ds -V ds The consistent short-circuit current values ​​on the curves prove their authenticity. Figure 7 The image shows the photoresponsivity-photocurrent versus optical power density curves of the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction-based phototransistor of Example 1 under different optical power densities with an 808nm laser gate voltage of 60V. Figure 7 It can be seen that when the optical power density is 47.87 mW·cm -2 At that time, the photoresponsivity reached its maximum value of 492.8 mA·W. -1 This indicates that as the optical power density increases, the photoresponsivity first increases and then decreases, while the photocurrent increases with the increase of optical power density. Figure 8 The graphs show the specific detectivity and external quantum efficiency of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1, under different optical power densities with an 808nm laser gate voltage of 60V. Figure 8 It can be seen that when the optical power density is 47.87 mW·cm -2 At that time, both the specific detectivity and the external quantum efficiency reached their maximum values, which were 1.8 × 10⁻⁶ respectively. 11 Jones and 76%. This indicates that the specific detectivity and external quantum efficiency have the same trend, both increasing first and then decreasing with increasing optical power density.

[0050] Figure 9The image shows the response speed curve of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction in Example 1 under an 808nm laser with a gate voltage of 60V. Figure 9 It can be seen that at a frequency of 1Hz, the rise and fall speeds of this phototransistor are 583μs and 553μs, respectively. Figure 10 The image shows a comparison of the photoresponsivity-external quantum efficiency versus optical power density between the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction and the phototransistor based on the SnSe2 / 2H-MoTe2 heterojunction in Example 1 under 808nm laser illumination and a gate voltage of 60V. Figure 10 It can be seen that when the optical power density is 45.57 mW / cm² 2 At that time, the responsivity of the phototransistor based on SnSe2 / 2H-MoTe2 heterojunction was 13 mA / W, while the responsivity of the phototransistor based on SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction was improved by 38 times. The external quantum efficiency of the phototransistor based on SnSe2 / 2H-MoTe2 heterojunction was 2%, while the external quantum efficiency of the phototransistor based on SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction was also improved by 38 times.

[0051] Example 2

[0052] The difference from Example 1 is that the thickness of SnSe2 is 20-30 nm, the thickness of MoTe2 is 20-30 nm, and the thickness of Bi2Se3 is 15-30 nm.

[0053] Figure 11 Optical microscope images and electrical properties of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction prepared in Example 2 are shown. Image (a) shows an optical microscope image, revealing that the overlap area of ​​the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction is 90.83 μm. 2 (a) 2H-MoTe2 is on top, Bi2Se3 is in the middle, and SnSe2 is at the bottom; (b) Electrical performance, i.e., the V of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction under different optical power densities of an 808nm laser. ds =0V, V g The graph shows the relationship between photoresponsivity and optical power density at 60V. Given that SnSe2 is connected to the drain and 2H-MoTe2 to the source, from... Figure 11(b) It can be seen that, compared with the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction and the SnSe2 / 2H-MoTe2 heterojunction in Example 1, the performance of the phototransistor based on the SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction prepared in Example 2 is also significantly improved. With increasing optical power density, the photoresponse first increases and then decreases. When the optical power density is 0.62 mW·cm⁻¹, the photoresponse decreases. -2 At that time, the photoresponsivity reached its maximum value of 310 mA·W. -1 Compared with SnSe2 / 2H-MoTe2 heterojunctions, SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunctions show a significant improvement in photoresponsivity performance, demonstrating the reproducibility of the Bi2Se3 interlayer's effect on improving the optoelectronic performance of SnSe2 / 2H-MoTe2 heterojunctions.

[0054] 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 sandwich phototransistor based on a two-dimensional topological insulator, characterized in that, The phototransistor is fabricated by first transferring a topological insulator nanosheet onto a SnSe2 nanosheet on a SiO2 / Si substrate to form a SnSe2 / topological insulator heterojunction, and then transferring a 2H-MoTe2 nanosheet onto the topological insulator nanosheet of the SnSe2 / topological insulator heterojunction, wherein the SnSe2 nanosheet and the 2H-MoTe2 nanosheet do not contact each other to form a SnSe2 / topological insulator / 2H-MoTe2 heterojunction. A metal bonding layer and an Au electrode are deposited on the SnSe2 nanosheet and the 2H-MoTe2 nanosheet, respectively, and the transistor is annealed at 150~300℃ under a protective atmosphere. The topological insulator nanosheet is a Bi2Se3 or Bi2Te3 nanosheet.

2. The sandwich phototransistor based on a two-dimensional topological insulator according to claim 1, characterized in that, The SnSe2 nanosheets have a thickness of 10-70 nm; the topological insulator nanosheets have a thickness of 5-50 nm; and the 2H-MoTe2 nanosheets have a thickness of 10-70 nm.

3. The sandwich phototransistor based on a two-dimensional topological insulator according to claim 2, characterized in that, The SnSe2 nanosheets are N-type doped SnSe2 nanosheets, which are obtained by mechanical exfoliation on a cleaned SiO2 / Si substrate. The topological insulator nanosheet is obtained by depositing a Cr / Au or Ti / Au layer onto a SiO2 / Si substrate and then pressing and peeling the topological insulator tape onto the Cr / Au or Ti / Au layer onto the SiO2 / Si substrate. The 2H-MoTe2 nanosheets were obtained on PDMS films by mechanical exfoliation.

4. The sandwich phototransistor based on a two-dimensional topological insulator according to claim 1, characterized in that, The metal bonding layer is Cr or Ti with a thickness of 3-15 nm, and the Au electrode has a thickness of 20-200 nm.

5. The method for fabricating a sandwich phototransistor based on a two-dimensional topological insulator according to any one of claims 1-4, characterized in that, The specific steps include the following: S1. SnSe2 nanosheets were obtained on a cleaned 300nm SiO2 / Si substrate by mechanical exfoliation. The sample surface was then soaked in acetone to remove residual adhesive and other small organic molecules. SnSe2 nanosheets of appropriate size were selected by optical metallographic microscopy. S2. Using a dry transfer process, topological insulator nanosheets are stacked onto SnSe2 nanosheets through a three-dimensional micro-region transfer platform, and then annealed at 100~150℃ under a protective gas to obtain SnSe2 / Bi2Se3 heterojunctions with clean interfaces and tight contact. S3. Using a dry transfer process, 2H-MoTe2 nanosheets were stacked onto Bi2Se3 nanosheets via a three-dimensional micro-region transfer platform, and then annealed at 100~150℃ under a protective gas to obtain SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunctions with clean interfaces and tight contact. S4. Electrode patterns are lithographically patterned and developed on SnSe2 nanosheets and 2H-MoTe2 nanosheets using an ultraviolet lithography machine. A metal bonding layer / Au electrode is deposited by electron beam evaporation or thermal evaporation system. After immersion in acetone to remove the electrode pattern, the electrode pattern is obtained. The electrode pattern is then annealed in an inert gas at 150~300℃ to obtain a phototransistor based on a SnSe2 / Bi2Se3 / 2H-MoTe2 heterojunction, which is a sandwich phototransistor based on a two-dimensional topological insulator.

6. The method for fabricating a sandwich phototransistor based on a two-dimensional topological insulator according to claim 5, characterized in that, The preparation methods of the topological insulator nanosheets in step S2 are mechanical exfoliation, gold-assisted exfoliation-transfer, and physical vapor deposition.

7. The fabrication method of the two-dimensional topological insulator sandwich phototransistor according to claim 6, characterized in that, The gold-assisted lift-transfer method specifically involves mechanically lifting a single crystal wafer with a topological insulator onto a SiO2 / Si substrate coated with a Cr / Au or Ti / Au layer using adhesive tape. A clean and undamaged sample with a thickness of 5-50 nm is then obtained on the new SiO2 / Si substrate through dry transfer and gold etching solution.

8. The method for fabricating a sandwich phototransistor based on a two-dimensional topological insulator according to claim 5, characterized in that, The protective gas in step S2 is nitrogen or argon; the annealing time is 0.3 to 2 hours.

9. The application of the sandwich phototransistor based on two-dimensional topological insulator as described in any one of claims 1-4 in the field of logic circuit components or optoelectronic devices with visible-near-infrared light response.

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