A broadband optical detector for dynamically encrypted communication and a method of manufacturing the same

Abstract

The application belongs to the technical field of light detectors. A preparation method of a broadband light detector for dynamic encryption communication is provided, which comprises the following steps: S1, providing a SiO2 / Si substrate; S2, sequentially transferring a first transition metal sulfide and a second transition metal sulfide on the SiO2 / Si substrate by directional transfer to form a transition metal sulfide layer; S3, spin-coating a PbSe QDs solution or a PbS QDs solution on the transition metal sulfide layer to form a quantum dot film with uniform quantum dots; S4, dropping EDT acetonitrile solution on the surface of the quantum dot film, standing for a preset time, and then spin-coating to remove excess ligands and reaction byproducts; S5, placing the quantum dot film on a heating table for annealing treatment to complete the preparation of a mixed-dimensional quantum dot / transition metal sulfide heterostructure light detector. The energy barrier at the quantum dot / transition metal sulfide heterostructure can be independently and cooperatively regulated by a drain-source voltage and a gate-source voltage, and the security of the photoelectric detector can be improved.

Description

Technical Field

[0001] This application relates to the field of photodetector technology, and more specifically, to a broadband photodetector for dynamic encrypted communication and its fabrication method. Background Technology

[0002] The advent of the big data era has led to a continuous surge in the amount of information processed and transmitted daily, and the demand for secure data transmission in various fields is constantly increasing, placing higher requirements on the reliability and encryption of communication systems. Traditional encryption methods rely on software algorithms, which face the potential threat of quantum computing. Therefore, there is an urgent need for solutions to achieve secure communication at the device level.

[0003] As a key interface between signal and electronic processing in communication systems, photodetectors are an ideal choice for embedding physical layer hardware-level encryption functions. However, traditional photodetectors based on bulk semiconductors are limited by their thick geometry and rigid band structure, resulting in limited structural flexibility and electrical tunability. These limitations hinder the integration of real-time encryption functions. Summary of the Invention

[0004] The purpose of this application is to provide a broadband optical detector for dynamic encrypted communication and its fabrication method, which can solve at least one of the technical problems mentioned above. The specific solution is as follows: According to a specific embodiment of this application, this application proposes a method for fabricating a broadband optical detector for dynamic encrypted communication, comprising: Step S1: Provide a SiO2 / Si substrate; Step S2: The first transition metal sulfide and the second transition metal sulfide are sequentially transferred on the SiO2 / Si substrate by directional transfer to form a transition metal sulfide layer; Step S3: Spin-coat a PbSe QDs solution or a PbS QDs solution onto the transition metal sulfide layer to form a uniform quantum dot film; Step S4: Add EDT acetonitrile solution dropwise to the surface of the quantum dot film, allow the reaction to stand for a preset time, and then spin-coat to remove excess ligands and reaction byproducts; Step S5: Place the photodetector on a heating stage for annealing to complete the fabrication of the hybrid quantum dot / transition metal sulfide heterostructure photodetector; wherein, the energy barrier at the quantum dot / transition metal sulfide heterostructure can be independently and collaboratively controlled by the drain-source voltage and the gate-source voltage.

[0005] In some embodiments, the first transition metal sulfide comprises MoSe2; the second transition metal sulfide comprises MoTe2.

[0006] In some embodiments, prior to step S3, the method further includes: dissolving PbSe QDs or PbS QDs in n-hexane to form a PbSe QDs solution or PbS QDs solution with a concentration of 10-35 mg / mL.

[0007] In some embodiments, step S4 is repeated at least twice before step S5.

[0008] In some embodiments, step S1 further includes: providing a P-type highly doped silicon wafer with a SiO2 thickness of 200 nm-400 nm, cleaning it with deionized water, ethanol, acetone and isopropanol respectively, then drying the silicon wafer with a nitrogen gun, and placing it in a drying oven at 50℃-80℃ for 2-4 hours.

[0009] In some embodiments, step S2 is followed by: fabricating Ti / Au source / drain electrodes using photolithography, thermal evaporation, and lift-off techniques.

[0010] In some embodiments, the thickness of Ti is 8nm-12nm and the thickness of Au is 70nm-90nm.

[0011] In some embodiments, the annealing process performed on the heating table includes: annealing on a heating table at 70°C-100°C for 10-30 minutes in a nitrogen atmosphere.

[0012] In some embodiments, in step S4, the preset time for the static reaction is 20-60 seconds; the spin coating speed is 1500-3000 rpm; and the spin coating time is 20-60 seconds.

[0013] According to a specific embodiment of this application, this application also proposes a photodetector prepared according to any one of the methods described above, comprising: SiO2 / Si substrate; A transition metal sulfide layer of MoSe2 / MoTe2 heterojunction structure is disposed on the SiO2 / Si substrate; Ti / Au source and drain electrode layers are disposed at both ends of the MoSe2 / MoTe2 heterojunction structure; PbSe QDs or PbS QDs thin film layers are disposed on the transition metal sulfide layer; The energy barrier at the PbSe QDs / MoSe2 / MoTe2 or PbS QDs / MoSe2 / MoTe2 heterostructure can be independently and collaboratively controlled by the drain-source voltage and the gate-source voltage.

[0014] Compared with the prior art, the above-described solutions of this application have at least the following beneficial effects: This application proposes a dynamically encrypted broadband photodetector based on quantum dot-controlled van der Waals heterojunctions and its fabrication method. This photodetector integrates encryption functionality at the device level, supporting secure transmission of independent data across two channels. A hybrid-dimensional photodetector is constructed by combining quantum dots with transition metal sulfide van der Waals heterojunctions. On one hand, quantum dots possess a high light absorption coefficient, significantly improving the photodetector's light absorption efficiency and thus enhancing its photoelectric detection performance. On the other hand, the introduction of quantum dots creates a dynamically reconfigurable energy barrier at the transition metal sulfide heterojunction interface. The height and shape of this barrier can be independently and collaboratively controlled by the drain-source voltage (Vds) and gate-source voltage (Vgs). This prevents attackers from deducing information from the other channel even if they eavesdrop on the signal of a single voltage channel or only measure the total current. Any attempt to simulate a legitimate transmitter requires precise control of both voltages simultaneously, which is physically extremely difficult to achieve. Only authorized parties with knowledge of the device characteristics can decode the photocurrent sequence and decouple the information, thereby increasing the confidentiality of communication. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 This is a schematic flowchart of the photodetector fabrication method provided in the embodiments of this application.

[0016] Figure 2 This is a schematic diagram of the photodetector manufacturing process provided in Embodiment 1 of this application.

[0017] Figure 3 This is a schematic diagram of the photodetector manufacturing process provided in Embodiment 2 of this application.

[0018] Figure 4 The diagram shows an experimental result of the photodetector responsivity test provided in an embodiment of this application.

[0019] Figure 5 The diagram shows an experimental result of the photodetector detectivity test provided in an embodiment of this application.

[0020] Figure 6 The diagram shows an experimental result of photodetector gain testing provided in an embodiment of this application.

[0021] Figure 7 A schematic diagram of the dual-voltage modulated photoresponse and band arrangement of the photodetector provided in the embodiments of this application.

[0022] Figure 8 A schematic diagram of the dual-voltage modulated photoresponse and band arrangement of the photodetector provided in the embodiments of this application.

[0023] Figure 9 This is a schematic diagram of dual-channel information transmission of a photodetector provided in an embodiment of this application.

[0024] Figure 10 This is a schematic diagram of dual-channel information transmission encoding of a photodetector provided in an embodiment of this application.

[0025] Figure 11 This is a schematic diagram of the dual-channel information transmission signal of the photodetector provided in an embodiment of this application. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the article or device that includes said element.

[0028] Two-dimensional van der Waals materials, due to their superior optoelectronic properties and physical performance, can achieve various working mechanisms through external electric field modulation. They can also be flexibly integrated with other materials to construct hybrid-dimensional van der Waals heterostructures, providing richer design freedom for developing photodetectors with diverse architectures and functions. This opens up new avenues for realizing multifunctional devices that integrate high-performance detection and secure data transmission, perfectly meeting the urgent needs of the data-centric era for information security and efficient processing.

[0029] Based on this, this application proposes a broadband photodetector for dynamic encrypted communication and its fabrication method. The photodetector includes: a SiO2 / Si substrate; a transition metal sulfide layer of a MoSe2 / MoTe2 heterojunction structure disposed on the SiO2 / Si substrate; a Ti / Au source / drain electrode layer disposed at both ends of the MoSe2 / MoTe2 heterojunction structure; and a PbSe QDs or PbS QDs thin film layer disposed on the transition metal sulfide layer. The energy barrier at the PbSe QDs / MoSe2 / MoTe2 or PbS QDs / MoSe2 / MoTe2 heterostructure can be independently and collaboratively controlled by the drain-source voltage and the gate-source voltage.

[0030] The photodetector proposed in this application integrates quantum dots into a transition metal sulfide heterostructure, which significantly improves the device's photodetector performance. Furthermore, the doping of quantum dots creates a reconfigurable energy barrier structure at the heterostructure interface, endowing the device with tunable photoresponse. Through a dual control mechanism of drain-source voltage (Vds) and gate-source voltage (Vgs), multi-level tunability of the photocurrent state is successfully achieved, thereby constructing a photoresponse detector with multi-state encryption characteristics, providing a hardware-level encryption method for secure physical layer communication.

[0031] The optional embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0032] like Figure 1 As shown in the specific embodiments of this application, this application proposes a method for fabricating a broadband optical detector for dynamic encrypted communication, comprising the following steps: Step S1: Provide a SiO2 / Si substrate; Step S2: The first transition metal sulfide and the second transition metal sulfide are sequentially transferred on the SiO2 / Si substrate by directional transfer to form a transition metal sulfide layer; Step S3: Spin-coat a lead selenide quantum dot (PbSe QDs) solution or a lead sulfide quantum dot (PbS QDs) solution onto the transition metal sulfide layer to form a uniform quantum dot film; Step S4: Add a 1,2-ethylenedithiol (EDT) acetonitrile solution to the surface of the quantum dot film, allow the reaction to stand for a preset time, and then spin-coat to remove excess ligands and reaction byproducts; Step S5: Place the photodetector on a heating stage for annealing to complete the fabrication of the hybrid quantum dot / transition metal sulfide heterostructure photodetector; wherein, the energy barrier at the quantum dot / transition metal sulfide heterostructure can be independently and collaboratively controlled by the drain-source voltage and the gate-source voltage.

[0033] In some embodiments, step S1 further includes: providing a P-type highly doped silicon wafer with a SiO2 thickness of 200 nm-400 nm, cleaning it with deionized water, ethanol, acetone, and isopropanol respectively, then drying the silicon wafer with a nitrogen gun, and placing it in a drying oven at 50℃-80℃ for 2-4 hours. This ensures the cleanliness of the substrate, which is beneficial for the subsequent deposition of transition metal sulfides and quantum dots.

[0034] like Figure 2 , Figure 3 As shown, in some embodiments, in step S2, the first transition metal sulfide includes MoSe2, MoS2, WS2, and ReS2; the second transition metal sulfide includes MoTe2, WSe2, and ReSe2. The first and second transition metal sulfide flakes, prepared by mechanical exfoliation, are sequentially transferred to a SiO2 / Si substrate using a directional transfer method. Exemplarily, MoSe2 is transferred onto the SiO2 / Si substrate using a dry transfer method, followed by a directional transfer method to transfer MoTe2 onto the MoSe2.

[0035] In some embodiments, step S2 is followed by: fabricating Ti / Au source and drain electrodes using photolithography, thermal evaporation, and lift-off techniques. For example, the Ti thickness is 8 nm-12 nm, and the Au thickness is 70 nm-90 nm. After deposition, a lift-off process is used to remove the photoresist and excess metal, ultimately forming regular source and drain electrodes at both ends of the heterojunction.

[0036] In some embodiments, prior to step S3, a step of preparing a PbSe QDs solution or a PbS QDs solution is included: Pre-synthesized and purified PbSe QDs or PbS QDs are dissolved in n-hexane to form a PbSe QDs solution or PbS QDs solution with a concentration of 10-35 mg / mL. This PbSe QDs solution or PbS QDs solution is then drop-coated using a spin coater to cover the entire surface of the photodetector, and spin-coated at 1000-3000 rpm for 10-60 seconds to ensure uniform quantum dot film formation.

[0037] In some embodiments, step S4 is repeated at least twice to ensure sufficient exchange. In some embodiments, in step S4, the preset resting reaction time is 20-60 seconds; the spin coating speed is 1500-3000 rpm; and the spin coating time is 20-60 seconds.

[0038] In some embodiments, the annealing process on the heating stage includes: transferring the device that has completed ligand exchange to a glove box filled with high-purity nitrogen, and annealing it on a heating stage at 70°C-100°C for 10-30 minutes in a nitrogen environment.

[0039] According to a specific embodiment of this application, this application also proposes a photodetector prepared according to any one of the methods described above, comprising: a SiO2 / Si substrate; a transition metal sulfide layer of a MoSe2 / MoTe2 heterojunction structure disposed on the SiO2 / Si substrate; a Ti / Au source / drain electrode layer disposed at both ends of the MoSe2 / MoTe2 heterojunction structure; and a PbSe QDs or PbS QDs thin film layer disposed on the transition metal sulfide layer; wherein the energy barrier at the PbSe QDs / MoSe2 / MoTe2 or PbS QDs / MoSe2 / MoTe2 heterostructure can be independently and collaboratively controlled by the drain-source voltage and the gate-source voltage.

[0040] Example 1: Prepare a P-type highly doped silicon wafer with 300 nm thick SiO2, clean it with deionized water, ethanol, acetone and isopropanol respectively, then blow the silicon wafer dry with a nitrogen gun and dry it in a drying oven at 60°C for two hours. MoSe2 was transferred onto the silicon wafer using a dry transfer method, followed by directional transfer. MoTe2; Ti / Au (10 / 80 nm) was prepared as the source and drain electrodes using photolithography, thermal evaporation, and lift-off techniques. The deposition process was completed. Then, the photoresist and excess metal are removed by a stripping process, and finally regular source and drain electrodes are formed at both ends of the heterojunction.

[0041] The pre-synthesized and purified PbSe QDs were dissolved in n-hexane to prepare a homogeneous solution with a concentration of 25 mg / mL. The PbSe QDs solution was then dropped onto the entire device surface using a spin coater and spin-coated at 2500 rpm for 30 seconds to form a uniform quantum dot film.

[0042] A 1 mmol / L EDT acetonitrile solution was dropped onto the surface of the quantum dot film and allowed to stand for 30 seconds. This was followed by spin coating at 2000 rpm for 30 seconds to remove excess ligands and reaction byproducts. To ensure sufficient exchange, this drop-stand-spin coating cycle was repeated twice.

[0043] The device with completed ligand exchange was transferred to a glove box filled with high-purity nitrogen, placed on a heating stage, and annealed at 90°C for 10 minutes to complete the fabrication of the mixed-dimensional PbSe QDs / MoTe2 / MoSe2 heterostructure device.

[0044] Example 2: Prepare a P-type highly doped silicon wafer with 350 nm thick SiO2, clean it with deionized water, ethanol, acetone and isopropanol respectively, then blow the silicon wafer dry with a nitrogen gun and dry it in a drying oven at 70°C for three hours. MoSe2 was transferred onto the silicon wafer using a dry transfer method, followed by directional transfer. MoTe2; Ti / Au (12 / 90 nm) was prepared as source and drain electrodes using photolithography, thermal evaporation and lift-off techniques. After deposition, the photoresist and excess metal were removed by lift-off process, and finally regular source and drain electrodes were formed at both ends of the heterojunction.

[0045] The pre-synthesized and purified PbS QDs were dissolved in n-hexane to prepare a homogeneous solution with a concentration of 30 mg / mL. The PbS QDs solution was then dropped onto the entire device surface using a spin coater and spin-coated at 2500 rpm for 40 seconds to form a uniform quantum dot film.

[0046] A 1 mmol / L EDT acetonitrile solution was dropped onto the surface of the quantum dot film and allowed to stand for 50 seconds. This was followed by spin coating at 2500 rpm for 50 seconds to remove excess ligands and reaction byproducts. This drop-stand-spin coating cycle was repeated twice to ensure sufficient exchange.

[0047] The device with completed ligand exchange was transferred to a glove box filled with high-purity nitrogen and placed on a heating stage. It was then annealed at 90°C for 20 minutes to complete the fabrication of the mixed-dimensional PbS QDs / MoTe2 / MoSe2 heterostructure device.

[0048] This application proposes a dynamically encrypted broadband photodetector based on quantum dot-controlled van der Waals heterojunctions. It constructs a hybrid-dimensional photodetector by combining quantum dots with transition metal sulfide van der Waals heterojunctions. Quantum dots possess a high light absorption coefficient, which can significantly improve the light absorption efficiency of the device, thereby enhancing its photoelectric detection performance. For example... Figures 4-6 As shown, where, Figure 4 The graph shows the responsivity test results of photodetectors with and without quantum dot structures. It can be seen that in the range of 500nm-1500nm, the responsivity of photodetectors with quantum dot structures is much greater than that without quantum dot structures. Figure 5 The graph shows the detectivity test results of photodetectors with and without quantum dot structures. It can be seen that in the range of 500nm-1500nm, the detectivity of photodetectors with quantum dot structures is much greater than that without quantum dot structures. Figure 6The graph shows the gain test results of photodetectors with and without quantum dot structures. It can be seen that in the range of 500nm-1500nm, the gain of photodetectors with quantum dot structures is much greater than that without quantum dot structures.

[0049] Furthermore, the dynamically encrypted broadband photodetector based on quantum dot-controlled van der Waals heterojunctions proposed in this application integrates encryption functionality at the device level, supporting secure transmission of independent data through dual channels. A hybrid-dimensional photodetector is constructed by combining quantum dots with transition metal sulfide van der Waals heterojunctions. The introduction of quantum dots creates a dynamically reconfigurable energy barrier at the interface of the transition metal sulfide heterojunction, such as... Figure 7 , Figure 8 As shown: In V ds At -3 V, when a gate voltage of -30 V is applied, the Fermi levels of both MoSe2 and MoTe2 decrease. However, due to the electrostatic shielding effect of the underlying material MoSe2, the Fermi level decrease is more significant, leading to a widening of the heterojunction depletion region and increased band bending, thus increasing the electron transport barrier. Simultaneously, the negative gate voltage induces recombination between holes and majority carrier electrons, reducing the dark current. Under illumination, only a small number of photogenerated carriers can overcome the barrier and be collected, resulting in a weak photocurrent. Conversely, when a gate voltage of 30 V is applied, the Fermi level of MoSe2 is higher than that of MoTe2, altering the band bending direction and lowering the electron transport barrier, allowing more photogenerated electrons to be collected by the source, thus achieving a higher photocurrent. At V... ds Under a gate voltage of +3 V, the gate modulation mechanism exhibits the opposite pattern. When a gate voltage of -30 V is applied, the band bending at the heterojunction interface intensifies, creating a higher electron transport barrier. This leads to a large number of photogenerated electrons being localized at the MoSe2 / MoTe2 interface, generating a significant grating voltage effect and thus obtaining a larger photocurrent. However, when a gate voltage of 30 V is applied, the band bending is suppressed, the barrier decreases, the number of localized electrons decreases, the grating voltage effect weakens, and the photocurrent decreases accordingly.

[0050] Therefore, the height of the carrier transport barrier and the degree of band bending of the device can be determined by the drain-source voltage (V). ds ) and gate-source voltage (V gs The system allows for independent and coordinated control of the photocurrent. This prevents attackers from deducing information about the other channel even if they eavesdrop on the signal of a single voltage channel or only measure the total current. Any attempt to simulate a legitimate transmitter requires precise control of both voltages simultaneously, which is physically extremely difficult to achieve. Only authorized parties with knowledge of the device's characteristics can decode the photocurrent sequence and decouple the information, thus increasing security.

[0051] like Figures 9-11As shown, based on our PbSe QDs / MoTe2 / MoSe2 heterostructure device, in V ds and V gs The photoelectric response characteristics under dual regulation are defined by V ds Two states and V gs The two states can generate four distinct and easily distinguishable non-volatile photocurrent output states. These four output states correspond to different combinations of input voltages, forming the basis of physical layer encryption. During information transmission, the information to be transmitted is encoded by ACSII and then input to the signal generator, modulating V... ds and V gs As two independent information carrier channels, the receiving end uses the photodetector of this application to detect the photocurrent signal, decouples the received signal according to a preset input-output mapping relationship, and finally extracts the original information of each channel. The core of this encryption mechanism lies in: since the output current state is V ds and V gs The mapping result is a synergistic effect, not a simple linear superposition. This means that even if an attacker intercepts the photocurrent sequence output by the device, they cannot decipher the voltage channel settings corresponding to each photocurrent state, and therefore cannot obtain the information carried by the voltage channels. Only by knowing the nonlinear response characteristics of the device and the complete four-state mapping rules (such as...) Figure 10 Only authorized parties (as shown) can complete the decoding, thus enabling built-in encryption at the device level.

[0052] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0053] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for fabricating a broadband optical detector for dynamic encrypted communication, characterized in that, include: Step S1: Provide a SiO2 / Si substrate; Step S2: A first transition metal sulfide and a second transition metal sulfide are sequentially transferred onto the SiO2 / Si substrate by directional transfer to form a transition metal sulfide layer; the first transition metal sulfide includes MoSe2; the second transition metal sulfide includes MoTe2. Step S3: Spin-coat PbS QDs solution onto the transition metal sulfide layer to form a uniform quantum dot film; Step S4: Add EDT acetonitrile solution dropwise to the surface of the quantum dot film, allow the reaction to stand for a preset time, and then spin-coat to remove excess ligands and reaction byproducts; in step S4, the preset reaction time is 20-60 seconds; the spin-coating speed is 1500-3000 rpm; and the spin-coating time is 20-60 seconds. Step S5: Place the photodetector on a heating stage for annealing to complete the fabrication of the hybrid quantum dot / transition metal sulfide heterostructure photodetector; wherein, the introduction of quantum dots constructs a dynamically reconfigurable energy barrier at the interface of the transition metal sulfide heterostructure, and the energy barrier at the quantum dot / transition metal sulfide heterostructure can be independently and collaboratively controlled by the drain-source voltage and the gate-source voltage. Before step S5, step S4 is repeated at least twice; Before step S3, the method further includes: dissolving PbS QDs in n-hexane to form a PbS QDs solution with a concentration of 10-35 mg / mL.

2. The method according to claim 1, characterized in that, Step S1 further includes: providing a P-type highly doped silicon wafer with a SiO2 thickness of 200 nm-400 nm, cleaning it with deionized water, ethanol, acetone and isopropanol respectively, then drying the silicon wafer with a nitrogen gun, and placing it in a drying oven at 50℃-80℃ for 2-4 hours.

3. The method according to claim 1, characterized in that, Step S2 is followed by: fabricating Ti / Au source and drain electrodes using photolithography, thermal evaporation, and lift-off techniques.

4. The method according to claim 3, characterized in that, The thickness of Ti is 8nm-12nm, and the thickness of Au is 70nm-90nm.

5. The method according to claim 1, characterized in that, The annealing process on the heating table includes annealing on a heating table at 70°C-100°C for 10-30 minutes in a nitrogen atmosphere.

6. A photodetector prepared by the method according to any one of claims 1-5, characterized in that, include: SiO2 / Si substrate; A transition metal sulfide layer of MoTe2 / MoSe2 heterojunction structure is disposed on the SiO2 / Si substrate; Ti / Au source and drain electrode layers are disposed at both ends of the MoTe2 / MoSe2 heterojunction structure; A PbS QDs thin film layer is disposed on a transition metal sulfide layer; The energy barrier at the PbS QDs / MoTe2 / MoSe2 heterostructure can be independently and collaboratively controlled by the drain-source voltage and the gate-source voltage.

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