Bicolor photodetector based on van der waals heterojunction and preparation method thereof

Abstract

The application belongs to the technical field of semiconductor photoelectric detection, and discloses a dual-color photoelectric detector based on a van der Waals heterojunction and a preparation method thereof. In the detector, the substrate is a light-transmitting substrate and serves as a light incidence surface of the dual-color photoelectric detector, an aluminum nitride buffer layer is arranged on the substrate, a gallium nitride layer is arranged on the aluminum nitride buffer layer, a molybdenum disulfide layer is adhered to the gallium nitride layer through van der Waals force, a black phosphorus layer is adhered to the molybdenum disulfide layer through van der Waals force, a gallium nitride contact electrode is led out from the gallium nitride layer, a molybdenum disulfide contact electrode is led out from the molybdenum disulfide layer, a black phosphorus contact electrode is led out from the black phosphorus layer, an isolation layer is used to realize electrical isolation between the molybdenum disulfide contact electrode and the gallium nitride layer and between the black phosphorus contact electrode and the gallium nitride layer, and a protective layer is formed on the top surface to realize device protection. Based on the above detector, high-sensitivity, low-crosstalk and dual-band independent detection of ultraviolet-infrared can be realized without complex optical elements.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor photoelectric detection technology, and more specifically, relates to a dual-color photodetector based on van der Waals heterojunction and its fabrication method. Background Technology

[0002] Photoelectric detection technology is the core of optical information sensing, playing a crucial supporting role in the efficient operation of modern information processing and intelligent sensing systems. Based on this, ultraviolet-infrared dual-color detection technology, by combining information from both ultraviolet and infrared bands, significantly improves the reliability and efficiency of detection in complex environments, and has enormous application potential in fields such as environmental monitoring, fire detection, and autonomous driving.

[0003] To achieve balanced response in both the ultraviolet and infrared bands, traditional dual-band detection technologies primarily include beam splitting systems, bonding, and heteroepitaxial methods. Beam splitting systems use optical elements such as prisms, filters, and beam splitters to separate the incident light by wavelength, sending each wavelength into separate ultraviolet and infrared detection units. However, beam splitting systems suffer from system complexity and poor accuracy. Bonding methods involve bonding ultraviolet and infrared material chips face-to-face to create a stacked structure, but this approach suffers from severe optical crosstalk. Heteroepitaxial methods involve directly epitaxially growing materials of another wavelength band on a substrate; however, this method faces lattice mismatch issues, resulting in poor device response.

[0004] Constructing a high-sensitivity, low-crosstalk ultraviolet-infrared dual-band photodetector without the need for complex optical components is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a dual-color photodetector based on van der Waals heterojunction and its preparation method, the purpose of which is to achieve high-sensitivity, low-crosstalk independent detection of ultraviolet-infrared dual bands without the need for complex optical components.

[0006] To achieve the above objectives, this invention is proposed.

[0007] According to a first aspect of the present invention, a dual-color photodetector based on a van der Waals heterojunction is provided, comprising: a substrate, an aluminum nitride buffer layer, a p-type doped gallium nitride layer and its contact electrode, an n-type molybdenum disulfide layer and its contact electrode, a p-type black phosphorus layer and its contact electrode, an isolation layer and a protective layer. The substrate is a light-transmitting substrate and serves as the light incident surface of the dual-color photodetector. An aluminum nitride buffer layer is disposed on the substrate, and a gallium nitride layer is disposed on the aluminum nitride buffer layer. A molybdenum disulfide layer is bonded to the gallium nitride layer by van der Waals forces to form a first van der Waals heterojunction. A black phosphorus layer is bonded to the molybdenum disulfide layer by van der Waals forces to form a second van der Waals heterojunction. The gallium nitride layer, molybdenum disulfide layer, and black phosphorus layer form a pnp-type van der Waals heterojunction structure. Gallium nitride contact electrodes are led out from the gallium nitride layer, molybdenum disulfide contact electrodes are led out from the molybdenum disulfide layer, and black phosphorus contact electrodes are led out from the black phosphorus layer. An isolation layer is used to achieve electrical isolation between different molybdenum disulfide contact electrodes and the gallium nitride layer, and between the black phosphorus contact electrode and the gallium nitride layer. A protective layer is formed on the top surface of the pnp-type van der Waals heterojunction structure to protect the device.

[0008] According to a second aspect of the present invention, a method for fabricating a dual-color photodetector based on a van der Waals heterojunction is provided, comprising: Step S1: Sequentially deposit an aluminum nitride buffer layer and a p-type doped gallium nitride layer on the substrate, and then clean the surface of the resulting structure. Step S2: Deposit an isolation layer on the p-type doped gallium nitride layer, open a first window and a second window to expose gallium nitride on the currently deposited isolation layer, form a gallium nitride contact electrode in the first window that contacts the gallium nitride layer, and bond a molybdenum disulfide layer to the gallium nitride layer at the second window based on a two-dimensional material transfer process to form a first van der Waals heterojunction. Step S3: Based on a two-dimensional material transfer process, a p-shaped black phosphorus layer is bonded to the molybdenum disulfide layer to form a second van der Waals heterojunction, and a molybdenum disulfide contact electrode is formed on the molybdenum disulfide layer, a black phosphorus contact electrode is formed on the black phosphorus layer, and a protective layer for protecting the black phosphorus is formed.

[0009] In summary, compared with the prior art, the technical solutions conceived in this invention have the following main advantages: (1) Utilizing the advantages of van der Waals heterointegration of two-dimensional materials: GaN is combined with MoS2 and BP through van der Waals forces, eliminating the need to consider lattice matching issues. This fundamentally solves the problems of high defect density and high dark current caused by lattice mismatch in traditional heteroepitaxial schemes, achieving high-quality heterointegration with low defect density and effectively ensuring detection response sensitivity. (2) It can achieve simultaneous independent detection in two bands: p-gallium nitride / molybdenum sulfide heterojunction forms a type I band arrangement. Under 365 nm ultraviolet light irradiation, photogenerated electron-hole pairs are separated under the drive of the built-in electric field at the p-gallium nitride / molybdenum sulfide heterojunction interface. Electrons are injected into the molybdenum sulfide layer, and holes remain in the p-gallium nitride layer. They can be collected through the gallium nitride contact electrode and the molybdenum disulfide contact electrode to form an ultraviolet light response current; black phosphorus / molybdenum sulfide heterojunction forms a type II band arrangement. Under 1550 nm infrared light irradiation, photogenerated carriers are separated at the molybdenum sulfide / black phosphorus interface. Electrons flow to the molybdenum sulfide layer, and holes remain in the black phosphorus layer. They can be collected through the molybdenum disulfide contact electrode and the black phosphorus contact electrode to form an infrared light response current; (3) Low crosstalk between the two bands: The dual-color photodetector adopts a back-incidence optical path design. Ultraviolet light is incident from one side of the p-gallium nitride layer, which causes the p-gallium nitride layer to produce strong intrinsic absorption of 365 nm ultraviolet light, greatly attenuating the intensity of ultraviolet light reaching the molybdenum sulfide layer and black phosphorus layer, thereby suppressing the optical crosstalk of ultraviolet light to the infrared detection channel. That is, when the current is ultraviolet light irradiation, only obvious ultraviolet light response current is generated instead of infrared light response current. By calculating the integral of the spectral overlap region, compared with the normal incidence mode, the optical crosstalk in the back-incidence mode is reduced from about 11.24% to 1.2%. Furthermore, the introduction of the MoS2 intermediate layer as an electron collection layer and hole blocking barrier layer physically blocks the diffusion path of infrared photogenerated carriers to the ultraviolet detection channel, and can also effectively suppress electrical crosstalk. That is, when the current is infrared light irradiation, only a significant infrared light response current is generated instead of an ultraviolet light response current. Therefore, this structure and the back-incidence working mode significantly reduce crosstalk between the two bands, providing a key guarantee for the independent detection of infrared and ultraviolet signals. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of a two-color photodetector based on a van der Waals heterojunction in one embodiment of the present invention.

[0011] Figure 2 This is a method for fabricating a dual-color photodetector based on a van der Waals heterojunction according to one embodiment of the present invention.

[0012] Figure 3 This is a physical image of the detector fabricated according to one embodiment of the present invention.

[0013] Figure 4 Figure 1 shows the photoelectric performance test results of the detector under 365 nm ultraviolet light in one embodiment of the present invention; wherein, Figure 2a shows the change of the responsivity and specific detectivity of the detector under 365 nm ultraviolet light with incident light power density, and Figure 3b shows the rising edge of the ultraviolet response current of the detector when the ultraviolet light is irradiated and the falling edge of the ultraviolet response current when the ultraviolet light is removed.

[0014] Figure 5 Figure 1 shows the photoelectric performance test results of the detector under 1550 nm infrared illumination in one embodiment of the present invention; wherein, Figure 2a shows the change of the responsivity and specific detectivity of the detector under 1550 nm infrared illumination with incident light power density, and Figure 3b shows the rising edge of the infrared response current of the detector when the infrared light is irradiated and the falling edge of the infrared response current when the infrared light is withdrawn.

[0015] Figure 6 These are time-resolved photocurrent curves of the detector corresponding to different wavelength bands in one embodiment of the present invention; a is the current response curve of the p-GaN / MoS2 heterojunction under illumination in different wavelength bands from 350 nm to 2000 nm, and b is the current response curve of the BP / MoS2 heterojunction under illumination in different wavelength bands from 350 nm to 2000 nm. Detailed Implementation

[0016] 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 embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0017] like Figure 1 The diagram shows a schematic of a dual-color photodetector based on a van der Waals heterojunction according to an embodiment of the present invention, which includes: a substrate, an aluminum nitride buffer layer, a p-type doped gallium nitride layer (p-GaN layer) and its contact electrode, an n-type molybdenum disulfide layer (MoS2 layer) and its contact electrode, a p-type black phosphorus layer (BP layer) and its contact electrode, an isolation layer (not shown in the figure), and a protective layer (not shown in the figure). The substrate is a transparent substrate and serves as the light incident surface of the dual-color photodetector. An aluminum nitride buffer layer is disposed on the substrate, and a gallium nitride layer is disposed on the aluminum nitride buffer layer. A molybdenum disulfide layer is bonded to the gallium nitride layer by van der Waals forces to form a first van der Waals heterojunction. A black phosphorus layer is bonded to the molybdenum disulfide layer by van der Waals forces to form a second van der Waals heterojunction. The gallium nitride layer, the molybdenum disulfide layer, and the black phosphorus layer form a pnp-type van der Waals heterojunction structure. Gallium nitride contact electrodes are led out from the gallium nitride layer, molybdenum disulfide contact electrodes are led out from the molybdenum disulfide layer, and black phosphorus contact electrodes are led out from the black phosphorus layer. An isolation layer is used to achieve electrical isolation between different molybdenum disulfide contact electrodes and the gallium nitride layer, as well as between the black phosphorus contact electrode and the gallium nitride layer. A protective layer is formed on the top surface of the pnp-type van der Waals heterojunction structure to achieve device protection.

[0018] It should be noted that p-type doped gallium nitride layers need to achieve their p-type conductivity through doping, while molybdenum disulfide layers can naturally exhibit n-type conductivity without additional doping, and black phosphorus can also naturally exhibit p-type conductivity without additional doping.

[0019] In one embodiment, the isolation layer is a silicon dioxide isolation layer.

[0020] In one embodiment, the protective layer is an h-boron nitride protective layer (h-BN protective layer), which can slow down the oxidation of BP in air.

[0021] In one embodiment, the substrate is sapphire.

[0022] In one embodiment, the thickness of the gallium nitride layer ranges from 500 to 1000 nm, the thickness of the molybdenum disulfide layer ranges from 50 to 150 nm, and the thickness of the black phosphorus layer ranges from 50 to 150 nm. This thickness design ensures, on the one hand, that the black phosphorus layer adequately absorbs infrared light and, on the other hand, that the GaN layer absorbs ultraviolet light under back incidence, while also guaranteeing high contact quality between the two van der Waals heterojunctions.

[0023] In one embodiment, the molybdenum disulfide layer is a molybdenum disulfide nanosheet, and the black phosphorus layer is a black phosphorus nanosheet. The nanosheets are relatively easy to obtain, and single-crystal thin films can be obtained relatively quickly. They also have a large specific surface area, which can absorb and generate more photogenerated carriers more efficiently, thereby further optimizing the response performance of the device.

[0024] In one embodiment, the dual-color photodetector further includes an ultraviolet light response current detection circuit and an infrared light response current detection circuit; one end of the ultraviolet light response current detection circuit is connected to a gallium nitride contact electrode, and the other end is connected to a molybdenum disulfide contact electrode to form a closed loop for detecting the ultraviolet light response current; one end of the infrared light response current detection circuit is connected to a molybdenum disulfide contact electrode, and the other end is connected to a black phosphorus contact electrode to form a closed loop for detecting the infrared light response current.

[0025] The advantages of the dual-color photodetector provided by this invention are as follows: (1) Utilizing the advantages of van der Waals heterointegration of two-dimensional materials: GaN is combined with MoS2 and BP through van der Waals forces, eliminating the need to consider lattice matching issues. This fundamentally solves the problems of high defect density and high dark current caused by lattice mismatch in traditional heteroepitaxial schemes, achieving high-quality heterointegration with low defect density and effectively ensuring detection response sensitivity. (2) It can achieve simultaneous independent detection in two bands: p-gallium nitride / molybdenum sulfide heterojunction forms a type I band arrangement. Under 365 nm ultraviolet light irradiation, photogenerated electron-hole pairs are separated under the drive of the built-in electric field at the p-gallium nitride / molybdenum sulfide heterojunction interface. Electrons are injected into the molybdenum sulfide layer, and holes remain in the p-gallium nitride layer. They can be collected through the gallium nitride contact electrode and the molybdenum disulfide contact electrode to form an ultraviolet light response current; black phosphorus / molybdenum sulfide heterojunction forms a type II band arrangement. Under 1550 nm infrared light irradiation, photogenerated carriers are separated at the molybdenum sulfide / black phosphorus interface. Electrons flow to the molybdenum sulfide layer, and holes remain in the black phosphorus layer. They can be collected through the molybdenum disulfide contact electrode and the black phosphorus contact electrode to form an infrared light response current; (3) Low crosstalk between the two bands: The dual-color photodetector adopts a back-incidence optical path design. Ultraviolet light is incident from the p-gallium nitride layer, which causes the p-gallium nitride layer to produce strong intrinsic absorption of 365 nm ultraviolet light, greatly attenuating the intensity of ultraviolet light reaching the molybdenum sulfide layer and black phosphorus layer, thereby suppressing the optical crosstalk of ultraviolet light to the infrared detection channel. That is, when the current is ultraviolet light irradiation, only obvious ultraviolet light response current is generated instead of infrared light response current. By calculating the integral of the spectral overlap region, compared with the normal incidence mode, the optical crosstalk in the back-incidence mode is reduced from about 11.24% to 1.2%. Furthermore, the introduction of the MoS2 intermediate layer as an electron collection layer and hole blocking barrier layer physically blocks the diffusion path of infrared photogenerated carriers to the ultraviolet detection channel, and can also effectively suppress electrical crosstalk. That is, when the current is infrared light irradiation, only a significant infrared light response current is generated instead of an ultraviolet light response current. Therefore, this structure and the back-incidence working mode significantly reduce crosstalk between the two bands, providing a key guarantee for the independent detection of infrared and ultraviolet signals.

[0026] In summary, the dual-color photodetector provided by this invention can achieve independent detection in both the ultraviolet and infrared bands with high sensitivity and low crosstalk.

[0027] like Figure 2 The following is a method for fabricating a dual-color photodetector based on a van der Waals heterojunction according to an embodiment of the present invention, which mainly includes steps S1 to S3. Each step is described in detail below.

[0028] Step S1: Sequentially deposit an aluminum nitride buffer layer and a p-type doped gallium nitride layer on the substrate, and then clean the surface of the resulting structure.

[0029] Specifically, in step S1, an aluminum nitride buffer layer can be deposited on the sapphire substrate using metal-organic chemical vapor deposition (MOCVD), followed by the deposition of a p-type doped gallium nitride layer. Subsequently, surface cleaning is performed, for example, firstly by removing organic matter: ultrasonic cleaning with acetone and isopropanol (frequency 40 kHz, power 100 W) for 10 min each; then rinsing with deionized water for 10 min; and finally, surface dehydration is completed using a centrifugal drying device (2000 rpm, 30 s).

[0030] Step S2: Deposit an isolation layer on the p-type doped gallium nitride layer, and open a first window and a second window to expose gallium nitride on the currently deposited isolation layer. Form a gallium nitride contact electrode in contact with the gallium nitride layer in the first window. Based on the two-dimensional material transfer process, bond an n-type molybdenum disulfide layer to the gallium nitride layer at the second window to form a first van der Waals heterojunction.

[0031] Specifically, in step S2, a 100 nm thick SiO2 isolation layer can be deposited on the cleaned p-GaN surface using plasma-enhanced chemical vapor deposition (PECVD) to create windows. Since the area of ​​p-GaN is larger than the structure stacked above it, the isolation layer can achieve electrical isolation between the molybdenum disulfide contact electrode and the gallium nitride layer, as well as between the black phosphorus contact electrode and the gallium nitride layer.

[0032] In one embodiment, in step S2, the window can be etched using a dry etching process. Taking the SiO2 isolation layer as an example, AZ5214 photoresist is used to form a 3.5±0.2 μm film layer by spin coating (4000 rpm, 30 s), followed by pre-baking (97℃, 2 min 30 s) - exposure - development for 35 s, and then inductively coupled plasma etching is used to etch the SiO2 film to expose the p-GaN at the bottom.

[0033] In one embodiment, in step S2, a first window and a second window can be etched simultaneously; then, the area outside the first window is protected by photoresist, and a gallium nitride contact electrode that contacts the gallium nitride layer is formed in the first window; then, the photoresist is removed by development, and the molybdenum disulfide layer is bonded to the gallium nitride layer at the second window based on a two-dimensional material transfer process to form a first van der Waals heterojunction.

[0034] Step S2 can also be implemented using other processes. For example, a first window can be etched first, and a gallium nitride contact electrode that contacts the gallium nitride layer can be formed in the first window. Then, a second window can be etched, and a molybdenum disulfide layer can be bonded to the gallium nitride layer at the second window using a two-dimensional material transfer process to form a first van der Waals heterojunction.

[0035] Step S3: Based on the two-dimensional material transfer process, the p-shaped black phosphorus layer is bonded to the molybdenum disulfide layer to form a second van der Waals heterojunction, and a molybdenum disulfide contact electrode is formed on the molybdenum disulfide layer, a black phosphorus contact electrode is formed on the black phosphorus layer, and a protective layer for protecting the black phosphorus is formed.

[0036] In one embodiment, the execution process of step S3 can be as follows: First, a p-shaped black phosphorus layer is bonded to a molybdenum disulfide layer using a two-dimensional material transfer process to form a second van der Waals heterojunction. At least some areas of the molybdenum disulfide layer are not covered by the black phosphorus layer. Black phosphorus contact electrodes and molybdenum disulfide contact electrodes are simultaneously formed in the areas where the black phosphorus layer and molybdenum disulfide layer are not covered by the black phosphorus layer. A protective layer is formed on the top layer.

[0037] The above execution process can simplify the process. It is understandable that other processes can also be used to achieve step S3.

[0038] In one embodiment, steps S2 and S3 can both be performed using a thermal evaporation process to form the contact electrode. For example, a 20 nm / 50 nm thick Ni / Au metal layer can be deposited using a thermal evaporation device as the contact electrode.

[0039] In one embodiment, the process of bonding the material layer to be transferred to the target material layer to form a van der Waals heterojunction based on a two-dimensional material transfer process includes: First, one side of PDMS is flatly attached to the surface of a glass slide. The pre-prepared material layer to be transferred is then transferred to the other side of the PDMS. After aligning the material layer on the PDMS with the target material layer, pressure is applied to ensure complete adhesion between the PDMS and the target material layer. The temperature is raised to 75°C–85°C and maintained for 10–20 minutes. Subsequently, the PDMS is cooled and peeled off, thus transferring the material layer to the target material layer. Preferably, the pre-prepared material layer to be transferred is a nanosheet of the material to be transferred, prepared by mechanical exfoliation and attached to Scotch tape. Obtaining nanosheets is relatively simple, allowing for relatively quick acquisition of single-crystal thin films. These nanosheets also possess a large specific surface area, enabling more efficient absorption and generation of photogenerated carriers, thereby further optimizing the device's response performance.

[0040] For example, in step S2, the material layer to be transferred is a molybdenum disulfide layer, and the target material layer is a gallium nitride layer. Specifically: first, one side of the PDMS is flatly attached to the surface of a glass slide; then, the pre-prepared molybdenum disulfide layer is transferred to the other side of the PDMS; after aligning the molybdenum disulfide layer on the PDMS with the second window, pressure is applied to ensure complete adhesion between the PDMS and the gallium nitride layer; the temperature is raised to 75°C~85°C and maintained for 10min~20min; subsequently, the temperature is cooled and the PDMS is peeled off, thus transferring the molybdenum disulfide layer to the gallium nitride layer. Preferably, the pre-prepared molybdenum disulfide layer is a molybdenum disulfide nanosheet prepared by mechanical peeling and attached to Scotch tape.

[0041] In practice, a clean glass slide can be prepared as the transfer substrate. A PDMS film of approximately 8 mm × 8 mm is cut and first, the PDMS is smoothly attached to the surface of the slide, ensuring no air bubbles remain. Then, the soft film is peeled off to expose the adhesive layer of the PDMS. Scotch tape, pre-prepared using a mechanical peeling method and containing MoS2 nanosheets, is evenly applied to the PDMS with the material side facing down. Gently press to transfer the MoS2 nanosheets to the PDMS surface under van der Waals forces. Place the p-GaN substrate on the transfer platform and activate vacuum fixation. Mount the PDMS-attached glass slide face down in the slot and secure it with two adjustable screws. Adjust the microscope focus and substrate position to locate the material to be transferred on the p-GaN substrate. Adjust the slide position and microscope focus to locate a suitable two-dimensional material on the PDMS and move it directly above the desired transfer location on the substrate. Slowly lower the stage by adjusting the knob, and when the PDMS is close to contact the substrate, finely adjust the pressure until complete adhesion. The substrate was heated to 80 °C at a current of 6.5 A (the purpose of heating was to reduce the adhesion between PDMS and the nanosheets). After holding the temperature for 15 min, the heating was turned off, and the slide was slowly lifted after cooling to 30 °C. When the lifted area was close to the target two-dimensional material, the PDMS and the substrate were slowly separated. At this point, the MoS2 nanosheets had been transferred to the target area of ​​the p-GaN substrate.

[0042] The method for transferring the black phosphorus layer in step S3 can refer to the method for transferring the molybdenum disulfide layer described above.

[0043] In one embodiment, the protective layer is an h-boron nitride protective layer. The h-boron nitride protective layer can also be transferred onto the BP layer using the two-dimensional material transfer process described above, in order to slow down the oxidation of the BP by air.

[0044] like Figure 3 The image shown is a physical diagram of the detector fabricated according to one embodiment of the present invention.

[0045] like Figure 4The figure shown is a graph illustrating the photoelectric performance test results of the detector under 365 nm ultraviolet light illumination in one embodiment of the present invention; wherein, figure a shows the changes in responsivity and specific detectivity of the detector under 365 nm ultraviolet light illumination as a function of incident light power density. Under 365 nm ultraviolet light illumination, when the light power density is 6.8 mW / cm², 2 At this time, the device achieves a maximum responsivity of 125 mA / W and a maximum efficiency of 1.8 × 10⁻⁶ at a bias of 0 V. 11 Jones's specific detectivity; Figure b shows the rising edge of the UV response current when the UV light is applied and the falling edge when the UV light is removed. The rise time of the device is 250 μs and the fall time is 700 μs; from Figure 4 It can be seen from this that the detector has a relatively excellent ultraviolet response.

[0046] like Figure 5 The figure shown is a graph illustrating the photoelectric performance test results of the detector in one embodiment of the present invention under 1550 nm infrared illumination; wherein, figure a shows the changes in responsivity and specific detectivity of the detector under 1550 nm infrared illumination as a function of incident light power density. Under 1550 nm infrared illumination, when the light power density is 26.2 mW / cm² 2 At this time, the device achieves a maximum responsivity of 160 mA / W and a maximum power of 5.1 × 10⁻⁶ at a bias of 0 V. 13 Jones's specific detectivity; Figure b shows the rising edge of the infrared response current when the infrared light is irradiated and the falling edge of the infrared response current when the infrared light is withdrawn. The rise time of the device is 30 μs and the fall time is 50 μs; from Figure 5 It can be seen from this that the detector has a relatively excellent infrared response.

[0047] like Figure 6The figures show time-resolved photocurrent curves for different wavelengths. Figure a shows the current response curve of the p-GaN / MoS2 heterojunction under illumination from 350 nm to 2000 nm. The p-GaN / MoS2 heterojunction exhibits a significant photoresponse at 365 nm, while also absorbing ultraviolet light at 350 nm and 405 nm. It does not absorb any longer wavelengths of visible or infrared light. Figure b shows the current response curve of the BP / MoS2 heterojunction under illumination from 350 nm to 2000 nm. The BP / MoS2 heterojunction exhibits a stable photoelectric response in the 1550 nm infrared band, but shows no significant response to ultraviolet light. Its detection range covers from 850 nm to 2000 nm. The two heterojunctions show a significant difference in response wavelength in the visible-to-near-infrared transition region, indicating that the response spectra of the two detection channels do not overlap, effectively avoiding optical crosstalk caused by spectral overlap. The spectral selectivity between the two-color detection channels and their effective isolation in the heterojunction structure were fully verified, realizing independent response and low crosstalk detection of the dual-band signals.

[0048] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" are intended to illustrate the present invention and are not intended to limit the present invention.

[0049] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A dual-color photodetector based on a van der Waals heterojunction, characterized in that, include: The substrate, aluminum nitride buffer layer, p-type doped gallium nitride layer and its contact electrode, n-type molybdenum disulfide layer and its contact electrode, p-type black phosphorus layer and its contact electrode, isolation layer and protective layer; The substrate is a light-transmitting substrate and serves as the light incident surface of the dual-color photodetector. An aluminum nitride buffer layer is disposed on the substrate, and a gallium nitride layer is disposed on the aluminum nitride buffer layer. A molybdenum disulfide layer is bonded to the gallium nitride layer by van der Waals forces to form a first van der Waals heterojunction. A black phosphorus layer is bonded to the molybdenum disulfide layer by van der Waals forces to form a second van der Waals heterojunction. The gallium nitride layer, molybdenum disulfide layer, and black phosphorus layer form a pnp-type van der Waals heterojunction structure. Gallium nitride contact electrodes are led out from the gallium nitride layer, molybdenum disulfide contact electrodes are led out from the molybdenum disulfide layer, and black phosphorus contact electrodes are led out from the black phosphorus layer. An isolation layer is used to achieve electrical isolation between different molybdenum disulfide contact electrodes and the gallium nitride layer, and between the black phosphorus contact electrode and the gallium nitride layer. A protective layer is formed on the top surface of the pnp-type van der Waals heterojunction structure to protect the device.

2. The dual-color photodetector based on a van der Waals heterojunction as described in claim 1, characterized in that, The thickness of the gallium nitride layer ranges from 500 to 1000 nm, the thickness of the molybdenum disulfide layer ranges from 50 to 150 nm, and the thickness of the black phosphorus layer ranges from 50 to 150 nm.

3. The dual-color photodetector based on a van der Waals heterojunction as described in claim 2, characterized in that, The molybdenum disulfide layer is a molybdenum disulfide nanosheet, and the black phosphorus layer is a black phosphorus nanosheet.

4. The dual-color photodetector based on a van der Waals heterojunction as described in claim 1, characterized in that, The protective layer is an h-boron nitride protective layer.

5. The dual-color photodetector based on a van der Waals heterojunction as described in claim 1, characterized in that, The dual-color photodetector further includes an ultraviolet light response current detection circuit and an infrared light response current detection circuit; one end of the ultraviolet light response current detection circuit is connected to the gallium nitride contact electrode, and the other end is connected to the molybdenum disulfide contact electrode to form a closed loop for detecting the ultraviolet light response current. One end of the infrared light response current detection circuit is connected to the molybdenum disulfide contact electrode, and the other end is connected to the black phosphorus contact electrode to form a closed loop for detecting the infrared light response current.

6. A method for fabricating a dual-color photodetector based on a van der Waals heterojunction, characterized in that, include: Step S1: Sequentially deposit an aluminum nitride buffer layer and a p-type doped gallium nitride layer on the substrate, and then clean the surface of the resulting structure. Step S2: Deposit an isolation layer on the p-type doped gallium nitride layer, open a first window and a second window to expose gallium nitride on the currently deposited isolation layer, form a gallium nitride contact electrode in the first window that contacts the gallium nitride layer, and bond a molybdenum disulfide layer to the gallium nitride layer at the second window based on a two-dimensional material transfer process to form a first van der Waals heterojunction. Step S3: Based on a two-dimensional material transfer process, a p-shaped black phosphorus layer is bonded to the molybdenum disulfide layer to form a second van der Waals heterojunction, and a molybdenum disulfide contact electrode is formed on the molybdenum disulfide layer, a black phosphorus contact electrode is formed on the black phosphorus layer, and a protective layer for protecting the black phosphorus is formed.

7. The method for fabricating a dual-color photodetector based on a van der Waals heterojunction as described in claim 6, characterized in that, When forming the first van der Waals heterojunction in step S2 and / or forming the second van der Waals heterojunction in step S3, the process of bonding the material layer to be transferred to the target material layer to form the van der Waals heterojunction based on the two-dimensional material transfer process includes: First, one side of PDMS is flatly attached to the surface of a glass slide, and the pre-prepared material layer to be transferred is transferred to the other side of PDMS. After aligning the material layer to be transferred on PDMS with the target material layer, pressure is applied to make PDMS and the target material layer completely adhere. The temperature is raised to 75℃~85℃ and maintained for 10min~20min. Then, the temperature is cooled and the PDMS is peeled off, thus transferring the material layer to be transferred onto the target material layer.

8. The method for fabricating a dual-color photodetector based on a van der Waals heterojunction as described in claim 7, characterized in that, The pre-prepared transfer material layer consists of nanosheets of the transfer material attached to Scotch tape, prepared by mechanical exfoliation.

9. The method for fabricating a dual-color photodetector based on a van der Waals heterojunction as described in claim 6, characterized in that, In step S2, the execution order is as follows: First, simultaneously open a first window and a second window to expose gallium nitride on the currently deposited isolation layer; Subsequently, the area outside the first window is protected by photoresist, and a gallium nitride contact electrode that contacts the gallium nitride layer is formed in the first window; Subsequently, the photoresist is removed by development, and the molybdenum disulfide layer is bonded to the gallium nitride layer at the second window using a two-dimensional material transfer process to form a first van der Waals heterojunction.

10. The method for fabricating a dual-color photodetector based on a van der Waals heterojunction as described in claim 6, characterized in that, In step S3, the execution order is as follows: First, a p-shaped black phosphorus layer is bonded to the molybdenum disulfide layer using a two-dimensional material transfer process to form a second van der Waals heterojunction, wherein at least a portion of the molybdenum disulfide layer is not covered by the black phosphorus layer. Black phosphorus contact electrodes and molybdenum disulfide contact electrodes are simultaneously formed in the areas of the black phosphorus layer and the molybdenum disulfide layer not covered by the black phosphorus layer; The protective layer is formed on the top layer.

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