Dual-gate pressure modulated near-infrared photodetector and preparation method thereof

Abstract

The application discloses a near-infrared photoelectric detector with double-gate pressure regulation and a preparation method thereof. The photoelectric detector comprises a silicon wafer substrate, an in-plane separated double-gate structure, a hexagonal boron nitride layer, a corner double-layer graphene layer and a source electrode and a drain electrode. The in-plane separated double-gate structure is arranged on the top of the silicon wafer substrate, and a gap exists between the two gates. The hexagonal boron nitride layer is arranged above the in-plane separated double-gate structure and is connected to the silicon wafer substrate on both sides. The corner double-layer graphene layer is arranged above the hexagonal boron nitride layer, and the center of the corner double-layer graphene layer corresponds to the gap of the in-plane separated double-gate structure. One end of the source electrode and the drain electrode is arranged on both sides of the top of the corner double-layer graphene layer, and the other end is arranged on both sides of the silicon wafer substrate. The photoelectric detector can realize multi-mode near-infrared photocurrent detection, has a corresponding relationship between the light responsivity and the wavelength change and strong correlation to the polarization direction, and has obvious photoelectric detection effect.

Description

Technical Field

[0001] This invention relates to photodetectors, and more specifically to a near-infrared photodetector with dual gate voltage modulation and its fabrication method. Background Technology

[0002] Since Novoselov et al. obtained graphene through mechanical exfoliation in 2004, two-dimensional materials have attracted widespread attention due to the changes in physical and chemical properties brought about by the quantum size effect. Two-dimensional materials refer to crystalline materials composed of a single atomic layer, in which electrons move freely only in two-dimensional planes. Because only two dimensions are considered, the transport of thermal charge, heat, and photons is strictly confined to the two-dimensional plane, resulting in significant changes in the electrical and optical properties of two-dimensional materials. Therefore, graphene is currently mostly used to make photodetectors.

[0003] Monolayer graphene pn junctions are a common type of photodetector. Their significant characteristic is the ability to effectively control the concentration and type of charge carriers using gate voltage. However, to achieve tunable mode operation, pn junction photodetectors are limited to a few gate electrode types, such as top-gate / low-gate dual electrodes, thus preventing multi-mode near-infrared photocurrent detection. Furthermore, in existing photodetectors, the near-infrared light response does not show a significant change with the polarization direction of the incident light, exhibiting a weak correlation, resulting in limited photodetection performance. Summary of the Invention

[0004] This invention provides a near-infrared photodetector with dual gate voltage modulation and its fabrication method. The photodetector of this invention can realize multi-mode near-infrared photocurrent detection under dual gate voltage modulation. At the same time, the photodetector has a corresponding relationship between the photoresponsivity and the wavelength and a strong correlation with the polarization direction, which makes the photodetector effect obvious.

[0005] The technical solution of the present invention is as follows:

[0006] A near-infrared photodetector with dual gate voltage modulation includes a silicon substrate, an in-plane discrete dual-gate structure, a hexagonal boron nitride layer, a corner bilayer graphene layer, and a source and a drain.

[0007] The in-plane separated dual-gate structure is disposed on the top of the silicon substrate, and there is a slit between the two gates;

[0008] The hexagonal boron nitride layer is disposed above the in-plane split dual-gate structure, and its two sides overlap the silicon wafer substrate;

[0009] The corner bilayer graphene layer is disposed above the hexagonal boron nitride layer, and the center of the corner bilayer graphene layer corresponds to the slit of the in-plane separated double gate structure.

[0010] One end of the source and drain are respectively located on the top two sides of the corner bilayer graphene layer, and the other end of the source and drain are respectively located on both sides of the silicon substrate.

[0011] This invention fabricates an in-plane separated dual-gate structure with left and right electrodes and electrode slits on a silicon substrate, and uses a corner-turned double-layer graphene layer on the top layer to create a near-infrared photodetector controlled by dual gate voltages. Under the control of dual gate voltages, the photodetector of this invention can switch between multiple modes while maintaining the same gate voltage. The photodetector of this invention can obtain the corresponding relationship between photoresponsivity and wavelength and the strong correlation with polarization direction under incident light of different wavelengths, resulting in significant photodetection performance.

[0012] Furthermore, the width of the slit is 200 nm. The width of the slit can be set according to the actual situation; the 200 nm width here is only a preferred implementation method.

[0013] Furthermore, the width of both the source and drain electrodes is 5 μm. The width of the source and drain electrodes can be set according to the actual situation; the 5 μm width here is only a preferred implementation method.

[0014] Furthermore, the rotation angle of the bilayer graphene layer is 4.5°. By controlling the change in the rotation angle, the light absorption enhancement effect in different frequency bands can be achieved, compensating for the low light absorption rate of single-layer graphene. The rotation angle can be set according to the actual situation; 4.5° here is only a preferred implementation method, where the effect of a 4.5° rotation angle on light absorption is more obvious.

[0015] Furthermore, the two gates of the in-plane separated dual-gate structure are two symmetrically arranged rectangular metal electrodes with a thickness of 35nm ± 1nm. The thickness of the in-plane separated dual-gate structure can be set according to the actual situation; the 35nm ± 1nm thickness here is only a preferred embodiment.

[0016] Furthermore, the in-plane separated dual-gate structure, source, and drain are made of the same material, namely gold or palladium.

[0017] The present invention also provides a method for fabricating the above-mentioned dual-gated near-infrared photodetector, comprising the following steps:

[0018] S1. An in-plane separated dual-gate structure was prepared on a silicon substrate by two electron beam direct writing processes.

[0019] S2. A layered structure with a hexagonal boron nitride layer fixed at the bottom of a corner bilayer graphene layer was prepared by dry transfer. The layered structure and the in-plane separated double gate structure were aligned under a microscope to ensure that the slit area was in the center of the corner bilayer graphene layer. After alignment, they were bonded and fixed.

[0020] S3. The source and drain electrodes are fabricated by direct electron beam writing between the silicon substrate and the two sides of the corner bilayer graphene layer.

[0021] Furthermore, the specific process of preparing the in-plane separated double-gate structure using two electron beam direct writing steps in step S1 is as follows:

[0022] First, perform the electron beam direct writing process:

[0023] After coating the surface of the silicon substrate with PMMA electron beam adhesive and baking it, the surface of the silicon substrate is exposed with an electron beam. Then, the exposed area is developed at low temperature using a mixed solution of methyl isobutyl ketone and isopropanol. After low temperature development, a titanium film and a gold film are deposited on the surface of the silicon substrate. Finally, the PMMA is dissolved and the metal film on it is removed using an acetone stripping process, resulting in a silicon substrate with square metal markers and metal blocks in an I-shaped array.

[0024] After completing the first electron beam direct writing, a second electron beam direct writing is performed:

[0025] First, an electron beam dose test is performed on the in-plane separated dual-gate structure with a set target slit width to determine the electron beam dose corresponding to the target slit width. Then, the corresponding electron beam dose is used to align the metal marker with the design area according to the overlay process and expose it to obtain a titanium-gold gate structure pattern with the target slit width. Then, low-temperature development is performed, and after development, titanium and gold films are deposited again to finally prepare the in-plane separated dual-gate structure with the target slit width.

[0026] Furthermore, the specific process of fixing and bonding the layered structure composed of the hexagonal boron nitride layer and the corner bilayer graphene layer onto the in-plane separated dual-gate structure in step S2 is as follows:

[0027] Mechanically exfoliated graphene is cut, and the cut graphene is picked up one by one using a PDMS / PC film. Finally, hexagonal boron nitride is picked up to obtain a layered structure in which the hexagonal boron nitride layer is fixed at the bottom of the corner bilayer graphene layer. Then, the layered structure and the in-plane separated dual-gate structure are aligned under a microscope to ensure that the slit region is in the center of the corner bilayer graphene layer. After alignment, the layered structure is attached above the in-plane separated dual-gate structure. The PC film is melted at high temperature and removed with chloroform solution. Finally, the layered structure is retained on the surface of the in-plane separated dual-gate structure.

[0028] Furthermore, in step S3, the specific process of fabricating the source and drain electrodes by direct electron beam writing between the silicon substrate and the two sides of the corner bilayer graphene layer is as follows:

[0029] First, PMMA electron beam resist is coated onto the surface of a silicon substrate. Then, the coated silicon substrate surface is baked. Next, electron beam direct writing is performed on the surface of the silicon substrate to expose different sized exposure areas layer by layer, so that the source and drain pattern areas of the layout design on the PMMA resist are fully exposed. Then, the exposed and denatured PMMA is removed using a low-temperature development technique. A chromium film and a gold film are deposited on the corresponding areas of the source and drain pattern areas. Finally, the undenatured PMMA and the metal film on top are removed together using an acetone stripping method, thus preparing the source and drain electrodes.

[0030] The beneficial effects of this invention are as follows:

[0031] This invention provides a near-infrared photodetector with dual gate voltage modulation. By fabricating an in-plane separated dual-gate structure on a silicon substrate, the photodetector can switch between different modes when different voltages are applied to the left and right gates. Simultaneously, this invention incorporates a corner-rotating double-layer graphene layer on the in-plane separated dual-gate structure, enabling the photodetector to achieve enhanced light absorption in different frequency bands. When detecting incident light of different wavelengths under the same gate voltage, the corresponding relationship between the photoresponsivity and wavelength, as well as a strong correlation with the polarization direction, can be obtained, resulting in a significantly improved detection effect for the photodetector of this invention. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the near-infrared photodetector of the present invention;

[0033] Figure 2 This is a photocurrent scanning imaging result of the near-infrared photodetector of the present invention in pn junction mode under dual gate voltage modulation;

[0034] Figure 3 This is a photocurrent scanning imaging result of the near-infrared photodetector of the present invention in np junction mode under dual gate voltage modulation;

[0035] Figure 4 This is a photocurrent scanning imaging result of the near-infrared photodetector of the present invention in Schottky junction mode under dual gate voltage modulation;

[0036] Figure 5 This is a graph showing the relationship between the light responsivity and wavelength of the near-infrared photodetector of the present invention under different polarization directions.

[0037] In the figure: 1. Silicon substrate; 2. In-plane split dual-gate structure; 3. Hexagonal boron nitride layer; 4. Corner bilayer graphene layer; 5. Source; 6. Drain; 7. Slit. Detailed Implementation

[0038] The accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. To better illustrate this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0039] Example 1:

[0040] Existing single-layer graphene pn junction photodetectors suffer from technical problems such as the inability to achieve multi-mode near-infrared photocurrent detection and weak correlation between the near-infrared light response and the polarization direction of the incident light, resulting in poor photodetection performance.

[0041] Twisted bilayer graphene (tBLG) has attracted widespread attention due to its unique optical and electrical transport properties. Besides unconventional superconductivity in bilayer graphene at specific twist angles, special physical properties such as ferromagnetism, Mott insulation, and topological valley transport have also been discovered. Furthermore, due to the chemical stability of the graphene material system and its photoelectric response covering the ultraviolet, visible, infrared, and radio frequency bands, it has broad potential as an active optoelectronic device. In particular, the close bonding of different graphene layers at a certain angle in the tBLG structure leads to band structure reconstruction, forming a density of states saddle point, or van Hoff singularity (vHS), in the overlapping region of the Dirac cone, exhibiting a high density of states. When the energy difference between the conduction band and valence band vHS is equal to the incident photon energy, tBLG exhibits a significant enhancement in light absorption. The energy difference between vHS increases with the twist angle of the tBLG; therefore, by controlling the change in the twist angle, light absorption enhancement effects in different frequency bands can be achieved, compensating for the low light absorption rate of single-layer graphene.

[0042] Meanwhile, in-plane split dual-gated electrodes are simple to fabricate and have a wide range of applications. They can be used in light-emitting and detection devices, and are also commonly integrated with waveguides to form on-chip heterogeneous integrated functional structures. This structure allows the near-infrared light response to change with the polarization direction of the incident light. However, the behavior of the near-infrared light response with the polarization direction of the incident light in photodetectors has not been thoroughly understood and discussed, and pn junction devices based on tBLG have rarely been explored. Based on this, this embodiment provides a near-infrared photodetector with dual-gated voltage modulation.

[0043] like Figure 1As shown, a near-infrared photodetector with dual gate voltage modulation includes a silicon substrate 1, an in-plane separated dual-gate structure 2, a hexagonal boron nitride layer 3, a corner bilayer graphene layer 4, a source electrode 5, and a drain electrode 6.

[0044] The in-plane separated dual-gate structure 2 is disposed on the top of the silicon substrate 1, and there is a slit 7 between the two gates;

[0045] The hexagonal boron nitride layer 3 is disposed above the in-plane separated dual-gate structure 2, and overlaps on both sides of the silicon wafer substrate 1.

[0046] The corner bilayer graphene layer 4 is disposed above the hexagonal boron nitride layer 3, and the center of the corner bilayer graphene layer 4 corresponds to the slit 7 of the in-plane separated double gate structure 2.

[0047] One end of the source electrode 5 and the drain electrode 6 are respectively disposed on the top two sides of the corner double-layer graphene layer 4, and the other end of the source electrode 5 and the drain electrode 6 are respectively disposed on the two sides of the silicon wafer substrate 1.

[0048] The slit 7 has a width of 200 nm, the source electrode 5 and the drain electrode 6 each have a width of 5 μm, the corner bilayer graphene layer 4 has a corner angle of 4.5°, the two gates of the in-plane separated dual-gate structure 2 are two symmetrically arranged rectangular metal electrodes with a thickness of 35 nm ± 1 nm, and the dual-gate structure, source electrode 5 and drain electrode 6 are made of the same material, which is gold or palladium.

[0049] In this embodiment, the widths of slit 7, source 5, and drain 6 can be set according to the actual situation, and the rotation angle of the corner bilayer graphene can also be set according to the actual situation. The data listed above is only a preferred implementation method.

[0050] Example 2:

[0051] This embodiment provides a method for preparing the dual-gated near-infrared photodetector of Example 1 above. The materials used are: silicon substrate 1, Au target, polymethyl methacrylate, isopropanol, methyl isobutyl ketone, and acetone. The combined amounts and screening criteria are as follows:

[0052] Silicon substrate 1: High resistivity type, n-type, with a resistivity of less than 1000 Ω·cm, and a size of 1cm*1cm;

[0053] Au target material: solid particles, 99.999% purity;

[0054] Polymethyl methacrylate (PMMA) A5: 950K

[0055] Isopropanol: C3H8O, 500mL±5mL;

[0056] Methyl isobutyl ketone: C6H 12 O, 30mL±5mL;

[0057] Acetone: C3H6O, 200mL±5mL.

[0058] A method for fabricating a near-infrared photodetector with dual gate voltage modulation specifically includes the following steps:

[0059] S1. Fabrication of in-plane separated double-gate structure 2:

[0060] This structure was obtained by two electron beam direct writing processes followed by film deposition. The specific process is as follows:

[0061] First, perform the electron beam direct writing process:

[0062] PMMA electron beam adhesive was spin-coated onto the surface of silicon substrate 1 at 3000 rpm for 1 minute. Subsequently, the coated silicon substrate 1 was baked at 180°C for 3 minutes, and the surface of silicon substrate 1 was exposed using an electron beam with a dose of 1600 μC / cm2 and a beam current of 3 nA. After that, the exposed area was developed at low temperature (about 15°C) for 3 minutes using a mixed solution of methyl isobutyl ketone and isopropanol. After low temperature development, a 2 nm titanium film and a 35 nm gold film were deposited on the surface of silicon substrate 1. Finally, the PMMA was dissolved and the metal film on it was removed using an acetone liftoff process, resulting in silicon substrate 1 with a square metal marker (20 μm × 20 μm) and a metal block (200 μm × 200 μm) with an I-shaped array.

[0063] After completing the first electron beam direct writing, a second electron beam direct writing is performed:

[0064] First, an electron beam dose test was performed on the in-plane separated dual-gate structure 2 with a slit 7 of 200nm spacing to determine that the electron beam dose corresponding to the 200nm slit 7 was 3000μC / cm2. Then, the corresponding electron beam dose was used to align the metal marker with the design area according to the overlay process and expose it to obtain a titanium-gold gate structure pattern with a slit width of 200nm. Then, low-temperature development was performed, and after development, titanium and gold films were deposited again to finally prepare an in-plane separated dual-gate structure with a slit width of 200nm.

[0065] Preparation of a layered structure (tBLG / hBN structure) consisting of S2, hexagonal boron nitride layer 3, and corner bilayer graphene layer 4:

[0066] The mechanically exfoliated graphene was cut, and the cut graphene was picked up one by one using a PDMS / PC film. Finally, hexagonal boron nitride (hBN) was picked up to obtain a layered structure in which the hexagonal boron nitride layer 3 was fixed at the bottom of the corner bilayer graphene layer 4. Then, the layered structure and the above-mentioned in-plane separated dual-gate structure 2 were aligned under a microscope to ensure that the 200nm slit 7 region was located at the center of the corner bilayer graphene layer 4. After alignment, the layered structure was attached to the top of the in-plane separated dual-gate structure 2. The PC film was melted at a high temperature of 170°C and removed with chloroform solution. Finally, the layered structure was retained on the surface of the in-plane separated dual-gate structure 2.

[0067] Preparation of S3, source 5, and drain 6:

[0068] The specific process of performing a third electron beam direct writing to fabricate the source electrode 5 and drain electrode 6 between the two sides of the silicon substrate 1 and the corner bilayer graphene layer 4 is as follows:

[0069] First, PMMA electron beam resist was spin-coated onto the surface of silicon substrate 1 at 4000 rpm for 1 minute to obtain a smooth and uniform interface with a thickness of 600 nm. Then, the coated silicon substrate 1 was baked at 170°C for 3.5 minutes to ensure that the PMMA remained stable after baking. Afterward, an electron beam current of 10 nA and an electron beam dose gradient of 800 C / cm2 were used to perform electron beam direct writing on the surface of the coated silicon substrate 1, layer by layer, to expose exposure areas of different sizes. This ensured that the source 5 and drain 6 pattern areas on the PMMA resist were fully exposed. Then, a low-temperature development technique (about 15°C) was used to remove the exposed and denatured PMMA. A 1 nm chromium film and a 35 nm gold film were deposited on the corresponding areas of the source 5 and drain 6 pattern areas. Finally, the undenatured PMMA and the metal film on top were removed together using an acetone stripping method, thus preparing source 5 and drain 6.

[0070] The performance of the near-infrared photodetector prepared above will be tested, analyzed and characterized.

[0071] Two digital source meters (K2400) are used to apply left and right gate voltages using their voltage sources. The source and drain are connected through another digital source meter. While applying source and drain bias voltages, the current between the source and drain electrodes is collected. This is used to test the current imaging of the photodetector in different modes when different voltages are applied to the two gates. At the same time, a supercontinuum light source is used as the incident light, and a bandpass filter is used to obtain light of the corresponding wavelength. The photoresponsivity and polarization dependence of the photodetector are measured using a Soleber germanium detector.

[0072] like Figures 2-4As shown, when different voltages are applied to the left and right gates, the photodetector can switch between pn junction, np junction, and transistor modes. Under gate voltage modulation, the Seebeck coefficient contrast (SlSr) is maximized near the pn junction region. When the photodetector switches from a pn junction to an np junction, i.e. from... Figures 2 to 3 The polarity of the photocurrent will also change accordingly, with a magnitude of approximately 1.5 nA, and... Figure 2 The photocurrent of the pn junction is comparable in magnitude. When the voltages at the left and right gates are equal to the voltage at the electrical neutral point, a photocurrent of approximately 3 nA can also be observed from the Schottky junction formed between the source / drain contact and the corner bilayer graphene (tBLG). Figure 4 As shown, the photocurrent formed near the Schottky junction is distributed at the edges of the source and drain electrodes, mainly originating from the junction region formed by band bending at the metal and tBLG interface. Therefore, when different voltages are applied to the two gates in the in-plane separated dual-gate structure 2 of this invention, the photodetector can switch between different modes.

[0073] Figure 5 The photoresponsivity of the photodetector under different polarization directions is presented when the incident wavelengths are 850 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1550 nm, and 1600 nm, with a fixed power of 100 μW. The figure is divided into two curves, showing the changes in photoresponsivity as a function of wavelength for the np junction under X-polarized light (perpendicular to the slit 7 of the in-plane separated double-gate structure 2) and the np junction under Y-polarized light (parallel to the slit 7 of the in-plane separated double-gate structure 2). For this photodetector, the translational symmetry along the Y-axis is not broken, so the incident light passes through the slit 7, and the hexagonal boron nitride layer 3, the slit 7, and the silicon substrate 1 together form a resonant Fabry-Perot cavity. However, for X-polarized light, since slit 7 is only 200 nm long, much smaller than the wavelength of near-infrared light, an enhanced electric field appears at the boundary of the gold thin film. However, it cannot pass through slit 7 to form a resonant mode. Therefore, the |E|² of the photodetector differs under different polarization directions, and the photodetector has different electromagnetic responses to light with different polarization directions. It can be observed that the photoresponsivity decreases with increasing wavelength in the X-polarization direction, while in the Y-polarization direction it first increases and then decreases with increasing wavelength, with a peak around 1100 nm. Therefore, the photoresponsivity of the photodetector of this invention exhibits a strong correlation with the polarization direction and its relationship with wavelength.

[0074] In summary, the near-infrared photodetector of the present invention, by fabricating an in-plane separated dual-gate structure on a silicon substrate, allows the photodetector to switch between different modes when different voltages are applied to the left and right gates. Simultaneously, the present invention incorporates a corner-rotating double-layer graphene layer on the in-plane separated dual-gate structure, enabling the photodetector to achieve enhanced light absorption in different frequency bands. When detecting incident light of different wavelengths under the same gate voltage, the corresponding relationship between the photoresponsivity and wavelength, as well as a strong correlation with the polarization direction, can be obtained, resulting in a significantly improved detection effect of the photodetector of the present invention.

[0075] Example 3:

[0076] In the process of preparing the near-infrared photodetector, after the silicon substrate 1 is developed at low temperature and coated, the interface of the in-plane separated dual electrodes has chemical contaminants due to the repeated coating and removal of adhesive. Therefore, a mixed solution of concentrated sulfuric acid and hydrogen peroxide can be used to clean the interface, and finally a clean in-plane separated dual-gate structure 2 is prepared.

[0077] Using the same cleaning method described above, the entire structure can be cleaned again after the near-infrared photodetector is fabricated, so as to obtain a near-infrared photodetector with a clean surface.

[0078] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A near-infrared photodetector with dual gate voltage modulation, characterized in that, It includes a silicon wafer substrate (1), an in-plane split dual-gate structure (2), a hexagonal boron nitride layer (3), a corner bilayer graphene layer (4), a source electrode (5), and a drain electrode (6); The in-plane separated dual-gate structure (2) is disposed on the top of the silicon substrate (1), and there is a slit (7) between the two gates; the width of the slit (7) is 200 nm; The hexagonal boron nitride layer (3) is disposed above the in-plane split dual gate structure (2) and overlaps on both sides of the silicon wafer substrate (1); The corner bilayer graphene layer (4) is disposed above the hexagonal boron nitride layer (3), and the center of the corner bilayer graphene layer (4) corresponds to the slit (7) of the in-plane separated double gate structure (2); One end of the source electrode (5) and the drain electrode (6) are respectively disposed on the top two sides of the corner double-layer graphene layer (4), and the other end of the source electrode (5) and the drain electrode (6) are respectively disposed on the two sides of the silicon wafer substrate (1). In this invention, by applying different voltages to the left and right gates of the in-plane split dual-gate structure (2), the near-infrared photodetector can switch between pn junction, np junction and transistor modes.

2. The near-infrared photodetector with dual gate voltage modulation according to claim 1, characterized in that, The widths of the source (5) and drain (6) are both 5 μm.

3. The near-infrared photodetector with dual gate voltage modulation according to claim 1, characterized in that, The rotation angle of the corner bilayer graphene layer (4) is 4.5°.

4. The near-infrared photodetector with dual gate voltage modulation according to claim 1, characterized in that, The two gates of the in-plane separated dual-gate structure (2) are two symmetrically arranged rectangular metal electrodes with a thickness of 35nm±1nm.

5. A near-infrared photodetector with dual gate voltage modulation according to claim 1, characterized in that, The in-plane separated dual-gate structure (2), source (5), and drain (6) are made of the same material, namely gold or palladium.

6. A method for fabricating a near-infrared photodetector with dual gate voltage modulation as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. An in-plane separated dual-gate structure (2) is prepared on a silicon substrate (1) by two electron beam direct writing processes; and a slit (7) exists between the two gates; the width of the slit (7) is 200 nm. S2. A layered structure with a hexagonal boron nitride layer (3) fixed at the bottom of a corner bilayer graphene layer (4) was prepared by dry transfer. The layered structure and the in-plane separated double gate structure (2) were aligned under a microscope to ensure that the area of ​​the slit (7) was in the center of the corner bilayer graphene layer (4). After alignment, they were bonded and fixed. S3. The source (5) and drain (6) are prepared by direct writing with an electron beam between the two sides of the silicon substrate (1) and the corner double graphene layer (4); In this invention, by applying different voltages to the left and right gates of the in-plane split dual-gate structure (2), the near-infrared photodetector can switch between pn junction, np junction and transistor modes.

7. The method for fabricating a near-infrared photodetector with dual gate voltage modulation according to claim 6, characterized in that, The in-plane separated double-gate structure (2) was prepared by two electron beam direct writing processes in step S1. The specific process is as follows: First, perform the electron beam direct writing process: After PMMA electron beam adhesive is coated on the surface of silicon substrate (1), it is baked and then exposed to the surface of silicon substrate (1) by electron beam. Then, the exposed area is developed at low temperature using a mixed solution of methyl isobutyl ketone and isopropanol. After low temperature development, a titanium film and a gold film are deposited on the surface of silicon substrate (1). Finally, PMMA is dissolved and the metal film on it is removed using an acetone stripping process to obtain a silicon substrate (1) with square metal markers and metal blocks in an I-shaped array. After completing the first electron beam direct writing, a second electron beam direct writing is performed: First, an electron beam dose test is performed on the in-plane separated dual-gate structure (2) with a set target slit width to determine the electron beam dose corresponding to the target slit width. Then, the corresponding electron beam dose is used to align the metal marker with the design area of ​​the layout based on the overlay process to obtain a titanium gold gate structure pattern with the target slit width. Then, low-temperature development is performed, and after development, titanium film and gold film are deposited again. Finally, the in-plane separated dual-gate structure (2) with the target slit width is prepared.

8. The method for fabricating a near-infrared photodetector with dual gate voltage modulation according to claim 6, characterized in that, The specific process of fixing and attaching the layered structure composed of the hexagonal boron nitride layer (3) and the corner bilayer graphene layer (4) onto the in-plane separated double gate structure (2) in step S2 is as follows: The mechanically exfoliated graphene was cut, and the cut graphene was picked up one by one using a PDMS / PC film. Finally, hexagonal boron nitride was picked up to obtain a layered structure in which the hexagonal boron nitride layer (3) was fixed at the bottom of the corner bilayer graphene layer (4). Then, the layered structure and the in-plane separated double gate structure (2) were aligned under a microscope to ensure that the area of ​​the slit (7) was in the center of the corner bilayer graphene layer (4). After alignment, the layered structure was attached to the top of the in-plane separated double gate structure (2). The PC film was melted at high temperature and removed with chloroform solution. Finally, the layered structure was retained on the surface of the in-plane separated double gate structure (2).

9. A method for fabricating a near-infrared photodetector with dual gate voltage modulation according to claim 6, characterized in that, In step S3, the specific process of directly writing the source (5) and drain (6) between the silicon substrate (1) and the two sides of the corner bilayer graphene layer (4) using an electron beam is as follows: First, PMMA electron beam resist is coated onto the surface of a silicon substrate (1). Then, the surface of the coated silicon substrate (1) is baked. After that, electron beam is used to directly write the exposure areas of different sizes on the surface of the silicon substrate (1) so that the source (5) and drain (6) pattern areas of the layout design on the PMMA resist are fully exposed. Then, the PMMA after exposure denaturation is removed by low temperature development technology. A chromium film and a gold film are deposited at the corresponding locations of the source (5) and drain (6) pattern areas. Finally, the undenatured PMMA and the metal film on top are removed together by acetone stripping method, thus preparing the source (5) and drain (6).

Images