A local field-driven terahertz photodetector and its fabrication method

Abstract

This invention relates to the technical field of photodetector fabrication, and more specifically, to an in-plane localized field-driven terahertz photodetector and its fabrication method. The fabrication method includes: S1. etching protrusions on the upper surface of a substrate; S2. transferring a graphene film onto the pretreated substrate, with the graphene film covering the protrusions; patterning the graphene film to form a patterned graphene layer; S3. fabricating a source metal electrode and a drain metal electrode to obtain the terahertz photodetector. The terahertz photodetector includes a substrate with integrally formed protrusions, and a patterned graphene layer covering the protrusions; a source metal electrode and a drain metal electrode are disposed on the substrate, respectively located on both sides of the protrusions, and both have gaps between them and the protrusions. This invention enables high-speed photodetection over a wide spectral range from visible light to terahertz wavelengths without an external bias voltage, and the response time can reach the microsecond level.

Description

Technical Field

[0001] This invention relates to the technical field of photodetector fabrication, and more specifically, to an in-plane local field driven terahertz photodetector and its fabrication method. Background Technology

[0002] Wide-spectrum, low-power, and fast photodetectors are a core requirement of modern optoelectronics, especially in applications extending into the terahertz band. Traditional detection schemes often face limitations in response speed, sensitivity, and power consumption. According to existing research, two-dimensional semi-metals such as graphene, due to their unique zero-bandgap band structure, are widely used in photodetectors. However, to generate asymmetric temperature gradients or Fermi levels, traditional graphene detectors typically rely on asymmetric contacts, localized doping, or heterojunction construction. On the one hand, these methods are not only complex in manufacturing processes, but the introduced defects and interface barriers often reduce carrier mobility, limiting the device's response speed. On the other hand, ferroelectric materials, due to their spontaneous polarization properties, can provide a non-volatile built-in electric field, and are considered an ideal platform for achieving self-driven photodetection. However, the inherent wide bandgap and low mobility of pure ferroelectric materials severely limit their detection band and response speed. In recent years, existing research has attempted to use ferroelectric materials as gate dielectrics to construct ferroelectric field-effect transistors (FeFETs), utilizing polarization fields to control the semiconductor channel. However, existing domain inversion FeFETs or layered heterojunction FeFETs still rely on space-constrained depletion regions to generate photocurrent, or employ stacked heterojunction structures, which introduce van der Waals gaps, impurity contamination, and interface defects. These factors all hinder efficient carrier transport; at the same time, it is still difficult to maintain microsecond-level response in a wide spectral range from visible light to terahertz. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing detectors in maintaining microsecond-level response in a wide spectral range from visible light to terahertz, and to provide an in-plane local field driven terahertz photodetector and its fabrication method, which can achieve high-speed photodetection in a wide spectral range from visible light to terahertz without external bias voltage, and the response time can reach the microsecond level.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for fabricating an in-plane local field-driven terahertz photodetector is provided, comprising the following steps: S1. Take a substrate layer and etch a protrusion on the upper surface of the substrate layer; pre-treat the substrate layer with the protrusion. S2. Take a graphene film, transfer the graphene film onto the pretreated substrate, and cover the protrusion with the graphene film; perform patterning processing on the graphene film to form a patterned graphene layer; S3. Source metal electrodes and drain metal electrodes are prepared at both ends of the patterned graphene layer to obtain a terahertz photodetector driven by an in-plane local field.

[0005] This invention discloses a method for fabricating an in-plane localized field-driven terahertz photodetector. The method involves etching protrusions on the upper surface of a substrate to form a ridge shape, providing a localized in-plane polarization field to directly drive photogenerated carrier transport. A patterned graphene layer covers the protrusions, and due to the self-polarizing ferroelectric properties of the substrate with the protrusions, the in-plane localized field-driven terahertz photodetector achieves microsecond-level response broadband photodetection without any external bias. It exhibits broadband absorption from the visible to the terahertz band, extending the response wavelength range to the visible to the terahertz band. It possesses a wide spectral detection range and high response speed, reducing device power consumption, improving the response efficiency and integration potential of ferroelectric photodetectors, and supporting non-volatile, repeatable self-driven photoresponse.

[0006] Further, step S1 includes the following steps: S11. Take a substrate layer, pattern it on the upper surface of the substrate layer by photolithography, and then etch out the protrusions; S12. Perform ultraviolet ozone cleaning treatment on the surface of the substrate layer with protrusions to form a hydrophilic surface on the surface of the protrusions and the substrate layer.

[0007] Furthermore, in step S11, the etching gas used during etching includes any one or more of SF6, CF4, C3F8, CHF3, Ar, O2, and H2.

[0008] Further, step S2 includes the following steps: S21. Take a graphene film and transfer the graphene film onto the pretreated substrate layer, with the graphene film covering the protrusion and the substrate layer; S22. Perform a spin-drying process on the substrate layer covered with the graphene film to make the graphene film adhere to the protrusion; S23. The graphene film is patterned to form a patterned graphene layer.

[0009] Furthermore, the patterned graphene layer is in contact with both the source metal electrode and the drain metal electrode; the patterned graphene layer forms a graphene channel between the source metal electrode and the drain metal electrode; the source metal electrode and the drain metal electrode are arranged on the substrate layer along a channel direction parallel to the graphene channel; and there are gaps between the protrusion and the source metal electrode and between the protrusion and the drain metal electrode.

[0010] Furthermore, the gap is greater than or equal to 1µm.

[0011] Furthermore, the substrate and the protrusion are made of any one of lithium niobate, lithium tantalate, barium titanate, lead zirconate titanate, and sodium bismuth titanate, and the spontaneous polarization direction of the protrusion is parallel to the channel direction.

[0012] Furthermore, the protrusion has a first rectangular structure, and the patterned graphene layer has a second rectangular structure; in the direction parallel to the channel, the length of the protrusion is less than the laying length of the patterned graphene layer; in the direction perpendicular to the channel, the length of the protrusion is greater than or equal to the laying length of the patterned graphene layer.

[0013] Furthermore, the source metal electrode is any one or more of Al, Ag, Au, Bi, Cr, Ti, and Ni, and the drain metal electrode is any one or more of Al, Ag, Au, Bi, Cr, Ti, and Ni.

[0014] The present invention also provides an in-plane local field driven terahertz photodetector, comprising a substrate layer, wherein a protrusion is integrally formed on the substrate layer, and a patterned graphene layer is disposed on the protrusion; a source metal electrode and a drain metal electrode are disposed on the substrate layer, the source metal electrode and the drain metal electrode are respectively located on both sides of the protrusion, and a gap is provided between the protrusion and the source metal electrode and between the protrusion and the drain metal electrode; the source metal electrode and the drain metal electrode are both in contact with the patterned graphene layer.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses an in-plane localized field-driven terahertz photodetector and its fabrication method. The method involves etching protrusions on the upper surface of a substrate to form a ridge shape, providing a localized in-plane polarization field to directly drive photogenerated carrier transport. A patterned graphene layer covers the protrusions, and due to the self-polarizing ferroelectric properties of the substrate with the protrusions, the in-plane localized field-driven terahertz photodetector achieves microsecond-level response broadband photodetection without any external bias. It exhibits broadband absorption from the visible to the terahertz band, extending the response wavelength range to the visible to the terahertz band. It possesses a wide spectral detection range and high response speed, reducing device power consumption, improving the response efficiency and integration potential of ferroelectric photodetectors, and supporting non-volatile, repeatable self-driven photoresponse. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for fabricating an in-plane local field driven terahertz photodetector according to the present invention. Figure 2 This is a schematic diagram of the photocurrent distribution of the device prepared by the method of the present invention under a scanning photocurrent microscope. Figure 3 This is a schematic diagram showing the photoresponse of the device prepared by the method of the present invention under different laser powers under 532 nm laser irradiation. Figure 4 This is a schematic diagram showing the photoresponse of the device prepared by the method of the present invention under different laser powers under 10 μm laser irradiation. Figure 5 This is a schematic diagram showing the photoresponse of the device prepared by the method of the present invention under different laser powers when irradiated with 119 μm laser. Figure 6 This is a schematic diagram showing the photoresponse of the device prepared by the method of the present invention under laser irradiation of different wavelengths in the visible to terahertz band. Figure 7 This is a schematic diagram showing the photoresponse of the device prepared by the method of the present invention under different laser modulation frequencies under 532 nm laser irradiation. Figure 8 This is a schematic diagram showing the photoresponse of the device prepared by the method of the present invention under different laser modulation frequencies under 10 μm laser irradiation. Figure 9 This is a schematic diagram showing the photoresponse of the device prepared by the method of the present invention under different laser modulation frequencies under 119 μm laser irradiation. Figure 10 This is a schematic diagram of the structure of a first embodiment of a terahertz photodetector driven by an in-plane local field according to the present invention; Figure 11 This is a top-view structural schematic diagram of the first embodiment of the in-plane local field driven terahertz photodetector of the present invention. Figure 12 This is a schematic diagram of the structure of a second embodiment of a terahertz photodetector driven by an in-plane local field according to the present invention; Figure 13 This is a top-view structural schematic diagram of a second embodiment of a terahertz photodetector driven by an in-plane local field according to the present invention. Figure 14 This is a top-view structural schematic diagram of a third embodiment of an in-plane local field driven terahertz photodetector according to the present invention.

[0017] In the attached figure: 100, substrate layer; 110, protrusion; 200, patterned graphene layer; 300, source metal electrode; 400, drain metal electrode. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments. The accompanying drawings are for illustrative purposes only, representing schematic diagrams rather than actual physical objects, and should not be construed as limiting the scope of this patent. To better illustrate the embodiments of the present invention, 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.

[0019] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0020] Example 1 like Figure 1 The first embodiment of a method for fabricating an in-plane local field-driven terahertz photodetector according to the present invention is shown, comprising the following steps: S1. Take a substrate layer 100 and etch a protrusion 110 on the upper surface of the substrate layer 100; pre-treat the substrate layer 100 with the protrusion 110. S2. Take a graphene film and transfer it onto the pretreated substrate 100. Cover the protrusion 110 with the graphene film. Pattern the graphene film to form a patterned graphene layer 200. S3. Source metal electrode 300 and drain metal electrode 400 are fabricated at both ends of the patterned graphene layer 200 to obtain an in-plane local field driven terahertz photodetector.

[0021] The present invention features a raised portion 110 etched on the upper surface of the substrate layer 100, forming a ridge shape in the substrate portion. This provides a local in-plane polarization field to directly drive the transport of photogenerated carriers. The patterned graphene layer 200 covers the raised portion 110, and due to the ferroelectric properties of the substrate layer 100 with the raised portion 110, the terahertz photodetector driven by the local in-plane field can achieve a broadband photodetector with microsecond-level response without any external bias voltage. It has a broadband absorption range from visible light to terahertz, and the response wavelength range can be extended to the visible light to terahertz band. It has a wide spectral detection range and high response speed, which can reduce the operating power consumption of the device, improve the response efficiency and integration potential of the ferroelectric photodetector, and also support non-volatile and repeatable self-driven photodetector response.

[0022] Example 2 This embodiment is a second embodiment of a method for fabricating an in-plane local field driven terahertz photodetector. This embodiment is similar to the first embodiment. In this embodiment, step S1 includes the following steps: S11. Take substrate 100, pattern it on the upper surface of substrate 100 by photolithography, and then etch out the protrusion 110. Specifically, pattern the etching mask using a maskless photolithography system. Preferably, a maskless ultraviolet lithography machine is used as the maskless photolithography system. Ultraviolet photoresist is used and spin-coated at 1000~7000 rpm with a photoresist layer thickness of 0.5~2μm. Preferably, spin-coated at 4000 rpm with a photoresist layer thickness of 1μm. Then, the protrusion 110 is etched using a reactive ion etching system. The etching gas used during etching includes any one or more of SF6, CF4, C3F8, CHF3, Ar, O2, and H2. Preferably, CHF3 and Ar are selected. The volumetric flow rate of both etching gases is 50 sccm, the etching pressure in the etching chamber is 30 mTorr, the RF power is 150 W, and the etching time is 5 min.

[0023] S12. Perform ultraviolet ozone cleaning treatment on the surface of the substrate layer 100 with protrusion 110 to form a hydrophilic surface on the surface of the protrusion 110 and the substrate layer 100; specifically, use an ultraviolet ozone cleaner for cleaning, preferably, the cleaning time is 30 minutes.

[0024] In this embodiment, step S2 includes the following steps: S21. Take a graphene film and transfer it onto the pretreated substrate 100. The graphene film covers the protrusion 110 and the substrate 100. Specifically, the transfer of the graphene film can be completed by wet transfer or dry transfer. It should be noted that the selected graphene film is a single-layer structure. S22. The substrate layer 100 covered with graphene film is subjected to spin drying treatment to make the graphene film adhere to the protrusion 110; specifically, a spin coater is used for rapid drying. Preferably, the spin coater is set to a speed of 4000 rpm and a rotation time of 2 min. Due to the strong flexibility of the single-layer graphene film, the graphene film can be tightly attached to the protrusion 110. S23. Pattern the graphene film to form a patterned graphene layer 200.

[0025] Specifically, the patterned graphene layer 200 is in contact with both the source metal electrode 300 and the drain metal electrode 400; the patterned graphene layer 200 forms a graphene channel between the source metal electrode 300 and the drain metal electrode 400, and the source metal electrode 300 and the drain metal electrode 400 are arranged on the substrate layer 100 along a channel direction parallel to the graphene channel. There are gaps between the protrusion 110 and the source metal electrode 300, and between the protrusion 110 and the drain metal electrode 400; the gaps reduce the electrostatic shielding of the electrodes against the ferroelectric field, and preferably, the gaps are greater than or equal to 1µm.

[0026] In this embodiment, the substrate 100 and the protrusion 110 are made of any one of lithium niobate, lithium tantalate, barium titanate, lead zirconate titanate, and sodium bismuth titanate, and the spontaneous polarization direction of the protrusion 110 is parallel to the channel direction. Preferably, the substrate 100 and the protrusion 110 are made of X-cut single-crystal lithium niobate, and their spontaneous polarization direction is parallel to the channel direction.

[0027] Preferably, in step S1, the etched protrusion 110 can be configured as a first rectangular structure; in step S2, the graphene film is patterned to obtain a patterned graphene layer 200 constituting a second rectangular structure. In the horizontal direction and parallel to the channel direction, the length of the protrusion 110 is less than the laying length of the patterned graphene layer 200; in the horizontal direction and perpendicular to the channel direction, the length of the protrusion 110 is greater than or equal to the laying length of the patterned graphene layer 200. In this embodiment, in the horizontal direction, the length of the first rectangular structure parallel to the channel direction is 2~50µm, and the length of the first rectangular structure perpendicular to the channel direction is 2~1000µm; in the direction perpendicular to the horizontal direction, the thickness of the first rectangular structure is 10~40nm. In this embodiment, in the horizontal direction, the second rectangular structure has a laying length of 2~50µm parallel to the channel direction and a laying length of 2~1000µm perpendicular to the channel direction. It should be noted that the laying length refers to the length of the patterned graphene layer 200 in the horizontal direction after it has been transferred onto the substrate layer 100. It should also be noted that the patterned graphene layer 200 can be configured with other shapes, and the protrusion 110 can also be configured with other shapes. Furthermore, the protrusion 110 can be positioned at a symmetrical midpoint on the upper surface of the substrate layer 100, or it can be positioned closer to the source metal electrode 300 or the drain metal electrode 400, ensuring that the patterned graphene layer 200 covers the protrusion 110.

[0028] In this embodiment, step S3 specifically includes: performing photolithography and sputtering on both ends of the patterned graphene layer 200, followed by deposition or evaporation to form a source metal electrode 300 and a drain metal electrode 400. Then, the photoresist is removed using acetone to obtain an in-plane localized field driven terahertz photodetector. It should be noted that the two ends of the patterned graphene layer 200 refer to the two ends along the channel direction. It should also be noted that the source metal electrode 300 and drain metal electrode 400 can be configured to be completely located on the upper surface of the patterned graphene layer 200, or they can be configured to partially cover the upper surface of the patterned graphene layer 200 and partially located on the upper surface of the substrate layer 100, ensuring that the two metal electrodes are in contact with the patterned graphene layer 200 on the substrate layer 100.

[0029] In this embodiment, the source metal electrode 300 is any one or more of Al, Ag, Au, Bi, Cr, Ti, and Ni, and the drain metal electrode 400 is any one or more of Al, Ag, Au, Bi, Cr, Ti, and Ni. It should be noted that the source metal electrode 300 and the drain metal electrode 400 can be made of the same metal material or different metal materials. Preferably, Au is selected as the source metal electrode 300, and Cr or Ti is used as the buffer layer between the substrate layer 100 and the source metal electrode 300; and Au is selected as the drain metal electrode 400, and Cr or Ti is used as the buffer layer between the substrate layer 100 and the drain metal electrode 400. In this embodiment, the shapes of the source metal electrode 300 and the drain metal electrode 400 can be any one of circular, square, rectangular, rhomboid, regular polygonal, or irregular shapes.

[0030] This invention modulates ferroelectric polarization into a localized transverse driving field, directly dominating the transport of high-mobility non-equilibrium carriers. Theoretically, it can provide a built-in transverse electric field for directional driving of photocarriers within a short timescale. Furthermore, the patterned graphene layer 200 possesses a zero-bandgap structure and extremely high carrier mobility, maintaining a photosensitive system without intrinsic spectral cutoff and a strong dispersive band structure with high carrier mobility. Using a single layer of graphene as both the conductive and photosensitive layer enables broad-spectrum absorption and rapid charge transport from the visible to the terahertz band. The in-plane localized field-driven terahertz photodetector prepared by the method of this invention covers the detection wavelength range from visible light (532 nm) to the terahertz band (119 μm) without an external bias voltage. Therefore, by etching lithium niobate to form protrusions 110, the electric dipole spacing can be shortened, allowing the in-plane ferroelectric field parallel to the surface generated by spontaneous polarization to be localized within the graphene channel. This localized electric field within the surface disrupts the symmetrical distribution of photocurrent within the graphene channel, directly driving rapid directional drift of charge carriers without the need for external bias voltage, and suppressing electron-hole recombination, thereby generating a photocurrent response. This terahertz photodetector can also simultaneously avoid carrier collection confined by domain walls and transport performance degradation caused by stacked heterostructure interfaces, thus enhancing the broadband detection and high-speed response capabilities of the terahertz photodetector.

[0031] In this embodiment, the photocurrent distribution of a portion of the terahertz photodetector driven by an in-situ local field (including a portion of the patterned graphene layer 200 and a portion of the patterned graphene layer 200 overlapping with the source metal electrode 300 and the drain metal electrode 400) is imaged using a scanning photocurrent microscope operating at a wavelength of 10 μm. Figure 2As shown, the photocurrent symmetry within the graphene channel is broken by an in-plane oriented polarized electric field. This in-plane ferroelectric field induces a directional photocurrent distribution in the region above the protrusion 110, thereby generating a net photocurrent. This driving effect supports multiple wavelength bands, enabling terahertz photodetectors driven by in-plane localized fields to operate without any external bias voltage. V ds In the self-driven mode (=0), stable and directional photocurrent output can be achieved, which can effectively improve the detection efficiency in a wide spectrum environment and significantly reduce the overall operating power consumption of the terahertz photodetector.

[0032] In this embodiment, the in-plane localized field-driven terahertz photodetector combines a high-mobility monolayer patterned graphene layer 200 with a substrate layer 100 having a specific etched morphology and protrusions 110. The patterned graphene layer 200 exhibits photosensitivity without intrinsic spectral cutoff, while the substrate layer 100 with protrusions 110 provides a wavelength-independent built-in electrostatic field, together achieving a broad-spectrum response from the visible light to the terahertz band. During photodetection, the in-plane localized field-driven terahertz photodetector maintains a bias voltage. V ds =0, when the laser irradiates the patterned graphene layer 200, current or voltage signals are obtained at the source metal electrode 300 and the drain metal electrode 400.

[0033] like Figure 3 , Figure 4 and Figure 5 The figures show the optical response of a terahertz photodetector driven by an in-plane local field under different laser powers of 532 nm, 10 μm, and 119 μm laser illumination. On a double logarithmic coordinate system, the photocurrent increases linearly with increasing power. Figure 6 The diagram shows the optical response of an in-plane local field driven terahertz photodetector under different wavelengths of laser illumination in the visible to terahertz band. As the excitation wavelength changes, the in-plane local field driven terahertz photodetector exhibits a significant response in the visible to terahertz band.

[0034] In this embodiment, the patterned graphene layer 200 has a strong dispersive band structure with high carrier mobility. The ferroelectric polarization of the substrate layer 100 with protrusions 110 is modulated into a localized lateral driving field, directly dominating the Dirac photocarrier transport in the patterned graphene layer 200, thereby achieving microsecond-level photoelectric response capabilities from visible light (532 nm), mid-infrared (10 μm) to the terahertz band (119 μm). Figure 7 , Figure 8 and Figure 9The figures show the photoresponse of the in-plane local field-driven terahertz photodetector under different laser modulation frequencies at 532 nm, 10 μm, and 119 μm laser illumination. The response times of the in-plane local field-driven terahertz photodetector at wavelengths of 532 nm, 10 μm, and 119 μm are 21.2 μs, 6.7 μs, and 37.9 μs, respectively.

[0035] The in-plane local field driven terahertz photodetector prepared by the method of the present invention has good structural stability and device performance, supports broadband detection from visible light to terahertz band, can achieve microsecond-level response speed without external bias voltage, can reduce device power consumption, and improve device response performance and integration potential.

[0036] Example 3 like Figure 10 and Figure 11 The illustration shows a first embodiment of an in-plane localized field-driven terahertz photodetector according to the present invention. It includes a substrate 100, on which a protrusion 110 is integrally formed, and a patterned graphene layer 200 is disposed on the protrusion 110. A source metal electrode 300 and a drain metal electrode 400 are disposed on the substrate 100, located on opposite sides of the protrusion 110, with gaps between the protrusion 110 and the source metal electrode 300, and between the protrusion 110 and the drain metal electrode 400. Both the source metal electrode 300 and the drain metal electrode 400 are in contact with the patterned graphene layer 200. This in-plane localized field-driven terahertz photodetector can be prepared using the preparation method described in Embodiment 1 or Embodiment 2. In this embodiment, the protrusion 110 and the substrate 100 are both made of lithium niobate, specifically, X-cut single-crystal lithium niobate; the patterned graphene layer 200 is a single-layer structure, and the source metal electrode 300 and the drain metal electrode 400 are both Au.

[0037] The in-plane local field driven terahertz photodetector of the present invention has a lithium niobate substrate layer with protrusions 110, which can provide a local in-plane polarization field to directly drive the transport of photogenerated carriers; the monolayer patterned graphene layer 200 has a broad spectrum absorption from visible light to terahertz wavelengths, and the response wavelength range can be extended to the visible light to terahertz wavelength range; since the substrate layer 100 with protrusions 110 has spontaneously polarized ferroelectric properties, the in-plane local field driven terahertz photodetector can achieve a broadband photodetector with microsecond-level response in a state without any external bias voltage, which can reduce the operating power consumption of the device and improve the response performance and integration potential of the device.

[0038] Specifically, such as Figure 10 and Figure 11As shown, the length of the protrusion 110 in the direction perpendicular to the channel is... The length is 2~1000µm in the direction parallel to the channel. The thickness is 2~50µm. The length of the patterned graphene layer 200 is 10~40nm; the laying length of the patterned graphene layer 200 in the direction perpendicular to the channel is... The laying length is 2~1000µm, parallel to the trench direction. The gap is 2~50µm. The gap between the protrusion 110 and the source metal electrode 300, and between the protrusion 110 and the drain metal electrode 400, is provided. .

[0039] Example 4 This embodiment is a second embodiment of an in-plane local field-driven terahertz photodetector. This embodiment is similar to embodiment three, except that, as Figure 12 and Figure 13 As shown, in the direction parallel to the channel, the length of the patterned graphene layer 200 is the same as the length of the substrate layer 100, and the source metal electrode 300 and the drain metal electrode 400 cover the two ends of the patterned graphene layer 200 respectively; in the direction perpendicular to the channel, the length of the source metal electrode 300 and the drain metal electrode 400 is greater than the length of the patterned graphene layer 200, and there is a step between the protrusion 110 and the edge of the substrate layer 100.

[0040] Example 5 This embodiment is a third embodiment of an in-plane local field-driven terahertz photodetector. This embodiment is similar to embodiments three or four, except that, as Figure 14 As shown, in the direction parallel to the channel, the laying length of the patterned graphene layer 200 is greater than the length of the protrusion 110 and less than the length of the substrate layer 100; in the direction perpendicular to the channel, the length of the protrusion 110 is the same as the length of the substrate layer 100.

[0041] In the specific implementation of the above embodiments, the technical features can be combined in any non-contradictory way. For the sake of brevity, not all possible combinations of the above technical features are described. However, as long as the combination of these technical features is not contradictory, it should be considered to be within the scope of this specification.

[0042] 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 method for fabricating a terahertz photodetector driven by an in-plane local field, characterized in that, Includes the following steps: S1. Take a substrate layer (100) and etch a protrusion (110) on the upper surface of the substrate layer (100); pre-treat the substrate layer (100) with the protrusion (110); S2. Take a graphene film and transfer it onto the pretreated substrate (100), with the graphene film covering the protrusion (110); perform patterning treatment on the graphene film to form a patterned graphene layer (200). S3. Source metal electrode (300) and drain metal electrode (400) are respectively prepared at both ends of the patterned graphene layer (200) to obtain a terahertz photodetector driven by an in-plane local field.

2. The method for fabricating an in-plane localized field-driven terahertz photodetector according to claim 1, characterized in that, Step S1 includes the following steps: S11. Take a substrate layer (100), pattern it on the upper surface of the substrate layer (100) by photolithography, and then etch out the protrusion (110). S12. Perform ultraviolet ozone cleaning treatment on the surface of the substrate layer (100) with protrusions (110) to form a hydrophilic surface on the surface of the protrusions (110) and the substrate layer (100).

3. The method for fabricating an in-plane localized field-driven terahertz photodetector according to claim 2, characterized in that, In step S11, the etching gas used during etching includes any one or more of SF6, CF4, C3F8, CHF3, Ar, O2, and H2.

4. The method for fabricating an in-plane localized field-driven terahertz photodetector according to claim 1, characterized in that, Step S2 includes the following steps: S21. Take a graphene film and transfer the graphene film onto the pretreated substrate (100), with the graphene film covering the protrusion (110) and the substrate (100); S22. The substrate layer (100) covered with the graphene film is subjected to a spin drying process to make the graphene film adhere to the protrusion (110); S23. The graphene film is patterned to form a patterned graphene layer (200).

5. The method for fabricating an in-plane localized field-driven terahertz photodetector according to any one of claims 1 to 4, characterized in that, The patterned graphene layer (200) is in contact with both the source metal electrode (300) and the drain metal electrode (400); the patterned graphene layer (200) forms a graphene channel between the source metal electrode (300) and the drain metal electrode (400); the source metal electrode (300) and the drain metal electrode (400) are arranged on the substrate layer (100) along a channel direction parallel to the graphene channel; the protrusion (110) has gaps between itself and the source metal electrode (300) and between itself and the drain metal electrode (400).

6. The method for fabricating an in-plane localized field-driven terahertz photodetector according to claim 5, characterized in that, The gap is greater than or equal to 1µm.

7. The method for fabricating an in-plane localized field-driven terahertz photodetector according to claim 5, characterized in that, The substrate (100) and the protrusion (110) are made of any one of lithium niobate, lithium tantalate, barium titanate, lead zirconate titanate, and sodium bismuth titanate, and the spontaneous polarization direction of the protrusion (110) is parallel to the channel direction.

8. The method for fabricating an in-plane localized field-driven terahertz photodetector according to claim 5, characterized in that, The protrusion (110) is a first rectangular structure, and the patterned graphene layer (200) is a second rectangular structure; in the direction parallel to the channel, the length of the protrusion (110) is less than the laying length of the patterned graphene layer (200); in the direction perpendicular to the channel, the length of the protrusion (110) is greater than or equal to the laying length of the patterned graphene layer (200).

9. The method for fabricating an in-plane localized field-driven terahertz photodetector according to any one of claims 1 to 4, characterized in that, The source metal electrode (300) is any one or more of Al, Ag, Au, Bi, Cr, Ti, and Ni, and the drain metal electrode (400) is any one or more of Al, Ag, Au, Bi, Cr, Ti, and Ni.

10. A terahertz photodetector driven by an in-plane local field, characterized in that, The substrate includes a substrate (100), on which a protrusion (110) is integrally formed, and a patterned graphene layer (200) is covered on the protrusion (110); a source metal electrode (300) and a drain metal electrode (400) are provided on the substrate (100), the source metal electrode (300) and the drain metal electrode (400) are respectively located on both sides of the protrusion (110), and gaps are provided between the protrusion (110) and the source metal electrode (300) and between the protrusion (110) and the drain metal electrode (400); the source metal electrode (300) and the drain metal electrode (400) are both in contact with the patterned graphene layer (200).

Images