Photoconductive switch based on nano-microsphere array and preparation method thereof

Abstract

The invention discloses a photoconductive switch based on a nano-microsphere array and a preparation method thereof, and mainly solves the problem that the light energy utilization rate of the existing photoconductive switch is low. The device comprises a semi-insulating substrate (1), two metal electrodes (2), two external connection electrodes (3) and a nano-microsphere array (4), and the two metal electrodes are distributed at the two ends of the surface of the semi-insulating substrate; the two external connection electrodes are respectively positioned on the two metal electrodes; the nano-microsphere array is distributed and arranged on the surface of the light incident side of the semi-insulating substrate in a rectangular shape, the diameter of each nano-microsphere is 50-250 nm, the nano-microsphere is made of any one of Ag, Cu and Al, and the distances among all the nano-microspheres are equal. The output power of the photoconductive switch is improved, the dark-state leakage current of the photoconductive switch is reduced, the utilization rate of electric energy is improved, and the photoconductive switch can be used for an ultra-wideband electromagnetic pulse generator and a solid-state compact pulse power supply.

Description

Technical Field

[0001] This invention belongs to the field of microelectronics technology, and specifically relates to a photoconductive switching device that can be used in ultra-wideband electromagnetic pulse generators and solid-state compact pulse power supplies. Background Technology

[0002] Photoconductive switches are a novel type of device that uses rapid laser pulses to excite electron transitions within a semiconductor device, generating a large number of photogenerated carriers and controlling the material's conductivity to achieve device switching. Compared to traditional spark gap switches, turn-off thyristors, and metal-oxide-semiconductor field-effect transistors (MOSFETs), photoconductive switches offer advantages such as fast closing time, short bounce time, high repetition frequency, immunity to electromagnetic interference, and miniaturization, achieving a balance between power capacity and repetition frequency. Currently, a key challenge in the development of photoconductive switches is the low utilization rate of excitation light energy, which affects the output power of the device.

[0003] Patent application number 202310744520.2 discloses an optical structure for improving the light energy utilization of a gallium arsenide photoconductive switch. This optical structure consists of a photoconductive switch, a cylindrical lens, four mirrors, and a plano-concave cylindrical mirror. The first mirror, cylindrical lens, photoconductive switch, and second mirror are arranged horizontally from top to bottom, with their centers facing each other. The left end face of the cylindrical lens is bonded to the reflecting surface of the third mirror, and the right end face is bonded to the reflecting surface of the fourth mirror. The axis passes through the center of the third and fourth mirrors. A plano-concave cylindrical mirror is placed inside a circular through-hole in the middle of the first mirror. The gallium arsenide photoconductive switch, the third mirror, the first mirror, the plano-concave cylindrical mirror, and the fourth mirror constitute a sealed space containing the cylindrical lens. This optical structure design allows the pulsed laser to be reflected multiple times through the substrate material, increasing the optical path of the trigger laser within the device and improving the energy utilization of the pulsed laser. However, many problems still exist. Not only do we need to consider the position of the lens and the mirror, but with the increase in the number of optical mirrors, we also need to consider the alignment problem. At the same time, using various optical mirrors essentially increases the optical path of the trigger light in the substrate material, which is not conducive to the high-frequency response of the device.

[0004] Patent document CN201610211004.3 discloses a low on-resistance GaAs photoconductive switch with a high-reflectance film and an anti-reflection film. It includes a GaAs substrate, a highly doped n+-GaAs layer on the electrode region of the GaAs substrate electrode surface, a metal layer on the surface of the highly doped n+-GaAs layer, a high-reflectance film on the non-electrode region of the GaAs substrate electrode surface, and an anti-reflection film on the back electrode surface of the GaAs substrate. While this device can reduce the reflection loss of pulsed laser light at the incident surface and allow unabsorbed laser light to pass through the substrate a second time, increasing the optical path length within the device and thus improving light utilization, this solution still has several problems:

[0005] One reason is that the lattice mismatch between the thin film material and the substrate generates stress, which affects the quality of the thin film.

[0006] Secondly, the photoconductive switch needs to be irradiated by lasers multiple times during operation, which may damage the thin film material, directly affecting the reliability of the photoconductive switch and even causing it to fail.

[0007] Third, thermal stress generated between the multilayer stacked structures can cause the film to crack, reducing the antireflective and antireflective effects of the film. Summary of the Invention

[0008] To address the shortcomings of the prior art, this invention provides a photoconductive switch based on a nanosphere array and its fabrication method. One objective is to steadily improve the light energy utilization rate, increase the number of charge carriers during device operation, and improve the output power of the device. Another objective is to reduce the dark-state leakage current of the device and improve the power utilization rate.

[0009] The key technology to achieve the purpose of this invention is to design a structure of a metal microsphere nanoarray to change the propagation path of light and the distribution of electromagnetic field on the device surface.

[0010] Based on the above technical concept, the technical solution of the present invention is implemented as follows:

[0011] 1. A photoconductive switch based on a nanosphere array, comprising a semi-insulating substrate 1, two metal electrodes 2 and two external connecting electrodes 3, characterized in that: the surface of the semi-insulating substrate 1 on the light-incident side is distributed with a nanosphere array 4; the nanosphere array is arranged in a two-dimensional pattern in a rectangular arrangement, with the distance between each pair of adjacent microspheres being the same.

[0012] Preferably, the nanosphere array 4 has a diameter of 50 nm to 250 nm and is made of any one of Ag, Cu, and Al.

[0013] Preferably, the semi-insulating substrate 1 is a cube with a side length of 6mm to 14mm and a thickness of 0.35mm to 1mm, and the material is any one of silicon carbide, gallium nitride, gallium arsenide, gallium oxide, and diamond.

[0014] Preferably, the two metal electrodes 2 are located on the same side or opposite side of the semi-insulating substrate, with one on the left side of the substrate and the other on the right side, and the horizontal distance between them is 1mm to 8mm, and they are in ohmic contact with the semi-insulating substrate.

[0015] Each metal electrode employs one of the following: Ni / Ti / Pt / Au composite metal layer, Ti / Pt / Au composite metal layer, W / Ti / Au composite metal layer, Ni / Ti / Au composite metal layer, or Ni / Au composite metal layer.

[0016] Preferably, the two external connecting electrodes 3 are located on the surfaces of two metal electrodes, and both are made of copper, gold or copper-gold material with a length of 6mm to 10mm, a width of 3mm to 7mm and a thickness of 0.05mm to 0.1mm.

[0017] 2. A method for fabricating a photoconductive switch based on a nanosphere array, characterized by comprising the following steps:

[0018] S1: Clean the semi-insulating substrate 1, then uniformly coat its front side with photoresist, expose and develop the front side through a mask with a prepared pattern, and prepare the required electrode pattern.

[0019] S2: Evaporate and sputter metal onto a semi-insulating substrate with an electrode pattern to form a metal layer.

[0020] S3: The semi-insulating substrate with the metal layer is peeled off to remove the metal layer in the non-electrode pattern area to form metal electrode 2.

[0021] S4: The desired nanosphere array pattern is prepared on the light-incident side of a semi-insulating substrate using ultraviolet nanoimprinting technology.

[0022] S5: Sputter metal onto one side of the fabricated nanosphere array pattern to form a nanometal layer.

[0023] S6: Peel off the light-incident side of the semi-insulating substrate on which the nano-metal layer has been prepared, and remove the metal in the non-nano-microsphere array pattern area to form nano-microsphere array 4.

[0024] S7: Weld external connecting electrodes 3 onto the metal electrodes, one of which is welded to the left half of the left metal electrode and the other to the right half of the right metal electrode to form a photoconductive switch device.

[0025] Compared with the prior art, the present invention has the following advantages because it has a nanosphere array distributed on the light-incident surface of the semi-insulating substrate:

[0026] Firstly, it can change the propagation path of light and the distribution of electromagnetic field on the surface of the device, increasing the interaction length and probability between light and matter. At the same time, it adopts a rectangular array structure of nanospheres with the same distance between each pair of adjacent microspheres to achieve better matching between the array and the strip-shaped light spot, thereby improving the utilization rate of light energy.

[0027] Secondly, electrons in the metal nanospheres can absorb photons and move into the substrate, increasing the operating current of the device and improving its output power.

[0028] Third, by utilizing the low conductivity of the oxide film formed on the metal surface of nanospheres, the dark-state resistance of the device can be improved, the leakage current of the device can be reduced, and the power utilization rate of the device can be increased. Attached Figure Description

[0029] Figure 1 Device structure diagram of the present invention;

[0030] Figure 2 Preparation of this invention Figure 1 A schematic diagram of the device's flow chart. Detailed Implementation

[0031] The following detailed description of specific examples of the present invention is provided in conjunction with the accompanying drawings.

[0032] Reference Figure 1 This example is a photoconductive switch based on a nanosphere array, comprising a semi-insulating substrate 1, two metal electrodes 2, two external connecting electrodes 3, and a nanosphere array 4, wherein:

[0033] The semi-insulating substrate 1 is a cube with a side length of 6mm to 14mm and a thickness of 0.35mm to 1mm, and the material is any one of silicon carbide, gallium nitride, gallium arsenide, gallium oxide, and diamond.

[0034] The two metal electrodes 2 are located on the same side or opposite side of the semi-insulating substrate 1, with one on the left side of the substrate and the other on the right side. The horizontal distance between them is 1mm to 8mm, and they are in ohmic contact with the semi-insulating substrate. Each metal electrode is made of one of the following: Ni / Ti / Pt / Au composite metal layer, Ti / Pt / Au composite metal layer, W / Ti / Au composite metal layer, Ni / Ti / Au composite metal layer, or Ni / Au composite metal layer.

[0035] The two external connecting electrodes 3 are located on the surfaces of two metal electrodes, and are made of copper, gold or copper-gold material with a length of 6mm to 10mm, a width of 3mm to 7mm and a thickness of 0.05mm to 0.1mm.

[0036] The nanosphere array 4 is located on the light-incident side of the semi-insulating substrate, and its diameter is 50nm to 250nm. The nanosphere array is arranged in a two-dimensional pattern in a rectangular arrangement, with the distance between each two adjacent microspheres being the same. The material is any one of Ag, Cu, and Al.

[0037] Reference Figure 2 This example provides three implementation methods for fabricating photoconductive switches based on nanosphere arrays:

[0038] Example 1: A photoconductive switch with a metal electrode of Ni / Ti / Pt / Au, an external connecting electrode of Cu, and a nanosphere array diameter of 200 nm made of Al was fabricated on a silicon carbide semi-insulating substrate.

[0039] Step 1: Prepare an electrode pattern on a silicon carbide semi-insulating substrate, as shown in 2a.

[0040] A silicon carbide semi-insulating substrate with a side length of 10 mm and a thickness of 1 mm was sequentially immersed in BOE solution, deionized water, acetone, isopropanol, and deionized water for ultrasonic cleaning for 120 s, 180 s, 600 s, 180 s, and 180 s, respectively. Then, photoresist was uniformly coated on the front side. The front side was exposed and developed through a mask with a pre-prepared pattern to prepare the two electrode patterns required.

[0041] Step 2: Prepare an electrode metal layer on a silicon carbide semi-insulating substrate, as shown in 2b.

[0042] The silicon carbide semi-insulating substrate with two electrode patterns was first subjected to evaporation of Ni metal with a thickness of 400 nm, and then subjected to argon gas and a vacuum of 1 × 10⁻⁶. -5 In an environment with a pressure of 1 Pa, the magnetron sputtering gas pressure was set to 1 Pa, and the sputtering power was 5 W / cm². 2 Under the specified process conditions, Ti / Pt / Au layers with thicknesses of 300nm / 300nm / 1000nm were sequentially sputtered and deposited to form metal layers.

[0043] Step 3: Fabricate a metal electrode on a silicon carbide semi-insulating substrate, as shown in 2c.

[0044] The blue film is attached to the surface of the metal layer and then peeled off to remove most of the metal layer outside the two electrode pattern areas. The semi-insulating substrate is then immersed in the stripping solution for 600 seconds to remove the remaining metal layer in the non-electrode pattern areas.

[0045] Then, the silicon carbide semi-insulating substrate was immersed in acetone, isopropanol, and deionized water for 300s, 180s, and 180s respectively, and then dried with nitrogen to remove residual photoresist and stripping solution, forming two metal electrodes 2.

[0046] Step 4: Fabricate a nanosphere array pattern on a silicon carbide semi-insulating substrate, as shown in 2d.

[0047] A layer of polymethyl methacrylate was spin-coated onto a silicon carbide semi-insulating substrate between two metal electrodes. A template of a rectangular, equally spaced nanosphere array with a diameter of 200 nm was pressed onto the uniformly distributed polymethyl methacrylate using a pressure of 1 Pa.

[0048] Then, irradiate polymethyl methacrylate with ultraviolet light for 250 seconds. After the polymethyl methacrylate undergoes a cross-linking reaction and is completely cured, remove the template and demold to obtain a rectangular array of equally spaced microspheres with a diameter of 200 nm.

[0049] The residual polymethyl methacrylate in the grooves of the microsphere array on the substrate is then removed by etching, forming a rectangular, equally spaced nanosphere array pattern with a diameter of 200 nm.

[0050] Step 5: Prepare an Al nanometal layer on a silicon carbide semi-insulating substrate, as shown in 2e.

[0051] At a vacuum degree of 1×10 -5 In an argon atmosphere at 1 Pa, the magnetron sputtering pressure was set to 1 Pa, and the sputtering power to 5 W / cm². 2 Under the specified process conditions, Al was sputtered and deposited to form an Al nanometal layer with a thickness of 200 nm.

[0052] Step 6: Prepare an Al nanosphere array on a silicon carbide semi-insulating substrate, as shown in 2f.

[0053] The blue film is attached to the surface of the Al nano metal layer, and then peeled off, removing most of the metal layer in the non-nano microsphere array pattern area. The semi-insulating substrate is then immersed in the stripping solution for 600 seconds to remove the remaining metal layer in the non-nano microsphere array pattern area.

[0054] Next, the silicon carbide semi-insulating substrate was immersed in acetone, isopropanol, and deionized water for 300s, 180s, and 180s respectively, and then dried with nitrogen to remove residual photoresist and stripping solution.

[0055] Then, the silicon carbide semi-insulating substrate with the metal layer is peeled off to remove the metal layer in the non-nanosphere array pattern area, forming a rectangular equally spaced Al nanosphere array with a diameter of 200 nm.

[0056] Step 7: Weld external connecting electrodes to form a photoconductive switch, as shown in 2g.

[0057] Two Cu metal sheets, each 10 mm long, 5 mm wide, and 0.05 mm thick, were selected as external connecting electrodes. One of them was welded to the left half of the left metal electrode, and the other was welded to the right half of the right metal electrode, thus completing the fabrication of the photoconductive switch.

[0058] Example 2: A photoconductive switch with a 250 nm diameter nanosphere array and Cu material was fabricated on a gallium arsenide semi-insulating substrate, consisting of a Ni / Ti / Au metal layer as the metal electrode, a Cu / Au metal layer as the external connecting electrode, and a gallium arsenide semi-insulating substrate.

[0059] Step 1: Fabricate electrode patterns on a gallium arsenide semi-insulating substrate, as shown in 2a.

[0060] The specific implementation of this step is the same as step 1 in Example 1.

[0061] Step 2: Prepare an electrode metal layer on a gallium arsenide semi-insulating substrate, as shown in 2b.

[0062] For the gallium arsenide semi-insulating substrate with two electrode patterns, a 500 nm thick layer of Ni metal is first evaporated, and then the substrate is placed in a vacuum of 5 × 10⁻⁶. -5 In an argon atmosphere at 1.5 Pa, with a magnetron sputtering pressure of 1.5 Pa and a sputtering power of 5 W / cm², 2 Under the specified process conditions, Ti / Au metals were sequentially sputtered and deposited with thicknesses of 500 nm and 1000 nm to form metal layers.

[0063] Step 3: Fabricate a metal electrode on a gallium arsenide semi-insulating substrate, as shown in 2c.

[0064] The specific implementation of this step is the same as step 3 in Example 1.

[0065] Step 4: Fabricate a nanosphere array pattern on a gallium arsenide semi-insulating substrate, as shown in 2d.

[0066] 4.1) Spin-coat a layer of polymethyl methacrylate on a gallium arsenide semi-insulating substrate between two metal electrodes, and press a template with a 250 nm rectangular equally spaced nanosphere array pattern onto the uniformly distributed polymethyl methacrylate using a pressure of 0.8 Pa.

[0067] 4.2) Irradiate polymethyl methacrylate with ultraviolet light for 300s. After the polymethyl methacrylate undergoes a cross-linking reaction and is completely cured, remove the template and demold to obtain a rectangular array of equally spaced microspheres with a diameter of 250nm.

[0068] 4.3) Use an etching process to remove the residual polymethyl methacrylate in the grooves of the microsphere array on the substrate to form a rectangular microsphere array pattern with a diameter of 250 nm.

[0069] Step 5: Prepare Cu nanometal layer on gallium arsenide semi-insulating substrate, as shown in 2e.

[0070] At a vacuum degree of 5×10 -5 In an argon atmosphere at 0.8 Pa, the magnetron sputtering pressure was set to 0.8 Pa and the sputtering power to 5 W / cm². 2 Under the specified process conditions, Cu nanometal layers were formed by sputtering deposition with a thickness of 250 nm.

[0071] Step 6: Fabricate Cu nanosphere arrays on gallium arsenide semi-insulating substrates, as shown in 2f.

[0072] The specific implementation of this step is the same as step 6 in Example 1.

[0073] Step 7: Weld external connecting electrodes to form a photoconductive switch, as shown in 2g.

[0074] Two Cu / Au metal layer sheets with a length of 6 mm, a width of 3 mm, and a layer thickness of 0.05 mm and 0.001 mm respectively were selected as external connecting electrodes. One of them was welded to the left half of the left metal electrode and the other was welded to the right half of the right metal electrode to complete the fabrication of the photoconductive switch.

[0075] Example 3: A photoconductive switch with a Ni / Au metal layer as the metal electrode, Au as the external connecting electrode, and Ag as the material of the nanosphere array with a diameter of 150 nm was fabricated on a gallium nitride semi-insulating substrate.

[0076] Step A: Prepare an electrode pattern on a semi-insulating substrate, as shown in 2a.

[0077] The specific implementation of this step is the same as step 1 in Example 1.

[0078] Step B: Prepare an electrode metal layer on a gallium nitride semi-insulating substrate, as shown in 2b.

[0079] A 500 nm thick Ni metal layer was first evaporated onto a gallium nitride semi-insulating substrate with two electrode patterns.

[0080] Then, at a vacuum degree of 2×10 -5 Au was magnetron sputtered to a thickness of 1000 nm in an argon atmosphere at pressure 1.2 Pa to form a metal layer. The magnetron sputtering process parameters were: gas pressure 1.2 Pa and sputtering power 5 W / cm². 2 .

[0081] Step C: Fabricate a metal electrode on a gallium nitride semi-insulating substrate, as shown in 2c.

[0082] The specific implementation of this step is the same as step 3 in Example 1.

[0083] Step D: Fabricate a nanosphere array pattern on a gallium nitride semi-insulating substrate, as shown in 2d.

[0084] D1) Spin-coat a layer of polymethyl methacrylate on a gallium nitride semi-insulating substrate between two metal electrodes, and press a template with a 150 nm rectangular equally spaced nanosphere array pattern onto the uniformly distributed polymethyl methacrylate using a pressure of 0.8 Pa.

[0085] D2) Irradiate polymethyl methacrylate with ultraviolet light for 250s. After the polymethyl methacrylate undergoes a cross-linking reaction and is completely cured, remove the template and demold to obtain a rectangular microsphere array groove with equal spacing.

[0086] D3) Use an etching process to remove the residual polymethyl methacrylate in the grooves of the microsphere array on the substrate, forming a rectangular, equally spaced microsphere array pattern with a diameter of 150 nm.

[0087] Step E: Prepare an Ag nanometal layer on a gallium nitride semi-insulating substrate, as shown in 2e.

[0088] At a vacuum degree of 2×10 -5 Ag nanolayers with a thickness of 150 nm were formed by magnetron sputtering in an argon atmosphere at a pressure of 1.2 Pa. 2 .

[0089] Step F: Prepare an array of Ag nanospheres on a gallium nitride semi-insulating substrate, as shown in 2f.

[0090] The specific implementation of this step is the same as step 6 in Example 1.

[0091] Step G: Weld external connecting electrodes to form a photoconductive switch, as shown in 2g.

[0092] Two Cu metal sheets, each 8 mm long, 4 mm wide, and 0.05 mm thick, were selected as external connecting electrodes.

[0093] One of the external connecting electrodes is welded to the left half of the left metal electrode, and the other external connecting electrode is welded to the right half of the right metal electrode, thus completing the fabrication of the photoconductive switch.

[0094] The above descriptions are merely a few specific examples of the present invention and do not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure of the present invention. For example, in addition to silicon carbide, gallium arsenide, and gallium nitride used in this example, gallium oxide and diamond can also be used as the material for the semi-insulating substrate; in addition to the Ni / Ti / Pt / Au composite metal layer, Ti / Pt / Au composite metal layer, and Ni / Au composite metal layer used in this example, any one of Ti / Pt / Au composite metal layer and W / Ti / Au composite metal layer can also be used as the material for the metal electrode; the diameter of the nanospheres and the size of the external connecting electrodes can be changed according to the wavelength of the actual pulsed laser and the size of the metal electrodes, in addition to the parameters used in Examples 1 to 3. However, these modifications and changes based on the ideas of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A photoconductive switch based on a nanosphere array, comprising a semi-insulating substrate (1), two metal electrodes (2) and two external connection electrodes (3), characterized in that: The semi-insulating substrate (1) has a nano-microsphere array (4) distributed on the surface of the light incident side to change the propagation path of light on the device surface and the electromagnetic field distribution, thereby increasing the interaction length and probability between light and matter; The nano-microsphere array (4) is arranged in a two-dimensional manner and in a rectangular shape, and the distance between every two adjacent microspheres is the same, so as to better match the strip-shaped light spot and improve the light energy utilization rate.

2. The device according to claim 1, characterized in that The nano-microsphere array (4) has a diameter of 50nm to 250nm and is made of any one of Ag, Cu and Al.

3. The device according to claim 1, characterized in that The semi-insulating substrate (1) is a cube with a side length of 6 mm to 14 mm and a thickness of 0.35 mm to 1 mm, and is made of any one of silicon carbide, gallium nitride, gallium arsenide, gallium oxide, and diamond.

4. The device according to claim 1, characterized in that The two metal electrodes (2) are located on the same side or different sides of the semi-insulating substrate, one is located on the left side of the substrate and the other is located on the right side, the horizontal distance between the two is 1 mm to 8 mm, and they are in ohmic contact with the semi-insulating substrate; Each metal electrode is made of one of a Ni / Ti / Pt / Au composite metal layer, a Ti / Pt / Au composite metal layer, a W / Ti / Au composite metal layer, a Ni / Ti / Au composite metal layer or a Ni / Au composite metal layer.

5. The device according to claim 1, characterized in that The two external connection electrodes (3) are respectively located on the surfaces of the two metal electrodes and are both made of copper, gold or copper-gold material with a length of 6 mm to 10 mm, a width of 3 mm to 7 mm and a thickness of 0.05 mm to 0.1 mm.

6. A method for preparing a photoconductive switch based on a nanosphere array, characterized in that: The steps include: S1: Clean the semi-insulating substrate 1, then evenly apply photoresist on the front side thereof, expose and develop the front side through a mask with a prepared pattern, and prepare a required electrode pattern. S2: Evaporating and sputtering metal on the semi-insulating substrate with the electrode pattern prepared thereon to form a metal layer. S3: Peeling off the semi-insulating substrate prepared with the metal layer to remove the metal layer in the non-electrode pattern area to form a metal electrode 2. S4: Prepare the required nanosphere array pattern on the light-incident side of the semi-insulating substrate through ultraviolet nanoimprinting technology. S5: sputtering metal on the side where the nano-microsphere array pattern is prepared to form a nano-metal layer. S6: peeling off the light-incident side of the semi-insulating substrate on which the nano-metal layer is prepared, removing the metal in the non-nano-microsphere array pattern area, and forming a nano-microsphere array 4. S7: Weld external connection electrodes 3 on the metal electrodes, one of which is welded to the left half of the left metal electrode, and the other is welded to the right half of the right metal electrode, to form a photoconductive switching device.

7. The method according to claim 6, characterized in that In step S1, the semi-insulating substrate is cleaned by sequentially placing the semi-insulating substrate into BOE solution, deionized water, acetone, isopropanol, and deionized water for ultrasonic cleaning for 120s, 180s, 600s, 180s, and 180s, respectively.

8. The method according to claim 6, characterized in that In step S4, the desired nanosphere array pattern is prepared on the light incident side of the semi-insulating substrate by using ultraviolet nanoimprint technology, and the implementation includes the following: A layer of polymethyl methacrylate is spin-coated on the semi-insulating substrate between the electrodes, and the template is pressed onto the evenly distributed polymethyl methacrylate with a pressure of 0.5 Pa to 1 Pa; Then, the polymethyl methacrylate is irradiated with ultraviolet light for 30s to 300s, and after the polymethyl methacrylate undergoes a cross-linking reaction and is completely cured, the template is removed and demoulded; The residual polymethyl methacrylate in the grooves on the substrate is then removed by an etching process to form a nano-microsphere array pattern.

9. The method according to claim 6, characterized in that In step S6, the light incident side of the semi-insulating substrate on which the nano-metal layer is prepared is stripped to remove the metal layer in the non-electrode pattern area, and the implementation includes the following steps: First, a blue film is attached to the semi-insulating surface, and then it is torn off to remove most of the metal layer in the non-electrode pattern area; then the front side of the semi-insulating substrate is immersed in a stripping solution for 600 seconds to remove the residual metal layer in the non-electrode pattern area; Then, the semi-insulating substrate was immersed in acetone, isopropanol, and deionized water for 300 s, 180 s, and 180 s, respectively, and then dried with nitrogen to remove residual photoresist and stripping solution.

10. The method according to claim 6, characterized in that The steps S2 and S5 are to sputter the semi-insulating substrate by placing the semi-insulating substrate wafer in a vacuum chamber filled with argon gas at a degree of vacuum better than 5×10 -4 Pa environment, the magnetron sputtering gas pressure is set to 0.5Pa~1.5Pa, and the sputtering power is 5W / cm 2 , sputtering deposition is carried out on different target materials in turn.

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