Si nanowire array-4H-SiC nanowire array, preparation method thereof and application in ultraviolet photodetector

Abstract

The present invention belongs to the field of optoelectronic technology, specifically, a Si nanowire array-4H-SiC nanowire array, a preparation method thereof and an application in an ultraviolet photodetector. The ultraviolet photodetector comprises, from bottom to top, a metal electrode, a single crystal Si substrate, a Si nanowire array, a 4H-SiC nanowire array and a metal electrode. The preparation of the ultraviolet photodetector comprises the following steps: (1) pretreatment of silicon carbide and silicon single crystal wafer; (2) growth and transfer of silicon carbide nanowire array; (3) growth of silicon nanowire array; (4) welding of silicon nanowire array and silicon carbide nanowire array to prepare an ultraviolet photodetector. The preparation method of the ultraviolet photodetector of the present invention is simple and low in cost. The pn junction structure formed by the Si-4H-SiC nanowire array has a high responsiveness, improves light utilization, and can greatly increase the detection performance of the ultraviolet photodetector.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic technology, and specifically relates to a Si nanowire array-4H-SiC nanowire array, a preparation method thereof and an application in an ultraviolet photoelectric detector. Background Art

[0002] With the progress of contemporary science and technology and the development of optical communication technology, the application fields of optoelectronic technology are becoming more and more extensive. Among them, ultraviolet detection technology is a new detection technology developed after infrared detection. It is mainly used in biochemical detection, combustible gas tail flame detection and other fields. At the same time, ultraviolet communication is also a means of information transmission with great development potential. Up to now, commercialized ultraviolet detectors are mainly based on semiconductor inorganic materials, among which materials such as SiC with small thermal expansion coefficient and good wear resistance and Si with abundant production and high conductivity have good application prospects.

[0003] Among low-dimensional nanomaterials, nanowire arrays are the most mature and commercially valuable nanostructures. Semiconductor nanowire arrays perpendicular to the electrodes have high photogenerated electron transmission efficiency, highly ordered orientation structure, and large specific surface area. High-quality nanowire arrays grown by doping with metal and non-metal elements can be widely used in device preparation and other superior properties, making them a research hotspot in the field of new semiconductor materials. Therefore, nanowire arrays are one of the most active research topics in the preparation of photoelectric detection devices.

[0004] However, the ultraviolet photodetectors reported so far are almost all prepared based on a single nanoarray such as zinc oxide and gallium nitride. There are still few reports on ultraviolet photodetectors prepared using different materials and Si nanowire arrays-4H-SiC nanowire arrays. For example, document 1 (Journal of Materials Chemistry C, 2013, 1 (31): 4779-4786) reports a method for preparing SiC nanoarrays for preparing photoelectric devices, but the SiC nanoarrays prepared therein require expensive equipment and complex catalyst assistance, resulting in the following disadvantages in the preparation process: (1) Cracking is required at extremely high temperatures, and ideal experimental conditions are difficult to ensure. (2) Due to the use of catalyst epitaxial growth, it is difficult to achieve industrial mass production. Existing invention patent 1 (patent name: A silicon carbide-germanium / graphene heterojunction photodetector device and its manufacturing method, CN202011598568.X) reports a photoelectric device with a simple structure and stable performance, but the preparation process requires expensive chemical vapor deposition equipment, and the sensitivity of germanium to ultraviolet light is not ideal. Existing invention patent 2 (patent name: A silicon carbide / tin disulfide heterojunction phototransistor and its preparation method and application, CN202110251925.3) uses silicon carbide as a substrate to prepare a photoelectric device composed of two different materials with a heterojunction. However, from the pictures given in the patent, it can be seen that the thickness of the tin disulfide film prepared by this method cannot be guaranteed, and the light absorption capacity of the silicon carbide / tin disulfide heterojunction device needs to be optimized. Document 2 (Scientific Reports, 6 (), 23457) reports a method of preparing a SiC-based photodetector using magnetron sputtering combined with Schottky contact. Although this method can ensure that the device can work normally under high-speed operation, its dark current is too high, resulting in poor sensitivity of the device.

[0005] It can be seen from the above-mentioned invention patents and literature that the process of preparing photodetectors based on different materials has the following disadvantages: (1) The ideal nanowire array needs to be epitaxially grown on the substrate with the help of a catalyst, and the traditional catalyst is difficult to meet the growth of high-quality arrays; (2) The device has poor photoelectric performance, and the heterojunction formed by the nanowire arrays of different materials has a poor bonding effect and cannot maintain an ideal response effect to ultraviolet light; (3) The product cost is high, and most reports require expensive equipment such as chemical vapor deposition systems and complicated preparation processes. It can be seen that the preparation of Si-nanowire array-4H-SiC nanowire array photodetectors still faces many problems to be solved, and a preparation method with simple process, low cost and stable performance is urgently needed to overcome the technical defects of the existing preparation methods. Summary of the invention

[0006] In view of the above-mentioned technical deficiencies, the present invention provides a Si nanowire array-4H-SiC nanowire array, a preparation method thereof and an application in ultraviolet photodetectors. The present invention uses commercial SiC single crystals as raw materials, and prepares 4H-SiC nanowire arrays by anodization; uses single crystal silicon as a substrate, and grows Si nanowire arrays by metal ion-assisted etching, and finally generates Joule heat between two different nanowire arrays through stress and applied voltage to form a pn junction, thereby obtaining a ultraviolet light detector based on Si nanowire array-4H-SiC nanowire array. The present invention provides a photodetector of Si nanowire array-4H-SiC nanowire array with high quality, large output, no need for expensive equipment, safe and easy operation, and high sensitivity. The present invention is expected to solve the bottleneck problem that the current traditional silicon-based photodetector has low photoelectric conversion efficiency under light irradiation and a limited working spectral range.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] The preparation method of Si nanowire array-4H-SiC nanowire array comprises the following steps:

[0009] (1) Sample pretreatment: The n-type 4H-SiC single crystal wafer and the p-type single crystal silicon wafer are respectively subjected to surface cleaning treatment to obtain a treated 4H-SiC single crystal wafer and a treated single crystal silicon wafer;

[0010] (2) Preparation of 4H-SiC nanowire arrays: Anodizing a 4H-SiC single crystal in an electrolyte to grow a 4H-SiC nanowire array, then applying a reverse DC voltage for 20-60 seconds, which is a pretreatment for mechanical exfoliation of the nanowire array, and then mechanical exfoliating to obtain a 4H-SiC nanowire array;

[0011] (3) Preparation of Si nanowire arrays: depositing metal nanoparticles on the surface of a processed single crystal silicon wafer, then etching and growing them in a sealed environment, and then removing the surface metal ions to obtain a Si nanowire array;

[0012] (4) Preparation of Si nanowire array-4H-SiC nanowire array: The 4H-SiC nanowire array of step (2) is transferred to the Si nanowire array of step (3), and a stress of 50-100N is applied in the vertical direction at a temperature of 400-500°C, and the mixture is naturally cooled to room temperature to obtain a Si nanowire array-4H-SiC nanowire array.

[0013] Preferably, the surface cleaning treatment method of the n-type 4H-SiC single crystal in step (1) is: ultrasonically cleaning the n-type 4H-SiC single crystal in acetone, ethanol, and deionized water in sequence, then immersing it in a mixed solution of hydrofluoric acid and ethanol, and then vacuum drying and nitrogen protection to obtain a treated 4H-SiC single crystal.

[0014] Preferably, the surface cleaning treatment method of the p-type single crystal silicon wafer in step (1) is: ultrasonically cleaning the p-type single crystal silicon wafer in acetone, ethanol, and deionized water in sequence, then immersing it in a mixed solution of concentrated sulfuric acid and H2O2, and then immersing it in an HF solution to remove surface oxides, thereby obtaining a treated single crystal silicon wafer.

[0015] Preferably, the electrolyte in step (2) consists of hydrofluoric acid solution, ethanol solution and hydrogen peroxide, the volume fraction of the hydrofluoric acid solution is 40%, the volume fraction of the ethanol solution is 99%, the volume fraction of the hydrogen peroxide is 30%, and the volume ratio of the three is 2-7:6:1.

[0016] Preferably, the method of anodization in step (2) is: adjusting the duty cycle of the pulse power supply to 30-50%, fixing the voltage to 15V, the cycle to 0.8ms, and the reaction time to 6-10min.

[0017] Preferably, the metal nanoparticles in step (3) are Ag nanoparticles, and the deposition method is: placing the treated single crystal silicon wafer with the surface oxide removed into a mixed solution of silver nitrate and hydrofluoric acid to deposit the silver nanoparticles for a deposition time of 60-120 seconds;

[0018] Wherein, the molar ratio of silver nitrate to hydrofluoric acid is 0.01-0.05:4.6.

[0019] Preferably, the method for etching growth in a sealed environment in step (3) is: at room temperature, a single crystal silicon wafer sample on which metal nanoparticles have been deposited is placed in a polytetrafluoroethylene beaker filled with a mixed solution of HF and H2O2, and sealed to etch the Si nanowire array, wherein the volume fractions of HF and H2O2 are 8-12% and 1-2% respectively, and the etching time is 40-50 min.

[0020] Preferably, the method for removing surface metal ions in step (3) is: placing the etched single crystal silicon wafer into a remover and soaking it for 100-140 minutes, wherein a nitric acid solution with a concentration of 6.5-7.5 mol / L is used as the remover.

[0021] The present invention also protects a Si nanowire array-4H-SiC nanowire array prepared by the preparation method, wherein the Si nanowire array-4H-SiC nanowire array has a thickness of 10-50 μm, a thickness of 10-50 μm for the Si nanowire array, and a thickness of the single crystal silicon substrate of 200-400 μm.

[0022] The present invention also protects the use of Si nanowire array-4H-SiC nanowire array in the preparation of ultraviolet photodetectors, characterized in that the ultraviolet photodetectors are prepared according to the following steps:

[0023] Conductive silver paste is coated on the 4H-SiC nanowire array, and conductive silver paste is coated on the single crystal silicon substrate or aluminum film is deposited and used as metal electrodes. The two metal electrodes are connected to the wire together, and then a voltage of 60V is applied. The Joule heat generated by the current is used to weld the array tip. The welding time is 30-60 minutes.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The ultraviolet photodetector prepared by the present invention comprises two metal electrodes, between which are connected, from top to bottom, a 4H-SiC nanowire array, a pn junction formed by the nanowire array, a silicon nanowire array, and a single crystal silicon substrate. The thickness of the silicon carbide nanowire array is 10-50 μm, the thickness of the silicon nanowire array is 10-50 μm, and the thickness of the single crystal silicon substrate is 200-400 μm.

[0026] 2. The photoelectric detection device of Si nanowire array-4H-SiC nanowire array prepared by the present invention optimizes the catalyst ratio to carry out epitaxial growth of nanowire array, which solves the current technical problem of poor growth quality of nanowire array. It has stable performance, strong process controllability and simple preparation process, and is expected to obtain large-area, low-power consumption photoelectric detection devices.

[0027] 3. In the preparation process of the present invention, the pn structure formed by the prepared Si nanowire array-4H-SiC nanowire array utilizes the rapid flow of tip contact current between nanoarrays to generate Joule heat to promote the efficient combination of different nanoarrays, and has excellent photoelectric detection performance, not only with high detection rate and high response speed, but also can achieve a wider spectral response range. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a structural diagram of the Si nanowire array-4H-SiC nanowire array ultraviolet photodetector prepared in Examples 1-3 of the present invention;

[0029] Figure 2This is a SEM image of the SiC nanowire array prepared in Example 1 of the present invention at a scale of 30 μm;

[0030] Figure 3 This is a SEM image of the Si nanowire array prepared in Example 1 of the present invention at a scale of 50 μm;

[0031] Figure 4 This is an IV curve of the Si nanowire array-4H-SiC nanowire array ultraviolet photodetector prepared in Example 2 of the present invention under a 365nm excitation light source;

[0032] Figure 5 This is an IT curve diagram of the Si nanowire array-4H-SiC nanowire array ultraviolet photodetector prepared in Example 3 of the present invention under a 365nm excitation light source and 0V. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0034] Example 1

[0035] The preparation method of Si nanowire array-4H-SiC nanowire array comprises the following steps:

[0036] (1) Sample pretreatment of n-type 4H-SiC single crystal: A commercial n-type 4H-SiC single crystal was used as the raw material, wherein the mass fraction of N doping was 9.8%, and it was cut into 2 cm × 2 cm single crystal pieces using a silicon knife, and then cleaned; the specific cleaning method is: the n-type 4H-SiC single crystal piece was ultrasonically cleaned in acetone, ethanol, and deionized water for 15 min in turn to make the sample surface cleaner; then the clean n-type 4H-SiC single crystal piece was immersed in a mixed solution of hydrofluoric acid and ethanol with a volume ratio of 1:1.2 for 2 min to remove the oxide formed on the surface of the n-type 4H-SiC single crystal piece; after taking out the cleaned n-type 4H-SiC single crystal piece, it was dried in a vacuum drying oven at 50°C for 10 min, and after drying, it was stored in a centrifuge tube filled with nitrogen to prevent oxidation of the sample surface, thereby obtaining a treated 4H-SiC single crystal piece;

[0037] Sample pretreatment of p-type single crystal silicon wafers: a low-doped p-type double-sided polished single crystal silicon wafer with a thickness of 300 μm and a resistivity of 1 Ω·cm was placed in acetone, ethanol, and pure water for ultrasonic cleaning in turn, and the cleaned p-type single crystal silicon wafer was placed in a solution of H2SO4 (volume fraction of 98%) and H2O2 (volume fraction of 35%) with a volume ratio of 2:1 and immersed for 35 minutes at room temperature, and then placed in a 5% HF solution with a volume fraction and immersed for 5 minutes to remove the surface oxide, thereby obtaining a treated single crystal silicon wafer;

[0038] (2) preparing the electrolyte required for growing 4H-SiC nanowire arrays: using 40% hydrofluoric acid solution, 99% ethanol solution and 30% hydrogen peroxide solution by volume, and uniformly mixing the solution in a volume ratio of 3:6:1 as the electrolyte, adding TritonX-100 in a volume fraction of 0.012%; then heating to 60°C until the temperature of the electrolyte stabilizes, and then adding hydrochloric acid to the electrolyte in an amount of 0.5 mL of hydrochloric acid per 30 mL of electrolyte. The role of hydrochloric acid is to optimize the electrolyte configuration scheme and prepare higher quality nanoarrays;

[0039] (3) Preparation of 4H-SiC nanowire arrays: An anodization experiment was performed on the 4H-SiC single crystal chips treated in step (1) in the electrolyte of step (2), specifically: some parameters of the power supply were set to fixed values, the duty cycle of the pulse power supply was adjusted to 30%, the voltage was fixed to 15V, the cycle was 0.8ms, the reaction time was 6min, and then the pulse current was changed to a reverse DC voltage, and etching was performed for 20s to pre-treat the nanoarray for mechanical exfoliation, and then the 4H-SiC nanowire array was exfoliated from the 4H-SiC single crystal chip to obtain a 4H-SiC nanowire array with a diameter of 30nm;

[0040] The mechanical peeling method is: using double-sided tape to peel off a large-area 4H-SiC nanowire array film from a 4H-SiC single crystal small chip substrate, and then removing the double-sided tape with ethanol to obtain a 4H-SiC nanowire array;

[0041] (4) Preparation of silicon substrate for growing Si nanowire array: Silicon nanowire array was prepared by metal-assisted chemical etching, specifically, the p-type single crystal silicon wafer cleaned in step (1) was placed in a mixed solution containing AgNO3 (0.01 mol / L) and HF (4.6 mol / L), and Ag nanoparticles were deposited for 60 s. After taking out, the silicon wafer was placed in pure water. At room temperature, the silicon wafer sample on which Ag nanoparticles had been deposited was placed in a polytetrafluoroethylene beaker containing a mixed solution of HF and H2O2, and sealed to etch the Si nanowire array, wherein the volume fractions of HF and H2O2 were 8% and 1%, respectively, and the etching time was 45 min.

[0042] The sample after etching was placed in a HNO3 solution with a molar concentration of 6.5 mol / L and immersed in dark for 100 minutes to remove the silver particles on the surface, and then the sample was taken out from the nitric acid solution, and the residual nitric acid solution on the sample was removed by slowly rinsing with deionized water, and the sample was dried with a nitrogen breeze to obtain a silicon substrate for growing Si nanowire arrays with a diameter of 80 nm and a length of 15 μm;

[0043] (5) Preparation of Si nanowire array-4H-SiC nanowire array: The 4H-SiC nanowire array was transferred to the silicon substrate on which the Si nanowire array was grown. The temperature was set to 400°C and a stress of 50N was applied for preliminary nanoarray connection. The array was naturally cooled to room temperature to obtain a Si nanowire array-4H-SiC nanowire array.

[0044] Preparation of ultraviolet photodetector based on Si nanowire array-4H-SiC nanowire array: The surface of 4H-SiC nanowire array is coated with conductive silver paste, and the wires are led out. A layer of aluminum film is deposited on the silicon wafer substrate by thermal evaporation. The total thickness of the ultraviolet photodetector is 450nm, and it is annealed in a nitrogen atmosphere at 400°C for 40s. Electrodes are prepared with a window area of ​​1cm×1cm as electrodes, and wires are led out. Then, in a nitrogen atmosphere, a Keithley2450 instrument is used to periodically apply a 50V voltage to the device to connect the nanoarrays for 40 minutes. Joule heat is used to weld the tips of the nanoarrays until the current is stable and packaged, completing the ultraviolet photodetector device based on the Si nanowire array-4H-SiC nanowire array.

[0045] Example 2

[0046] The preparation method of Si nanowire array-4H-SiC nanowire array comprises the following steps:

[0047] The preparation step (1) is the same as that of Example 1, except that:

[0048] (2) preparing the electrolyte required for growing 4H-SiC nanowire arrays: preparing 40% hydrofluoric acid solution, 99% ethanol solution and 30% hydrogen peroxide solution respectively by volume fraction, and uniformly mixing the solution in a volume ratio of 2:6:1 as the electrolyte, adding TritonX-100 in a volume fraction of 0.05% to the electrolyte; then heating to 70°C until the temperature of the electrolyte stabilizes, and then adding hydrochloric acid to the electrolyte in an amount of: adding 1.0 mL of hydrochloric acid to every 30 mL of the electrolyte;

[0049] (3) Preparation of 4H-SiC nanowire arrays: An anodic oxidation experiment was performed on a 4H-SiC single crystal wafer. Specifically, some parameters of the power supply were set to fixed values, the duty cycle of the pulse power supply was adjusted to 40%, the voltage was fixed to 15 V, the cycle was 0.8 ms, the reaction time was 8 min, and then the pulse current was changed to a reverse DC voltage, and etching was performed for 30 s to obtain a 4H-SiC nanowire array with a diameter of 35 nm.

[0050] The 4H-SiC nanowire array is peeled off from the 4H-SiC single crystal chip. The peeling method is: using double-sided tape to peel off a large area of ​​4H-SiC nanowire array film from the 4H-SiC single crystal chip substrate, and then removing the double-sided tape with ethanol to obtain the 4H-SiC nanowire array;

[0051] (4) Preparation of silicon substrate for growing Si nanowire array: Silicon nanowire array was prepared by metal-assisted chemical etching, specifically, the p-type single crystal silicon wafer cleaned in step (1) was placed in a mixed solution containing AgNO3 (0.03 mol / L) and HF (4.6 mol / L), and Ag nanoparticles were deposited for 90 seconds. After taking out, the silicon wafer was placed in pure water. At room temperature, the silicon wafer sample on which Ag nanoparticles had been deposited was placed in a polytetrafluoroethylene beaker containing a mixed solution of HF and H2O2, and sealed to etch the Si nanowire array, wherein the volume fractions of HF and H2O2 were 10% and 1.5%, respectively, and the etching time was 50 minutes.

[0052] The sample after etching was placed in a HNO3 solution with a molar concentration of 7.0 mol / L and immersed in dark for 120 min to remove the silver particles on the surface, and then the sample was taken out from the nitric acid solution, and the residual nitric acid solution on the sample was removed by slowly rinsing with deionized water, and the sample was dried with a nitrogen breeze to obtain a silicon substrate for growing Si nanowire arrays with a diameter of 90 nm and a length of 20 μm;

[0053] (5) Preparation of Si nanowire array-4H-SiC nanowire array: The 4H-SiC nanowire array was transferred to the silicon substrate on which the Si nanowire array was grown. The temperature was set to 450°C and a stress of 75N was applied for preliminary nanoarray connection. The nanowire array was naturally cooled to room temperature to obtain a Si nanowire array-4H-SiC nanowire array.

[0054] Preparation of ultraviolet photodetector device based on Si nanowire array-4H-SiC nanowire array: The front side of Si nanowire array-4H-SiC nanowire array is coated with conductive silver paste, and the wires are led out. A layer of aluminum film is deposited on the back side of the silicon wafer by thermal evaporation. The total thickness of the ultraviolet photodetector is 500nm, and it is annealed in a nitrogen atmosphere at 500°C for 60s. Electrodes are prepared with a window area of ​​1cm×1cm as the electrode, and wires are led out. Then, in a nitrogen atmosphere, a Keithley2450 instrument is used to periodically apply a voltage of 75V to the device to connect the nanoarrays for 30 minutes. Joule heat is used to weld the tips of the nanoarrays until the current is stable and packaged, completing the photodetector device based on the Si nanowire array-4H-SiC nanowire array.

[0055] Example 3

[0056] The preparation method of Si nanowire array-4H-SiC nanowire array comprises the following steps:

[0057] The preparation step (1) is the same as that of Example 1, except that:

[0058] (2) preparing the electrolyte required for growing 4H-SiC nanowire arrays: preparing 40% hydrofluoric acid solution, 99% ethanol solution and 30% hydrogen peroxide solution respectively, and uniformly mixing the solution in a volume ratio of 7:6:1 as the electrolyte, adding TritonX-100 in a volume fraction of 0.12% to the electrolyte, and then heating to 80°C until the temperature of the electrolyte stabilizes, and then adding hydrochloric acid to the electrolyte in an amount of: adding 1.5 mL of hydrochloric acid to every 30 mL of the electrolyte;

[0059] (3) Preparation of 4H-SiC nanowire arrays: An anodization experiment was conducted on a small n-type 4H-SiC single crystal wafer. Specifically, some parameters of the power supply were set to fixed values, the duty cycle of the pulse power supply was adjusted to 50%, the voltage was fixed to 15 V, the cycle was 0.8 ms, the reaction time was 10 min, and then the pulse current was changed to a reverse DC voltage, and etching was performed for 50 s to obtain a 4H-SiC nanowire array with a diameter of 40 nm.

[0060] The 4H-SiC nanowire array is peeled off from the n-type 4H-SiC single crystal chip. The peeling method is: using double-sided tape to peel off a large area of ​​4H-SiC nanowire array film from the n-type 4H-SiC single crystal chip substrate, and then removing the double-sided tape with ethanol to obtain the 4H-SiC nanowire array;

[0061] (4) Preparation of silicon substrate for growing Si nanowire array: Silicon nanowire array was prepared by metal-assisted chemical etching, specifically, the p-type single crystal silicon wafer cleaned in step (1) was placed in a mixed solution containing AgNO3 (0.05 mol / L) and HF (4.6 mol / L), and Ag nanoparticles were deposited for 120 s. After taking out, the silicon wafer was placed in pure water. At room temperature, the silicon wafer sample on which Ag nanoparticles had been deposited was placed in a polytetrafluoroethylene beaker containing a mixed solution of HF and H2O2, and sealed to etch the Si nanowire array, wherein the volume fractions of HF and H2O2 were 12% and 2.0%, respectively, and the etching time was 60 min.

[0062] The sample after etching was placed in a HNO3 solution with a molar concentration of 7.5 mol / L and immersed in the dark for 140 min to remove the silver particles on the surface, and then the sample was taken out from the nitric acid solution, and the residual nitric acid solution on the sample was removed by slowly rinsing with deionized water, and the sample was dried with a nitrogen breeze to obtain a silicon substrate for growing Si nanowire arrays with a diameter of 100 nm and a length of 25 μm;

[0063] (5) Preparation of Si nanowire array-4H-SiC nanowire array: The 4H-SiC nanowire array was transferred to the silicon substrate on which the Si nanowire array was grown, the temperature was set to 500°C, and a stress of 100N was applied for preliminary nanoarray connection, and the array was naturally cooled to room temperature to obtain the Si nanowire array-4H-SiC nanowire array.

[0064] Preparation of photoelectric detection device based on Si nanowire array-4H-SiC nanowire array: The front side of Si nanowire array-4H-SiC nanowire array is coated with conductive silver paste, and the wires are led out. A layer of aluminum film is deposited on the back side of the silicon wafer by thermal evaporation. The total thickness of the ultraviolet photodetector is 550nm, and the electrode is prepared by annealing at 600℃ in a nitrogen atmosphere for 80s. A window area of ​​1cm×1cm is used as the electrode, and the wires are led out. Then, in a nitrogen atmosphere, a Keithley2450 instrument device is used to periodically apply a voltage of 100V to connect the nanoarrays for 20 minutes. The nanoarray tip is welded using Joule heat until the current is stable and packaged, completing the photoelectric detection device based on the Si nanowire array-4H-SiC nanowire array.

[0065] Research Methods: Electrical and optoelectronic measurements of the fabricated devices were performed using a four-probe station combined with a semiconductor characterization system (Keithley4200-CSC), and these data were recorded using a computer controlled by a Labview program. The light source was a 365nm UV lamp, and the light intensity was measured using a CEL-NP2000 power meter.

[0066] Results and Discussion

[0067] Figure 1 This is a structural diagram of an ultraviolet photodetector device based on the Si nanowire array-4H-SiC nanowire array pn junction prepared in Example 1 of the present invention.

[0068] Figure 2 This is the SEM image of the SiC nanowire array prepared in the present invention at a scale of 30 μm. Figure 2 The results show that perfectly aligned and vertically oriented SiC nanowire array structures with uniform length of 35 μm were prepared. The layered structure in the SiC nanowire array is inferred to be caused by the DC current etching SiC from the matrix during the electrochemical corrosion process.

[0069] Figure 3 This is the SEM image of the Si nanowire array prepared in the present invention at a scale of 50 μm. Figure 3 The results demonstrate the preparation of fairly uniform, high-density, large-scale and well-aligned Si nanowire arrays.

[0070] Figure 4 This is the IV curve of the Si nanowire array-4H-SiC nanowire array ultraviolet photodetector prepared in the present invention in the dark state and under a 365nm excitation light source. Figure 4 The results show that the dark current is symmetrical and linear in the dark state, indicating that ohmic contact occurs between the pn junction nanowire array and the metal electrode. -2 ) and an applied voltage of 1.0V, the device current at both ends of the pn junction nanowire array increased significantly from 6.58nA (dark condition) to 81.2nA. ​​This shows that the prepared Si nanowire array-4H-SiC nanowire array pn junction UV photodetector can be highly sensitive to UV light and has enhanced performance, which can be attributed to the nanowire array having a higher specific surface area, lower oxygen vacancy density, lower reflectivity and enhanced UV light absorption, and on the other hand, it can be attributed to the effective separation of photogenerated carriers by the formed pn junction.

[0071] Figure 5 The IT curve of the Si nanowire array-4H-SiC nanowire array ultraviolet photodetector prepared by the present invention under 365nm excitation light source and 0V, Figure 5 The results show that the prepared Si nanowire array-4H-SiC nanowire array pn junction UV photodetector can achieve sensitive detection of 365nm UV light at 0V and has self-powered characteristics. The fast switching performance in the on and off states shows that the constructed pn junction UV photodetector can have excellent stability and reproducibility.

[0072] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and variations. The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and their protection scope is not limited thereto. Equivalent substitutions or changes made by those skilled in the art on the basis of the present invention are all within the protection scope of the present invention, and the protection scope of the present invention shall be subject to the claims.

Claims

1. A method for preparing Si nanowire array-4H-SiC nanowire array, characterized in that: The steps include: (1) Sample pretreatment: The n-type 4H-SiC single crystal wafer and the p-type single crystal silicon wafer are respectively subjected to surface cleaning treatment to obtain a treated 4H-SiC single crystal wafer and a treated single crystal silicon wafer; (2) Preparation of 4H-SiC nanowire arrays: Anodizing a 4H-SiC single crystal wafer in an electrolyte to grow a 4H-SiC nanowire array, then applying a reverse DC voltage for 20-60 seconds, and then mechanically exfoliating to obtain a 4H-SiC nanowire array; (3) Preparation of Si nanowire arrays: depositing metal nanoparticles on the surface of a processed single crystal silicon wafer, then etching and growing them in a sealed environment, and then removing the surface metal ions to obtain a Si nanowire array; (4) Preparation of Si nanowire array-4H-SiC nanowire array: The 4H-SiC nanowire array of step (2) is transferred to the Si nanowire array of step (3), and a stress of 50-100N is applied in the vertical direction at a temperature of 400-500°C, and the mixture is naturally cooled to room temperature to obtain a Si nanowire array-4H-SiC nanowire array.

2. The method for preparing the Si nanowire array-4H-SiC nanowire array according to claim 1, characterized in that: The surface cleaning treatment method of the n-type 4H-SiC single crystal in step (1) is: ultrasonically cleaning the n-type 4H-SiC single crystal in acetone, ethanol, and deionized water in sequence, then immersing it in a mixed solution of hydrofluoric acid and ethanol, and then vacuum drying and nitrogen protection to obtain a treated 4H-SiC single crystal.

3. The method for preparing the Si nanowire array-4H-SiC nanowire array according to claim 1, characterized in that: The surface cleaning treatment method of the p-type single crystal silicon wafer in step (1) is: ultrasonically cleaning the p-type single crystal silicon wafer in acetone, ethanol, and deionized water in sequence, then soaking it in a mixed solution of concentrated sulfuric acid and H2O2, and then soaking it in an HF solution to remove surface oxides, thereby obtaining a treated single crystal silicon wafer.

4. The method for preparing the Si nanowire array-4H-SiC nanowire array according to claim 1, characterized in that: The electrolyte in step (2) is composed of hydrofluoric acid solution, ethanol solution and hydrogen peroxide, the volume fraction of the hydrofluoric acid solution is 40%, the volume fraction of the ethanol solution is 99%, the volume fraction of the hydrogen peroxide is 30%, and the volume ratio of the three is 2-7:6:

1.

5. The method for preparing the Si nanowire array-4H-SiC nanowire array according to claim 1, characterized in that: The method of anodization in step (2) is as follows: the duty cycle of the pulse power supply is adjusted to 30-50%, the voltage is fixed to 15V, the cycle is 0.8ms, and the reaction time is 6-10min.

6. The method for preparing the Si nanowire array-4H-SiC nanowire array according to claim 1, characterized in that: In step (3), the metal nanoparticles are Ag nanoparticles, and the deposition method is as follows: placing the treated single crystal silicon wafer with the surface oxide removed into a mixed solution of silver nitrate and hydrofluoric acid to deposit the silver nanoparticles for a deposition time of 60-120 seconds; Wherein, the molar ratio of silver nitrate to hydrofluoric acid is 0.01-0.05:4.

6.

7. The method for preparing the Si nanowire array-4H-SiC nanowire array according to claim 1, characterized in that: The method for etching growth in a sealed environment in step (3) is as follows: at room temperature, a single crystal silicon wafer sample on which metal nanoparticles have been deposited is placed in a mixed solution of HF and H2O2, and sealed to etch the Si nanowire array, wherein the volume fractions of HF and H2O2 are 8-12% and 1-2% respectively, and the etching time is 40-50 min.

8. The method for preparing the Si nanowire array-4H-SiC nanowire array according to claim 1, characterized in that: The method for removing surface metal ions in step (3) is: placing the etched single crystal silicon wafer into a remover and soaking it for 100-140 minutes, wherein a nitric acid solution with a concentration of 6.5-7.5 mol / L is used as the remover.

9. A Si nanowire array-4H-SiC nanowire array prepared by the preparation method according to any one of claims 1 to 8, wherein in the Si nanowire array-4H-SiC nanowire array, the thickness of the 4H-SiC nanowire array is 10-50 μm, the thickness of the Si nanowire array is 10-50 μm, and the thickness of the single crystal silicon substrate is 200-400 μm.

10. Use of the Si nanowire array-4H-SiC nanowire array according to claim 9 in preparing an ultraviolet photodetector, characterized in that: The ultraviolet photodetector is prepared according to the following steps: Conductive silver paste is coated on the 4H-SiC nanowire array, and conductive silver paste is coated on the single crystal silicon substrate or aluminum film is deposited and used as metal electrodes. The two metal electrodes are connected to the wire together, and then a voltage of 60V is applied. The Joule heat generated by the current is used to weld the array tip. The welding time is 30-60 minutes.

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