ZnO / Si heterojunction self-driven ultraviolet photoelectric detector

Abstract

The invention belongs to the technical field of optical detection, and particularly relates to a ZnO / Si heterojunction self-driven ultraviolet photoelectric detector which sequentially comprises a metal Ag point electrode, an ITO transparent conductive electrode, a ZnO nanoparticle film layer, a Si inverted pyramid substrate and a metal Ag back electrode from top to bottom. Wherein the ZnO nano-particle film layer is prepared by a chemical coprecipitation method, a spin-coating method and the like. The Si inverted pyramid structure substrate is prepared by using a metal auxiliary etching method. Results show that the prepared thin film device shows good self-driven optical detection performance and has the advantages of stable performance, high response speed and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of light detection, and in particular relates to a self-driven photoelectric detector and a preparation method thereof. Background Art

[0002] The development of self-powered photodetectors has important scientific significance and application value. This technology realizes the direct conversion of light energy into electrical energy through the photovoltaic effect (such as photovoltaic effect, thermoelectric effect or piezoelectric effect), without the need for external power drive, thereby significantly improving energy utilization efficiency and reducing system power consumption. Its advantages in miniaturization and integration give it broad application prospects in wearable devices, Internet of Things sensors and on-chip optoelectronic systems. In addition, its self-driving characteristics enable it to demonstrate unique reliability in special scenarios such as extreme environments (such as space and deep-sea exploration) and biomedical implantable devices. Research on self-powered photodetectors not only promotes the development of optoelectronic devices towards low power consumption and self-powered direction, but also provides new solutions for the utilization of renewable energy and the integration of intelligent systems.

[0003] Zinc oxide (ZnO), a wide-bandgap direct-bandgap semiconductor, has attracted considerable attention due to its exceptional physicochemical properties. This material exhibits significant application value in optoelectronic devices, particularly in the fabrication of light-emitting diodes (LEDs), semiconductor lasers, and photodetectors, due to its low-temperature crystallization, tunable etching properties, and excellent chemical and thermal stability (capable of withstanding high-temperature environments). Using silicon substrates as a platform for optoelectronic devices effectively leverages the established complementary metal oxide semiconductor (CMOS) fabrication process, providing a reliable technical path for achieving high-performance optoelectronic integrated systems. This heterogeneous integration strategy not only maintains the scalability of silicon-based electronic devices but also facilitates the development of novel functional devices. Notably, conventional photodetectors are limited by their limited effective photosensitive area, resulting in significant bottlenecks in their photoresponse performance. In recent years, design strategies based on micro- and nanophotonic structures have provided new approaches to address this challenge. By constructing three-dimensional micro- and nanostructures with high surface areas, the interaction between light and matter can be effectively enhanced, significantly improving carrier separation efficiency. Research shows that this structural engineering can not only break through the physical limitations of traditional planar devices, but also achieve the preparation of cost-effective devices through self-driving mechanisms, laying an important foundation for the development of a new generation of intelligent sensing systems. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for producing a ZnO nanoparticle / Si inverted gold character

[0005] A self-powered photodetector with a tower heterojunction and its preparation method can address the mediocre performance issues currently faced by ZnO / Si self-powered photodetectors. This invention addresses the technical issues addressed in achieving the aforementioned objectives by improving the performance of the photodetector through methods such as metal-assisted etching, plasma etching, magnetron sputtering, hydrothermal processing, and chemical co-precipitation. Specifically, a Si inverted pyramid structure is fabricated on a Si surface through methods such as metal-assisted etching and plasma etching; and a ZnO nanoparticle film layer is fabricated on a silicon substrate through magnetron sputtering, hydrothermal processing, and chemical co-precipitation, resulting in a self-powered photodetector with superior performance.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned purpose is a self-driven photodetector based on ZnO nanoparticle / Si pyramid heterojunction, which is characterized by a layered structure, which includes, from top to bottom, a metal Ag point electrode, an ITO transparent conductive electrode, ZnO nanoparticles, a Si inverted pyramid structure single crystal substrate and a metal Ag back electrode.

[0007] A method for preparing a self-driven photodetector based on a ZnO nanoparticle / Si inverted pyramid heterojunction comprises the following steps:

[0008] (1) Substrate cutting and polishing: First, the silicon wafer was cut into the required size (2×2 cm) by laser for subsequent experiments. The cleaned Si substrate was dried; in order to better remove the surface damage layer of the Si substrate, the Si substrate was chemically polished.

[0009] (2) Si substrate cleaning: Before spin coating the ZnO film, we need to clean the chemically polished substrate to remove the metal ions and organic matter remaining on the substrate during the production process;

[0010] (3) Place the dried Si substrate in a mixed solution of Cu(NO3)2, HF and H2O2 at a corrosion temperature of 55°C to 65°C for 4 to 10 minutes, then rinse with deionized water to remove the residual corrosion solution; use 68% concentrated nitric acid to remove the Cu nanoparticles remaining on the surface of the single-crystalline silicon substrate at room temperature for 5 to 8 minutes; then rinse with deionized water to remove the residual concentrated nitric acid; then place the single-crystalline silicon substrate in a 10% HF solution for 5 to 10 minutes to remove the oxide layer naturally formed on the surface of the single-crystalline silicon substrate during the texturing process; then rinse with deionized water to remove the residual HF on the surface of the single-crystalline silicon substrate;

[0011] (4) Slowly add 5-7 g of zinc acetate powder to 100-150 ml of methanol solution, immediately heat the solution to 50-70 degrees Celsius, and continuously stir to obtain a transparent solution 1. Then, dissolve 2-5 g of potassium hydroxide powder in 50-60 ml of methanol at a temperature of 50-70 degrees Celsius and continuously stir to obtain a mixed solution 2. Finally, add solution 2 dropwise to solution 1 under stirring for 10-20 minutes, stir for 1-3 hours, let it stand, cool to room temperature, remove the supernatant, and wash the precipitate with methanol 1-4 times;

[0012] (5) uniformly dispersing the ZnO powder obtained in step (4) in a solvent to obtain a ZnO nanoparticle dispersion;

[0013] (6) The ZnO nanoparticle dispersion obtained in step (5) is evenly spin-coated on the surface of the Si inverted pyramid substrate prepared in step (4).

[0014] (7) The sample obtained in step (6) was placed in a tubular resistance furnace and heat treated in an air atmosphere at a temperature of 200 to 400 degrees Celsius at a temperature increase rate of 5 degrees Celsius per minute. The temperature was maintained at 200 to 400 degrees Celsius for 90 minutes, and then naturally cooled to room temperature.

[0015] (8) Taking out the sample obtained in step (7), placing the sample in a vacuum chamber, using radio frequency magnetron sputtering technology, bombarding a metal ITO target with ionized argon ions, and depositing a metal ITO electrode on the ZnO quantum dot film layer and the Si surface; the ITO target is an ITO non-metallic target with a target purity of 99.99%; using direct current magnetron sputtering technology, bombarding a metal Ag target with ionized argon ions, and depositing a metal Ag electrode on the Si surface; the Ag target is an Ag metal target with a target purity of 99.99%; the argon gas pressure is maintained at 5.0 Pascals, the target spacing is 50 mm, and the deposition temperature of the metal ITO film is 20 to 25 degrees Celsius;

[0016] (9) Metal Cu wires were drawn out using silver paste on the ZnO nanoparticle film layer and the Ag electrode on the Si surface to complete the device preparation.

[0017] Preferably, in step (1), the Si substrate is a P-type Si single crystal substrate with a resistivity of 0.4-1.1 ohm·cm; the specific operation process of the polishing is as follows: preparing an HF solution with a mass fraction of 5 mass percent, placing the divided Si wafer in the solution, and washing for 1 minute to remove the oxide layer on the surface of the Si wafer; placing the Si wafer with the surface oxide layer removed in a 25 mass percent NaOH solution, and polishing at 90°C to remove the damaged layer on the surface of the Si substrate.

[0018] Preferably, in step (2), the cleaning process is the most commonly used RCA (Radio Corporation of American) standard cleaning process in the crystalline silicon solar cell production line. This method was first proposed by the American Radio Corporation. The specific cleaning operation steps are as follows: first, place the polished Si substrate in a 5% by mass HF solution and clean it for 1 minute to remove the oxide layer on the surface of the silicon wafer; then use deionized water (5 megohm cm) to clean the Si substrate for 3 minutes to remove the residual HF solution on the surface; then perform SC-I cleaning, weigh 20 ml of NH4OH, 20 ml of H2O2 and 100 ml of H2O through a measuring cylinder, prepare SC-I cleaning solution, and clean it in a water bath at 65°C for 5 minutes to remove solid particles and metal impurities on the surface of the Si substrate; then use ultrapure water to clean the Si substrate. The Si wafer treated in the previous step was cleaned at 65°C for 5 minutes to remove heavy metals, alkalis and metal oxides on the surface of the Si substrate; then rinsed with ultrapure water for 3 minutes to remove the residual SC-II cleaning solution; then cleaned with HF solution with a mass fraction of 5% by mass for 1 minute to remove the oxide layer on the surface of the Si substrate; then rinsed with deionized water for 3 minutes; finally, the Si substrate was rinsed with an N2 air gun to remove moisture on the surface of the Si substrate.

[0019] Preferably, in step (8), the ITO target material is an ITO non-metallic target with a target purity of 99.99%; the argon gas pressure is maintained at 5.0 Pascals, the target spacing is 50 mm, and the deposition temperature of the metal ITO film is 20 to 25 degrees Celsius; the Ag target material is an Ag metal target with a target purity of 99.99%; the vacuum degree of the vacuum chamber is 5×10 -5 Pascal, vacuum

[0020] The conditions are achieved by a mechanical pump and a molecular pump bipolar vacuum pump. Preferably, in step (9), the metal electrode and the wire material are Ag and Cu respectively, wherein the purity of Ag is 99.9% and the diameter of the Cu wire is 0.1 mm.

[0021] The device having the self-driven light detection capability can be used in the preparation of self-driven photodetectors.

[0022] The beneficial technical effects of the present invention are:

[0023] The invention prepares a pyramid micro-nano structure on a Si substrate, and then spin-coats the prepared ZnO nanoparticle dispersion on the Si substrate with the pyramid micro-nano structure to develop a thin film device with self-driven light detection capability. Test results show that the prepared thin film device has obvious sensitivity to light, that is, when the operating voltage is 0 volts, the device current increases significantly under light conditions. The response of the prepared thin film device to light increases with the increase of light intensity. At the same time, the device has the advantages of good periodic repeatability and fast response speed. Compared with the existing self-driven photodetectors, the preparation method of the device involved in the present invention is simple, low-cost, and has the advantages of significant light response performance, and can be widely used in the field of photodetectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the XRD characterization diagram of the prepared ZnO nanoparticles after annealing.

[0025] Figure 2 TEM characterization image of the prepared ZnO nanoparticles.

[0026] Figure 3 SEM image of ZnO nanoparticles spin-coated on an inverted pyramid Si substrate.

[0027] Figure 4 Schematic diagram of the structure for measuring the light detection performance of the prepared device.

[0028] Figure 5 is the periodic response performance of the device to light when the applied voltage is 0 volt. DETAILED DESCRIPTION

[0029] The present invention uses metal-assisted etching to form pyramidal micro-nanostructures on a Si semiconductor to reduce reflectivity. A ZnO nanoparticle film is then deposited on the Si semiconductor pyramid substrate using spin coating, chemical co-precipitation, and high-temperature annealing. Transparent conductive ITO electrodes are deposited using radio frequency magnetron sputtering, followed by metallic Ag electrodes using direct current magnetron sputtering. The device is then connected using point electrodes and metal wires. When exposed to light, the device exhibits significant light response at an applied voltage of 0 volts due to the photoelectric effect and the presence of a built-in electric field.

[0030] The present invention is described in detail below with reference to examples and drawings.

[0031] The present invention is a self-driven photodetector based on a ZnO nanoparticle / Si pyramid structure heterojunction. The detector comprises a Si semiconductor substrate with an inverted pyramid micro-nanostructure and ZnO nanoparticles. The Si substrate with the pyramid micro-nanostructure serves as a carrier for a ZnO nanoparticle thin film layer, which is disposed on the surface of the inverted pyramid Si substrate. The Si substrate for the inverted pyramid micro-nanostructure is P-type single crystal Si with a resistivity of 0.4-1.1 ohm·cm and a (100) crystal orientation.

[0032] Furthermore, the surface of the ZnO nanoparticle film layer also has an ITO transparent conductive electrode sputtered by radio frequency magnetron sputtering technology with a thickness of 70 to 100 nm, and the metal Ag back electrode is prepared by DC magnetron sputtering technology with a thickness of 50 to 100 nm.

[0033] Furthermore, Ag electrodes are sputtered on both the ITO transparent conductive electrode and the metal Ag back electrode, and then silver paste is applied to each of them, and wires are led out to obtain a device.

[0034] The method for preparing the above device specifically comprises the following steps:

[0035] (1) Si substrate cutting and polishing: First, the silicon wafer was cut into the required size (2×2 cm) by laser for subsequent experiments. The cleaned Si substrate was dried; in order to better remove the surface damage layer of the Si substrate, the Si substrate was chemically polished.

[0036] (2) Si substrate cleaning: Before spin coating the ZnO film, we need to clean the chemically polished substrate to remove the metal ions and organic matter remaining on the substrate during the production process.

[0037] (3) Place the dried Si substrate in a mixed solution of Cu(NO3)2, HF and H2O2 at a corrosion temperature of 55°C to 65°C for 4 to 10 minutes, then rinse with deionized water for 3 minutes to remove the residual corrosion solution; use 68% concentrated nitric acid to remove the Cu nanoparticles remaining on the surface of the single crystal silicon substrate at room temperature for 5 to 8 minutes; then rinse with deionized water for 3 minutes to remove the residual concentrated nitric acid; then place the single crystal silicon substrate in a 10% HF solution for 5 to 10 minutes to remove the oxide layer naturally formed on the surface of the single crystal silicon substrate during the texturing process; then rinse with deionized water for 3 minutes to remove the residual HF on the surface of the single crystal silicon substrate.

[0038] (4) Slowly add 5-7 g of zinc acetate powder to 100-150 ml of methanol solution, immediately heat the solution to 50-70 degrees Celsius, and continuously stir to obtain a transparent solution 1. Then, dissolve 2-5 g of potassium hydroxide powder in 50-60 ml of methanol at a temperature of 50-70 degrees Celsius and continuously stir to obtain a mixed solution 2. Finally, add solution 2 dropwise to solution 1 under stirring for 10-20 minutes, stir for 1-3 hours, let it stand, cool to room temperature, remove the supernatant, and wash the precipitate with methanol 1-4 times;

[0039] (5) uniformly dispersing the ZnO powder obtained in step (4) in a solvent to obtain a ZnO nanoparticle dispersion;

[0040] (6) evenly spin-coating the ZnO nanoparticle dispersion obtained in step (5) on the surface of the Si inverted pyramid substrate prepared in step (4);

[0041] (7) The sample obtained in step (6) was placed in a tubular resistance furnace and heat treated in an air atmosphere at a temperature of 200 to 400 degrees Celsius at a temperature increase rate of 5 degrees Celsius per minute. The temperature was maintained at 200 to 400 degrees Celsius for 90 minutes, and then naturally cooled to room temperature.

[0042] (8) Taking out the sample obtained in step (7), and then placing the sample in a vacuum chamber, using radio frequency magnetron sputtering technology, using ionized argon ions to bombard a metal ITO target, and depositing a metal ITO electrode on the ZnO quantum dot film layer and the Si surface; the ITO target is an ITO non-metallic target, and the target purity is 99.99%; using direct current magnetron sputtering technology, using ionized argon ions to bombard a metal Ag target, and depositing a metal Ag electrode on the Si surface; the Ag target is an Ag metal target, and the target purity is 99.99%; the argon gas pressure is maintained at 5.0 Pascals, the target spacing is 50 mm, and the deposition temperature of the ITO film and the Ag film is 20 to 25 degrees Celsius;

[0043] (9) Metal Cu wires were drawn out using silver paste on the ZnO nanoparticle film layer and the Ag electrode on the Si surface to complete the device preparation.

[0044] The device having the self-driven light detection capability can be used in the preparation of self-driven photodetectors.

[0045] The effects of the present invention are further illustrated below in conjunction with the performance measurement results:

[0046] Figure 1 The XRD pattern of the prepared ZnO nanoparticles shows that the ZnO nanoparticles have good crystallinity.

[0047] Figure 2The TEM characterization image of the prepared ZnO nanoparticles shows that the size of the prepared ZnO nanoparticles is 5 to 10 nanometers.

[0048] Figure 3 The SEM image of ZnO nanoparticles spin-coated on an inverted pyramid Si substrate shows that the ZnO nanoparticles are evenly distributed on the surface of the inverted pyramid Si substrate after spin coating.

[0049] Figure 4 The figure shows the device's periodic response to light under an applied voltage of 0 volts. The test voltage is 0 volts. As shown in the figure, by varying the lighting environment, the fabricated thin-film device exhibits excellent light response, with advantages such as stable performance and fast response speed. At a test voltage of 0 volts, under illumination with a wavelength of 365 nanometers (optical power density of 10 milliwatts per square centimeter), the photocurrent of the thin-film device is approximately 0.25 milliamperes. These characteristics further demonstrate that this thin-film device can be used to develop new self-powered photodetection devices.

[0050] Figure 5 Schematic diagram of the structure for measuring the light detection performance of the prepared device.

Claims

1. A method for preparing a self-driven photodetector based on a ZnO nanoparticle / Si pyramid heterojunction, comprising the following steps: (1) Substrate cutting and polishing: First, the silicon wafer was cut into the required size (2×2 cm) by laser for subsequent experiments. The cleaned Si substrate was dried; in order to better remove the surface damage layer of the Si substrate, the Si substrate was chemically polished. (2) Si substrate cleaning: Before spin coating the ZnO film, we need to clean the chemically polished substrate to remove the metal ions and organic matter remaining on the substrate during the production process. (3) Place the dried Si substrate in a mixed solution of Cu(NO3)2, HF and H2O2 at a corrosion temperature of 55°C to 65°C for 4 to 10 minutes, then rinse with deionized water to remove the residual corrosion solution; use 68% concentrated nitric acid to remove the Cu nanoparticles remaining on the surface of the single crystal silicon substrate at room temperature for 5 to 8 minutes; then rinse with deionized water to remove the residual concentrated nitric acid; then place the single crystal silicon substrate in a 10% HF solution for 5 to 10 minutes to remove the oxide layer naturally formed on the surface of the single crystal silicon substrate during the texturing process; then rinse with deionized water to remove the HF remaining on the surface of the single crystal silicon substrate. (4) Slowly add zinc acetate powder to the methanol solution, immediately heat it to a certain temperature, and stir continuously to obtain a transparent solution 1. Then dissolve potassium hydroxide powder in methanol at the same temperature and stir continuously to obtain a mixed solution 2. Finally, add solution 2 dropwise to solution 1 under stirring, stir for a certain time, let it stand, cool to room temperature, remove the supernatant, and wash the precipitate with methanol; (5) uniformly dispersing the ZnO powder obtained in step (4) in a solvent to obtain a ZnO nanoparticle dispersion; (6) evenly spin-coating the ZnO nanoparticle dispersion obtained in step (5) on the surface of the Si pyramid substrate prepared in step (4); (7) The sample obtained in step (6) is placed in a tubular resistance furnace and heat treated at a certain temperature with a temperature rise rate of 5 degrees Celsius per minute. After reaching the set temperature, it is maintained for a period of time and then naturally cooled to room temperature; (8) Taking out the sample obtained in step (7), placing the sample in a vacuum chamber, using radio frequency magnetron sputtering technology, bombarding a metal ITO target with ionized argon ions, and depositing a metal ITO electrode on the ZnO quantum dot film layer and the Si surface; the ITO target is an ITO non-metallic target with a target purity of 99.99%; using direct current magnetron sputtering technology, bombarding a metal Ag target with ionized argon ions, and depositing a metal Ag electrode on the Si surface; the Ag target is an Ag metal target with a target purity of 99.99%, the argon gas pressure is maintained at 5.0 Pascals, the target spacing is 50 mm, and the deposition temperature of the metal ITO film is 20 to 25 degrees Celsius; (9) Metal Cu wires were drawn out using silver paste on the ZnO nanoparticle film layer and the Ag electrode on the Si surface to complete the device preparation.

2. The method for preparing a self-driven photodetector based on a ZnO nanoparticle / Si pyramid heterojunction according to claim 1, characterized in that: The concentration of the precursor zinc acetate powder in step (4) is one or more of 0.05M, 0.1M, 0.2M, and 0.3M; the heating temperature is one or more of 55 degrees Celsius, 60 degrees Celsius, 65 degrees Celsius, 70 degrees Celsius, 75 degrees Celsius, and 80 degrees Celsius.

3. The method for preparing a self-driven photodetector based on a ZnO nanoparticle / Si pyramid heterojunction according to claim 1, characterized in that: The solvent in step (5) is one or more of water, methanol, ethanol, isopropanol, and ethylene glycol.

4. The method for preparing a self-driven photodetector based on a ZnO nanoparticle / Si pyramid heterojunction according to claim 1, characterized in that: The spin coating speed in step (6) is one or more of 1000 rpm, 1500 rpm, 2000 rpm, and 3000 rpm, and the spin coating time is one or more of 5 s, 10 s, 15 s, and 30 s.

5. The method for preparing a self-driven photodetector based on ZnO nanoparticle / Si pyramid heterojunction according to claim 1, characterized in that: The heat treatment temperature in step (7) is one or more of 200 degrees Celsius, 250 degrees Celsius, 300 degrees Celsius, 350 degrees Celsius, 400 degrees Celsius, 450 degrees Celsius, and 500 degrees Celsius; the holding time is one or more of 60 minutes, 90 minutes, 120 minutes, and 160 minutes.

6. The method for preparing a self-driven photodetector based on ZnO nanoparticle / Si pyramid heterojunction according to claim 1, characterized in that: It includes a metal Ag point electrode, an ITO transparent conductive electrode, ZnO nanoparticles, an inverted pyramid structure Si semiconductor substrate and a metal Ag back electrode. The ZnO nanoparticles are arranged on the surface of the inverted pyramid structure Si semiconductor substrate, the ITO transparent conductive electrode is on the surface of the ZnO nanoparticle film layer, the metal Ag back electrode is on the surface of the Si substrate, and the metal Ag point electrodes are respectively placed on the surfaces of the ITO transparent conductive electrode and the Ag back electrode.

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