Nano-Vacuum Optical Mixer with Transparent Electrode Work Function Regulation and Its Preparation Method

Abstract

The present invention discloses a nano-vacuum optical mixer for regulating the work function of a transparent electrode and a preparation method thereof, belonging to the field of semiconductor photodetectors and millimeter wave / terahertz devices. The optical mixer includes a back electrode, a semiconductor layer, a nano-insulating layer, and a transparent electrode sequentially arranged from bottom to top; wherein the area occupied by the nano-insulating layer is smaller than that of the semiconductor layer and the transparent electrode, forming a nano-air channel; the transparent electrode can regulate the work function to achieve matching with the work function of the semiconductor layer. The present invention adopts a transparent electrode, which increases the utilization rate of incident light, thereby significantly improving the photocurrent and responsivity of the device; at the same time, by regulating the work function of the transparent electrode, the work functions of semiconductor layers with different doping types and concentrations can be matched, realizing effective regulation and optimization of the threshold voltage, photocurrent, and dark current.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor photodetectors and millimeter-wave / terahertz devices, and particularly relates to a nano-vacuum optical mixer with transparent electrode work function regulation and a preparation method thereof. Background Art

[0002] Millimeter waves and terahertz waves are electromagnetic waves with frequencies ranging from 30 GHz to 10 THz, and have wide applications in fields such as next-generation high-speed wireless communication, high-resolution radar detection and imaging. For the generation of millimeter waves and terahertz waves, optical mixing is a simple and cost-effective method for generating millimeter waves and terahertz waves. By adjusting the wavelengths of the two laser beams for mixing, the widest frequency tunability in the range from GHz to THz can be provided. The optoelectronic conversion devices for generating millimeter waves and terahertz waves by optical mixing are currently mainly two types: semiconductor photoconductive antennas and photodiodes.

[0003] Due to its simple structure and relatively simple external circuit requirements, the photoconductive antenna has been widely studied and applied. However, it requires a high operating voltage, and there are high electric fields and high current densities at the edges of the photoconductive antenna, which easily lead to device failures. Overall, the radiation efficiency of terahertz waves generated based on photoconductive antennas is still very low. Compared with photoconductive antennas, photodiodes require a lower operating voltage. However, the low output power and energy conversion efficiency in the high-frequency band are still bottleneck problems faced by these two types of optical mixers, namely photoconductive antennas and photodiodes. Currently, the power level of terahertz sources generated by optical mixing at 1 THz is still in the μW order of magnitude. One of the main factors affecting the radiation power and conversion efficiency of these two types of semiconductor optical mixers in the high-frequency band is the limited drift velocity (usually up to 10 7 cm / s order of magnitude) caused by carrier scattering in the semiconductor. This scattering not only causes device thermal breakdown and energy loss, but also limits the saturation current and maximum output power of the device. Vacuum is an ideal medium for electron ballistic transport. Electron ballistic transport without scattering can achieve high response speed and large bandwidth, and electrons can move in it at a speed close to the speed of light (10 10 cm / s). However, the distance between the anode and cathode of traditional vacuum phototubes is relatively far, which not only limits the response speed and bandwidth, but also leads to problems such as large volume, high operating voltage, and the need for vacuum packaging.

[0004] The nano-air-channel photodiode is a new type of optoelectronic device that has emerged in recent years. The distance between its cathode and anode is only dozens of nanometers, which is less than the mean free path of electrons in air. Therefore, it can operate in air without the need for vacuum packaging, and has the advantages of miniaturized integration and compatibility with semiconductor processes. It is one of the most promising solutions for realizing optical mixers. As an external photoelectric effect device of the electron emission type, the performance of the nano-air-channel optical mixer is greatly affected by the work functions of the cathode and anode. When different doping types and doping concentrations of semiconductors are used for the cathode, the work function of the anode should match that of the semiconductor to improve the performance of the optical mixer. However, the work function of traditional metal electrodes is generally fixed and it is difficult to perfectly match the work function of the semiconductor cathode, which will lead to problems such as high threshold voltage and small photocurrent. Moreover, for the optical mixer with a normal incidence structure, the metal electrode will reflect most of the incident light, greatly reducing the light utilization rate and responsivity of the device. In addition, most of the reported preparation methods of nano-air-channel photodiodes currently use semiconductor etching processes, and the resulting etching losses and defects will capture photo-generated carriers, reducing the device responsivity and high-frequency characteristics. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the present invention proposes a nano-vacuum optical mixer with a transparent electrode work function regulation and its preparation method. The aim is to provide a technical solution for a nano-vacuum optical mixer that can regulate and optimize the matching of the work function of the transparent electrode for semiconductors with different doping types, different doping concentrations, and different material systems. At the same time, it also has the characteristics of being transparent to incident light, suitable for the optical mixer with a normal incidence structure, capable of operating in the room temperature atmosphere, high responsivity, high output power, high conversion efficiency, simple process, no semiconductor etching damage, and batch preparation.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A nano-vacuum optical mixer with a transparent electrode work function regulation, characterized in that: the optical mixer includes a back electrode, a semiconductor layer, a nano-insulating layer, and a transparent electrode arranged in sequence from bottom to top; wherein, the area occupied by the nano-insulating layer is smaller than that of the semiconductor layer and the transparent electrode; a nano-air channel is formed between the semiconductor layer and the transparent electrode and outside the edge of the nano-insulating layer; the transparent electrode can regulate the work function to achieve matching with the work function of the semiconductor layer.

[0008] Furthermore, the transparent electrode realizes work function regulation through methods such as acid-base treatment, mechanical polishing treatment, plasma treatment, high-temperature deposition, annealing, etc.; different treatment methods are used to regulate the work function of the transparent electrode, so as to achieve matching with the work functions of semiconductor layers of different materials and optimize the characteristics of the nano-air-channel optical mixer.

[0009] Further, the function of the semiconductor layer is to absorb photons and convert them into electron-hole pairs. When the semiconductor layer is p-type doped, it serves as the cathode, with a negative bias applied to the back electrode and a positive bias applied to the transparent electrode as the anode. When the semiconductor layer is n-type doped, it serves as the anode, with a positive bias applied to the back electrode and a negative bias applied to the transparent electrode as the cathode.

[0010] Further, the material of the back electrode is a conductive material, including metals and metalloids. The material of the transparent electrode is a transparent conductive material, including indium tin oxide (ITO), gallium-doped zinc oxide (GZO), and aluminum-doped zinc oxide (AZO).

[0011] Further, the nano-insulating layer is an insulating material that can be wet-etched. The thickness of the nano-insulating layer determines the distance between the anode and the cathode, and also determines the length of the nano-air channel.

[0012] Further, the length of the nano-air channel is less than the average free path of electron scattering in air (the average free path of scattering is about 70 nm under 1 standard atmosphere), and electrons can achieve ballistic transport without a vacuum environment.

[0013] The present invention also provides a method for fabricating a nano-vacuum optical mixer with transparent electrode work function regulation, which is characterized by including the following steps:

[0014] S1. Deposit a back electrode on the lower surface of the semiconductor layer;

[0015] S2. Deposit a nano-insulating layer on the upper surface of the semiconductor layer;

[0016] S3. Deposit a transparent electrode above the nano-insulating layer;

[0017] S4. Lithographically form a pattern above the transparent electrode, and use photoresist to protect the photosensitive surface of the optical mixer;

[0018] S5. Perform wet etching to remove the transparent electrode and the nano-insulating layer outside the photosensitive surface area protected by the photoresist, and laterally etch the nano-insulating layer so that the area occupied by the nano-insulating layer is smaller than that of the semiconductor layer and the transparent electrode, and form a nano-air channel between the semiconductor layer and the transparent electrode and outside the edge of the nano-insulating layer;

[0019] S6. Regulate the work function of the transparent electrode by, but not limited to, acid-base treatment, mechanical polishing treatment, plasma treatment, high-temperature deposition, and annealing methods to achieve its matching with the work function of the semiconductor layer.

[0020] The basic working principle of the nano-vacuum optical mixer with transparent electrode work function regulation proposed by the present invention is as follows:

[0021] When an n-type semiconductor layer is adopted, the semiconductor layer serves as the anode and the transparent electrode serves as the cathode. A forward bias voltage is applied to the semiconductor layer. At this time, the semiconductor layer is in a reverse depletion state, and a two-dimensional hole gas layer is formed near the surface of the semiconductor layer close to the nano-insulating layer under a large voltage. Two laser beams with different wavelengths are combined and incident on the photosensitive surface of the optical mixer, pass through the transparent electrode and enter the semiconductor layer. After the semiconductor layer absorbs photons, a large number of electron-hole pairs are generated in the depletion region. The holes migrate under the action of the electric field to the interface between the semiconductor layer and the nano-insulating layer to form a two-dimensional hole gas with a high concentration. At the same time, the carrier multiplication effect occurs under a high electric field, doubling the number of holes. The two-dimensional hole gas with a high concentration induces a two-dimensional electron gas with a high concentration near the lower surface of the transparent electrode close to the nano-insulating layer through Coulomb attraction. There is a strong electric field vertically distributed between the edge of the transparent electrode and the semiconductor layer, pulling out the electrons in the two-dimensional electron gas with a high concentration on the lower surface of the transparent electrode to the surface and transporting them through the nano-air channel to the semiconductor layer. At the same time, the lateral Coulomb repulsion force between the electrons in the two-dimensional electron gas also significantly reduces the emission barrier of the edge electrons, making it easier for the electrons in the transparent electrode to be emitted into the nano-air channel. In this way, the photo-generated electrons generated by the semiconductor layer absorbing photons can continuously induce the electrons in the transparent electrode to be emitted and transported through the nano-air channel ballistically to the semiconductor layer and the back electrode to generate a high-frequency photocurrent modulated by the frequency corresponding to the wavelength difference of the two laser beams. This high-frequency photocurrent can be radiated into a millimeter-wave terahertz signal through the antenna.

[0022] When a p-type semiconductor layer is adopted, the semiconductor layer serves as the cathode and the transparent electrode serves as the anode. A forward bias voltage is applied to the transparent electrode. At this time, the semiconductor layer is in a reverse depletion state, and a two-dimensional electron gas layer is formed near the surface of the semiconductor layer close to the nano-insulating layer under a large voltage. Two laser beams with different wavelengths are combined and incident on the photosensitive surface of the optical mixer, pass through the transparent electrode and enter the semiconductor layer. After the semiconductor layer absorbs photons, a large number of electron-hole pairs are generated in the depletion region. The electrons migrate under the action of the electric field to the interface between the semiconductor layer and the nano-insulating layer to form a two-dimensional electron gas with a high concentration. At the same time, the carrier multiplication effect occurs under a high electric field, doubling the number of electrons. There is a strong electric field vertically distributed between the edge of the transparent electrode and the semiconductor layer, pulling out the electrons in the two-dimensional electron gas with a high concentration on the surface of the semiconductor layer to the surface and transporting them through the nano-air channel to the transparent electrode. At the same time, the lateral Coulomb repulsion force between the electrons in the two-dimensional electron gas also significantly reduces the emission barrier of the edge electrons, making it easier for the electrons in the semiconductor layer to be emitted into the nano-air channel. In this way, the photo-generated electrons generated by the semiconductor layer absorbing photons can continuously be emitted from the surface of the semiconductor layer and transported through the nano-air channel ballistically to the transparent electrode to generate a high-frequency photocurrent modulated by the frequency corresponding to the wavelength difference of the two laser beams. This high-frequency photocurrent can be radiated into a millimeter-wave terahertz signal through the antenna.

[0023] The advantages of the present invention are as follows:

[0024] 1. By using a transparent electrode that simultaneously has high conductivity and high incident light transmittance, the absorption rate of incident light by the semiconductor layer is significantly increased, thereby significantly increasing the photocurrent and responsivity of the nano-air-channel diode optical mixer.

[0025] 2. The work function of the transparent electrode can be adjusted by methods such as acid-base treatment, mechanical polishing treatment, plasma treatment, high-temperature deposition, annealing, etc., so as to adopt different treatment methods for the work function of the semiconductor layer to match the work function for energy band regulation and optimize the characteristics of the nano-air-channel optical mixer. For example, when an n-type semiconductor is used, a treatment method of reducing the work function of the transparent electrode can be adopted to reduce the threshold voltage and increase the photocurrent; when a p-type semiconductor is used, a treatment method of increasing the work function of the transparent electrode can be adopted to reduce the dark current of the device.

[0026] 3. The preparation method proposed by the present invention is simple and low-cost, and can be realized only by coating, photolithography and wet etching, without etching the semiconductor layer, which can avoid damage and generate defects that affect the device performance. Description of the Drawings

[0027] Figure 1 Schematic diagram of a device of an n-Si-based nano-vacuum mixer based on an ITO transparent electrode proposed by the present invention; where: 11, n-Si semiconductor layer; 12, Al back electrode; 13, nano-air channel; 14, SiO2 nano-insulating layer; 15, ITO transparent electrode.

[0028] Figure 2 Schematic diagram of a device of a p-InGaAs-based nano-vacuum optical mixer based on an AZO transparent electrode proposed by the present invention; where: 21, p-InGaAs semiconductor layer; 22, Ti / Au back electrode; 23, nano-air channel; 24, Al2O3 nano-insulating layer; 25, AZO transparent electrode.

[0029] Figure 3 Schematic diagram of a device of a p-Ge-based nano-vacuum optical mixer based on a GZO transparent electrode proposed by the present invention; where: 31, p-Ge semiconductor layer; 32, Ti / Au back electrode; 33, nano-air channel; 34, HfO2 nano-insulating layer; 35, GZO transparent electrode.

[0030] Figure 4 Preparation method of an n-Si-based nano-vacuum optical mixer based on an ITO transparent electrode proposed by the present invention.

[0031] Figure 5 Preparation method of a p-InGaAs-based nano-vacuum optical mixer based on an AZO transparent electrode proposed by the present invention.

[0032] Figure 6 A preparation method of a p-Ge-based nano-vacuum optical mixer based on a GZO transparent electrode proposed by the present invention. Specific implementation manners

[0033] The technical solutions in the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Embodiment 1

[0035] An n-Si-based nano-vacuum optical mixer based on an ITO transparent electrode, as Figure 1 shown. In this embodiment, the semiconductor layer 11 is a low-doped n-Si semiconductor layer. Below the semiconductor layer 11 is an Al back electrode 12. A 50-nm-thick SiO2 nano-insulating layer 14 is provided above the semiconductor layer 11. Above the SiO2 nano-insulating layer is an ITO transparent electrode 15; a nano-air channel 13 is formed between the ITO transparent electrode and the n-Si semiconductor layer and outside the SiO2 nano-insulating layer. The channel length is determined by the thickness of the SiO2 nano-insulating layer; the work function of the ITO transparent electrode is reduced by mechanical polishing, hydrogen plasma treatment, annealing, or inert gas sputtering, etc., to match the work function of the n-Si semiconductor layer.

[0036] The working process of this device is as follows: A negative bias voltage is applied to the ITO transparent electrode as the cathode, a positive bias voltage is applied to the Al back electrode, the n-Si semiconductor layer is used as the anode, and a depletion region is generated in the n-Si semiconductor layer body; under the irradiation of a double-wavelength combined laser of 850 nm and 850.5 nm, the n-Si semiconductor layer absorbs photons to generate electron-hole pairs. The generated photo-generated holes migrate to the interface between the n-Si semiconductor layer and the SiO2 nano-insulating layer under the action of the internal electric field to form a high-concentration two-dimensional hole gas, and a high-concentration two-dimensional electron gas is induced on the SiO2 / ITO side. Due to the Coulomb repulsion, the electrons at the edge of the 2DEG are easily emitted into the nano-air channel. At the same time, the electrons in the two-dimensional electron gas have a reduced potential barrier under the action of the applied electric field and tunnel into the nano-air channel. The electrons emitted into the nano-air channel are ballistically transported to the n-Si anode and the Al back electrode and collected, generating a photocurrent with an oscillation frequency of 207 GHz. This high-frequency photocurrent is radiated by the antenna to generate millimeter waves with a frequency of 207 GHz.

[0037] A preparation method of an n-Si-based nano-air channel vacuum optical mixer based on an ITO transparent electrode, as shown in 4, includes the following steps:

[0038] S1. Electron beam evaporation is used to deposit a 200-nm-thick Al back electrode 12 on the lower surface of the n-Si semiconductor layer 11.

[0039] S2. PECVD is used to deposit a 50-nm-thick SiO2 nano-insulating layer 14 on the upper surface of the n-Si semiconductor layer 11.

[0040] S3. Deposit a 100-nm-thick ITO transparent electrode 15 above the nano-insulating layer by magnetron sputtering.

[0041] S4. Use ultraviolet lithography to form a pattern to protect the ITO transparent electrode 15, and perform wet etching with BOE solution to remove the transparent electrode 15 outside the pattern and the nano-insulating layer 14. Since the etching rate of the ITO transparent electrode 15 is slower than that of the SiO2 nano-insulating layer 14, after the lateral etching of the SiO2 nano-insulating layer 14, a nano-air channel 13 is formed between the n-Si semiconductor layer 11 and the ITO transparent electrode 15 and outside the SiO2 nano-insulating layer.

[0042] S5. Reduce the work function of the ITO by hydrogen plasma treatment and annealing to match the work function of the n-Si semiconductor layer 11, so as to reduce the threshold voltage and increase the photocurrent.

[0043] Example 2

[0044] A p-InGaAs-based nano-vacuum optical mixer based on an AZO transparent electrode, as Figure 2 shown. In this example, the semiconductor layer 21 is a low-doped p-InGaAs semiconductor layer. Below the p-InGaAs semiconductor layer 21 is a Ti / Au back electrode 22. Above the p-InGaAs semiconductor layer 21, a 30-nm-thick Al2O3 nano-insulating layer 24 is provided. Above the Al2O3 nano-insulating layer is an AZO transparent electrode 25. A nano-air channel 23 is formed between the p-InGaAs semiconductor layer 21 and the AZO transparent electrode 25 and outside the Al2O3 nano-insulating layer. The channel length is determined by the thickness of the Al2O3 nano-insulating layer. Improve the work function of the AZO transparent electrode by oxygen plasma treatment and various acid-base ultrasonic treatments, etc., to match the work function of the p-InGaAs semiconductor layer 21.

[0045] The working process of the device is as follows: A positive bias voltage is applied to the AZO transparent electrode as the anode, a negative bias voltage is applied to the Ti / Au back electrode, the p-InGaAs semiconductor layer serves as the cathode, and a depletion region is generated within the p-InGaAs semiconductor layer; under the irradiation of a dual-wavelength combined beam of light at 1546 nm and 1554 nm, the p-InGaAs semiconductor layer absorbs photons to generate electron-hole pairs, and the generated photoelectrons migrate to the interface between the p-InGaAs semiconductor layer and the Al2O3 nano-insulating layer under the action of the internal electric field to form a two-dimensional electron gas. Due to the Coulomb repulsion, the electrons at the edge of the two-dimensional electron gas can easily overcome the potential barrier and be emitted into the nano-air channel. At the same time, under the action of the applied electric field, the potential barrier of the electrons within the two-dimensional electron gas decreases, and they tunnel into the nano-air channel. The electrons emitted into the nano-air channel are transported ballistically to the AZO transparent anode and collected, generating a photocurrent with an oscillation frequency of 1 THz. This high-frequency photocurrent is radiated by the antenna to generate a terahertz wave with a frequency of 1 THz.

[0046] A preparation method of a nano-vacuum optical mixer based on an AZO transparent electrode, as shown in 5, includes the following steps:

[0047] S1. Evaporate a 150-nm-thick Ti / Au electrode on the lower surface of the p-InGaAs semiconductor layer 21 by electron beam evaporation as the back electrode 22.

[0048] S2. Deposit a 30-nm-thick Al2O3 nano-insulating layer 24 on the upper surface of the p-InGaAs semiconductor layer 21 by ALD.

[0049] S3. Deposit an 80-nm-thick AZO transparent electrode 25 above the Al2O3 nano-insulating layer 24 by magnetron sputtering.

[0050] S4. Use photolithography to form a pattern to protect the AZO transparent electrode 25, and etch it with a NaOH solution to remove the transparent electrode and the nano-insulating layer outside the pattern. Since the corrosion rate of the AZO transparent electrode is slower than that of the Al2O3 nano-insulating layer 24, after the lateral corrosion of the Al2O3 nano-insulating layer 24, a nano-air channel 23 is formed between the p-InGaAs semiconductor layer 21 and the AZO transparent electrode 25 and outside the Al2O3 nano-insulating layer 24.

[0051] S5. Improve the work function of the AZO transparent electrode by controlling the deposition temperature and oxygen plasma treatment to match the work function of the p-InGaAs semiconductor layer 21 to reduce the dark current of the device.

[0052] Example 3

[0053] A p-Ge-based nano-vacuum optical mixer based on a GZO transparent electrode, as Figure 3As shown, the semiconductor layer 31 in this embodiment is a low-doped p-Ge semiconductor layer. Below the p-Ge semiconductor layer 31 is the Ti / Au back electrode 32. A 30-nm-thick HfO2 nano-insulating layer 34 is provided above the p-Ge semiconductor layer 31, and above the HfO2 nano-insulating layer is the GZO transparent electrode 35. A nano-air channel 33 is formed between the p-Ge semiconductor layer 31 and the GZO transparent electrode 35, outside the HfO2 nano-insulating layer. The channel length is determined by the thickness of the HfO2 nano-insulating layer. The work function of ITO is reduced by hydrogen plasma treatment and annealing, etc.

[0054] The working process of this device is as follows: A positive bias voltage is applied to the GZO transparent electrode as the anode, a negative bias voltage is applied to the Ti / Au back electrode, and the p-Ge semiconductor layer serves as the cathode. A depletion region is generated in the p-Ge semiconductor layer. Under the irradiation of the combined light of 1546 nm and 1554 nm wavelengths, the p-Ge semiconductor layer absorbs photons to generate electron-hole pairs. The generated photoelectrons migrate to the interface between the p-Ge semiconductor layer and the HfO2 nano-insulating layer under the action of the internal electric field to form a two-dimensional electron gas. Due to the Coulomb repulsion, the electrons at the edge of the two-dimensional electron gas can easily overcome the potential barrier and emit into the nano-air channel. At the same time, under the action of the applied electric field, the potential barrier of the electrons in the two-dimensional electron gas is reduced, and they tunnel into the nano-air channel. The electrons emitted into the nano-air channel are ballistically transported to the GZO transparent anode and collected, generating a photocurrent with an oscillation frequency of 1 THz. This high-frequency photocurrent is radiated by the antenna to generate a terahertz wave with a frequency of 1 THz.

[0055] A preparation method of a GZO transparent electrode-based nano-vacuum optical mixer, as shown in Figure 6, includes the following steps:

[0056] S1. Evaporate a 150-nm-thick Ti / Au electrode on the lower surface of the p-Ge semiconductor layer 31 by electron beam evaporation as the back electrode 32.

[0057] S2. Deposit a 30-nm-thick HfO2 nano-insulating layer 34 on the upper surface of the p-Ge semiconductor layer 31 by ALD.

[0058] S3. Deposit an 80-nm-thick GZO transparent electrode 35 above the HfO2 nano-insulating layer 34 by magnetron sputtering.

[0059] S4. Use photolithography to form a pattern to protect the GZO transparent electrode 35, and use a KOH solution for etching to remove the transparent electrode and the nano-insulating layer outside the pattern. Since the corrosion rate of the GZO transparent electrode is slower than that of the HfO2 nano-insulating layer 34, after the lateral corrosion of the HfO2 nano-insulating layer 34, a nano-air channel 33 is formed between the p-Ge semiconductor layer 31 and the GZO transparent electrode 35, outside the HfO2 nano-insulating layer 34.

[0060] S5. Reduce the work function of GZO by hydrogen plasma treatment and annealing to match the work function of the p-Ge semiconductor layer 31, so as to increase the saturation photocurrent.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A nano-vacuum optical mixer for regulating the work function of a transparent electrode, characterized in that The optical mixer described above includes a back electrode, a semiconductor layer, a nano-insulating layer, and a transparent electrode that are sequentially arranged from bottom to top; wherein, the area occupied by the nano-insulating layer is smaller than that of the semiconductor layer and the transparent electrode; a nano-air channel is formed between the semiconductor layer and the transparent electrode and outside the edge of the nano-insulating layer; the transparent electrode can regulate the work function to achieve a match with the work function of the semiconductor layer; the methods for the transparent electrode to regulate the work function include: acid-base treatment, mechanical polishing treatment, plasma treatment, high-temperature deposition, and annealing.

2. The nano-vacuum optical mixer for regulating the work function of a transparent electrode according to claim 1, wherein The function of the semiconductor layer is to absorb photons and convert them into electron-hole pairs; when the semiconductor layer is p-type doped, it serves as the cathode, a negative bias voltage is applied to the back electrode, and a positive bias voltage is applied to the transparent electrode as the anode; when the semiconductor layer is n-type doped, it serves as the anode, a positive bias voltage is applied to the back electrode, and a negative bias voltage is applied to the transparent electrode as the cathode.

3. The nano-vacuum optical mixer for regulating the work function of a transparent electrode according to claim 2, wherein, The length of the nano-air channel is less than the average free path of electron scattering in air.

4. The nano-vacuum optical mixer for regulating the work function of the transparent electrode according to claim 2, wherein The material of the back electrode is a conductive material; the material of the transparent electrode is a transparent conductive material.

5. The nano-vacuum optical mixer for regulating the work function of a transparent electrode according to claim 4, wherein The material of the transparent electrode is indium tin oxide, gallium-doped zinc oxide, or aluminum-doped zinc oxide.

6. The nano-vacuum optical mixer with transparent electrode work function regulation according to claim 4, characterized in that, The nano-insulating layer is an insulating material that can be wet-etched.

7. A preparation method of a nano-vacuum optical mixer for regulating the work function of a transparent electrode as described in claim 1, characterized in that, It includes the following steps: S1. Deposit a back electrode on the lower surface of the semiconductor layer; S2. Deposit a nano-insulating layer on the upper surface of the semiconductor layer; S3. Deposit a transparent electrode above the nano-insulating layer; S4. Photolithographically form a pattern above the transparent electrode, and use a photoresist to protect the photosensitive surface of the optical mixer; S5. Perform wet etching to remove the transparent electrode and the nano-insulating layer outside the photosensitive surface area protected by the photoresist, and laterally etch the nano-insulating layer so that the area occupied by the nano-insulating layer is smaller than that of the semiconductor layer and the transparent electrode, and form a nano-air channel between the semiconductor layer and the transparent electrode and outside the edge of the nano-insulating layer; S6. Regulate the work function of the transparent electrode to achieve a match with the work function of the semiconductor layer; The methods for the transparent electrode to regulate the work function include: acid-base treatment, mechanical polishing treatment, plasma treatment, high-temperature deposition, and annealing.

Images