CN112880822B - Photoelectrochemical photodetector and preparation method thereof - Google Patents

Abstract

The invention discloses a preparation method of a novel photoelectrochemical photodetector, which is characterized in that the method comprises: selecting a gallium nitride-based compound semiconductor material component according to the wavelength of light to be detected by the photodetector; The components form gallium nitride-based nanowires on the surface of the substrate; the gallium nitride-based nanowires are uniformly decorated with cocatalyst nanoparticles; the gallium nitride-based nanowires with the modified cocatalyst nanoparticles are encapsulated to obtain a photoelectrode ; and using the photoelectrode to prepare the photoelectrochemical photodetector. Photodetectors for different photodetection scenarios can be produced simply by adjusting the component contents in the nanowires during nanowire growth. Finally, the same process was adopted to prepare a new all-band photoelectrochemical photodetector with high responsivity, rapid response, economical and environmental protection, and self-powered energy. The invention pioneered the application of gallium nitride-based nanowires in the research of photoelectrochemical photodetectors, which is of great significance.

Description

Photoelectrochemical photodetector and preparation method thereof

technical field

The invention relates to the technical field of photoelectrochemical photodetectors, in particular to a photoelectrochemical photodetector and a preparation method thereof.

Background technique

Photodetectors (i.e., light detectors), i.e. devices that capture optical signals and convert them into electrical signals, are widely used in imaging, communications, sensing, computing, emerging wearable devices, and detection in the space field. Photodetectors are widely used in various fields of military and national economy. In the visible light or near-infrared band, it is mainly used for ray measurement and detection, industrial automatic control, photometric measurement, etc.; in the infrared band, it is mainly used in missile guidance, infrared thermal imaging, infrared remote sensing, etc.; in the ultraviolet band, it is mainly used for flame detection, missile warning, etc. , ozone monitoring and non-line-of-sight optical communication, etc.

Most of today's photodetectors are based on a simple metal-semiconductor-metal (MSM) structure. The MSM structure photodetector needs to apply an external bias during operation, which not only consumes power, but also has a great impact on responsivity and response speed. At the same time, in order to meet the needs of different applications, the material systems and structures involved in the research of MSM-structured photodetectors are chaotic and complex, and there is no unified design and preparation method, which cannot be adapted to large-scale production. detector needs.

SUMMARY OF THE INVENTION

(1) Technical problems to be solved

In order to solve the problems of poor overall photodetection performance of the above-mentioned traditional MSM or planar thin-film structured photodetector, and inability to adapt to the mass production of full-spectrum photodetectors, the present invention provides a photoelectrochemical photodetector and a preparation method thereof.

(2) Technical solutions

One aspect of the present invention provides a method for preparing a photoelectrochemical photodetector, the method comprising: selecting a gallium nitride-based material composition according to the wavelength of light to be detected by the photodetector; forming gallium nitride-based nanowires on the gallium nitride-based nanowires; modifying cocatalyst nanoparticles on the gallium nitride-based nanowires; encapsulating the gallium nitride-based nanowires on which the cocatalyst nanoparticles have been modified to obtain a photoelectrode; and preparing a photoelectrode Photoelectrochemical photodetectors.

Optionally, selecting the gallium nitride-based compound semiconductor material composition according to the wavelength of the light to be detected by the photodetector includes: according to the following formula: Eg=3.42eV+x×2.86eV−x(1−x)×1.0eV Determine the Al composition in Al _x Ga _1-x N corresponding to the wavelength of the light to be detected; or according to the following formula: Eg=3.42eV–x×2.65eV–x(1–x)×2.4eV The light wavelength corresponds to the In component in In _x Ga _1-x N, and Eg is the forbidden band width of the compound semiconductor, which corresponds to the absorption wavelength of different light bands, and the corresponding absorption wavelength can be obtained from the forbidden band width.

Optionally, forming gallium nitride-based nanowires on the surface of the substrate according to the composition further includes: forming a nanohole array structure on the substrate, the thickness of the nanohole array structure is less than or equal to 50 nm; positioning in the nanohole Filling the p-type doped or n-type doped gallium nitride-based material to form a composite layer, and continuing to form p-type doped or n-type doped gallium nitride-based materials on the surface of the composite layer at positions corresponding to the nanoholes nanowires; or the nanohole array structure of the composite layer is removed to form p-type doped or n-type doped gallium nitride-based nanowires on the surface of the substrate.

Optionally, forming GaN-based nanowires on the surface of the substrate according to the composition further includes: forming a p-type doped or n-type doped GaN-based thin film on the substrate, The GaN-based thin film is etched to form the p-type doped or n-type doped GaN-based nanowires on the surface of the substrate.

Optionally, forming gallium nitride-based nanowires on the surface of the substrate according to the above components includes: controlling the doping ratio of magnesium or silicon, and forming p-type doping or n-type doping with corresponding doping ratios on the substrate Hybrid GaN-based nanowires.

Optionally, before the co-catalyst nanoparticles are modified on the gallium nitride-based nanowire, the method further includes: when the gallium nitride-based nanowire is n-type doped, preparing a protective layer on the surface of the gallium nitride-based nanowire, The thickness of the protective layer is less than or equal to 10 nm.

Optionally, modifying the cocatalyst nanoparticles on the gallium nitride-based nanowires includes: disposing the gallium nitride-based nanowires in a precursor aqueous solution of a first concentration, and applying a wavelength corresponding to the energy band of the nanowires at the same time. Light irradiation to modify cocatalyst nanoparticles on the surface of gallium nitride-based nanowires.

Optionally, encapsulating the gallium nitride-based nanowires with modified cocatalyst nanoparticles to obtain a photoelectrode includes: fixing a wire on a substrate having the gallium nitride-based nanowires with modified cocatalyst nanoparticles. On the conductive area, the wires are clad and fixed together with the substrate, and the gallium nitride-based nanowires are exposed at the same time to form a packaged photoelectrode.

Optionally, fixing the wire on the conductive area of the substrate having the gallium nitride-based nanowires with modified cocatalyst nanoparticles includes: scraping off the oxide layer on the conductive area of the substrate, and after scraping off the oxide layer. A liquid alloy is coated on the conductive area of the wire, and conductive glue is coated on the surface of the wire between the wire and the conductive area and opposite to the position of the liquid alloy.

Optionally, using a photoelectrode to prepare a photoelectrochemical photodetector includes: arranging the photoelectrode, a reference electrode, and a counter electrode in an electrolyte solution with a second concentration at a certain distance to prepare a three-electrode system to form a photoelectrochemical photodetector. .

Optionally, forming gallium nitride-based nanowires on the surface of the substrate according to the composition further includes: forming nanopore array structures such as silicon dioxide, silicon nitride, titanium dioxide, pure metal, etc. on the substrate, and nanopore array structures and its thickness is not more than or equal to 50nm; positioning and filling gallium nitride-based materials in the nanoholes to form a composite layer, and continuing to form gallium nitride-based nanowires on the surface of the composite layer at positions corresponding to the nanoholes; or The silicon dioxide nanohole array structure of the composite layer is removed to form gallium nitride based nanowires on the substrate surface.

Optionally, forming gallium nitride-based nanowires on the surface of the substrate according to the composition further includes: forming a gallium nitride-based thin film on the substrate by a molecular beam epitaxy method, and drying the gallium nitride-based thin film Etching to form gallium nitride based nanowires on the surface of the substrate.

(3) Beneficial effects

A novel method for preparing a photoelectrochemical photodetector proposed by the present invention is based on gallium nitride (GaN)-based materials. By adjusting the alloy ratio of aluminum or indium relative to gallium, the bandgap of the material can be adjusted in a targeted manner to form a material that can be simultaneously A general preparation method for the preparation of a new type of photoelectrochemical photodetector with UV-visible-infrared detection wavelength of full spectrum and tunable bandgap. That is, according to the actual wavelength to be detected, the appropriate ratio of aluminum: gallium or indium: gallium is selected for the growth stage of the gallium nitride-based compound semiconductor material, and the band gap of the prepared gallium nitride-based nanowires is precisely controlled to obtain high quality of the corresponding wavelength. Single crystal GaN-based nanowires. Due to the same material system, the cocatalyst nanoparticle modification, photoelectrode encapsulation, and photoelectrochemical system preparation process are completely consistent, and there is no need to change the material system or adjust the process due to the detection wavelength requirements, which greatly reduces the manufacturing cost and has high applicability. Only adjusting parameters during nanowire growth can produce photodetectors for different photodetection scenarios. Finally, the same process flow was used to prepare a new all-band photoelectrochemical photodetector with high responsivity, rapid response, economical and environmental protection, and self-powered energy, which replaced the traditional MSM photodetector with poor performance. The invention pioneered the application of gallium nitride-based nanowires in the research of photoelectrochemical photodetectors, which is of great significance.

Another aspect of the present invention provides a novel photoelectrochemical photodetector, which is prepared by using the above-mentioned preparation method of the novel photoelectrochemical photodetector. The photodetector includes a photoelectrode with gallium nitride-based nanowires.

A new type of photoelectrochemical photodetector proposed by the present invention is directed to grow p-type doped or n-type doped gallium nitride-based nanowires on a substrate, which has a large specific surface area and is in contact with an interface formed by an electrolyte solution. It is beneficial to the separation and transport of photogenerated carriers. In addition, the modification of cocatalyst nanoparticles (such as platinum Pt or ruthenium Ru) on the GaN-based nanowires as the photoelectrode optimizes the adsorption and desorption processes of reactants/products and improves the water reduction of the photoelectrode in solution /oxidation reaction rate, ensuring the photoelectric conversion efficiency, obtaining a larger photoelectric response current, higher photoresponsivity, and the response time can be precisely adjusted according to actual needs. At the same time, the design of the photoelectrochemical device is further optimized, and the electrolyte solution environment is changed, and finally a new full-spectrum photoelectrochemical photodetector with high responsivity, high sensitivity, fast response, economical environmental protection, and self-powered energy (no additional electrical energy is required) is realized, which replaces the performance The inferior traditional MSM photodetector makes up for the blank of the photoelectrochemical photodetector made of GaN-based materials. The invention pioneered the application of gallium nitride-based nanowires in the research of photoelectrochemical photodetectors, which is of great significance.

Description of drawings

1A is a schematic diagram of an AlGaN nanowire in an embodiment of the present invention;

1B is a scanning electron microscope image of AlGaN nanowires in an embodiment of the present invention;

FIG. 2 is a schematic diagram of the modified cocatalyst nano-Pt particles in AlGaN nanowires according to an embodiment of the present invention;

3A is a schematic cross-sectional view of a package of an AlGaN nanowire photocathode according to an embodiment of the present invention;

3B is a schematic diagram of a package of an AlGaN nanowire photocathode according to an embodiment of the present invention;

4 is a schematic diagram of the preparation of a novel solar-blind ultraviolet photoelectrochemical photodetector in an embodiment of the present invention;

5 is a schematic diagram of a product of a novel solar-blind ultraviolet photoelectrochemical photodetector in an embodiment of the present invention;

6 is a schematic flowchart of a method for preparing a photoelectrochemical photodetector in an embodiment of the present invention;

FIG. 7 is a simple spectrum comparison diagram of a photoelectrochemical photodetector in an embodiment of the present invention;

8A is a schematic diagram of an AlGaN nanohole array of a solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

8B is a schematic diagram of an AlGaN nanopore array in which cocatalyst nanoparticles have been modified in a solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

9 is a schematic flowchart of a method for preparing a solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

10A is a schematic diagram of the first stage of the preparation process of the AlGaN nanohole array in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

10B is a schematic diagram of the first stage of the preparation process of AlGaN nanohole arrays in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

10C is a schematic diagram of the first stage of the preparation process of AlGaN nanohole arrays in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

10D is a first-stage schematic diagram of the AlGaN nanohole array preparation process in the method for preparing a solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

10E is a first-stage schematic diagram of the AlGaN nanohole array preparation process in the method for preparing a solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

10F is a schematic diagram of the first stage of the preparation process of AlGaN nanohole arrays in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

10G is a schematic diagram of the first stage of the preparation process of AlGaN nanohole arrays in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention;

FIG. 10H is a first-stage schematic diagram of the preparation process of AlGaN nanohole arrays in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention.

Detailed ways

Photoelectrochemical photodetectors are derived from photoelectrochemical reactions. Taking a p-type semiconductor as an example, the photoelectrochemical reaction is that the semiconductor is illuminated to generate photogenerated electrons and holes, the electrons undergo a reduction reaction at the semiconductor electrode, and the holes flow through the external circuit to the counter electrode for an oxidation reaction (the opposite is true for n-type semiconductors). The performance indicators tested in this process are the ratio of light/dark current, the response time, and the light intensity and wavelength of light are directly related, and a photoelectrochemical device dedicated to light detection is gradually derived from this. In the field of photoelectrochemical research, most of the research focuses on photocatalytic redox reactions under visible light conditions. There are few studies on photoelectrochemical photodetectors, and there are very few studies on photoelectrochemical photodetectors in the infrared and ultraviolet bands. , which can be said to be a completely new direction. Specifically, photoelectrochemical catalysis focuses on the study of chemical reaction mechanisms, such as the amount of hydrogen produced by semiconductor materials during photocatalytic reactions, how to increase the amount of hydrogen produced, and how to design reaction sites. The photoelectrochemical photodetector mainly studies the photo-dark current signal generated in the above-mentioned photoelectrochemical reaction process, which is used to reflect the relevant parameters of the detection light, and then realize various photoelectric detection functions.

In addition, the research direction of III-V nitride semiconductor materials mainly focuses on light-emitting diodes (Light Emitting Diode, namely LED) and power devices, and due to the extremely high cost of preparing nitrides by molecular beam epitaxy (Molecular Beam Epitaxy, or MBE), using The photoelectrochemical catalysis research of nitride nanomaterials is still in its infancy, not to mention the use of III-V nitride materials as photoelectrochemical photodetectors. Generally, UV light detection (non-solar-blind band) selects powder samples prepared by chemical methods (such as zinc oxide ZnO, titanium dioxide TiO ₂ , etc.), due to poor crystal quality and many defects, photo-generated electron-hole pairs are easy to recombine, directly resulting in poor light detection performance. The invention creatively proposes a GaN-based nanowire/nanopore structure, which is applied to a photoelectrochemical photodetector, overcomes the technical difficulties in the field, and achieves breakthrough technical effects.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

Example 1:

One aspect of the present invention proposes a novel solar-blind ultraviolet photoelectrochemical photodetector. FIG. 1A is a schematic diagram of AlGaN nanowires in an embodiment of the present invention. The novel solar-blind ultraviolet photoelectrochemical photodetector includes a photocathode, the photocathode includes a substrate 110, and also includes AlGaN nanowires 120 grown on the surface of the substrate 110, thereby constituting the photocathode of the novel photoelectrochemical photodetector proposed in the present invention The basic structure 100. The GaN-based nanowires include n-type GaN-based nanowires and p-type GaN-based nanowires. Those skilled in the art should understand that the nanowire structure can be a regular arrangement, such as a nanowire structure prepared by directional growth, or it can also include an irregularly arranged nanowire structure. The so-called "regular" can be understood as whether the arrangement of the nanowires has Periodicity; correspondingly, the so-called "irregularity" can be understood as whether the arrangement of nanowires has no periodicity, and can also be understood as the length and diameter of nanowires, the spacing between any adjacent nanowires, and the growth angle of nanowires (relative to the substrate) inconsistent, no rules to follow. In addition, the gallium nitride-based material can be selected as AlGaN in the present invention, and AlGaN is only a symbolic expression of the material, and does not represent the standard chemical formula of the material. Specifically, the chemical formula of the GaN-based material can be selected as Al _x Ga _{1 -xN} , one of _BxAlyGa1 - _xyN or InxAlyGa1 _{- xyN} , _0≤x < ₁ , 0≤y≤1. That is, the gallium nitride-based material may be AlGaN or InGaN, or a gallium nitride-based material such as AlInGaN, which is not limited in the present invention.

The photoelectrode mentioned in the claims of the present invention can be a photocathode or a photoanode, and can be specifically distinguished by its doping component (eg, magnesium doping or silicon doping), which corresponds to the reduction in the present invention. reaction or oxidation reaction. In order to clearly express the function of the photoelectrode in the present invention, the present invention is mainly described by taking the AlGaN photocathode as an example. Those skilled in the art should understand that it is not a limitation on the photoanode, nor is it a limitation on the non-AlGaN photoelectrode. As an embodiment of the present invention, the AlGaN nanowires 120 grown on the surface of the substrate 110 can be formed by molecular beam epitaxy (Molecular Beam Epitaxy, ie MBE) or metal organic chemical vapor deposition (Metal Organic Chemical Vapor Deposition, ie MOCVD), conventional Chemical vapor deposition method, halide vapor phase epitaxy or pulsed laser deposition method is used for preparation, which is not specifically limited in the present invention. Meanwhile, in order to express the AlGaN nanowires 120 of the present invention more clearly, the following mainly introduces molecular beam epitaxy (MBE) as the basic preparation method.

Compared with common oxide and nitride nanomaterials (such as gallium oxide nanostructures), the AlGaN nanowire 120 of the present invention has the advantages of high stability, high crystal quality, and adjustable band gap height matching, etc. It has excellent water reduction performance under blind light irradiation, which is reflected as excellent photodetection performance. In addition, for the AlxGa1 _{- xN} material, its band gap can be changed with the compositional doping, specifically:

Eg=3.42eV+x*2.86eV–x(1-x)*1.0eV…………………………(1)

Among them, Eg is the forbidden band width of the semiconductor, which corresponds to the absorption wavelength of different light bands.

Therefore, according to formula (1), by controlling the proportion of Al and Ga components in the preparation process, the band gap of the prepared photocathode can be precisely regulated to achieve light absorption in the solar-blind ultraviolet band. Correspondingly, for gallium nitride-based materials in B _{x AlyGa1 - xyN} or InxAlyGa1 _{- xyN} (0≤x<1, 0≤y≤1), the corresponding wavelength is calculated The formula can be transformed correspondingly, and it is subject to the actual preparation needs, which is not limited in the present invention.

In addition, the AlGaN nanowires with high crystal quality prepared by the present invention can be p-type doped materials, specifically, Mg atoms can be doped. When the p-type semiconductor is in contact with an aqueous solution, electron exchange occurs, and the end result is that the Fermi level of the water-semiconductor system is the same, and the p-type semiconductor energy band is bent, causing electrons to move toward the contact surface, and the surface is rich in electrons, which can be used for photodetection. The process will not cause any impact on the AlGaN nanomaterial or structure. Compared with oxide nanomaterials (such as gallium oxide nanostructures) that have not yet been able to achieve p-type doping, the stability is very high, which can be used as a photocathode. Correspondingly, as another embodiment of the present invention, it can also be used as a photoanode by changing to n-type doped AlGaN nanowires and applying a certain protective layer.

As an optional embodiment, the substrate 110 includes a conductive substrate, and the conductive substrate includes a standard low-resistance silicon substrate, such as a silicon wafer with overall conductive properties. The size of the photoelectrode is required, which is not limited in the present invention.

As an optional embodiment, the silicon substrate includes an n-type silicon substrate, and the n-type silicon substrate is an n-type silicon substrate of any crystal plane, such as a Si(111) plane substrate; and also includes a p-type silicon substrate, p-type silicon substrate. The silicon substrate is a p-type silicon substrate of any crystal plane, such as a Si (100) plane substrate. High crystal quality GaN-based nanowires can be stably formed on this substrate. Specifically, the silicon substrate is only an optional substrate in the present invention. In the present invention, the substrate includes any conductive solid substrate (which can be understood as a substrate with a conductive layer grown on the surface), including metal, conductive silicon and silicon A substrate covered with a metal film, silicon carbide, gallium nitride, gallium oxide, diamond, graphene, ITO (indium tin oxide) material, or other solid semiconductor conductive substrate or any solid substrate material covered with a conductive layer.

FIG. 1B is a scanning electron microscope image of AlGaN nanowires in an embodiment of the present invention. As an optional embodiment, the average length of a single nanowire of the AlGaN nanowire 120 is 10 nm-5000 nm, which can be selected in the range of 300 nm-400 nm; The specific surface area of the nanowires is made larger, and the rate of the redox reaction in the photodetection process is increased at the same time.

As an optional embodiment, the coverage (or filling rate) of the AlGaN nanowires 120 is 1%-99%, optionally about 70%. The coverage density is equivalent to the sum of the upper surface area of the nanowires and the percentage of the entire substrate surface area occupied, and is used to reflect the spacing between nanowires, the number of nanowires on a unit surface, and the like.

As an optional embodiment, the photoelectrode includes a photoanode formed by n-type GaN-based nanowires and a photocathode formed by p-type GaN-based nanowires, and also includes promoter nanoparticles distributed on the surface thereof.

As an optional embodiment, the GaN-based nanowires are n-type GaN-based nanowires, and the surface of the photoelectrode further includes a protective layer formed on the surface of the n-type GaN-based nanowires, and the thickness of the protective layer is less than or equal to 10 nm. For preventing photocorrosion of GaN-based nanowires, the protective layer is titanium dioxide (TiO ₂ ) or other materials that can play a protective role.

FIG. 2 is a schematic diagram of the modified cocatalyst nano-Pt particles in an AlGaN nanowire according to an embodiment of the present invention. As an optional embodiment, in the AlGaN nanostructure 200 of modified cocatalyst nanoparticles shown in FIG. 2 , the photocathode further includes cocatalyst nanoparticles 210 modified on the surface of the nanowires in the AlGaN nanowires 120 . The size of 210 is 0.1nm-1000nm. Correspondingly, the corresponding n-type gallium nitride-based nanowires in the present invention (such as AlGaN or InGaN nanowires, etc., which are not limited here, shall be subject to the protection scope defined in the claims), which can be used as the optoelectronics in the present invention. The photoanode of the chemical photodetector, the n-type nanowires can choose to form at least one protective layer on the surface of the nanowires before modifying the cocatalyst nanoparticles. In order to prevent the photocorrosion phenomenon of the n-type GaN-based nanowires from occurring, details are not repeated here.

On the nanowires of the AlGaN nanowires 120, photodeposition, or atomic layer deposition (ALD), electrodeposition (chemical loading method), and impregnation method (chemical loading method) are used to decorate the cocatalyst nanoparticles on the nanowires. line surface.

Specifically, when solar-blind ultraviolet light corresponding to the band gap of the AlGaN nanowires 120 is used to illuminate the AlGaN nanowires 120 in the photodeposition process, in the case of the semiconductor photoelectric effect, the nanowires of the AlGaN nanowires 120 absorb photons and generate photogenerated light. electron-hole pair. Then the photogenerated electrons diffuse to the surface of the nanowire. Since the photogenerated electron energy is greater than the reduction potential of the cocatalyst precursor group in the solution, the photogenerated electron diffused to the surface of the nanowire will reduce the cocatalyst precursor group modified on the surface of the AlGaN nanowire. , so that modified nanoparticles 210 are formed on the nanowire surfaces of the AlGaN nanowires 120 . Its particle size diameter can be 0.1nm-1000nm, optional 5nm, and it is modified on the surface of nanowires. In the subsequent photodetection process, the cocatalyst significantly enhanced the reduction reaction activity of the system, accelerated the reaction rate, and improved the photoresponse performance.

As an optional embodiment, the co-catalyst nanoparticles 210 include metal particles active in the water reduction reaction. As an optional embodiment, the metal particle material includes platinum, rhenium, palladium, iridium, rhodium, iron, cobalt or nickel, etc., or a multi-component alloy thereof. The alloy uses two metals at the same time, such as RuFe and RuCo. In the present invention, platinum (Pt) can be selected. The cocatalyst nanoparticles 210 need to have appropriate adsorption energy for water molecules and reduction products, and have higher water reduction activity, so that the reduction reaction is more intense, and the photocurrent signal during the light detection process is stronger. Correspondingly, for the photoanode, the cocatalyst nanoparticles can include metal particles with water oxidation reaction activity, including iridium, iron, cobalt, nickel or ruthenium, etc., or their multi-component alloys, which have a correspondingly higher Water oxidation activity, the oxidation reaction is more intense. Those skilled in the art should understand that the introduction of the cocatalyst modification material in this example does not limit the protection scope of the present invention, but is only an embodiment of the present invention.

FIG. 3A is a schematic cross-sectional view of the package of the AlGaN nanowire photocathode 300 in an embodiment of the present invention; FIG. 3B is a schematic view of the packaging of the AlGaN nanowire photocathode 300 in an embodiment of the present invention. As an optional embodiment, in order to successfully encapsulate the above-mentioned AlGaN nanowires 120 of the photocathode, the photoelectrochemical photodetector further includes: a wire 310 disposed in the conductive region of the substrate 110, the wire 310 and the photocathode are covered and fixed, The cured cladding structure 320 of the AlGaN nanowire 120 of the photocathode is exposed. As shown in FIG. 3B , a curing window 321 can be formed on the surface of the curing structure of the curing coating structure 320 , and the AlGaN nanowires 120 are exposed through the curing window 321 , so that in the subsequent photodetection process, the solar-blind ultraviolet light applied from the outside directly passes through The curing window 321 is irradiated onto the AlGaN nanowire 120 . The optional material of the substrate 110 here can be a p-type Si (100) surface silicon wafer with an area size of 1 cm×1 cm and a thickness between 0.01 mm and 1000 mm. At this time, the conductive area nanowires are arranged on the back of the substrate 110, As shown in Figure 3A. The wires are arranged on the backside of the substrate. The conductive area may be a certain area on the backside or the frontside of the silicon wafer except for the nanowires scraped with a diamond pen, which is not specifically limited in the present invention.

As an optional embodiment, the material of the wire 310 includes gold, silver, copper, etc., and the size of the wire 310 is selected to match the size of the substrate 110 . For example, the wire 310 may be selected to be about 1.2 cm wide and 5 cm long, and the material may be copper Cu. Conductive copper tape can also be used.

As an optional embodiment, the material of the cured encapsulation structure 320 includes a liquid material that can be cured and has insulating properties after curing, and the cured encapsulated structure 320 is epoxy resin or the like, which has wrapping and insulating effects.

As an optional embodiment, a liquid alloy 330 disposed in the conductive region of the substrate and a conductive glue 340 disposed on the surface of the wire 310 and opposite to the liquid alloy 330 are further included between the wire 310 and the substrate 110 . As an optional embodiment, the liquid alloy 330 is a liquid gallium indium (GaIn) alloy, and the purity of the liquid gallium indium (GaIn) alloy is optional between 90% and 99.99999%; the conductive adhesive 340 is silver glue. Specifically, the liquid alloy 330 can be in direct contact with the conductive surface of the substrate to form an ohmic contact, which can achieve better electrical conductivity and current stability. Similarly, the conductive glue that fixes the wire 310 and the substrate 110, and fixes the liquid alloy 330 between the wire 310 and the substrate 110 together, not only has the function of fixing and wrapping, but also has better conductivity and better conductivity. current stability. In addition, based on the above packaging method, a packaged photoelectrode with ohmic contact characteristics is prepared, which can better avoid the Schottky barrier formed by direct contact between the surface of the conductive area of the substrate and the metal wire, so as to facilitate current conduction.

4 is a schematic diagram of the preparation of a novel solar-blind ultraviolet photoelectrochemical photodetector in an embodiment of the present invention. As an optional embodiment, the photoelectrochemical photodetector 400 further includes: an electrolyte solution (not shown in the figure) in contact with the photocathode structure 300, and a reference electrode 420 and a counter electrode 430 in contact with the electrolyte solution. A certain distance is maintained between the electrode 420, the counter electrode 430 and the photocathode 300, and together they are accommodated by a light-transmitting container 410 having at least limited ability to absorb solar-blind ultraviolet light; wherein, the reference electrode 420, the counter electrode 430 and the photocathode 300 They are respectively connected with electrochemical workstations 440 with current monitoring function. The electrochemical workstation 440 has a photocurrent monitoring function. Therefore, it basically constitutes a photoelectrochemical photodetector based on a simple water reduction reaction as a photoelectric reaction mechanism.

As an optional embodiment, the electrolyte solution is an acidic or neutral electrolyte solution, the acidic electrolyte solution includes sulfuric acid, hydrochloric acid, and perchloric acid, the neutral electrolyte solution is sodium sulfate, and the concentration of the electrolyte solution is 0.5 mol/L; the reference electrode is Silver/silver chloride electrode; the counter electrode includes platinum electrode, carbon electrode. The above compositions and the above-mentioned AlGaN nanowire photocathode 300 together constitute a complete novel solar-blind ultraviolet photoelectrochemical photodetector. The novel solar-blind UV photoelectrochemical photodetector can further optimize the photodetection responsivity by modifying the cocatalyst.

Another aspect of the present invention proposes a novel solar-blind ultraviolet photoelectrochemical photodetector product. FIG. 5 is a product schematic diagram of the novel solar-blind ultraviolet photoelectrochemical photodetector in an embodiment of the present invention. The product includes the above-mentioned photoelectrochemical photodetector and an encapsulation structure 500 for encapsulating the photoelectrochemical photodetector. The encapsulation structure 500 includes a casing structure 510 for encapsulating the photoelectrochemical photodetector; the surface of the casing structure 510 is provided with an optical The window 511 is provided with a light-transmitting surface 520 matched with the optical window 511 for sealing the optical window 511. The distance between the light-transmitting surface 520 and the photocathode surface with the AlGaN nanowires 120 is greater than or equal to 0.01mm, and the distance can be Choose 0.2cm, but there is no limit to the specific spacing. The AlGaN nanowires 120 decorated with cocatalyst nanoparticles are irradiated on the photocathode 300 for solar-blind ultraviolet light through the light-transmitting surface 520 . The structure is simple, and the preparation materials are easy to obtain.

As an optional embodiment, the light-transmitting surface 520 includes a transparent material with limited ability to absorb solar-blind ultraviolet light; the shell structure 510 includes a shell structure formed of a polytetrafluoroethylene material. As an optional embodiment, a surface of the casing structure 510 is provided with a sealable/openable injection hole 530 , an exhaust hole 540 and at least three electrode holes 550 for arranging the photocathode, the reference electrode and the counter electrode respectively. , 560, 570. The manufacturing process requirement is low and the cost is low.

Example 2:

The present invention proposes a gallium nitride-based material nanowire structure applied to a photodetector, and correspondingly proposes a preparation method of the material structure, overcomes the technical difficulties in the field, and achieves a breakthrough and unexpected technology Effect. Among them, those skilled in the art should understand that the nanowire structure can be a regular arrangement, such as a nanowire structure prepared by directional growth, and can also include an irregularly arranged nanowire structure. The so-called "regular" can be understood as the arrangement of nanowires It has periodicity; the so-called "irregular" can be understood as the arrangement of the nanowires without periodicity, and can also be understood as the length, diameter, distance between adjacent nanowires, nanowires on the same substrate The growth angle of the line (relative to the substrate) is inconsistent, and there is no rule to follow. In addition, in the introduction of gallium nitride-based materials in the present invention, for example, AlGaN or InGaN is only a symbolic expression of the material, and does not represent the standard chemical formula of the material. Correspondingly, the chemical formula of AlGaN can be selected as Al _x Ga _{1- xN} , one of _BxAlyGa1 - _xyN or _{InxAlyGa1 - xyN} , 0≤x< ₁ , 0≤y≤1. That is, the gallium nitride-based material may be AlGaN or InGaN, or a gallium nitride-based material such as AlInGaN, which is not limited in the present invention.

The photoelectrode mentioned in the claims of the present invention can be a photocathode or a photoanode, and can be specifically distinguished by its doping component (eg, magnesium doping or silicon doping), which corresponds to the reduction in the present invention. reaction or oxidation reaction. In order to clearly express the function of the photoelectrode in the present invention, the present invention is mainly described by taking the photoelectrode of the AlGaN or InGaN nanowire structure as an example. Those skilled in the art should understand that the AlGaN or InGaN nanowire photocathode mentioned in the specification is not a limitation on a photoanode, nor a limitation on a non-AlGaN or InGaN photoelectrode.

As an embodiment of the present invention, the AlGaN nanowires grown on the surface of the substrate can be grown by molecular beam epitaxy (Molecular Beam Epitaxy, ie MBE) or metal organic chemical vapor deposition (Metal Organic Chemical Vapor Deposition, ie MOCVD), conventional chemical It can be prepared by vapor deposition method, halide vapor phase epitaxy, pulsed laser deposition and other methods, which are not specifically limited in the present invention. Meanwhile, in order to express the AlGaN nanowires of the present invention more clearly, the following mainly introduces molecular beam epitaxy (MBE) as the basic preparation method.

One aspect of the present invention proposes a method for preparing a photoelectrochemical photodetector. As shown in FIG. 6 , a schematic flowchart of a method for preparing a photoelectrochemical photodetector in an embodiment of the present invention, the method includes:

S610. Select the AlGaN or InGaN composition according to the wavelength of the light to be detected by the photodetector; in the gallium nitride-based material, by controlling different composition ratios of aluminum or indium, corresponding AlGaN or InGaN materials with different composition ratios can be obtained The band gap of the AlGaN or InGaN material varies with the composition ratio of Al/Ga, In/Ga, and Al/In/Ga, corresponding to different light absorption wavelengths. In this embodiment, the composition of aluminum in the gallium nitride-based material can be controlled, the composition of indium in the gallium nitride-based material can also be controlled, and the composition of aluminum and indium in the gallium nitride-based material can be controlled at the same time The modification control of fraction and component ratio is very simple and precise. Therefore, the preparation of the nanowire material corresponding to the wavelength of the full-spectrum light can be better adapted, and the preparation process is simplified. The above is only the introduction of AlGaN or InGaN in the gallium nitride-based material in the embodiment of the present invention. Correspondingly, the aluminum or indium in the gallium nitride-based material can be replaced by boron, and the corresponding composition adjustment can still be applied to the above solution.

S620, forming AlGaN nanowires or InGaN nanowires on the surface of the substrate according to the composition; as an embodiment of the present invention, the gallium nitride-based nanowire structure prepared by molecular beam epitaxy has a Nanomaterials and nitride nanomaterials (such as gallium oxide nanostructures) have the advantages of high stability, high crystal quality, and adjustable band gap height matching, which can ensure excellent water reduction/oxidation performance under light irradiation, that is, photodetection performance .

S630 , modifying cocatalyst nanoparticles on the AlGaN nanowires or InGaN nanowires; using a cocatalyst nanoparticle modification method (eg, photodeposition), such as atomic layer deposition (Atomic Layer Deposition), on the AlGaN nanowires or InGaN nanowires Deposition, ALD), electrodeposition method (chemical loading method), impregnation method (chemical loading method) to decorate the cocatalyst nanoparticles on the surface of nanowires.

S640, encapsulating the AlGaN nanowires or InGaN nanowires with modified cocatalyst nanoparticles to obtain a photoelectrode to prevent leakage of electricity from the side or back gaps of the substrate, and can also fix the epitaxy through the curing action of silver glue and epoxy resin, etc. piece.

S650, and preparing a photoelectrochemical photodetector by using a photoelectrode, the photoelectrochemical photodetector is composed of a photoelectrode, and the photoelectrode is irradiated by light to generate photogenerated electron-hole pairs, thereby forming a current with other components in the photodetector Circuit, the generated photocurrent can be detected by the outside world, which can reflect the photoelectric detection ability, which can be used in the fields of military, industry and communication.

For example, in the preparation process of molecular beam epitaxy, forming AlGaN nanowires or InGaN nanowires on the substrate surface according to the composition in S620 includes: setting aluminum (Al) according to the corresponding gallium nitride-based material composition The temperature program of the source furnace or the indium (In) source furnace and turning on or off, form gallium nitride based nanowires of the corresponding composition on the substrate. Optionally, using molecular beam epitaxy equipment, each elemental source in the source furnace will generate a corresponding atomic beam under ultra-high vacuum and a certain temperature, and the opening/closing and temperature setting of each furnace source can realize one or more The atomic beam generated by the furnace source is precisely controlled to control the generation of GaN-based materials of different compositions. In this embodiment, if the composition of aluminum in the gallium nitride-based material is controlled to grow AlGaN nanowires, it is only necessary to open the aluminum furnace source and the gallium source furnace, and close the indium furnace source; To grow InGaN nanowires, you only need to open the indium furnace source and the gallium source furnace, and close the aluminum furnace source. Therefore, by controlling the volume flow of the atomic beams of each furnace source and the opening and closing timing of each furnace source through the source furnace temperature, the technical solution of the present invention can further accurately control the composition ratio of the nanowire material.

As an optional embodiment, selecting the AlGaN or InGaN composition according to the wavelength of the light to be detected by the photodetector includes: according to the following formula: Eg=3.42eV+x×2.86eV-x(1-x)1.0eV AlGaN composition corresponding to the wavelength of light to be detected; or according to the following formula: Eg=3.42eV-x×2.65eV-x(1-x)2.4eV to determine the composition of InGaN corresponding to the wavelength of light to be detected. Figure 7 is a simple comparison diagram of the spectrum of the photoelectrochemical photodetector in an embodiment of the present invention. Generally, the wavelength of light less than 400 nm is in the ultraviolet region. Specifically, when the wavelength of light is less than 290 nm, it can reach the ultraviolet region of solar blindness; visible light The light wavelength is generally between 400nm-700nm; more than 700nm is the infrared light region, and the photoelectrochemical photodetector generally studies the visible light wavelength range. The energy band relationship of the photoelectrode semiconductor material of the photoelectrochemical photodetector is related to the absorption ability of the material to the corresponding light wavelength range, and the energy band relationship of the photoelectrode semiconductor material is related to the alloy composition ratio of the GaN-based nanomaterial. Therefore, only by controlling the composition ratio of aluminum or indium during the growth of nanowires, the band gap can be precisely regulated, and the full-band light absorption of infrared, visible light and ultraviolet can be realized.

As an optional embodiment, forming AlGaN nanowires or InGaN nanowires on the surface of the substrate according to the composition further includes: forming a nanohole array structure on the substrate, the thickness of the nanohole array structure is less than or equal to 50 nm; The p-type doped or n-type doped gallium nitride-based material is positioned and filled in the nanohole to form a composite layer, and the nanohole array structure of the composite layer is removed to form gallium nitride-based nanowires on the surface of the substrate.

Specifically, in the embodiment of the present invention, the reverse formation principle of nanowires/nanopores can be used to prepare a silica nanopore structure on the surface of the substrate, for example, a silica nanopore array layer with a thickness of up to 50 nm, nanopore The holes can be formed directly through the silicon dioxide layer with the substrate surface as the bottom surface. The gallium nitride-based crystal nuclei can be pre-formed in the nanopores of the silica nanopore structure, and then the nanopores can be filled by molecular beam epitaxy or MOCVD to form AlGaN nanomaterials or InGaN nanomaterials filled in the nanopores In addition, even if the GaN-based crystal nucleus is not formed in the nanopore, due to the inert nature of silicon dioxide, when the substrate is a silicon substrate or a sapphire substrate, for example, molecular beam epitaxy or MOCVD method can also directly A gallium nitride based material is formed on the bottom surface of the nanopore. Silica can be removed by chemical etching or optical etching, or it can be retained as an isolation layer. In the case of retention, it may affect the modification of cocatalyst nanoparticles. Therefore, silica can be optionally removed. Corresponding to the AlGaN nanomaterials or InGaN nanowires forming the nanopore size, the length may be 200 nm. Through the above method, it is faster and easier to form high-quality single-crystal gallium nitride-based nanowires with corresponding wavelengths, and the shape similarity of adjacent nanowires can also be improved. Among them, it should be noted that the removal of the silicon dioxide layer is not the key of this embodiment, and the confinement effect brought by it limits the growth of the thin film, so that the present invention can realize the controlled growth of nanowires in a defined area. In other words, even if the thickness of the silicon dioxide nanopore array layer is only 10-50 nm, the length of the formed AlGaN nanomaterial or InGaN nanowire can still grow to 200 nm after the nanopore structure is filled thereon.

As another embodiment of the present invention, forming AlGaN nanowires or InGaN nanowires on the surface of the substrate according to the composition further includes: forming a nanohole array structure on the substrate, and the thickness of the nanohole array structure is less than or equal to 50 nm; The gallium nitride-based material is positioned and filled in the nanohole to form a composite layer, and the gallium nitride-based nanowire is continuously formed on the surface of the composite layer at a position corresponding to the nanohole. At this time, the composite layer is not removed. On the one hand, the thickness of the composite layer is very small, for example, a composite layer of 20 nm can be selected; The other parts of the nanowires directly form nanowires, which actually protrude from the surface of the composite layer and can reach a size of several hundreds of nanometers or even microns, so the size of the nanowires will be much larger than the size of the composite layer. In this case, the function of the nanowires will not be affected.

As an optional embodiment, forming AlGaN nanowires or InGaN nanowires on the surface of the substrate according to the composition further includes: forming an AlGaN thin film or an InGaN thin film on the substrate, for the AlGaN thin film or the InGaN thin film Etching is performed to form the AlGaN nanowires or InGaN nanowires on the substrate surface. Specifically, in the embodiment of the present invention, an AlGaN film or InGaN film with high crystal quality can be directly formed on the substrate by molecular beam epitaxy or MOCVD, and then formed on the AlGaN film or InGaN film by micro-nano processing technology. Photoresist, silicon dioxide or metal islands, and then the AlGaN or InGaN thin films can be etched by dry etching methods such as inductively coupled plasma etching (Inductively Coupled Plasma, ICP). The silicon or metal is etched slowly, and the remaining unprotected parts are etched faster to form AlGaN nanowires or InGaN nanowires on the substrate. Wherein, the corresponding substrate may be a silicon wafer or a sapphire substrate. Through the above method, it is more direct and convenient to form high-quality single-crystal gallium nitride-based nanowires of corresponding wavelengths, and the shape similarity of adjacent nanowires can be better, the shape of the nanowires is more stable, and the shape is regular and controllable.

As an optional embodiment, forming AlGaN nanowires or InGaN nanowires on the surface of the substrate according to the above components includes: controlling the doping ratio of magnesium or silicon, and forming p-type doping with a corresponding doping ratio on the substrate Or n-doped AlGaN nanowires or InGaN nanowires. Specifically, as an embodiment of the present invention, in the preparation process of the molecular beam epitaxy method, by controlling the switch of the silicon (Si) source furnace and/or the magnesium (Mg) source furnace and the source furnace temperature, the nanowire material can be precisely controlled. doping concentration.

As an optional embodiment, during the preparation process of molecular beam epitaxy, forming AlGaN nanowires or InGaN nanowires on the surface of the substrate according to the composition includes: disposing the substrate in a preparation chamber, and at a first temperature Degas the preparation chamber for at least the first time, transfer the substrate set in the preparation chamber to the buffer chamber, degas the buffer chamber at the second temperature for at least the second time, and transfer the substrate in the buffer chamber to the growth chamber for Growth of AlGaN nanowires or InGaN nanowires. Specifically, in this embodiment, taking the formation of AlGaN nanowires as an example, molecular beam epitaxy (MBE) equipment can be used, and a p-type Si (100) substrate (ie, a silicon wafer) can be used as the substrate to transfer the silicon wafer into the The MBE equipment preparation chamber (such as the load lock chamber) is used for degassing preparation, so that the MBE equipment can reach the corresponding vacuum degree, for example, the vacuum degree can reach 10 ^-9 , and the baking and degassing time at the first temperature of 200°C is kept at least satisfactorily The first time is 1 hour, after that, the silicon wafer in the preparation chamber is sent to the buffer chamber, and the baking and degassing time is kept at the second temperature of 600°C for at least 2 hours for the second time, so as to remove the water in the buffer chamber as much as possible. and adsorption of gas molecules on silicon wafers. After the degassing is completed, the silicon wafer is transferred to the growth chamber for the growth of AlGaN nanowires.

As an optional embodiment, in the preparation process of molecular beam epitaxy, by controlling the opening or closing of the aluminum (Al) source furnace or the indium (In) source furnace, the heating program of the source furnace is controlled according to the corresponding AlGaN or InGaN group. The following steps are: forming AlGaN nanowires or InGaN nanowires of the corresponding composition on the substrate, including: after the substrate is transferred to the growth chamber, controlling to open a gallium (Ga) source furnace communicated with the growth chamber, with the first equivalent A high pressure beam of gallium as a source of gallium and a first volume flow of plasma nitrogen as a source of nitrogen are maintained at a third temperature for at least a third time to form GaN seeds on the surface of the substrate. Specifically, in this embodiment, a molecular beam epitaxy (MBE) equipment can be used, and a p-type Si (100) substrate (ie, a silicon wafer) can be used as the substrate, and after the silicon wafer enters the growth chamber, the opening and the growth chamber are controlled to be opened The connected gallium source furnaces use the first equivalent pressure (BEP) 6.0×10 ^-8 Torr gallium beam as the gallium source and the first volume flow rate of 1sccm plasma nitrogen to form high-brightness nitrogen plasma as the nitrogen source. Keep the temperature at 500°C for at least a third time for 1 minute to form GaN seeds on the surface of the silicon wafer, increase the possibility of nucleation, and form a base for the growth of nanowires on the silicon wafer, so that higher crystal quality can be grown on the silicon wafer. of nanowires.

As an optional embodiment, in the preparation process of molecular beam epitaxy, by controlling the opening or closing of the aluminum (Al) source furnace or the indium (In) source furnace, the heating program of the source furnace is controlled according to the corresponding AlGaN or InGaN group. and forming AlGaN nanowires or InGaN nanowires of corresponding composition on the substrate, further comprising: controlling to open the aluminum source furnace or the indium source furnace, and under the condition that the first volume flow of plasma nitrogen is used as the nitrogen source, in the first AlGaN nanowires or InGaN nanowires of corresponding composition are formed on the surface of the substrate by maintaining the aluminum beam current of the second equivalent pressure or the indium beam current of the third equivalent pressure at four temperatures, and cooperating with the gallium beam current of the fourth equivalent pressure Wire. Specifically, in this embodiment, taking the formation of AlGaN nanowires as an example, the aluminum source furnace is controlled to open, and the plasma nitrogen with the first volume flow of 1 sccm is used as the nitrogen source, and the second temperature is kept at a fourth temperature of 610° C. AlGaN nanowires of corresponding composition are formed on the surface of the silicon wafer by using an aluminum beam with an equivalent pressure of 2.0×10 ^-8 Torr and a gallium beam with a fourth equivalent pressure of 3.0×10 ^-8 Torr. If InGaN nanowires are formed, due to the difference between aluminum and indium, it is necessary to turn on the indium furnace source and keep the aluminum furnace source closed, and replace the corresponding aluminum beam current parameters with an indium beam current with a third equivalent pressure of 4.0×10 ^-8 Torr , other steps can be left unchanged. Therefore, the alloy ratio between aluminum and indium in the nanowires can be precisely controlled by the above method, so as to achieve AlGaN nanowires or InGaN nanowires with corresponding light wavelengths. The composition ratio of aluminum or indium is estimated by comparing the BEP of aluminum or indium and gallium beams, and the BEP ratio is adjusted by controlling the temperature to achieve the purpose of regulating the composition. For example, in the preparation process of AlGaN nanowires corresponding to ultraviolet light, The purpose of adjusting the Al composition is achieved by adjusting the equivalent pressure (BEP) of aluminum between 6×10 ^-8 Torr and 1×10 ^-8 Torr; or, the preparation process of InGaN nanowires corresponding to visible light and infrared light Among them, the purpose of adjusting the In composition is achieved by adjusting the BEP of indium between 4×10 ^-8 Torr and 1×10 ^-8 Torr.

As an optional embodiment, in the preparation process of molecular beam epitaxy, by controlling the opening or closing of the aluminum (Al) source furnace or the indium (In) source furnace, the heating program of the source furnace is controlled according to the corresponding AlGaN or InGaN group. According to the method of forming AlGaN nanowires or InGaN nanowires of corresponding composition on the substrate, it also includes: when controlling the opening or closing of the aluminum (Al) source furnace or the indium (In) source furnace, the temperature of the magnesium source furnace is the first The magnesium source furnace or the silicon source furnace is controlled to be turned on or off at the fifth temperature or when the silicon source furnace is the sixth temperature, so that the AlGaN nanowires or InGaN nanowires of the corresponding composition formed on the substrate become p-type doped or n-doped type doping. The photoelectrode is divided into photoanode or photocathode. Correspondingly, p-type doped AlGaN nanowires or InGaN nanowires can better complete the water reduction reaction, especially when the surface is modified with cocatalyst nanoparticles, it can be used for photoelectrochemistry system photocathode. Generally, by doping a certain proportion of magnesium, the doped AlGaN nanowires or InGaN nanowires can become p-type doped materials. This doping method can achieve better material stability and will not treat the doped materials. Cause any impact, the later water reduction reaction response is better. On the contrary, n-type doped AlGaN nanowires or InGaN nanowires can better complete the water oxidation reaction, especially when their surfaces are modified with cocatalyst nanoparticles, they can be used as photoanodes in photoelectrochemical systems. Generally, a certain proportion of silicon can be doped to make the doped AlGaN nanowire or InGaN nanowire an n-type doped material, and this doping method can obtain a better response to the water oxidation reaction. Specifically, in this embodiment, taking the preparation of p-type AlGaN nanowires as an example, when the aluminum (Al) source furnace is controlled to be turned on and the indium (In) source furnace is ensured to be turned off, the magnesium source furnace is turned on, and the magnesium source furnace is turned on at the temperature of the magnesium source furnace. The fifth temperature is 360° C., so that the AlGaN nanowires of the corresponding composition formed on the substrate become p-type doped. On the contrary, if the preparation of n-type InGaN nanowires is taken as an example, the silicon source furnace needs to be opened, and the sixth reaction temperature of the silicon source furnace is 1180°C.

As an optional embodiment, modifying the cocatalyst nanoparticles on the AlGaN nanowires or InGaN nanowires includes: disposing the AlGaN nanowires or InGaN nanowires in a precursor aqueous solution of a first concentration, and simultaneously applying and The light with the corresponding wavelength is irradiated to modify the cocatalyst nanoparticles on the surface of the AlGaN nanowire or the InGaN nanowire. Specifically, in this embodiment, taking the preparation of p-type AlGaN nanowire modified co-catalyst Pt nanoparticles as an example, a certain concentration of chloroplatinic acid solution can be selected as the precursor aqueous solution, and the grown p-type Al _x Ga _{1 -x} N nanowires are placed in 50 mL of deionized water, in a sealed container, the reaction temperature is maintained at 10 °C by circulating water cooling, and a certain degree of vacuum is maintained. A chloroplatinic acid solution with a concentration of 10 mg/ml was injected into the container, and light with a wavelength corresponding to the band gap of the AlxGa1 _{- xN} nanowire was applied, and the light was kept for more than 30 minutes. Due to the semiconductor photoelectric effect, the Al _x Ga _1-x N nanowires absorb photons to generate photo-generated electron-hole pairs. Then the photogenerated electrons diffuse to the surface of the nanowires. Since the energy of the photogenerated electrons is greater than the reduction potential of the platinate ([PtCl ₆ ] ^2- ) group in the solution, the photogenerated electrons diffused to the surface of the nanowires will reduce the [ PtCl ₆ ] ^2- , forming platinum particles on the surface of nanowires, that is, the photodeposition process. After the photodeposition reaction is completed, the sample is taken out and cleaned to obtain p-type AlGaN nanowires modified with platinum nanoparticles of the co-catalyst, wherein the particle size of the platinum particles can reach 0.1 nm-1000 nm. For n-type nanowires, it is only necessary to replace the precursor aqueous solution of chloroplatinic acid with a ruthenium chloride solution of equal concentration. By distributing and modifying the cocatalyst nanoparticles on the surface of the nanowire, the photoelectrode can make the reaction more intense, the reaction speed is faster, and the photocurrent is larger in the process of water reduction/oxidation reaction.

As an optional embodiment, before the AlGaN nanowires or InGaN nanowires are decorated with the cocatalyst nanoparticles, the method further includes: when the AlGaN nanowires or InGaN nanowires are n-type doped A protective layer is prepared on the surface of the wire. Since n-type doping is easier to achieve in the preparation process of molecular beam epitaxy, in the process of photodeposition or photodetection, the grown nanowires are easily corroded by the photogenerated holes generated by themselves, thus causing a certain impact on the photoanode. Therefore, it is necessary to prepare a nanowire protective layer on the surface of the nanowires on the basis of the nanowires of the photoanode, which has the tunnel conduction effect, and at the same time meets the requirements of good electrical conductivity and will not affect the photodetection performance. Specifically, in this embodiment, taking the preparation of n-type InGaN nanowires as an example, before photodepositing them to modify the cocatalyst nanoparticles, a layer of non-ferrous metals is directly deposited on the surface of the n-type InGaN nanowires by atomic layer deposition. A shaped protective layer, the material of the protective layer can be TiO ₂ or a material with similar properties, so as to prevent the photocorrosion of the n-type InGaN nanowire material in the case of hole enrichment. Taking the amorphous TiO ₂ protective layer as an example, tetrakis(dimethylamino) titanium(IV) TEMAT and water can be used as precursors in the preparation process, and the precursor containers are kept at 65 °C and 25 °C, respectively. Co-deposition is carried out for 60 cycles. Each cycle includes the process of feeding titanium precursor for 0.1 seconds, plasma nitrogen for 10 seconds, water vapor for 0.1 seconds, and _N2 for 10 seconds. Finally, amorphous TiO can be formed on the surface of n-type InGaN nanowire materials. ₂ protective layers.

As an optional embodiment, encapsulating AlGaN nanowires or InGaN nanowires with modified cocatalyst nanoparticles to obtain a photoelectrode includes: fixing a wire on the AlGaN nanowires or InGaN nanowires with modified cocatalyst nanoparticles On the conductive area of the substrate of the wire, the wire is clad and fixed together with the substrate, and the AlGaN nanowire or InGaN nanowire is exposed at the same time to form a packaged photoelectrode. When encapsulating the photoelectrode, it is necessary to pay attention to lead out the wires, and also need to pay attention to exposing the nanowires of the photoelectrode to the outside. When pulling out the wire, it should be noted that one end of the wire needs to be opposite to the predetermined conductive area of the silicon wafer. The photocathode nanowires are exposed so that the light of the corresponding light wavelength can be directly irradiated to the nanowires.

As an optional embodiment, fixing the wire on the conductive area of the substrate having the AlGaN nanowires or InGaN nanowires with modified cocatalyst nanoparticles includes: scraping off the oxide layer on the conductive area of the substrate, A liquid alloy is applied on the conductive area where the oxide layer has been scraped off, and conductive glue is applied on the surface of the wire between the wire and the conductive area and opposite to the position of the liquid alloy. In order to prevent the direct contact between the used substrate and the metal wire, which will form a Schottky barrier, which is not conducive to current conduction, it is necessary to prepare a photoelectrode with ohmic contact characteristics. Specifically, in the embodiment of the present invention, taking a silicon wafer as a substrate as an example, the silicon dioxide (SiO 2 ) layer naturally grown on the back of the silicon wafer is scraped off with a diamond knife, and the silicon dioxide (SiO ₂ ) layer after scraping the silicon dioxide layer is scraped off with a diamond knife. The conductive area on the backside of the sheet is coated with a liquid alloy (eg, gallium indium (GaIn) alloy) to form an ohmic contact. Then, the conductive adhesive silver (Ag) adhesive is applied on the copper (Cu) strip of the wire, and it is compacted with the back of the silicon wafer coated with gallium indium alloy. Finally, the whole photoelectrode is encapsulated with epoxy resin, leaving only nanometers The wire growth surface is exposed, thereby completing the preliminary encapsulation of the photoelectrode, avoiding the formation of the Schottky potential barrier, and facilitating the conduction of the photocurrent.

As an optional embodiment, using a photoelectrode to prepare a photoelectrochemical photodetector includes: disposing a photoelectrode, a reference electrode, and a counter electrode in an electrolyte solution of a second concentration at a certain distance to prepare a three-electrode system to form a photoelectrochemical system. light detector. Specifically, in the embodiment of the present invention, taking the photocathode three-electrode system for preparing p-type AlGaN nanowires as an example, an electrolyte solution solution (with a second concentration of 0.5mol/L sulfuric acid (H ₂ SO ₄ ) is added to the light-transmitting container ) aqueous solution as an example), and then the above prepared Al _x Ga _1-x N nanowire electrode (photocathode), reference electrode (take silver/silver chloride (Ag/AgCl) as an example), counter electrode (take silver/silver chloride (Ag/AgCl) as an example), respectively The platinum Pt mesh electrode is placed in the electrolyte solution solution, the preparation of the three-electrode system is completed, and the photoelectrochemical photodetector of the present invention is basically formed. The electro-chemical workstation is connected to the conductive end of each electrode, and the test parameters of the electrochemical workstation are set through the computer, that is, the test or application of the light detection performance can be carried out. Correspondingly, taking the photoanode of n-type InGaN nanowires as an example, the electrolyte solution solution can be replaced with a 1 mol/L hydrobromic acid solution. The preparation process of the three-electrode system is simple and feasible, which greatly simplifies the preparation process of the photodetector, making it suitable for mass production.

Another aspect of the present invention provides a photoelectrochemical photodetector, which is prepared by using the above-mentioned method for preparing a photoelectrochemical photodetector, and the photodetector includes a photoelectrode with gallium nitride-based nanowires.

Example 3:

One aspect of the present invention proposes a solar-blind UV photoelectrochemical photodetector. FIG. 8A is a schematic diagram of a solar-blind UV photoelectrochemical photodetector GaN-based nanohole array in an embodiment of the present invention, and FIG. 8B is a schematic diagram of the present invention. As shown in a schematic diagram of a GaN-based nanopore array with modified cocatalyst nanoparticles in a solar-blind UV photoelectrochemical photodetector in one embodiment, the photodetector includes a photoelectrode, the photoelectrode includes a substrate 810, and further includes The GaN-based nanohole 840 array 830 formed on the surface of the 810 constitutes the basic structure 800 of the photocathode of the novel photoelectrochemical photodetector proposed by the present invention.

Among them, those skilled in the art should understand that the nanopore structure can be a regular arrangement, such as a nanopore structure prepared by directional growth, or it can also include an irregular disordered nanopore structure. The so-called "regular" can be understood as the nanopore structure. Whether the arrangement is periodic. l In addition, the gallium nitride-based material can be selected as AlGaN in the present invention, and AlGaN is only a symbolic expression of the material, and does not represent the standard chemical formula of the material. Specifically, the chemical formula of the GaN-based group can be selected from one of _BxAlyGa1 - _xyN or InxAlyGa1 _{- xyN} , _0≤x < ₁ , 0≤y≤1. That is, the gallium nitride-based material may be AlGaN or InGaN, or a gallium nitride-based material such as AlInGaN, which is not limited in the present invention.

The photoelectrode mentioned in the claims of the present invention can be a photocathode or a photoanode, and can be specifically distinguished by its doping component (eg, magnesium doping or silicon doping), which corresponds to the reduction in the present invention. reaction or oxidation reaction. In order to clearly express the function of the photoelectrode in the present invention, the present invention is mainly described by taking the AlGaN photocathode as an example. Those skilled in the art should understand that it is not a limitation on the photoanode, nor is it a limitation on the non-AlGaN photoelectrode.

As an embodiment of the present invention, the AlGaN nanohole arrays grown on the substrate can be conventionally chemically produced by molecular beam epitaxy (Molecular Beam Epitaxy, ie MBE) or metal organic chemical vapor deposition (Metal Organic Chemical Vapor Deposition, ie MOCVD). It can be prepared by vapor deposition method, halide vapor phase epitaxy, pulsed laser deposition and other methods, which are not specifically limited in the present invention. Meanwhile, in order to express the AlGaN nanohole array of the present invention more clearly, the following mainly introduces metalorganic chemical vapor deposition (MOCVD) as the basic preparation method.

Directional formation of high-crystalline quality n-type doped AlGaN nanohole arrays on the substrate surface due to its high stability, high crystal quality, and high performance compared to common oxide and nitride nanomaterials (such as gallium oxide nanostructures) The advantages of gap height matching and adjustable, etc., can ensure excellent water oxidation performance under solar-blind light irradiation, that is, light detection performance. In addition, for AlGaN material, its band gap can be changed with composition doping, specifically:

Eg=3.42eV+x*2.86eV-x(1-x)*1.0eV…………………………(1)

Eg is the forbidden band width of the semiconductor, corresponding to different absorption wavelengths.

Therefore, according to formula (1), by controlling the proportion of Al and Ga components in the preparation process, the band gap of the prepared photoanode can be precisely regulated to achieve light absorption in the solar-blind ultraviolet band.

In addition, the AlGaN nanopores with high crystal quality prepared by the present invention can be p-type doped materials, specifically, silicon Si atoms can be doped, and in the subsequent photoelectrochemical reaction process, they move to the electrolyte solution/semiconductor interface as electrons instead of electrons. Any impact on AlGaN nanomaterials or structures, with very high stability relative to oxide nanomaterials (eg, gallium oxide nanostructures) that have not yet been realized. Correspondingly, the prepared AlGaN nanopore of the present invention can be a p-type doped material, specifically, magnesium Mg atoms can be doped, so as to be used as a photocathode. It should be noted that, in the structure of the photoanode, a protective layer of a certain thickness needs to be deposited on its surface to prevent it from being corroded by photo-generated holes during the photodetection process.

As shown in FIG. 8A , as an embodiment of the present invention, the AlGaN nanoholes 840 may be regular holes such as cylindrical holes or prisms, or irregular holes such as curved shapes. Optionally, the nanoholes 840 may be cylindrical holes. The diameter of the nanohole 840 is 0.1 μm-5 μm, and the optional diameter is 2 μm; the depth thereof is 50 nm-600 nm, and the optional depth is 200 nm. The specific surface area of the nanopore 840 array is made larger, and the specific surface area of the photodetection reaction is increased at the same time. In addition, the pore size of the nanopore 840 exceeds 500 nm, which is far beyond the design size of conventional nanopores, and is not considered a nanoscale structure in a certain sense. This size design can prevent the bubbles generated in the subsequent photodetection process from adhering to the inner surface of the nanopore 840 and causing difficulty in mass transfer of the solution, while the design of the large-diameter nanopore can easily lead to unstable performance such as short circuits, and is widely used in the field. There is no such large pore size nanopore design research in China, which will hinder those skilled in the art from implementing this scheme. Therefore, this is a breakthrough design solution in the art, which cannot be thought of by those skilled in the art.

As an embodiment of the present invention, the filling degree of the AlGaN nanohole array can be defined by patterning conditions, the spacing between adjacent nanoholes is 0.1 μm-5 μm, and the optional spacing is 2 μm. The specific surface area of the nanopore array is made larger, and the specific surface area of the photodetection reaction is increased at the same time.

As shown in FIGS. 8A-8B, as an embodiment of the present invention, the substrate 810 includes a sapphire substrate, a gallium nitride substrate, a gallium oxide substrate, a silicon carbide substrate, a silicon substrate, or a GaN-based material thin film. Substrates, etc. or other substrates with conductive properties. The optional substrate is a sapphire substrate, and in the embodiment of the present invention, the substrate material can be selected from aluminum oxide Al ₂ O ₃ or the like.

As an embodiment of the present invention, the GaN-based nanohole array is an n-type GaN-based nanohole array. The surface of the GaN-based nanohole array of the photoelectrode further includes a protective layer covering the surface of the nanohole array. The thickness of the protective layer is less than or equal to 10 nm. The layer material includes at least titanium dioxide. The protective layer is used to prevent the photocorrosion phenomenon of the nanopores. Correspondingly, the corresponding p-type gallium nitride-based nanoholes in the present invention (such as AlGaN or InGaN nanoholes, etc., which are not limited here, are subject to the protection scope defined in the claims), which can be used as the optoelectronics in the present invention. The photocathode of the chemical photodetector (corresponding to the gallium nitride-based nanowire photocathode in the foregoing embodiment), correspondingly, it is optional to directly modify the cocatalyst nanoparticles on the surface of the p-type nanopore, and it is not necessary to modify the cocatalyst. At least one protective layer is formed on the surface of the nanopore before the nanoparticle, which will not be repeated here.

Due to lattice matching, a stable and high-crystal quality AlGaN single crystal thin film can be epitaxially formed on the substrate 810, which is beneficial to the preparation of the nanohole array in the next step.

As shown in FIGS. 8A-8B, as an embodiment of the present invention, a buffer layer 820 is further included between the substrate 810 and the AlGaN nanohole array 830, the buffer layer 820 includes at least three intermediate layers, and the buffer layer material includes aluminum nitride . Since the lattices of the substrate 810 and the AlGaN nanohole array 830 do not match, the addition of the buffer layer 820 between the two is beneficial to obtain a stable and high crystal quality AlGaN single crystal thin film during the preparation process, which is beneficial to the next step. Preparation of nanopore arrays.

As an embodiment of the present invention, the buffer layer 820 includes at least three intermediate layers. The first intermediate layer formed on the substrate 810 may have a thickness of 3 μm and is used as a nucleation layer; the third intermediate layer formed on the first intermediate layer The thickness of the second intermediate layer can be 100 nm; the thickness of the third intermediate layer formed on the second intermediate layer can be 1 μm, which is used as a template layer. The above-mentioned plurality of intermediate layers are not shown in the drawings. The composition of the multi-layer intermediate layer is conducive to the formation of a more flat and smooth surface of the third intermediate layer (that is, the surface of the buffer layer 820 ), so that a stable and high crystal quality AlGaN single crystal film can be obtained during the preparation process, which is conducive to the next step of nanopores Preparation of arrays. Correspondingly, the corresponding p-type gallium nitride-based nanoholes in the present invention (such as AlGaN or InGaN nanoholes, etc., which are not limited here, are subject to the protection scope defined in the claims), which can be used as the optoelectronics in the present invention. The photocathode of the chemical photodetector (corresponding to the gallium nitride-based nanowire photocathode in the foregoing embodiment), correspondingly, the gallium nitride-based nanopore structure can be formed directly on the surface of the substrate, without considering the The above buffer layer structure is added between the nanopore structure and the substrate.

As shown in FIG. 8B , as an embodiment of the present invention, the surface of the AlGaN nanohole array is further covered with a protective layer 870 , the thickness of the protective layer 870 is less than or equal to 10 nm, and the optional thickness is 2 nm. In the embodiment of the present invention, the protective layer may be an amorphous titanium dioxide TiO ₂ protective layer, which covers the entire surface of the AlGaN nanohole array, including the inner surface of the nanohole, so as to prevent the AlGaN material from being rich in holes during the photodetection process. The photocorrosion effect occurs under the condition of the collection, which affects the overall performance of the photodetector.

As shown in FIG. 8B , as an embodiment of the present invention, the photoanode further includes co-catalyst nanoparticles 850 distributed on the surface of the protective layer, the co-catalyst nanoparticles 850 are metal particles active in water redox reaction, and the material of the metal particles includes platinum , iridium, iron, cobalt, nickel or ruthenium and their multi-component alloys, the alloy is the use of two metals at the same time, such as RuFe, RuCo, etc. In the present invention, ruthenium can be selected as the preparation choice of the co-catalyst nanoparticles. The diameter of the co-catalyst nanoparticles can be selected from 0.1 nm to 1000 nm, and can be selected as 2 nm for better and more modification in the nanopore array. The cocatalyst nanoparticles distributed on the nanopore array can make the AlGaN nanopore array have stronger water oxidation reaction, making the photodetector more intense and faster.

As shown in FIG. 8B , as an embodiment of the present invention, the surface of the AlGaN nanohole array further includes a first region 860 not covered with the protective layer 870 , and the first region 860 is disposed outside the nanohole region. The first area is formed on the surface of the nanohole array and does not overlap with the area where the nanohole is located, so as to prevent the occurrence of a short circuit, and in addition, the extraction electrode can be more stable and effective.

As an embodiment of the present invention, the first region 860 includes spot-welded indium balls for forming a conductive region of the photoanode and for extracting the photoanode. By spot welding the indium balls, a conductive area in ohmic contact with the surface of the nanohole array can be formed on the first area 860. The conductive area can be selected as a square area of 2mm×2mm, which can achieve better conductive characteristics and current stability, and can be fixed at the same time. The wire leads out the electrode, that is, the photoanode can be formed.

As an embodiment of the present invention, similar to the structure of the photoelectrochemical photodetector composed of the photocathode, the photoelectrochemical photodetector further includes: an electrolyte solution in contact with the photoanode, and a reference electrode and a counter electrode in contact with the electrolyte solution, A certain distance is maintained between the reference electrode, the counter electrode and the photoanode, wherein the distance is approximately equal to 0.01 mm; wherein the reference electrode, the counter electrode and the photoanode are respectively connected to an electrochemical workstation with a current monitoring function. Therefore, a photoelectrochemical photodetector based on a simple water oxidation reaction as a photoelectric reaction mechanism is basically constituted. The preparation conditions are simple, the purity requirements are low, and the working process has little effect on the electrode material.

As an embodiment of the present invention, the electrolyte solution includes an acidic or neutral electrolyte solution, the neutral electrolyte solution is sodium sulfate, the acidic electrolyte solution includes phosphate buffer solution or hydrobromic acid, and the concentration of the electrolyte solution is 0.01mol/L～5mol/L, In the present invention, a weakly acidic electrolyte solution such as 0.5mol/L hydrobromic acid solution can be selected; the reference electrode is silver/silver chloride (Ag/AgCl) electrode, etc.; the counter electrode includes platinum (Pt) electrode, carbon (C) electrode, etc. , the specific structure can be made into the form of mesh electrodes and so on. A complete novel solar-blind ultraviolet photoelectrochemical photodetector is formed by the above compositions and the above-mentioned AlGaN nanohole array photoanode. The novel solar-blind UV photoelectrochemical photodetector can further optimize the photodetection responsivity by modifying the cocatalyst nanoparticles.

Another aspect of the present invention provides a solar-blind ultraviolet photoelectrochemical photodetector product, which is similar in structure to that of a photocathode photodetector. The product includes the above-mentioned photodetector and a packaging structure for packaging the photodetector. The packaging structure It includes a casing structure that coats the photodetector to encapsulate it; an optical window is opened on a surface of the casing structure, a light-transmitting surface matched with the optical window and used to seal the optical window is arranged, and the light-transmitting surface is connected with an AlGaN nano-hole array. The surface of the photocathode is arranged at a certain distance, wherein the distance is approximately equal to 0.01mm. In this embodiment, the distance can be selected to be 0.2cm, which is used for the solar-blind ultraviolet light to be irradiated on the photoanode through the light-transmitting surface. Cocatalyst nanoparticles are distributed. AlGaN nanopore arrays. The structure is simple, and the preparation materials are easy to obtain.

As an embodiment of the present invention, the light-transmitting surface includes a transparent material with limited ability to absorb solar-blind ultraviolet light; the shell structure includes a shell structure formed of a polytetrafluoroethylene material. As an optional embodiment, a closed/openable injection hole, an exhaust hole and at least three electrode holes for arranging a photocathode, a reference electrode and a counter electrode are opened on one surface of the casing structure. The manufacturing process requirement is low and the cost is low.

A novel solar-blind ultraviolet photoelectrochemical photodetector product proposed by the present invention has the advantages of simple structure, low manufacturing process requirements, low cost, and simple packaging structure of the above-mentioned photoelectrochemical photodetector, which is convenient for practical application. And it is easy to mass-produce, realizing the commercialization of photoelectrochemical photodetectors.

Another aspect of the present invention provides a method for preparing a solar-blind ultraviolet photoelectrochemical photodetector, which is applied to the preparation of the above-mentioned photodetector. As shown in the schematic flow diagram, the preparation method includes:

S910, forming an AlGaN nanohole array on the surface of the substrate; specifically, as an embodiment of the present invention, metal organic chemical vapor deposition (MOCVD) can be selected to prepare it, and triethylboron can be selected in the preparation process Alkane (TEB), trimethylaluminum (TMAl), trimethylgallium (TMGa), ammonia ( _NH3 ) as growth precursors to provide B, Al, Ga, N sources, Si as n-type dopant source, _H2 was used as carrier gas. In gallium nitride-based materials, by controlling the composition ratio of different aluminum and gallium, corresponding AlGaN materials can be obtained. AlGaN materials with different composition ratios can make the energy band of the material itself correspondingly different, and the band gap varies with the doping composition. changed to correspond to different wavelengths of light absorption. In this embodiment, the composition of aluminum in the gallium nitride-based material can be controlled, and the modification and control of the composition ratio is very simple and accurate. Therefore, it can better adapt to the preparation of nanomaterials corresponding to the wavelength of broad spectrum light, and can also precisely control the formation of nanomaterials suitable for the wavelength of solar-blind ultraviolet light, which simplifies the preparation process. At the same time, doping the formed AlGaN nanohole array with silicon can obtain an n-type doped AlGaN nanohole array that is more suitable for photoanode, which is beneficial to improve the water oxidation reaction of the photodetector and improve the photocurrent response intensity and speed.

S920, modifying the cocatalyst nanoparticles on the nanopores of the AlGaN nanopore array; specifically, as an embodiment of the present invention, photodeposition or atomic layer deposition (Atomic Layer Deposition, ALD), electrodeposition method (chemical loading method), impregnation method (chemical loading method) to decorate the cocatalyst nanoparticles on the surface/side of the nanoporous structure.

S930, a photodetector is prepared by using the AlGaN nanopore array with the modified cocatalyst nanoparticles as a photoanode.

The photoanode functional layer is prepared on the surface of the substrate to ensure a higher crystal quality AlGaN nanopore array at a lower cost; a buffer layer is formed between the substrate and the AlGaN nanopore array, which improves the film formation effect of the AlGaN thin film. At the same time, the formation of high crystal quality AlGaN nanohole arrays is ensured; the surface of the AlGaN nanohole arrays is covered with an amorphous protective layer, which can prevent the photocorrosion effect of the photoanode during the photodetection process and affect the overall photodetection performance of the photodetector; In addition, the modification of cocatalyst nanoparticles on the surface of the protective layer further increased the reaction rate of water oxidation, thereby improving the response to UV light.

As shown in FIG. 10A, a schematic diagram of the first stage of the preparation process of the AlGaN nanohole array in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector in an embodiment of the present invention, as an embodiment of the present invention, an AlGaN nanohole array is formed on the surface of the substrate, It includes: pre-annealing the substrate 810; forming a buffer layer 820 on the pre-annealed substrate 810; optionally, before the growth, pre-heating the sapphire substrate in a H ₂ -NH ₃ environment at 1200° C. for 5 minutes The high-temperature annealing of the sapphire substrate makes the surface of the sapphire substrate cleaner and smoother, and is more suitable as a substrate for AlGaN nanohole arrays. AlGaN nanohole arrays may be formed on the surface of the buffer layer 820 of the substrate 810 by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), and the specific method is not limited. Before forming the AlGaN nanohole array, an AlGaN thin film 831 is pre-formed on the surface of the buffer layer 820. Optionally, a 200 nm AlGaN thin film is grown on the buffer layer at a temperature of 1150°C. By manipulating the thin film 831, a nanopore array is formed. By forming the thin film 831 first, a high crystal quality for forming the nanohole array can be ensured.

As an embodiment of the present invention, forming the buffer layer 820 on the pre-annealed substrate 810 includes: the buffer layer 820 includes at least two intermediate layers (not shown); an intermediate layer, the second intermediate layer is formed on the first intermediate layer under the second condition; the third intermediate layer is formed on the second intermediate layer under the third condition. Specifically, a buffer layer 820 is formed on the pre-annealed sapphire sink 810, and MOCVD can be used as a preparation method, including: using AlN as a buffer layer preparation material, first, at a temperature of 850°C-950°C, TMAl and NH ₃ The volume flow of 3 μm was controlled to form a low-temperature AlN nucleation layer with a thickness of 3 μm on the sapphire substrate 810 under the first conditions of 4 sccm and 3000 sccm, respectively, as the first intermediate layer; under the second conditions at a temperature of 850-1250 ℃, An AlN spacer layer with a thickness of 100 nm is formed on the first intermediate layer as the second intermediate layer; and a high temperature AlN with a thickness of 1 μm is formed on the second intermediate layer under the third condition of 1250 ° C and V/III of 180 Template layer, as the third intermediate layer. The formation of the multi-layer intermediate layer is beneficial to form a more flat and smooth surface of the third intermediate layer (ie, the surface of the buffer layer 820 ), so that a stable and high crystal quality AlGaN nanopore array can be obtained during the preparation process.

As an embodiment of the present invention, forming the AlGaN nanohole array on the surface of the buffer layer of the substrate includes: forming an AlGaN thin film on the buffer layer under the fourth condition; and etching the thin film to form the AlGaN nanohole array. As shown in FIG. 10A to FIG. 10F , as shown in the schematic diagram of the first stage of the preparation process of the AlGaN nanopore array in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector in each embodiment of the present invention, the cylindrical nanopore array is prepared by means of micro-nano processing technology. An AlGaN thin film may be formed on the third intermediate layer. As shown in FIG. 10A to FIG. 10B , the fourth condition described includes any preparation conditions used in the following steps: using photoresist with a type of S1813 as the etching sacrificial layer 910 in the subsequent etching process, and controlling the coating rate At 4000 rpm for 30 seconds, a photoresist sacrificial layer 910 with a thickness of about 1.2 μm is formed; as shown in FIG. 10C , a circle with a diameter of 2 μm is drawn on the mask 320, and the spacing between adjacent patterns is 2 μm, forming Array structure, the post-baking temperature was controlled at 115°C, and the time was 90 seconds; the pattern was defined using an Optical Aligner-SUSS MABA6 UV lithography machine, and contact exposure was used with a spacing of 60 μm and an exposure time of 7.5 seconds (step 3); then developed at AZ300MIF The exposed pattern is developed in solution for 50 seconds, so that a circular pattern 911 defined by the exposed and developed area corresponding to the position of the nano-hole is formed on the sacrificial layer 910, and washed in clean water. As shown in FIG. 10D , inductively coupled plasma (ICP) is optionally used to etch the AlGaN thin film first to realize the nanoporous structure 930 on the sacrificial layer 910 . As shown in FIG. 10E , the AlGaN thin film grown by MOCVD is etched using Oxford ICP 180, and the etched area is a circular pattern 911 defined by UV lithography. The etching gas was Cl ₂ /BCl ₃ /Ar, the gas flow was controlled at 10/25/25 sccm, the temperature was 50° C., the chamber pressure was 6 mTorr, the ICP power was 450 W, and the radio frequency power was 100 W. No sample was placed before the etching started, and the cavity was operated with the above process parameters to ensure the gas environment of the cavity. After the etching starts, the etching time is controlled to be 2.5 minutes, and AlGaN nanoholes with a depth of 200 nm are formed. The selection ratio of AlGaN and S1813 photoresist is 1:2, and the remaining thickness of S1813 photoresist after etching is about 800μm (step5). Use acetone, isopropanol, and water to wash off the remaining photoresist on the sample to complete the preparation of the nanopore array, as shown in Figure 10F.

As an embodiment of the present invention, the AlGaN nanohole array 830 can be formed on the surface of the buffer layer 820 of the substrate, including: forming small silicon dioxide islands on the surface of the buffer layer 820, and forming silicon dioxide islands on the surface of the buffer layer 820 The AlGaN nanohole array 830. The small islands may be protrusions or regions formed on the surface of the buffer layer 820, and are formed by using special processing techniques or special materials. Specifically, on the surface of the third intermediate layer of the buffer layer 820 , small silicon dioxide islands can be formed on the surface of the third intermediate layer by means of micro-nano processing technology, and then, by molecular beam epitaxy (MBE) or metal organic chemistry Vapor deposition method (MOCVD) directly conducts thin film growth on the surface of the third intermediate layer where the silicon dioxide islands have been formed. Since the silica islands have an inhibitory effect on the film growth, the locations of the silica islands do not form thin film material. Finally, the AlGaN nanohole array 830 is formed on the surface of the buffer layer 820 . As an embodiment of the present invention, the material of the above-mentioned small islands can be selected from materials such as silicon dioxide, titanium dioxide, silicon nitride or metal, and the above description of the small silicon dioxide islands is not intended to limit the materials of the small islands.

As an embodiment of the present invention, modifying the cocatalyst nanoparticles on the nanopores of the AlGaN nanopore array includes: forming an amorphous protective layer covering the surface of the nanopore array on the surface of the AlGaN nanopore array; modifying the cocatalyst on the surface of the protective layer nanoparticles. As shown in Fig. 10G, as shown in the schematic diagram of the first stage of the preparation process of AlGaN nanohole arrays in the preparation method of solar-blind ultraviolet photoelectrochemical photodetectors in various embodiments of the present invention, 2nm-thick amorphous TiO ₂ is optionally deposited by atomic layer deposition (ALD) for protection Layer (a-TiO ₂ ) 870 to prevent photocorrosion of the AlGaN material under hole-enriched conditions. In the deposition process, tetrakis (dimethylamino) titanium (IV) TEMAT and water were used as precursors, and the precursor containers were kept at 65° C. and 25° C. respectively. Co-deposition was performed for 60 cycles. Each cycle includes the process of feeding titanium precursor for 0.1s, purging N ₂ for 10 s, passing water vapor for 0.1 s, and purging N ₂ for 10 s. Atomic layer deposition method is used to form a covering surface of the nanopore array on the surface of the AlGaN nanopore array. The amorphous protective layer 870 is used to protect the nanohole array from cavitation corrosion. Because of its tunnel conduction effect, it has good conductivity and will not affect the detection performance.

As shown in FIG. 10H the schematic diagram of the first stage of the preparation process of the AlGaN nanohole array in the preparation method of the solar-blind ultraviolet photoelectrochemical photodetector in each embodiment of the present invention, the surface of the protective layer 870 can be optionally modified by photo-deposition method. 100 μL of 20 mg/mL ruthenium chloride (RuCl ₃ ) solution was added to 20 mL of deionized water, and the prepared a- _{TiO 2} /n-AlGaN nanopore array was placed in it. The hole array applies UV illumination corresponding to the band gap. Due to the semiconductor photoelectric effect, a-TiO ₂ /n-AlGaN nanohole arrays generate photo-generated electron-hole pairs after absorbing photons. Then the photogenerated electrons diffuse to the surface of the nanopore. Since the energy of the photogenerated electrons is greater than the reduction potential of Ru ³⁺ in the solution, the photogenerated electrons diffused to the surface of the nanopore will be reduced and modified on the surface of the a-TiO ₂ /n-AlGaN nanopore array. Ru ³⁺ , forming nano Ru particles, the nano particles can be 2nm.

As an embodiment of the present invention, using the AlGaN nanohole array with modified cocatalyst nanoparticles as a photoanode to prepare a photodetector includes: forming a first area not covered with a protective layer on the surface of the AlGaN nanohole array, and the first area is set outside the nanopore area; spot-welded indium balls are arranged on the first area to form a conductive area of the photoanode for drawing out the photoanode. The first area is formed on the surface of the nanohole array and does not overlap with the area where the nanohole is located, so as to prevent the occurrence of a short circuit, and in addition, the extraction electrode can be more stable and effective. By spot welding the indium balls, a conductive area in ohmic contact with the surface of the nanohole array can be formed on the first area 860. The conductive area can be selected as a square area of 2mm×2mm, which can achieve better conductive characteristics and current stability, and can be fixed at the same time. The wire leads out the electrode, that is, the photoanode can be formed.

As an embodiment of the present invention, a photodetector is prepared by using an AlGaN nanopore array with modified cocatalyst nanoparticles as a photoanode, and the photodetector also includes: disposing a reference electrode, a counter electrode, and a photoanode in an electrolyte solution at a certain distance to prepare a photodetector. The electrode system constitutes a photodetector. Therefore, a photoelectrochemical photodetector based on a simple water oxidation reaction as a photoelectric reaction mechanism is basically constituted. The preparation conditions are simple, the purity requirements are low, and the working process has little effect on the electrode material.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in further detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (11)

1. a preparation method applied to photoelectrochemical photodetector, is characterized in that, described method comprises: Selecting the gallium nitride-based material composition according to the wavelength of the light to be detected by the photodetector; Forming gallium nitride-based nanowires on the surface of the substrate according to the composition, which includes: setting the heating program of the aluminum source furnace or the indium source furnace and turning it on or off according to the corresponding gallium nitride-based material composition, on the substrate GaN-based nanowires of corresponding components are formed on it; modifying cocatalyst nanoparticles on the gallium nitride-based nanowires; Encapsulating the gallium nitride-based nanowires modified with cocatalyst nanoparticles to obtain a photoelectrode; and The photoelectrochemical photodetector is prepared by using the photoelectrode. 2 . The method according to claim 1 , wherein selecting the gallium nitride-based material composition according to the wavelength of the light to be detected by the photodetector comprises: 3 . According to the following formula: Eg = 3.42eV + x × 2.86eV – x(1 – x) × 1.0eV determining the AlxGa1 _{- xN} composition corresponding to the wavelength of the light to be detected; or According to the following formula: Eg = 3.42eV – x × 2.65eV – x(1 – x) × 2.4eV determining the In _x Ga _1-x N composition corresponding to the wavelength of the light to be detected; Among them, 0≤x<1, Eg is the forbidden band width of the semiconductor, corresponding to the absorption wavelength of different light bands. 3. The method of claim 1, wherein forming gallium nitride-based nanowires on the surface of the substrate according to the composition, further comprising: forming a nanohole array structure on the substrate, the thickness of the nanohole array structure is less than or equal to 50 nm; positioning and filling the nanopore with a gallium nitride-based material to form a composite layer, and Continue to form the gallium nitride-based nanowire on the surface of the composite layer at a position corresponding to the nanohole; or The nanopore array structure of the composite layer is removed to form the gallium nitride based nanowires on the surface of the substrate. 4. The method of claim 1, wherein forming gallium nitride-based nanowires on the surface of the substrate according to the composition, further comprising: forming a gallium nitride-based thin film on the substrate, The gallium nitride based thin film is etched to form the gallium nitride based nanowires on the surface of the substrate. 5. The method of claim 1, wherein forming gallium nitride-based nanowires on the surface of the substrate according to the composition comprises: The doping ratio of magnesium or silicon is controlled, and p-type doped or n-type doped gallium nitride-based nanowires with corresponding doping ratio are formed on the substrate. 6. The method according to claim 1, wherein modifying the cocatalyst nanoparticles on the gallium nitride-based nanowires comprises: The gallium nitride-based nanowires are placed in a precursor aqueous solution of a first concentration, and light irradiation with a wavelength corresponding to the energy band of the nanowires is applied simultaneously, so as to modify the surface of the gallium nitride-based nanowires with nano-promoter catalysts. particles. 7. The method according to claim 6, wherein before modifying the cocatalyst nanoparticles on the gallium nitride-based nanowires, the method further comprises: When the gallium nitride-based nanowire is n-type doped, a protective layer is formed on the surface of the gallium nitride-based, and the thickness of the protective layer is less than or equal to 10 nm. 8. The method according to claim 1, wherein the photoelectrode is obtained by encapsulating the gallium nitride-based nanowires with the modified cocatalyst nanoparticles, comprising: A wire is fixedly attached to the conductive area of the substrate with the modified cocatalyst nanoparticle on the gallium nitride-based nanowire, The wires are clad and fixed together with the substrate while exposing the gallium nitride-based nanowires to form a packaged photoelectrode. 9 . The method according to claim 8 , wherein the fixing and attaching a wire on the conductive area of the substrate with the gallium nitride-based nanowires having the modified cocatalyst nanoparticles comprises: 10 . scraping the oxide layer on the conductive area of the substrate, coating liquid alloy on the conductive area where the oxide layer has been scraped off, Conductive glue is coated on the surface of the wire between the wire and the conductive area and opposite to the position of the liquid alloy. 10. The method according to claim 1, wherein the preparing the photoelectrochemical photodetector by using the photoelectrode comprises: The photoelectrode, the reference electrode, and the counter electrode are arranged in the electrolyte solution of the second concentration at a certain interval to prepare a three-electrode system to constitute the photoelectrochemical photodetector, and the interval is greater than or equal to 0.01 mm. 11. A photoelectrochemical photodetector, characterized in that, prepared according to the preparation method of any one of claims 1-10, the photodetector comprises a photoelectrode having gallium nitride-based nanowires.

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