CN112880821B - Solar blind ultraviolet electrochemical photodetector and preparation method thereof - Google Patents
Solar blind ultraviolet electrochemical photodetector and preparation method thereof Download PDFInfo
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- CN112880821B CN112880821B CN201911203022.7A CN201911203022A CN112880821B CN 112880821 B CN112880821 B CN 112880821B CN 201911203022 A CN201911203022 A CN 201911203022A CN 112880821 B CN112880821 B CN 112880821B
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Images
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/429—Photometry, e.g. photographic exposure meter using electric radiation detectors applied to measurement of ultraviolet light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/305—Electrodes, e.g. test electrodes; Half-cells optically transparent or photoresponsive electrodes
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/403—Cells and electrode assemblies
- G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
- G01N27/4146—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS involving nanosized elements, e.g. nanotubes, nanowires
Abstract
The invention discloses a solar blind ultraviolet photoelectrochemical photodetector and a preparation method thereof, wherein the photodetector comprises a photoelectrode, the photoelectrode comprises a substrate and a p-type/n-type doped Gallium Nitride (GaN) based nanopore array formed on the surface of the substrate. In addition, the co-catalyst nano particles are modified on the GaN-based nano hole array to serve as the photoelectrode, so that the absorption and desorption processes of molecules are optimized, and the oxidation-reduction reaction rate of the photoelectrode in a solution is improved. Meanwhile, the design of a photoelectrochemical device is further optimized, the electrolyte solution environment is changed, and finally, a novel solar blind ultraviolet detector with high responsivity, high sensitivity, quick reaction, economy, environmental protection and self energy supply (without additional electric energy) is realized.
Description
Technical Field
The invention relates to the technical field of photoelectrochemical photodetectors, in particular to a solar blind ultraviolet photoelectrochemical photodetector and a preparation method thereof.
Background
Photodetectors (i.e., photo-detectors), i.e., devices that capture and convert optical signals into electrical signals, are widely used in the fields of imaging, communication, sensing, computing, emerging wearable devices, and detection in the aerospace field. The optical detector has wide application in various fields of military and national economy.
Most of the existing photodetectors are based on a simple Metal-Semiconductor-Metal (MSM) structure, and the MSM structure photodetectors need to apply an external bias during operation, which not only consumes power, but also needs to improve responsivity, response speed, and the like. Compared with the photoelectric detector composed of the traditional MSM semiconductor Schottky junction and the p-n/n-n junction, the photoelectrochemical photoelectric detector has the following advantages: additional electric energy is not needed; the light responsivity is higher, and the response time is adjustable; the manufacturing process is simple and the cost is low.
Although the photoelectrochemical light detector has great technical advantages over the conventional light detector, it is still in the beginning stage. The photoelectrochemical photodetector is developed from a photoelectrochemical reaction, and the research focus of the photoelectrochemical reaction is mainly artificial photosynthesis, namely the oxidation-reduction reaction under simulated sunlight (visible light wave band) and is used for photoelectrocatalysis research. The photoelectrochemical light detectors are not researched much, and comprise the research of photoelectrochemical light detectors of infrared light bands and ultraviolet light bands, while the photoelectrochemical light detectors of solar blind ultraviolet bands are lack of research.
The existing photoelectrochemical photodetector preparation materials are mainly powder materials or nanosheet materials, and have poor crystal quality, slow redox reaction rate and poor photodetection effect, such as gallium oxide nanomaterials. Therefore, it is very important to prepare a high-crystalline quality semiconductor suitable for a photoelectric chemical photodetector and apply the semiconductor to the solar blind ultraviolet detection field with great significance.
Disclosure of Invention
Technical problem to be solved
The invention provides a solar blind ultraviolet electrochemical optical detector, a product and a preparation method thereof, which are used for preparing a high-crystal-quality semiconductor material or structure and applying the semiconductor material or structure to the field of solar blind ultraviolet detection with great significance.
(II) technical scheme
One aspect of the invention provides a solar blind ultraviolet photoelectrochemical photodetector, which comprises a photoelectrode, wherein the photoelectrode comprises a substrate and a Gallium Nitride (GaN) based nanopore array formed on the surface of the substrate.
Optionally, the GaN-based nanopores have a diameter of 0.1-5 μm and a depth of 50-600 nm.
Optionally, the spacing between adjacent nanopores in the GaN-based nanopore array is between 0.1 μm and 5 μm.
Optionally, the substrate includes a sapphire substrate, a gallium nitride substrate, a gallium oxide substrate, a silicon carbide substrate, a silicon substrate, or a substrate provided with a GaN-based material thin film.
Optionally, a buffer layer is further included between the substrate and the GaN-based nanopore array, the buffer layer includes at least three intermediate layers, and the buffer layer is made of aluminum nitride, gallium nitride and the like.
Optionally, the buffer layer comprises a first intermediate layer formed on the substrate; a second intermediate layer formed on the first intermediate layer; a third intermediate layer formed on the second intermediate layer.
Optionally, the GaN-based nanopore array is an n-type GaN-based nanopore array, the surface of the GaN-based nanopore array of the photoelectrode further comprises a protective layer covering the surface of the nanopore array, the thickness of the protective layer is less than or equal to 10nm, and the protective layer material at least comprises titanium dioxide.
Optionally, the photoelectrode further comprises promoter nanoparticles distributed on the surface of the protective layer, wherein the promoter nanoparticles comprise metal particles which can be active in water reduction reaction, and the metal particle materials comprise platinum, rhenium, palladium, iridium, rhodium, iron, cobalt, nickel or the like and related multi-component alloys thereof. And can also be metal particles with water oxidation reaction activity, including iridium, iron, cobalt, nickel or ruthenium, and related multi-component alloys.
Optionally, the GaN-based nanopore array surface further comprises a first region uncovered by the protective layer, the first region being disposed outside the nanopore region.
Optionally, the first region includes a spot-bonded indium ball thereon for forming a conductive region of the photoelectrode for leading out the photoelectrode.
Optionally, the photoelectrochemical light detector further comprises: the distance between the reference electrode and the photoelectrode is more than or equal to 0.01 mm; the reference electrode, the counter electrode and the photoelectrode are respectively connected with an electrochemical workstation with a current monitoring function.
Optionally, the electrolyte solution comprises an acidic or neutral electrolyte solution, the neutral electrolyte solution is sodium sulfate, the acidic electrolyte solution comprises a phosphate buffer solution or hydrobromic acid, and the concentration of the electrolyte solution is 0.01-0.5 mol/L; the reference electrode is a silver/silver chloride (Ag/AgCl) electrode; the counter electrode includes a platinum (Pt) electrode and a carbon (C) electrode.
Another aspect of the present invention provides a solar blind ultraviolet photoelectrochemical photodetector product, which includes the above photodetector and an encapsulation structure for encapsulating the photodetector, wherein the encapsulation structure includes a housing structure for encapsulating the photodetector; an optical window is arranged on one surface of the shell structure, a light transmitting surface which is matched with the optical window and used for sealing the optical window is arranged, the light transmitting surface and the photocathode surface with the GaN-based nano-hole array are arranged at a certain interval, wherein the interval is approximately equal to 0.01mm, and the GaN-based nano-hole array is used for enabling solar blind ultraviolet light to irradiate the photoelectrode through the light transmitting surface and distributing the catalyst-assisting nano-particles.
Optionally, the optically transmissive surface comprises a transparent material with limited ability to absorb ultraviolet light for solar blindness; the shell structure comprises a shell structure formed of polytetrafluoroethylene material.
The invention also provides a preparation method of the solar blind ultraviolet photoelectrochemical photodetector, which is applied to the preparation of the photodetector and comprises the following steps: forming a GaN-based nanopore array on the surface of a substrate; modifying cocatalyst nano particles on nano holes of the GaN-based nano hole array; and preparing the photodetector by using the GaN-based nano-pore array modified with the cocatalyst nano-particles as a photoelectrode.
Optionally, forming a GaN-based nanopore array on a substrate surface, comprising: pre-annealing the substrate; forming a buffer layer on the pre-annealed substrate; and forming a GaN-based nano-pore array on the surface of the buffer layer of the substrate.
Optionally, forming a buffer layer on the pre-annealed substrate includes: the buffer layer at least comprises two intermediate layers; forming a first intermediate layer on a surface of a substrate in a first condition, and forming a second intermediate layer on the first intermediate layer in a second condition; a third intermediate layer is formed in a third condition on the second intermediate layer.
Optionally, forming a GaN-based nanopore array on a surface of a buffer layer of a substrate, includes: forming a GaN-based thin film on the buffer layer under a fourth condition; and etching the film to form the GaN-based nanopore array.
Optionally, forming a GaN-based nanopore array on a surface of a buffer layer of a substrate, includes: and forming islands on the surface of the buffer layer, and forming the GaN-based nano-hole array on the surface of the buffer layer on which the islands are formed, wherein the islands can be made of silicon dioxide, titanium dioxide, silicon nitride, metal or the like.
Optionally, modifying the promoter nanoparticles on the nanopores of the GaN-based nanopore array, comprising: forming a protective layer covering the surface of the nanopore array on the surface of the GaN-based nanopore array; and modifying the surface of the protective layer with cocatalyst nanoparticles.
Optionally, fabricating a photodetector using the GaN-based nanopore array modified with the promoter nanoparticles as a photoelectrode, comprises: forming a first region uncovered by the protective layer on the surface of the GaN-based nanopore array, wherein the first region is arranged outside the nanopore region; and arranging a conductive area for spot welding indium balls on the first area to form a photoelectrode, and leading out the photoelectrode.
Optionally, the method for preparing the photodetector by using the GaN-based nanopore array modified with the cocatalyst nanoparticles as the photoelectrode further comprises: and arranging the reference electrode, the counter electrode and the photoelectrode in an electrolyte solution at a certain interval to prepare a three-electrode system to form the photodetector.
(III) advantageous effects
The novel solar-blind ultraviolet photoelectrochemical photodetector provided by the invention has the advantages that the high-crystal-quality n-type doped GaN-based nanopore array is directionally formed on the surface of the substrate, the specific surface area is larger, the interface formed by the n-type doped GaN-based nanopore array and an electrolyte solution is in more contact, and the separation and the transportation of photon-generated carriers are facilitated. In addition, modified cocatalyst nanoparticles (such as ruthenium Ru) are used as the photoelectrode on the GaN-based nanopore array, so that the absorption and desorption processes of molecules are optimized, the water oxidation reaction rate of the photoelectrode in a solution is improved, the photoelectric conversion efficiency is ensured, larger photoelectric response current is obtained, higher light responsivity is obtained, and the response time can be accurately regulated according to actual requirements. Meanwhile, the design of a photoelectrochemical device is further optimized, the electrolyte solution environment is changed, and finally, a novel solar blind ultraviolet detector with high responsivity, high sensitivity, quick reaction, economy, environmental protection and self energy supply (without additional electric energy) is realized.
The novel solar blind ultraviolet photoelectrochemical photodetector product provided by the invention has the advantages of simple structure, low manufacturing process requirement and low cost, and the packaging structure of the product is very simple, so that the product is convenient for practical application and easy for large-scale production, and the commercialization of the photoelectrochemical photodetector is realized.
According to the preparation method of the novel photoelectrochemical photodetector, the high-crystal-quality n-type doped GaN-based nanopore array is formed on the surface of the substrate and serves as a photoelectrode functional layer, so that the higher-crystal-quality nanopore array is ensured at lower cost; a buffer layer is formed between the substrate and the GaN-based nano-pore array, so that the film forming effect of the GaN-based film is improved, and the formation of the GaN-based nano-pore array with high crystal quality is ensured; the surface of the GaN-based nanopore array is covered with a protective layer, so that the photo-corrosion effect of the photoelectrode in the photo-detection process can be prevented, and the overall photo-detection performance of the photo-detector is prevented from being influenced; in addition, the surface of the protective layer is modified with the cocatalyst nanoparticles, so that the water oxidation reaction rate is further improved, and the ultraviolet response is improved. The novel solar blind ultraviolet photoelectrochemical photodetector with high responsivity, quick reaction, economy, environmental protection and self energy supply is prepared by the method, the traditional MSM photodetector with poor performance is replaced, and meanwhile, the method is easy to manufacture, low in cost and easy to produce in a large scale, and is beneficial to realizing the commercialization of the photoelectrochemical photodetector.
Drawings
FIG. 1A is a schematic illustration of AlGaN nanowires in an embodiment of the present invention;
FIG. 1B is a scanning electron microscope image of AlGaN nanowires in an embodiment of the present invention;
FIG. 2 is a schematic representation of modified co-catalyst nano-Pt particles in AlGaN nanowires in accordance with an embodiment of the present invention;
FIG. 3A is a schematic cross-sectional view of an AlGaN nanowire photocathode according to an embodiment of the present invention;
FIG. 3B is a schematic illustration of an AlGaN nanowire photocathode package according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a novel solar blind UV electrochemical photodetector fabricated in accordance with an embodiment of the present invention;
FIG. 5 is a schematic diagram of a novel solar blind UV electrochemical photodetector in accordance with an embodiment of the present invention;
FIG. 6 is a flow chart illustrating a method for fabricating a photoelectrochemical photodetector according to an embodiment of the present invention;
FIG. 7 is a simplified comparison of spectra from a photoelectrochemical photodetector according to an embodiment of the present invention;
fig. 8A is a schematic diagram of an AlGaN nanopore array of a solar blind ultraviolet electrochemical photodetector in an embodiment of the present invention;
fig. 8B is a schematic diagram of an AlGaN nanopore array with decorated promoter nanoparticles for a solar blind uv electrochemical photodetector in accordance with an embodiment of the present invention;
FIG. 9 is a schematic flow chart of a method for manufacturing a solar blind UV electrochemical photodetector according to an embodiment of the present invention;
fig. 10A is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method for fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention;
fig. 10B is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method of fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention;
fig. 10C is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method for fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention;
fig. 10D is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method of fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention;
fig. 10E is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method for fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention;
fig. 10F is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method for fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention;
fig. 10G is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method for fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention;
fig. 10H is a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method of fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention.
Detailed Description
Photoelectrochemical photodetectors are evolved from photoelectrochemical reactions. Taking p-type semiconductor as an example, photo-electrochemical reaction, i.e., the semiconductor is illuminated to generate photo-generated electrons and holes, the electrons undergo reduction reaction at the semiconductor electrode, and the holes flow through an external circuit to the counter electrode to undergo oxidation reaction (the opposite occurs for n-type semiconductor). The performance index light/dark current ratio, response time, illumination intensity and optical wavelength are directly related in the process, and a photoelectrochemical device specially used for optical detection is gradually derived. In the field of photoelectrochemical research, most of researches are focused on photoelectrocatalysis redox reaction under visible light conditions, the research on photoelectrochemistry as a light detector is less, and the research on photoelectrochemical light detectors in infrared bands and ultraviolet bands is less, so that the research is a brand new direction. In particular, photoelectrochemical catalysis focuses on the study of the chemical reaction mechanism, such as studying the amount of hydrogen generated by a semiconductor material during a photoelectrocatalytic reaction, how to increase the amount of hydrogen generated, and how to design reaction sites. The photoelectrochemical light detector mainly researches a light dark current signal generated in the photoelectrochemical reaction process to reflect the relevant parameters of the detection light, thereby realizing various photoelectrochemical detection functions.
In addition, the research direction of the iii-v nitride semiconductor material mainly focuses on Light Emitting Diodes (LEDs) and power devices, and since the cost of preparing nitride by Molecular Beam Epitaxy (MBE) is very high, the research of photoelectrochemical catalysis by using nitride nano material is still in the beginning stage, and even the research of photoelectrochemical photodetector by using iii-v nitride material is not mentioned. Generally, ultraviolet detection (non-solar-blind band) is performed by selecting chemically prepared powder samples (such as ZnO, TiO and ZnO)2Etc.), the photo-generated electron-hole pairs are easy to recombine due to poor crystal quality and many defects, which directly results in poor photo-detection performance. The invention creatively provides a GaN-based nanowire/nanopore structure, which is applied to a photoelectrochemical photodetector, overcomes the technical problems in the field, and achieves breakthrough technical effects.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
Example 1:
one aspect of the present invention provides a novel solar blind ultraviolet photoelectrochemical photodetector,fig. 1A is a schematic view of an AlGaN nanowire according to an embodiment of the present invention. The novel solar blind ultraviolet photoelectrochemical photodetector comprises a photocathode, wherein the photocathode comprises a substrate 110 and AlGaN nanowires 120 growing on the surface of the substrate 110, so that a basic structure 100 of the novel photoelectrochemical photodetector photocathode provided by the invention is formed. The GaN-based nanowire comprises an n-type GaN-based nanowire and a p-type GaN-based nanowire. It will be understood by those skilled in the art that the nanowire structure may be a regular arrangement, such as a directionally grown nanowire structure, or may include a non-regular arrangement of nanowires, and that "regular" is understood to mean whether the arrangement of nanowires is periodic or not; accordingly, the term "irregular" refers to the non-periodic arrangement of the nanowires, and also refers to the length and diameter of the nanowires, the distance between any adjacent nanowires, and the non-uniform and irregular growth angle (relative to the substrate) of the nanowires. In addition, the gallium nitride-based material can be selected as AlGaN in the invention, AlGaN is only a symbolic expression of the material and does not represent a standard chemical formula of the material, and specifically, the chemical formula of the GaN-based material can be selected as AlxGa1-xN，BxAlyGa1-x-yN or InxAlyGa1-x-yAnd x is more than or equal to 0 and less than 1, and y is more than or equal to 0 and less than or equal to 1 in N. That is, the gallium nitride-based material may be AlGaN, InGaN, or a gallium nitride-based material such as AlInGaN, which is not limited in the present invention.
The photoelectrode referred to in the claims of the present invention may be a photocathode or a photoanode, and may be distinguished by its doping component (e.g. magnesium-doped or silicon-doped), corresponding to a reduction reaction or an oxidation reaction in the present invention. To clearly express the function of the photoelectrode in the invention, the invention is mainly described by taking the AlGaN photocathode as an example. It will be understood by those skilled in the art that it is not a limitation of photo-anodes nor of non-AlGaN photo-electrodes. As an embodiment of the present invention, the AlGaN nanowire 120 grown on the surface of the substrate 110 may be prepared by a Molecular Beam Epitaxy (MBE) method, a Metal Organic Chemical Vapor Deposition (MOCVD) method, a conventional Chemical Vapor Deposition method, a halide Vapor phase Epitaxy (hal) method, or a pulsed laser Deposition (pulsed laser Deposition), which is not particularly limited in the present invention. Meanwhile, in order to more clearly express the AlGaN nanowire 120 according to the present invention, the following description is mainly given by taking a Molecular Beam Epitaxy (MBE) as a basic preparation method.
Compared with common oxide and nitride nanometer materials (such as gallium oxide nanometer structures), the AlGaN nanowire 120 has the advantages of high stability, high crystal quality, adjustable band gap height matching and the like, can ensure excellent water reduction performance under solar blind light irradiation, and is reflected as excellent light detection performance. In addition, for AlxGa1-xN material, the band gap of which can vary with the doping of the component, in particular:
Eg＝3.42eV+x*2.86eV–x(1-x)*1.0eV………………………(1)
wherein Eg is the forbidden bandwidth of the semiconductor and corresponds to the absorption wavelengths of different optical bands.
Therefore, according to the formula (1), the band gap of the prepared photocathode can be accurately regulated and controlled by controlling the ratio of Al and Ga components in the preparation process, and the light absorption of the solar-blind ultraviolet band is realized. Accordingly, for BxAlyGa1-x-yN or InxAlyGa1-x-yN (x is more than or equal to 0 and less than 1, y is more than or equal to 0 and less than or equal to 1) and the like, and the corresponding wavelength calculation formula can be correspondingly transformed, particularly taking the actual preparation requirement as the standard, and the invention does not limit the wavelength calculation formula.
In addition, the AlGaN nanowire with high crystal quality prepared by the invention can be a p-type doped material, and particularly can be doped with Mg atoms. When a p-type semiconductor is contacted with an aqueous solution, electron exchange occurs, and the final result is that the fermi levels of a water-semiconductor system are the same, the energy band of the p-type semiconductor bends downwards, so that electrons move to a contact surface, the surface is rich in electrons, the AlGaN nano material or structure cannot be influenced in the light detection process, and compared with an oxide nano material (such as a gallium oxide nano structure) which cannot realize p-type doping, the stability is very high, and the p-type doped AlGaN nano material can be used as a photocathode. Correspondingly, as another embodiment of the present invention, the n-type doped AlGaN nanowire may be changed and a protective layer may be applied to serve as the photo-anode.
As an alternative 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 characteristics, and the size of the silicon substrate is selected to be 1cm × 1cm, and the specific size is required according to the size of the photoelectrode, which is not limited in the present invention.
As an alternative embodiment, the silicon substrate includes an n-type silicon substrate, which is an n-type arbitrary crystal plane silicon substrate, such as a Si (111) plane substrate; the silicon substrate also comprises a p-type silicon substrate, wherein the p-type silicon substrate is a p-type arbitrary crystal plane silicon substrate, such as a Si (100) plane substrate. GaN-based nanowires of high crystal quality can be stably formed on the substrate. Specifically, the silicon substrate is only an optional substrate in the present invention, and in the present invention, the substrate includes any solid substrate (which may be understood as a substrate with a conductive layer grown on the surface) that can conduct electricity, including metal, conductive silicon, and a substrate covered with a metal thin film on the silicon surface, 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 view of an AlGaN nanowire according to an embodiment of the present invention. As an alternative embodiment, the average length of a single nanowire of the AlGaN nanowire 120 is 10nm to 5000nm, optionally in the length range of 300nm to 400 nm; the average diameter of the single nanowire is 5nm-5000nm, and 60nm-80nm can be selected. The specific surface area of the nanowire is larger, and meanwhile, the oxidation-reduction reaction rate in the light detection process is increased.
As an alternative embodiment, the coverage (or fill factor) of the AlGaN nanowire 120 is 1% to 99%, and optionally about 70%. The coverage density is equivalent to the percentage of the total area of the upper surfaces of the nanowires to the area occupied on the entire surface of the substrate, and is used to reflect the spacing between nanowires, the number of nanowires per unit surface, and the like.
As an alternative embodiment, the photoelectrode comprises a photoanode formed by n-type GaN-based nanowires and a photocathode formed by p-type GaN-based nanowires, and the photoelectrode also comprises cocatalyst nanoparticles distributed on the surface of the photoelectrode.
As an optional embodiment, the GaN-based nanowire is an n-type GaN-based nanowire, the surface of the photoelectrode further comprises a protective layer formed on the surface of the n-type GaN-based nanowire, and the thickness of the protective layer is less than or equal to 10 nm. For preventing GaN-based nanowire from photo-corrosion, the protective layer is titanium dioxide (TiO)2) Or other materials that may serve a protective function.
Fig. 2 is a schematic diagram of a modified co-catalyst nano-Pt particle in an AlGaN nanowire according to an embodiment of the present invention. As an alternative embodiment, in the modified promoter nanoparticle AlGaN nanostructure 200 shown in fig. 2, the photocathode further includes a promoter nanoparticle 210 modified on the surface of the nanowire in the AlGaN nanowire 120, and the size of the promoter nanoparticle 210 is 0.1nm to 1000 nm. Correspondingly, the corresponding n-type gallium nitride-based nanowire (e.g., AlGaN or InGaN nanowire, etc., without limitation, according to the protection scope defined by the claims) in the present invention can be used as the photo-anode of the photo-electrochemical photodetector in the present invention, and before the co-catalyst nanoparticle is modified, the n-type nanowire can be selectively formed with at least one protective layer on the surface of the nanowire, where the protective layer can be a protective layer made of the above-mentioned titanium dioxide, etc., for preventing the n-type GaN-based nanowire from photo-corrosion, and details thereof are not repeated herein.
The promoter nanoparticles are modified on the surface of the AlGaN nanowire 120 by using an Atomic Layer Deposition (ALD) method, an electrodeposition method (chemical loading method), or an immersion method (chemical loading method).
Specifically, when the AlGaN nanowire 120 in the process of photo deposition is irradiated with solar blind ultraviolet light corresponding to the band gap of the AlGaN nanowire 120, the nanowire of the AlGaN nanowire 120 absorbs photons to generate a photo-generated electron-hole pair under the condition of the semiconductor photoelectric effect. Subsequently, the photo-generated electrons diffuse to the surface of the nanowire, and because the energy of the photo-generated electrons is greater than the reduction potential of the promoter precursor group in the solution, the photo-generated electrons diffused to the surface of the nanowire are reduced and modified to the promoter precursor group on the surface of the AlGaN nanowire, so that the modified nanoparticles 210 are formed on the surface of the nanowire of the AlGaN nanowire 120. The particle size diameter of the nano-wire can be 0.1nm-1000nm, optionally 5nm, and the nano-wire is modified on the surface of the nano-wire. In the subsequent light detection process, the cocatalyst obviously enhances the reduction reaction activity of the system, accelerates the reaction rate and improves the light response performance.
As an alternative embodiment, the promoter nanoparticles 210 comprise water-reducing reactive metal particles. As an alternative embodiment, the metal particle material includes platinum, rhenium, palladium, iridium, rhodium, iron, cobalt or nickel, or their multi-component alloys, i.e. alloys using two metals simultaneously, such as RuFe and RuCo. Platinum (Pt) is an option in the present invention. The promoter 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 stronger, and the photocurrent signal is stronger in the light detection process. Accordingly, if the photo-anode is used, the promoter nanoparticles may include metal particles with water oxidation activity, such as iridium, iron, cobalt, nickel or ruthenium, or their multi-component alloys, which have correspondingly higher water oxidation activity and stronger oxidation reaction. It should be understood by those skilled in the art that the description of the co-catalyst modifying material in this example is not intended to limit the scope of the present invention, but is merely an embodiment of the present invention.
FIG. 3A is a schematic cross-sectional view of an AlGaN nanowire photocathode 300 in an embodiment of the present invention; fig. 3B is a schematic illustration of an AlGaN nanowire photocathode 300 according to an embodiment of the present invention. As an alternative embodiment, in order to successfully encapsulate the AlGaN nanowire 120 of the photocathode, the photoelectrochemical photodetector further includes: a lead 310 disposed on the conductive region of the substrate 110, and a cured cladding structure 320 of the AlGaN nanowire 120 which covers and fixes the lead 310 and the photocathode and exposes the photocathode. As shown in fig. 3B, a curing window 321 may be formed on the surface of the curing structure of the curing cladding structure 320, and the AlGaN nanowire 120 is exposed through the curing window 321, so that in the subsequent light detection process, solar blind ultraviolet light applied from the outside directly irradiates the AlGaN nanowire 120 through the curing window 321. An alternative substrate 110 material here may be a p-type Si (100) plane silicon wafer with an area size of 1cm x 1cm and a thickness selected between 0.01mm and 1000mm when the conductive region nanowires are disposed on the back side of the substrate 110, as shown in fig. 3A. The conducting wire is arranged on the back surface of the substrate. The conductive region may be a region on the back surface or the front surface of the silicon wafer, where the nanowire is scraped by a diamond pen, and is not limited in the present invention.
As an alternative embodiment, the material of the conductive wires 310 includes gold, silver, copper, etc., and the size of the conductive wires 310 is selected to match the size of the substrate 110. For example, a wire 310 of about 1.2cm wide and 5cm long may be selected, and the material may be copper Cu. Conductive copper tape may also be used.
As an alternative embodiment, the material of the cured coating structure 320 includes a curable liquid material having an insulating property after being cured, and the cured coating structure 320 is epoxy resin or the like, which has a wrapping and insulating effect.
As an alternative embodiment, a liquid alloy 330 disposed on the conductive region of the substrate and a conductive paste 340 disposed on the surface of the conductive line 310 opposite to the liquid alloy 330 are further included between the conductive line 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 between 90% and 99.99999%; the conductive paste 340 is silver paste. In particular, the liquid alloy 330 may directly contact with a conductive surface of the substrate to form an ohmic contact, so as to achieve better conductive characteristics and current stability. The conductive adhesive, which also fixes the conductive wire 310 and the substrate 110 and fixes the liquid alloy 330 between the conductive wire 310 and the substrate 110, plays a role of fixing and wrapping, and also plays a better role in conductive property and current stability. In addition, based on the packaging method, the packaging photoelectrode with the ohmic contact characteristic is prepared, and the Schottky barrier formed by the direct contact between the surface of the substrate conductive area and the metal wire can be better avoided, so that the current conduction is facilitated.
Fig. 4 is a schematic diagram of a novel solar blind uv electrochemical photodetector according to an embodiment of the present invention. As an alternative embodiment, the photoelectrochemical photodetector 400 further comprises: an electrolyte solution (not shown) in contact with the photocathode structure 300, and a reference electrode 420 and a counter electrode 430 in contact with the electrolyte solution, the reference electrode 420 and the counter electrode 430 being spaced apart from the photocathode 300 and being accommodated together by a light-transmissive container 410 having a limited ultraviolet light absorption capacity at least for solar blind; the reference electrode 420, the counter electrode 430 and the photo cathode 300 are respectively connected to an electrochemical workstation 440 having a current monitoring function. The electrochemical workstation 440 has a photocurrent monitoring function. Therefore, the photoelectrochemical photodetector based on the simple water reduction reaction as the photoelectric reaction mechanism is basically formed, the preparation condition is simple, the requirement on the purity is low, and the working process has little influence on the electrode material.
As an alternative embodiment, the electrolyte solution is an acidic or neutral electrolyte solution, the acidic electrolyte solution comprises 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 a silver/silver chloride electrode; the counter electrode comprises a platinum electrode and a carbon electrode. The above components and the AlGaN nanowire photocathode 300 form a complete novel solar blind ultraviolet electrochemical photodetector. The novel solar blind ultraviolet photoelectrochemical photodetector can further optimize the responsivity of light detection by modifying a cocatalyst.
In another aspect of the present invention, a novel solar blind ultraviolet photoelectrochemical photodetector product is provided, and fig. 5 is a schematic diagram of a novel solar blind ultraviolet photoelectrochemical photodetector product according to an embodiment of the present invention. The product comprises the photoelectrochemical photodetector and the packaging structure 500 for packaging the photoelectrochemical photodetector, wherein the packaging structure 500 comprises a shell structure 510 for coating the photoelectrochemical photodetector to package the photoelectrochemical photodetector; the surface of the housing structure 510 is provided with an optical window 511, and a light-transmitting surface 520 matched with the optical window 511 and used for sealing the optical window 511 is provided, wherein the distance between the light-transmitting surface 520 and the surface of the photocathode provided with the AlGaN nanowire 120 is greater than or equal to 0.01mm, and the distance can be selected to be 0.2cm, but the specific distance is not limited. The AlGaN nanowire 120 modified with the promoter nanoparticles is irradiated to the photocathode 300 through the transparent surface 520 for solar blind ultraviolet light. The structure is simple, and the preparation material is easy to obtain.
As an alternative embodiment, the light-transmissive surface 520 includes a transparent material with limited ability to absorb ultraviolet light for solar blindness; the housing structure 510 includes a shell structure formed of a polytetrafluoroethylene material. As an alternative embodiment, a surface of the housing structure 510 is formed with a closable/openable injection hole 530, an exhaust hole 540, and at least 3 electrode holes 550, 560, 570 for respectively disposing a photocathode, a reference electrode, and a counter electrode. The manufacturing process requirement is low, and the cost is low.
Example 2:
the invention provides a gallium nitride-based material nanowire structure applied to a photodetector, and correspondingly provides a preparation method of the material structure, so that the technical problems in the field are overcome, and breakthrough and unexpected technical effects are achieved. Wherein, the nanowire structure can be a regular arrangement, such as a directionally grown nanowire structure, or can include a non-regular arrangement of nanowires, and the term "regular" can be understood as the arrangement of nanowires having periodicity; the term "irregular" refers to the arrangement of nanowires without periodicity, and refers to the condition that the lengths, diameters, distances between adjacent nanowires, growth angles (relative to the substrate) of nanowires are inconsistent and irregular on the same substrate. In addition, in the introduction of the gallium nitride-based material in the present invention, for example, AlGaN or InGaN is merely a symbol expression of the material and does not represent a standard chemical formula of the material, and accordingly, the chemical formula of AlGaN may be selected from AlxGa1-xN，BxAlyGa1-x-yN or InxAlyGa1-x-yAnd x is more than or equal to 0 and less than 1, and y is more than or equal to 0 and less than or equal to 1 in N. That is, the gallium nitride-based material may be AlGaN, InGaN, or a gallium nitride-based material such as AlInGaN, which is not limited in the present invention.
The photoelectrode referred to in the claims of the present invention may be a photocathode or a photoanode, and may be distinguished by its doping component (e.g. magnesium-doped or silicon-doped), corresponding to a reduction reaction or an oxidation reaction in the present invention. To clearly express the function of the photoelectrode in the invention, the invention is mainly described by taking the photoelectrode of an AlGaN or InGaN nanowire structure as an example. It should be understood by those skilled in the art that the AlGaN or InGaN nanowire photocathodes mentioned in the description are not limitations on photoanodes, nor are they limitations on non-AlGaN or InGaN photoelectrodes.
As an embodiment of the present invention, the AlGaN nanowire grown on the surface of the substrate may be prepared by a Molecular Beam Epitaxy Method (MBE) or a Metal Organic Chemical Vapor Deposition Method (MOCVD), a conventional Chemical Vapor Deposition method, a halide Vapor Epitaxy method, a pulsed laser Deposition method, and the like, which is not particularly limited in the present invention. Meanwhile, in order to express the AlGaN nanowire of the present invention more clearly, the Molecular Beam Epitaxy (MBE) is mainly used as a basic preparation method.
One aspect of the present invention provides a method for manufacturing a photoelectrochemical photodetector, as shown in fig. 6, which is a schematic flow chart of a method for manufacturing a photoelectrochemical photodetector according to an embodiment of the present invention, and the method includes:
s610, selecting AlGaN or InGaN components according to the wavelength of light to be detected of the light detector; the corresponding AlGaN or InGaN material can be obtained by controlling the component proportion of different aluminum or indium In the gallium nitride based material, and the band gaps of the AlGaN or InGaN material with different component proportions change along with the change of the component proportions of Al/Ga, In/Ga and Al/In/Ga and correspond to different light absorption wavelengths. In this embodiment, the composition of aluminum in the gallium nitride-based material, the composition of indium in the gallium nitride-based material, and the composition of aluminum and indium in the gallium nitride-based material can be controlled simultaneously, and the modification control of the composition ratio is very easy and accurate. Therefore, the preparation method can better adapt to the preparation of the nanowire material corresponding to the full-spectrum light wavelength, and the preparation process is simplified. The above is merely a description of AlGaN or InGaN in the gallium nitride-based material in the embodiment of the present invention, and accordingly, aluminum or indium in the gallium nitride-based material may be replaced by boron, and the above scheme may still be applied to the corresponding component adjustment.
S620, forming AlGaN nanowires or InGaN nanowires on the surface of the substrate according to the components; as an embodiment of the present invention, the gallium nitride-based nanowire structure prepared by molecular beam epitaxy has the advantages of high stability, high crystal quality, adjustable bandgap height matching, and the like, compared with common oxide and nitride nanomaterials (such as gallium oxide nanostructures), and thus can ensure excellent water reduction/oxidation performance, i.e., photodetection performance, under light irradiation.
S630, modifying cocatalyst nanoparticles on the AlGaN nanowires or the InGaN nanowires; the promoter nanoparticles are modified on the surface of the AlGaN nanowire or InGaN nanowire by a promoter nanoparticle modification method (such as a photo-Deposition method), such as an Atomic Layer Deposition (ALD) method, an electrodeposition method (a chemical loading method) method, and an impregnation method (a chemical loading method).
And S640, packaging the AlGaN nano wire or the InGaN nano wire with the modified cocatalyst nano particles to obtain a photoelectrode so as to prevent electric leakage of a gap on the side surface or the back surface of the substrate, and fixing an epitaxial wafer by curing action of silver colloid, epoxy resin and the like.
S650, preparing the photoelectrochemical photodetector by using the photoelectrode, wherein the photoelectrochemical photodetector comprises the photoelectrode, and the photoelectrode generates a photoproduction electron-hole pair after being irradiated by light, so that a current loop is formed by the photoelectrode and other components in the photodetector, and the generated photocurrent can be detected by the outside, so that the photoelectrochemical photodetector can reflect the photodetection capability and can be applied to the fields of military affairs, industry and communication.
For example, in the preparation process of the molecular beam epitaxy method, forming AlGaN nanowires or InGaN nanowires on the substrate surface according to the composition in S620 includes: and setting the temperature rise program and opening or closing of an aluminum (Al) source furnace or an indium (In) source furnace according to the corresponding gallium nitride-based material components, and forming the gallium nitride-based nanowires with the corresponding components on the substrate. Optionally, molecular beam epitaxy equipment is adopted, each elementary substance source in the source furnace can generate corresponding atomic beams under ultrahigh vacuum and certain temperature, and meanwhile, the atomic beams generated by one or more furnace sources can be accurately controlled by the on/off and temperature setting of each furnace source, so that the generation of gallium nitride-based materials with different components is controlled. In this embodiment, if the composition of aluminum in the gallium nitride-based material is controlled, and an AlGaN nanowire is grown, only the aluminum furnace source and the gallium source furnace need to be opened, and the indium furnace source needs to be closed; if the component of indium in the gallium nitride-based material is controlled, the InGaN nanowire grows only by opening the indium furnace source and the gallium source furnace and closing the aluminum furnace source. Therefore, the volume flow of the atomic beam of each furnace source is regulated and controlled through the temperature of the source furnace, and the opening and closing time of each furnace source.
As an alternative embodiment, selecting the AlGaN or InGaN composition according to the wavelength of the light to be detected by the light detector includes: according to the following formula: determining the AlGaN component corresponding to the wavelength of the light to be detected by the Eg-3.42 eV + x 2.86 eV-x (1-x) 1.0 eV; or according to the following formula: eg-3.42 eV-x × 2.65 eV-x (1-x) 2.4eV determines the InGaN composition corresponding to the wavelength of the light to be detected. Fig. 7 is a simplified spectrum comparison diagram of a photoelectrochemical photodetector according to an embodiment of the present invention, in which a general wavelength of light less than 400nm is an ultraviolet region, and specifically, when the wavelength of light is less than 290nm, a solar-blind ultraviolet region can be achieved; the wavelength of visible light is generally between 400nm and 700 nm; the wavelength range of infrared light is more than 700nm, and the photoelectrochemical photodetector generally researches the wavelength range of visible light. The energy band of the photoelectrode semiconductor material of the photoelectrochemical photodetector relates to the absorption capacity of the photoelectrode semiconductor material to a corresponding optical wavelength interval, and the energy band relation of the photoelectrode semiconductor material is related to the alloy component proportion of the gallium nitride-based nano material. Therefore, the band gap can be accurately regulated and controlled only by controlling the component proportion of aluminum or indium when the nanowire grows, and the full-band light absorption of infrared, visible light and ultraviolet is realized.
As an alternative embodiment, AlGaN nanowires or InGaN nanowires are formed on the substrate surface according to the composition, further comprising: forming a nanopore array structure on a substrate, wherein the thickness of the nanopore array structure is less than or equal to 50 nm; and positioning and filling the p-type doped or n-type doped gallium nitride-based material in the nano holes to form a composite layer, and removing the nano hole array structure of the composite layer to form the gallium nitride-based nano wires on the surface of the substrate.
Specifically, in the embodiment of the present invention, a silicon dioxide nanopore structure, for example, a silicon dioxide nanopore array layer with a thickness of up to 50nm, may be prepared on the surface of the substrate by using the reverse formation principle of the nanowire/nanopore, and the nanopore may be formed through the silicon dioxide layer directly with the substrate surface as the bottom surface. Gallium nitride-based crystal nuclei can be preformed in the nano-pores of the silicon dioxide nano-pore structure, and then the nano-pores are filled by a molecular beam epitaxy method or an MOCVD method to form AlGaN nano-materials or InGaN nano-materials to be filled in the nano-pores; in addition, even if gallium nitride-based crystal nuclei are not formed in the nanopores, due to the inert property of silicon dioxide, when the substrate is a silicon substrate or a sapphire substrate, the gallium nitride-based material can be directly formed on the bottom surfaces of the nanopores by, for example, molecular beam epitaxy or MOCVD. The silicon dioxide can be removed by chemical etching or optical etching, or can be retained as an isolation layer, and under the condition of retention, modification of the cocatalyst nanoparticles can be affected, so that the silicon dioxide can be selectively removed, and at the moment, the AlGaN nano material or InGaN nano wire with the nano-pore size is correspondingly formed, and the length can be 200 nm. By the method, the high-quality monocrystal gallium nitride-based nanowires with corresponding wavelengths can be formed more quickly and conveniently, and the shape similarity of adjacent nanowires can be better. It should be noted that whether the silicon dioxide layer is removed or not is not the key of the embodiment, and the domain limiting effect brought by the silicon dioxide layer limits the growth of the thin film, so that the invention can realize the control of the growth of the nanowire in the defined region. In other words, even if the thickness of the silicon dioxide nanopore array layer is only 10 to 50nm, the length of the formed AlGaN nanomaterial or InGaN nanowire can still be grown to 200nm after the nanopore structure is filled thereon.
As another embodiment of the present invention, forming AlGaN nanowires or InGaN nanowires on a surface of a substrate according to the composition further includes: forming a nanopore array structure on a substrate, wherein the thickness of the nanopore array structure is less than or equal to 50 nm; and positioning and filling the gallium nitride-based material in the nano holes to form a composite layer, and continuously forming gallium nitride-based nanowires on the surface of the composite layer at positions corresponding to the nano holes. At this time, the composite layer is not removed, on one hand, the thickness of the composite layer is very small, for example, a composite layer of 20nm can be selected; on the other hand, the nanowire can be directly formed along the position of the nanopore relative to other parts of the nanopore composite layer by a selective area growth method, and the nanowire actually protrudes out of the surface of the composite layer and can reach the size of hundreds of nanometers or even micron-sized, so that the size of the nanowire is far larger than that of the composite layer, and the function of the nanowire cannot be influenced under the condition that the composite layer is not removed.
As an alternative embodiment, AlGaN nanowires or InGaN nanowires are formed on the substrate surface according to the composition, further comprising: forming an AlGaN film or an InGaN film on the substrate, and etching the AlGaN film or the InGaN film to form the AlGaN nanowire or the InGaN nanowire on the surface of the substrate. Specifically, in the embodiment of the present invention, an AlGaN thin film or an InGaN thin film with high crystal quality may be directly formed on a substrate by a molecular beam epitaxy method or an MOCVD method, then a photoresist, a silicon dioxide, or a metal island is formed on the AlGaN thin film or the InGaN thin film by a micro-nano processing technique, and then the AlGaN thin film or the InGaN thin film may be subjected to positioning etching by a dry etching method such as an Inductively Coupled Plasma etching (ICP), where the silicon dioxide or the metal is etched at a slow speed, and the remaining unprotected portions are etched at a fast speed, so as to form an AlGaN nanowire or an InGaN nanowire on the substrate. Wherein, the corresponding substrate can be a silicon wafer or a sapphire substrate. By the method, the high-quality monocrystal gallium nitride-based nanowires with corresponding wavelengths can be formed more directly and conveniently, 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 alternative embodiment, forming AlGaN nanowires or InGaN nanowires on the substrate surface according to the above composition includes: and controlling the doping proportion of magnesium or silicon, and forming p-type doped or n-type doped AlGaN nanowires or InGaN nanowires with corresponding doping proportion on the substrate. Specifically, as an embodiment of the present invention, in the preparation process of the molecular beam epitaxy method, the doping concentration of the nanowire material can be precisely controlled by controlling the switches of the silicon (Si) source furnace and/or the magnesium (Mg) source furnace and the temperature of the source furnace.
As an alternative embodiment, in the molecular beam epitaxy preparation process, AlGaN nanowires or InGaN nanowires are formed on the substrate surface according to the composition, including: the substrate is arranged in the preparation cavity, the degassing of the preparation cavity at a first temperature at least meets the first time, the substrate arranged in the preparation cavity is conveyed to the buffer cavity, the degassing of the buffer cavity at a second temperature at least meets the second time, and the substrate in the buffer cavity is conveyed to the growth cavity to carry out the growth of the AlGaN nanowires or the InGaN nanowires. Specifically, in the present embodiment, for example, when forming an AlGaN nanowire, a Molecular Beam Epitaxy (MBE) device may be used, a p-type Si (100) substrate (i.e., a silicon wafer) is used as a substrate, and the silicon wafer is transferred into a MBE device preparation chamber (e.g., a load lock chamber) for degas preparation, so that the MBE device reaches a corresponding vacuum degree, for example, the vacuum degree may reach 10-9And keeping the baking degassing time at the first temperature of 200 ℃ for at least 1 hour, then sending the silicon wafer in the preparation cavity to a buffer cavity, and keeping the baking degassing time at the second temperature of 600 ℃ for at least 2 hours to remove the adsorption of water and gas molecules in the buffer cavity to the silicon wafer as far as possible. And after degassing is finished, conveying the silicon wafer to a growth cavity to grow the AlGaN nanowire.
As an alternative embodiment, In the preparation process of the molecular beam epitaxy method, by controlling the opening or closing of an aluminum (Al) source furnace or an indium (In) source furnace, controlling a temperature rise procedure of the source furnace, and forming AlGaN nanowires or InGaN nanowires of corresponding compositions on a substrate according to corresponding AlGaN or InGaN compositions, the method includes: after the substrate is conveyed to the growth cavity, controlling to open a gallium (Ga) source furnace communicated with the growth cavity, taking a gallium beam with a first equivalent pressure as a gallium source and plasma nitrogen with a first volume flow as a nitrogen source, and keeping at a third temperature for at least a third time to form GaN crystal seeds on the surface of the substrate. Specifically, in the present embodiment, a Molecular Beam Epitaxy (MBE) apparatus may be used, with a p-type Si (100) substrate (i.e., a silicon wafer) as a substrate, to control the opening and growth after the silicon wafer enters the growth chamberThe gallium source furnace with the long cavities communicated with each other has a first equivalent pressure (BEP) of 6.0 multiplied by 10-8The Torr gallium beam is used as a gallium source, high-brightness nitrogen plasma is formed by the first volume flow of 1sccm plasma nitrogen and used as a nitrogen source, the high-brightness nitrogen plasma is kept for at least 1 minute at a third temperature of 500 ℃ to form GaN seed crystals on the surface of the silicon wafer, the possibility of nucleation is increased, a base point is formed for the growth of the nanowire on the silicon wafer, and therefore the nanowire with higher crystal quality can be grown on the silicon wafer.
As an alternative embodiment, In the preparation process of the molecular beam epitaxy method, by controlling the opening or closing of an aluminum (Al) source furnace or an indium (In) source furnace, the control of the temperature rise procedure of the source furnace and according to the corresponding AlGaN or InGaN composition, AlGaN nanowires or InGaN nanowires of the corresponding composition are formed on a substrate, and the method further includes: and controlling to open the aluminum source furnace or the indium source furnace, keeping the aluminum beam current with the second equivalent pressure or the indium beam current with the third equivalent pressure at the fourth temperature under the condition that the plasma nitrogen with the first volume flow is used as a nitrogen source, and forming AlGaN nanowires or InGaN nanowires with corresponding components on the surface of the substrate by matching with the gallium beam current with the fourth equivalent pressure. Specifically, in the present embodiment, taking the formation of AlGaN nanowires as an example, an aluminum source furnace is controlled to be opened, and a second equivalent pressure of 2.0 × 10 is maintained at a fourth temperature of 610 ℃ under the condition that a first volume flow of 1sccm plasma nitrogen is used as a nitrogen source-8Torr of aluminum beam current, and the fourth equivalent pressure of 3.0X 10-8And forming AlGaN nanowires with corresponding components on the surface of the silicon wafer by the aid of the gallium beam current of 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 off, and a third equivalent pressure of 4.0 × 10 is used-8The indium beam current of the Torr replaces the corresponding aluminum beam current parameter, and other steps can be not modified. Therefore, the alloy ratio between aluminum and indium in the nanowire can be accurately controlled by the method, so that the AlGaN nanowire or the InGaN nanowire with corresponding light wavelength can be achieved. The component proportion of aluminum or indium is estimated by comparing the BEP of the aluminum or indium and gallium beams, and the BEP proportion is adjusted by controlling the temperature, so as to achieve the purpose of adjusting and controlling the components, for example, the equivalent pressure (BEP) of aluminum is adjusted to be 6 multiplied by 10 in the preparation process of AlGaN nano wires corresponding to ultraviolet light-8Torr to 1X 10-8The purpose of regulating and controlling the Al component is realized between Torr; or adjusting the BEP of indium to 4 × 10 in the preparation process of InGaN nanowire corresponding to visible light and infrared light-8Torr to 1X 10-8The purpose of regulating and controlling the In component is realized between Torr.
As an alternative embodiment, In the preparation process of the molecular beam epitaxy method, by controlling the opening or closing of an aluminum (Al) source furnace or an indium (In) source furnace, the control of the temperature rise procedure of the source furnace and according to the corresponding AlGaN or InGaN composition, AlGaN nanowires or InGaN nanowires of the corresponding composition are formed on a substrate, and the method further includes: and when the opening or closing of the aluminum (Al) source furnace or the indium (In) source furnace is controlled, the opening or closing of the magnesium source furnace or the silicon source furnace is controlled at the fifth temperature or the sixth temperature of the silicon source furnace, so that the AlGaN nanowires or the InGaN nanowires with corresponding components are formed on the substrate and become p-type doping or n-type doping. The photoelectrode is divided into a photoanode or a photocathode, correspondingly, the p-type doped AlGaN nanowire or InGaN nanowire can well complete the water reduction reaction, and particularly can be used as the photocathode of a photoelectrochemical system when the surface of the p-type doped AlGaN nanowire or InGaN nanowire is modified with cocatalyst nanoparticles. Generally, the doped AlGaN nanowire or InGaN nanowire can become a p-type doped material by doping magnesium in a certain proportion, the doping mode can obtain better material stability, no influence can be caused on the material to be doped, and the response of the later-stage water reduction reaction is better. In contrast, n-type doped AlGaN nanowires or InGaN nanowires can perform a better water oxidation reaction, and can be used as a photo-anode of a photoelectrochemical system, especially when the surface of the n-type doped AlGaN nanowires or InGaN nanowires is modified with co-catalyst nanoparticles. Generally, a certain proportion of silicon is doped, so that the doped AlGaN nanowire or InGaN nanowire becomes an n-type doped material, and the doping mode can obtain better response of 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 opened and the indium (In) source furnace is ensured to be closed, the magnesium source furnace is opened, and the temperature of the magnesium source furnace is 360 ℃ at the fifth temperature, so that the AlGaN nanowires with corresponding components formed on the substrate become p-type doped. In contrast, for the preparation of n-type InGaN nanowires, the silicon source furnace needs to be opened, and the sixth reaction temperature of the silicon source furnace is 1180 ℃.
As an alternative embodiment, modifying the promoter nanoparticles on the AlGaN or InGaN nanowires includes: the AlGaN nanowires or the InGaN nanowires are arranged in a precursor water solution with a first concentration, and light with a wavelength corresponding to the energy band of the nanowires is applied to irradiate the AlGaN nanowires or the InGaN nanowires, so that the promoter nanoparticles are modified on the surfaces of the AlGaN nanowires or the InGaN nanowires. Specifically, in this embodiment, taking preparation of Pt nanoparticles as an example of a promoter modified on p-type AlGaN nanowires, a chloroplatinic acid solution with a certain concentration may be selected as a precursor aqueous solution, and the grown p-type Al may be subjected to growthxGa1-xPutting the N nanowire into 50mL deionized water, keeping the reaction temperature at 10 ℃ in a sealed container by a circulating water cooling method, keeping a certain vacuum degree, introducing inert gas such as argon into the container as protective gas, injecting 1mL of chloroplatinic acid solution with the concentration of 10mg/mL into the container, and applying AlxGa1-xAnd (3) irradiating the N nanowires with wavelengths corresponding to the band gaps, and keeping the irradiation time for more than 30 minutes. Photoelectric effect of semiconductor, AlxGa1-xThe N nanowire generates a photo-generated electron-hole pair after absorbing photons. Then photogenerated electrons are diffused to the surface of the nanowire, and the energy of the photogenerated electrons is larger than that of platinate radical ([ PtCl ] in the solution6]2-) The reduction potential of the group, the photo-generated electrons diffused to the surface of the nanowire can reduce [ PtCl ] adsorbed on the surface of the nanowire6]2-And forming platinum particles on the surface of the nanowire, namely a photo-deposition process. And after the photo-deposition reaction is finished, taking out a sample and cleaning to obtain the p-type AlGaN nanowire for modifying the promoter platinum nanoparticles, wherein the particle size of the platinum particles can reach 0.1nm-1000 nm. For the n-type nanowire, the precursor aqueous solution chloroplatinic acid solution is only required to be changed into ruthenium chloride solution with equal concentration. By distributing and modifying the cocatalyst nanoparticles on the surface of the nanowire, the photoelectrode can have stronger reaction, faster reaction speed and larger photocurrent in the process of water reduction/oxidation reaction.
As an alternative embodiment, on the AlGaN nanowire or the InGaN nanowireBefore modifying the cocatalyst nanoparticles, the method further comprises the following steps: and when the AlGaN nanowire or the InGaN nanowire is doped in an n type, preparing a protective layer on the surface of the AlGaN nanowire or the InGaN nanowire. Since n-type doping is easy to implement in the molecular beam epitaxy preparation process, but in the process of light deposition or light detection, the grown nanowires are easy to be corroded by self-generated photo-generated cavities, so that a certain influence is caused on the photo-anode, and therefore, on the basis of the nanowires of the photo-anode, a nanowire protection layer which has a tunnel conduction effect and simultaneously satisfies that the good conductivity can not influence the photo-detection performance is prepared on the surface of the nanowires. Specifically, in this embodiment, taking the preparation of the n-type InGaN nanowire as an example, before performing photo-deposition to modify the promoter nanoparticles, an amorphous protection layer is directly deposited on the surface of the n-type InGaN nanowire by using an atomic layer deposition method, where the material of the protection layer may be TiO2Or materials with similar properties to prevent the n-type InGaN nanowire material from optical corrosion under the condition of hole enrichment. With amorphous TiO2For example, the passivation layer can be prepared by using tetra (dimethylamino) titanium (IV) TEMAT and water as precursors, and the precursor containers are kept at 65 ℃ and 25 ℃ respectively for 60 co-deposition cycles. Each period comprises the processes of introducing titanium precursor for 0.1 second, introducing plasma nitrogen for 10 seconds, introducing water vapor for 0.1 second, and introducing N2After 10 seconds of introduction, amorphous TiO can be formed on the surface of the n-type InGaN nanowire material2And a protective layer.
As an alternative embodiment, the step of encapsulating the AlGaN nanowire or the InGaN nanowire with the modified promoter nanoparticles to obtain the photoelectrode includes: and fixedly attaching a lead to a conductive area of the substrate provided with the AlGaN nano wires or the InGaN nano wires with the modified cocatalyst nano particles, coating and fixing the lead and the substrate, and simultaneously exposing the AlGaN nano wires or the InGaN nano wires to form the packaged photoelectrode. And (3) encapsulating the photoelectrode, paying attention to lead out a lead, and additionally, paying attention to expose the nanowire of the photoelectrode. When the lead is led out, attention needs to be paid to that one end of the lead is opposite to a preset conductive area of the silicon wafer, and the conductive area can be an area outside the nanowire scraped by a diamond pen on the back or the front of the silicon wafer. The exposed photocathode nanowire is beneficial to directly irradiating the nanowire with light with corresponding light wavelength.
As an alternative embodiment, the method for fixedly attaching a conducting wire to a conductive region of a substrate of an AlGaN nanowire or an InGaN nanowire provided with modified promoter nanoparticles includes: the method comprises the steps of scraping an oxide layer on a conductive area of a substrate, coating liquid alloy on the conductive area with the oxide layer being scraped, and coating conductive adhesive on the surface of a wire between the wire and the conductive area and opposite to the position of the liquid alloy. In order to prevent the schottky barrier formed by the direct contact between the substrate and the metal wire from being unfavorable for the current conduction, a photoelectrode with ohmic contact characteristic is required to be prepared. Specifically, in the embodiment of the present invention, taking a silicon wafer as an example of a substrate, a diamond knife is used to scrape naturally grown silicon dioxide (SiO) on the back of the silicon wafer2) And a layer, which is a liquid alloy (such as gallium indium (GaIn) alloy) coated on the conductive area of the back surface of the silicon wafer after the silicon dioxide layer is scraped off, so as to form ohmic contact. And then coating conductive adhesive silver (Ag) glue on a copper (Cu) wire, compacting the conductive adhesive silver (Ag) glue and the back of a silicon wafer coated with gallium-indium alloy, finally packaging and wrapping the whole photoelectrode by epoxy resin, and only leaving the growth surface of the nanowire exposed, thereby finishing primary packaging of the photoelectrode, avoiding the formation of a Schottky barrier and being beneficial to the conduction of photocurrent.
As an alternative embodiment, a photoelectrochemical photodetector is fabricated using a photoelectrode comprising: and arranging the photoelectrode, the reference electrode and the counter electrode in an electrolyte solution with a second concentration at a certain interval to prepare a three-electrode system, so as to form the photoelectrochemical photodetector. Specifically, in the embodiment of the present invention, taking a photocathode three-electrode system for preparing p-type AlGaN nanowires as an example, an electrolyte solution (sulfuric acid (H) with a second concentration of 0.5 mol/L) is added into a light-transmitting container2SO4) Aqueous solution as an example), followed by separately reacting Al prepared as described abovexGa1-xThe preparation method comprises the following steps of placing an N nanowire electrode (photocathode), a reference electrode (taking silver/silver chloride (Ag/AgCl) as an example) and a counter electrode (taking a platinum Pt mesh electrode as an example) in an electrolyte solution, and completing the preparation of a three-electrode system. At the conductive end of each electrodeAnd the test parameters of the electrochemical workstation are set by a computer after the electrochemical workstation is connected with the electrochemical workstation, so that the test or application of the optical detection performance can be carried out. Correspondingly, taking the photoanode of the n-type InGaN nanowire as an example, the electrolyte solution can be replaced by a hydrobromic acid solution of 1 mol/L. The preparation process of the three-electrode system is simple and easy to implement, and the preparation process of the optical detector is greatly simplified, so that the three-electrode system has the condition of large-scale production.
The invention also provides a photoelectrochemical photodetector which is prepared by applying the preparation method of the photoelectrochemical photodetector.
Example 3:
one aspect of the present invention provides a solar-blind ultraviolet photoelectrochemical photodetector, as shown in fig. 8A, which is a schematic diagram of a GaN-based nanopore array of a solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention, and fig. 8B, which is a schematic diagram of a GaN-based nanopore array of a solar-blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention, which has been modified with promoter nanoparticles, the photodetector includes a photoelectrode including a substrate 810 and a GaN-based nanopore 840 array 830 formed on a surface of the substrate 810, thereby forming a basic structure 800 of a photocathode of a novel photoelectrochemical photodetector according to the present invention.
Wherein, the skilled person will understand that the nanopore structure may be a regular arrangement, such as a directionally grown nanopore structure, or may comprise a non-regular disordered nanopore structure, and that "regular" may be understood as whether the nanopore arrangement has periodicity. In addition, the gallium nitride-based material can be selected as AlGaN in the invention, and AlGaN is only expressed by one symbol of the material and does not represent the standard chemical formula of the material. Specifically, GaN-based chemical formula can be selected from BxAlyGa1-x-yN or InxAlyGa1-x-yAnd x is more than or equal to 0 and less than 1, and y is more than or equal to 0 and less than or equal to 1 in N. That is, the gallium nitride-based material may be AlGaN, InGaN, or a gallium nitride-based material such as AlInGaN, which is not limited in the present invention.
The photoelectrode referred to in the claims of the present invention may be a photocathode or a photoanode, and may be distinguished by its doping component (e.g. magnesium-doped or silicon-doped), corresponding to a reduction reaction or an oxidation reaction in the present invention. To clearly express the function of the photoelectrode in the invention, the invention is mainly described by taking the AlGaN photocathode as an example. It will be understood by those skilled in the art that it is not a limitation of photo-anodes nor of non-AlGaN photo-electrodes.
As an embodiment of the present invention, the AlGaN nanopore array grown on the substrate may be prepared by a Molecular Beam Epitaxy (MBE) method or a Metal Organic Chemical Vapor Deposition (MOCVD) method, a conventional Chemical Vapor Deposition method, a halide Vapor phase Epitaxy (hda), a pulsed laser Deposition (pwld), and the like, which is not particularly limited in the present invention. Meanwhile, in order to more clearly express the AlGaN nanopore array of the present invention, a Metal Organic Chemical Vapor Deposition (MOCVD) method is mainly described as a basic preparation method.
The high-crystal-quality n-type doped AlGaN nanopore array is directionally formed on the surface of the substrate, and compared with common oxide and nitride nanometer materials (such as a gallium oxide nanometer structure), the high-crystal-quality n-type doped AlGaN nanopore array has the advantages of high stability, high crystal quality, adjustable band gap height matching and the like, and can ensure that the high-crystal-quality n-type doped AlGaN nanopore array has excellent water oxidation performance, namely optical detection performance, under the irradiation of solar blind light. In addition, for AlGaN materials, the band gap can vary with the compositional doping, specifically:
Eg＝3.42eV+x*2.86eV-x(1-x)*1.0eV………………………(1)
eg is the semiconductor forbidden band width and corresponds to different absorption wavelengths.
Therefore, according to the formula (1), the band gap of the prepared photo-anode can be accurately regulated and controlled by controlling the ratio of Al and Ga components in the preparation process, and the light absorption of the solar-blind ultraviolet band is realized.
In addition, the AlGaN nano-pores with high crystal quality prepared by the invention can be a p-type doped material, specifically, silicon Si atoms can be doped, and the AlGaN nano-pores move to an electrolyte solution/semiconductor contact surface to be electrons in the subsequent photoelectrochemical reaction process, so that the AlGaN nano-materials or the structure cannot be influenced at all, and the stability is very high compared with the situation that oxide nano-materials (such as gallium oxide nano-structures) cannot be realized. Accordingly, the AlGaN nanopore prepared by the present invention may be a p-type doped material, and specifically, may be doped with magnesium Mg atoms in preparation for use as a photocathode. In the structure of the photo-anode, a protective layer with a certain thickness needs to be deposited on the surface of the photo-anode to prevent the photo-anode from being corroded by photo-generated holes in the photo-detection process.
As shown in fig. 8A, as an embodiment of the present invention, the AlGaN nano hole 840 may be a regular hole such as a cylindrical hole or a prism, or an irregular hole such as a curved shape, and the optional nano hole 840 is a cylindrical hole. The diameter of the nanopore 840 is 0.1-5 μm, and the optional diameter is 2 μm; the depth is 50nm-600nm, 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 photo-detection reaction is increased. In addition, the pore size of the nanopore 840 exceeds 500nm, which far exceeds the design size of the conventional nanopore, and is not a nano-scale structure in a certain sense. The size design can prevent the solution mass transfer difficulty caused by the attachment of bubbles generated in the subsequent optical detection process on the inner surface of the nanopore 840, and the large-aperture nanopore design is easy to cause the condition of unstable performance such as short circuit, and the like, and the large-aperture nanopore design research is not available in the field, so that the implementation of the scheme by a person skilled in the art can be hindered. This is therefore a breakthrough design in the field, which cannot be envisaged by the person skilled in the art.
According to an embodiment of the present invention, the filling degree of the AlGaN nanopore array may be defined by a patterning condition, and the distance between adjacent nanopores is 0.1 μm to 5 μm, and the optional distance is 2 μm. The specific surface area of the nanopore array is larger, and the specific surface area of the light detection reaction is increased.
As shown in fig. 8A to 8B, the substrate 810 includes a sapphire substrate, a gallium nitride substrate, a gallium oxide substrate, a silicon carbide substrate, a silicon substrate, a substrate having a GaN-based material thin film, or the like, or other substrates having conductive properties. Can be used forThe substrate is selected to be sapphire substrate, and the substrate material can be selected to be aluminum oxide Al in the embodiment of the invention2O3And the like.
As an embodiment of the invention, the GaN-based nanopore array is an n-type GaN-based nanopore array, the surface of the GaN-based nanopore array of the photoelectrode further comprises a protective layer covering the surface of the nanopore array, the thickness of the protective layer is less than or equal to 10nm, and the protective layer material at least comprises titanium dioxide. The protective layer is used to prevent photo-erosion phenomenon of the nano-pores. Accordingly, the corresponding p-type gallium nitride-based nanopore (e.g., AlGaN or InGaN nanopore, etc., without limitation, according to the protection scope defined by the claims) in the present invention can be used as a photo-cathode of the photo-electrochemical photodetector in the present invention (corresponding to the gallium nitride-based nanowire photo-cathode in the foregoing embodiment), and correspondingly, the promoter nanoparticle can be directly modified on the surface of the p-type nanopore, and it is not necessary to form at least one protection layer on the surface of the nanopore before modifying the promoter nanoparticle, which is not described herein again.
Due to lattice matching, an AlGaN single crystal film with stable and high crystal quality can be epitaxially formed on the substrate 810, which is beneficial to the preparation of a nanopore array in the next step.
As shown in fig. 8A-8B, as an embodiment of the present invention, a buffer layer 820 is further included between the substrate 810 and the AlGaN nanopore array 830, the buffer layer 820 includes at least three intermediate layers, and the buffer layer material includes aluminum nitride. Because the lattices of the substrate 810 and the AlGaN nanopore array 830 are not matched, the buffer layer 820 is additionally arranged between the substrate 810 and the AlGaN nanopore array 830, so that the AlGaN single crystal thin film with stability and high crystal quality can be obtained in the preparation process, and the preparation of the nanopore array in the next step is facilitated.
As an embodiment of the present invention, the buffer layer 820 includes at least three intermediate layers, a first intermediate layer formed on the substrate 810, and may have a thickness of 3 μm for serving as a nucleation layer; a second intermediate layer formed on the first intermediate layer, and having a thickness of 100 nm; the third intermediate layer, which may be 1 μm thick, is formed on the second intermediate layer for use as a template layer. The above-mentioned intermediate layers are not shown in the drawings. The formation of the multiple intermediate layers is beneficial to forming a smoother and smoother third intermediate layer surface (namely the surface of the buffer layer 820), so that a stable AlGaN single crystal film with high crystal quality is obtained in the preparation process, and the preparation of a nanopore array in the next step is facilitated. Accordingly, for the corresponding p-type gallium nitride-based nanopore (e.g., AlGaN or InGaN nanopore, etc., without limitation, according to the scope of protection defined by the claims) in the present invention, it can be used as the photo-cathode of the photo-electrochemical photodetector in the present invention (corresponding to the gallium nitride-based nanowire photo-cathode in the foregoing embodiment), and correspondingly, the gallium nitride-based nanopore structure can be formed directly on the substrate surface, without considering the addition of the above buffer layer structure between the nanopore structure and the substrate.
As shown in fig. 8B, as an embodiment of the present invention, the AlGaN nano hole array further covers a protection layer 870 on the surface, and the thickness of the protection layer 870 is less than or equal to 10nm, and the optional thickness dimension is 2 nm. In the embodiment of the invention, the protective layer can be amorphous titanium dioxide TiO2And the protective layer covers the whole AlGaN nanopore array surface and comprises the inner surface of the nanopore so as to prevent the AlGaN material from generating optical corrosion effect under the condition of hole enrichment in the light detection process and influencing the overall performance of the light detector.
As shown in fig. 8B, as an embodiment of the present invention, the photo-anode further includes promoter nanoparticles 850 distributed on the surface of the protective layer, the promoter nanoparticles 850 are metal particles with water redox reaction activity, the material of the metal particles includes platinum, iridium, iron, cobalt, nickel, ruthenium, and the like, and multi-component alloys thereof, i.e., two metals, such as RuFe, RuCo, and the like, are used simultaneously. The invention can select ruthenium as the preparation selection of the cocatalyst nanoparticles, and the diameter size of the cocatalyst nanoparticles can be selected from 0.1nm to 1000nm, and can be selected as 2nm to better modify more in the nanopore array. The cocatalyst nanoparticles distributed on the nanopore array can enable the AlGaN nanopore array to have stronger water oxidation reaction, so that the optical response of the optical detector is stronger and the optical response speed is higher.
As shown in fig. 8B, as an embodiment of the present invention, the AlGaN nano hole array surface further includes a first region 860 not covered by the protection layer 870, and the first region 860 is disposed outside the nano hole region. The first area is formed on the surface of the nanopore array and is not overlapped with the area where the nanopore is located, so that the short circuit is prevented, and the extraction electrode can be more stable and effective.
As an embodiment of the present invention, the first region 860 includes a spot-bonded indium ball for forming a conductive region of the photo anode for extracting the photo anode. An ohmic contact conductive area can be formed on the first area 860 and the surface of the nanopore array by spot welding of indium balls, a square area with the size of 2mm multiplied by 2mm can be selected as the conductive area, better conductive characteristics and current stability can be achieved, and meanwhile, a lead extraction electrode can be fixed, namely, a photo-anode can be formed.
As an embodiment of the present invention, similar to the structure of the photoelectrochemical photodetector formed by 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, the reference electrode and the counter electrode being spaced apart from the photoanode by a distance, wherein the distance is approximately equal to 0.01 mm; the reference electrode, the counter electrode and the photo-anode are respectively connected with an electrochemical workstation with a current monitoring function. Therefore, the photoelectrochemical photodetector based on simple water oxidation reaction as a photoelectric reaction mechanism is basically formed, the preparation condition is simple, the purity requirement is low, and the working process has little influence on electrode materials.
In one 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 a phosphate buffer or hydrobromic acid, and the electrolyte solution has a concentration of 0.01mol/L to 5mol/L, and the present invention can select a weakly acidic electrolyte solution such as 0.5mol/L hydrobromic acid solution; the reference electrode is a silver/silver chloride (Ag/AgCl) electrode and the like; the counter electrode comprises a platinum (Pt) electrode, a carbon (C) electrode and the like, and the specific structure can be made into a mesh electrode and the like. The components and the AlGaN nanopore array photo-anode form a complete novel solar blind ultraviolet electrochemical photo-detector. The novel solar blind ultraviolet 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 has a structure similar to that of a photocathode photodetector, and includes the photodetector and a package structure for packaging the photodetector, where the package structure includes a housing structure for covering the photodetector to package the photodetector; an optical window is arranged on one surface of the shell structure, a light transmitting surface which is matched with the optical window and used for sealing the optical window is arranged, the light transmitting surface and the surface of a photocathode with an AlGaN nano-hole array are arranged at a certain interval, wherein the interval is approximately equal to 0.01mm, and the interval can be 0.2cm in the embodiment and is used for enabling solar blind ultraviolet light to irradiate the AlGaN nano-hole array with the cocatalyst nano-particles on the photo-anode through the light transmitting surface. The structure is simple, and the preparation material is easy to obtain.
As an embodiment of the present invention, the light-transmitting surface includes a transparent material having a limited ultraviolet light absorbing ability for solar blindness; the shell structure comprises a shell structure formed of polytetrafluoroethylene material. As an alternative embodiment, one surface of the housing structure is provided with a closable/openable injection hole, an exhaust hole, and at least 3 electrode holes for respectively arranging the photocathode, the reference electrode, and the counter electrode. The manufacturing process requirement is low, and the cost is low.
The novel solar blind ultraviolet photoelectrochemical photodetector product provided by the invention has the advantages of simple structure, low manufacturing process requirement and low cost, and the packaging structure of the product is very simple, so that the product is convenient for practical application and easy for large-scale production, and the commercialization of the photoelectrochemical photodetector is realized.
Another aspect of the present invention provides a method for manufacturing a solar blind ultraviolet photoelectrochemical photodetector, which is applied to manufacture the photodetector described above, as shown in fig. 9, which is a schematic flow chart of a method for manufacturing a solar blind ultraviolet photoelectrochemical photodetector according to an embodiment of the present invention, and the method includes:
s910, forming an AlGaN nanopore array on the surface of the substrate; specifically, as an embodiment of the present invention, Metal Organic Chemical Vapor Deposition (MOCVD) may be selected for itPreparation, during the preparation process, triethyl borane (TEB), trimethyl aluminum (TMAl), trimethyl gallium (TMGa) and ammonia (NH) can be selected3) As growth precursor to provide B, Al, Ga, N source, Si as N-type doping source, H2As a carrier gas. The corresponding AlGaN material can be obtained by controlling different component proportions of aluminum and gallium in the gallium nitride-based material, the AlGaN material with different component proportions can enable the energy bands of the material to be correspondingly different, and the band gap is changed along with the doped components so as to correspond to different light absorption wavelengths. In the embodiment, the composition of aluminum in the gallium nitride-based material can be controlled, and the modification control of the component ratio is very easy and accurate. Therefore, the preparation method can be better suitable for the preparation of the nano material corresponding to the wide-spectrum light wavelength, and can also be used for accurately controlling the formation of the nano material suitable for the solar blind ultraviolet light wavelength, thereby simplifying the preparation process. Meanwhile, the formed AlGaN nanopore array is doped by using silicon, so that an n-type doped AlGaN nanopore array more suitable for a photo-anode can be obtained, the water oxidation reaction of the photo-detector can be promoted, and the photocurrent response intensity and speed can be improved.
S920, modifying cocatalyst nanoparticles on the nano holes of the AlGaN nano hole array; specifically, as an embodiment of the present invention, the promoter nanoparticles are modified on the surface/side of the nanopore structure by using an Atomic Layer Deposition (ALD) method, an electrodeposition method (chemical loading method), or an immersion method (chemical loading method) on the nanopores of the AlGaN nanopore array.
S930, preparing the photodetector by using the AlGaN nanopore array modified with the cocatalyst nanoparticles as a photo-anode.
Preparing a photoanode functional layer on the surface of the substrate, so that an AlGaN nanopore array with higher crystal quality is ensured at lower cost; a buffer layer is formed between the substrate and the AlGaN nano-hole array, so that the film forming effect of the AlGaN film is improved, and the formation of the high-crystal quality AlGaN nano-hole array is ensured; the surface of the AlGaN nanopore array is covered with an amorphous protective layer, so that the photo-corrosion effect of the photo-anode in the photo-detection process can be prevented from affecting the overall photo-detection performance of the photo-detector; in addition, the surface of the protective layer is modified with the cocatalyst nanoparticles, so that the water oxidation reaction rate is further improved, and the ultraviolet response is improved.
As shown in fig. 10A, as a schematic diagram of a stage of a flow of fabricating an AlGaN nanopore array in a method for fabricating a solar blind ultraviolet electrochemical photodetector according to an embodiment of the present invention, forming an AlGaN nanopore array on a surface of a substrate according to an embodiment of the present invention includes: pre-annealing the substrate 810; forming a buffer layer 820 on the pre-annealed substrate 810; optionally, prior to growth, preceded by H2-NH3The sapphire substrate is annealed at the high temperature of 1200 ℃ for 5 minutes in the environment, so that the surface of the sapphire substrate is cleaner and smoother, and the sapphire substrate is more suitable for serving as a substrate of an AlGaN nanopore array. The AlGaN nano-pore array may be formed on the surface of the buffer layer 820 of the substrate 810 by a Metal Organic Chemical Vapor Deposition (MOCVD) method or a Molecular Beam Epitaxy (MBE) method, which is not limited. Before forming the AlGaN nanopore array, an AlGaN thin film 831 is preformed on the surface of the buffer layer 820, and optionally, a 200nm AlGaN thin film is grown on the buffer layer at the temperature of 1150 ℃. The thin film 831 is operated to form a nanopore array. By forming the thin film 831 first, the high crystal quality of the nanopore array can be ensured.
As an embodiment of the present invention, forming a buffer layer 820 on the pre-annealed substrate 810 includes: at least two intermediate layers (not shown) are included in the buffer layer 820; forming a first intermediate layer on the substrate 810 in a first condition, and forming a second intermediate layer on the first intermediate layer in a second condition; a third intermediate layer is formed in a third condition on the second intermediate layer. Specifically, the buffer layer 820 is formed on the pre-annealed sapphire substrate 810, and MOCVD can be selected as a preparation means, and the preparation means includes: AlN is used as a buffer layer preparation material, and TMAl and NH are firstly carried out at the temperature of 850-950 DEG C3The volume flow of the first layer is controlled to be 4sccm and 3000sccm respectively, and a low-temperature AlN nucleation layer with the thickness of 3 microns is formed on the sapphire substrate 810 as a first intermediate layer; forming an AlN spacing layer with the thickness size of 100nm on the first intermediate layer as a second intermediate layer under the second condition at the temperature of 850-1250 ℃; at 1250 ℃, V/IIIA high temperature AlN template layer of 1 μm thickness dimension was formed on the second intermediate layer as a third intermediate layer under a third condition of 180. The formation of the multiple intermediate layers is beneficial to forming a smoother and smoother third intermediate layer surface (namely the surface of the buffer layer 820), so that a stable and high-crystalline-quality AlGaN nanopore array is obtained in the preparation process.
As an embodiment of the present invention, an AlGaN nanopore array is formed on a surface of a buffer layer of a substrate, including: forming an AlGaN thin film on the buffer layer under a fourth condition; and etching the film to form the AlGaN nanopore array. As shown in fig. 10A to 10F, which are schematic diagrams of a stage of a flow of preparing an AlGaN nanopore array in a method for preparing a solar blind ultraviolet electrochemical photodetector according to embodiments of the present invention, a micro-nano processing technique is used to prepare a cylindrical nanopore array, wherein an AlGaN thin film may be formed on a third intermediate layer. As shown in fig. 10A to 10B, the fourth condition described includes any one of the preparation conditions used in the following steps: using the photoresist with the model number of S1813 as an etching sacrificial layer 910 of a subsequent etching process, controlling the coating rate at 4000 rpm for 30 seconds, and forming the photoresist sacrificial layer 910 with the thickness of about 1.2 μm; as shown in fig. 10C, a circle with a diameter of 2 μm is drawn on a mask 320, the distance between adjacent patterns is 2 μm, an array structure is formed, and the post-baking temperature is controlled at 115 ℃ for 90 seconds; using an Optical Aligner-SUSS MABA6 ultraviolet lithography machine to perform pattern definition, and adopting contact exposure, wherein the space is 60 μm, and the exposure time is 7.5 seconds (step 3); the exposed pattern is then developed in AZ300MIF developer for 50 seconds, so that a circular pattern 911 defined by the exposed and developed area corresponding to the nanopore location is formed on the sacrificial layer 910, and washed in clear water. As shown in fig. 10D, etching the AlGaN film using an Inductively Coupled Plasma (ICP) may be optional to first achieve a nanopore structure 930 on the sacrificial layer 910. As shown in fig. 10E, MOCVD grown AlGaN films were etched using Oxford ICP 180 in a circular pattern 911 defined by uv lithography. The etching gas is Cl2/BCl3and/Ar, wherein the gas flow is controlled to be 10/25/25sccm, the temperature is 50 ℃, the cavity pressure is 6mTorr, the ICP power is 450W, and the radio frequency power is 100W. Before etching, no sample is put in, the cavity is operated by using the technological parameters, and the cavity is ensured to be operatedA gaseous environment. And controlling the etching time to be 2.5 minutes after the etching starts, and forming AlGaN nano holes with the depth of 200 nm. The selectivity ratio of AlGaN to S1813 photoresist was 1:2, and the remaining thickness of S1813 photoresist after etching was about 800 μm (step 5). The remaining photoresist on the sample was washed away using acetone, isopropanol, water to complete the preparation of the nanopore array, as shown in fig. 10F.
As an embodiment of the present invention, an AlGaN nanopore array 830 may be formed on a surface of a buffer layer 820 of a substrate, including: silicon dioxide islands are formed on the surface of the buffer layer 820, and the AlGaN nanopore array 830 is formed on the surface of the buffer layer 820 where the silicon dioxide islands are formed. The islands may be protrusions or regions formed on the surface of the buffer layer 820, and may be formed by using a special process or a special material. Specifically, a small silicon dioxide island may be formed on the surface of the third intermediate layer of the buffer layer 820 by a micro-nano processing technique, and then a film is directly grown on the surface of the third intermediate layer on which the small silicon dioxide island is formed by Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD). Because the silicon dioxide island has a barrier effect on the growth of the film, the position of the silicon dioxide island can not form a film material. Finally, the AlGaN nanopore array 830 is formed on the surface of the buffer layer 820. As an embodiment of the present invention, the material of the island may be silicon dioxide, titanium dioxide, silicon nitride, or a metal, and the description of the silicon dioxide island is not limited to the island material.
As an embodiment of the present invention, modifying a cocatalyst nanoparticle on a nanopore of an AlGaN nanopore array includes: forming an amorphous protective layer covering the surface of the nanopore array on the surface of the AlGaN nanopore array; and modifying the surface of the protective layer with cocatalyst nanoparticles. As shown in fig. 10G, which is a schematic diagram of a stage of a flow of preparing an AlGaN nanopore array in a method for preparing a solar-blind ultraviolet electrochemical photodetector according to embodiments of the present invention, amorphous TiO with a thickness of 2nm may be deposited by an Atomic Layer Deposition (ALD) method2Protective layer (a-TiO)2)870, prevent the AlGaN material from undergoing photo-corrosion under the condition of hole enrichment. The deposition process adopts tetra (dimethylamino) titanium (IV) TEMAT and water as precursorsThe precursor tanks were kept at 65 ℃ and 25 ℃ respectively for 60 cycles of codeposition. Each period comprises the process of introducing titanium precursor for 0.1s, N2Purging for 10s, introducing water vapor for 0.1s, and introducing N2Purging for 10s, forming an amorphous protection layer 870 covering the surface of the nanopore array on the surface of the AlGaN nanopore array by an atomic layer deposition method, wherein the amorphous protection layer 870 is used for protecting the nanopore array from being corroded by a cavity, has a tunnel conduction effect, is good in conductivity, and cannot affect the detection performance.
As shown in fig. 10H, which is a schematic diagram of a stage of a flow of preparation of an AlGaN nanopore array in a method for preparing a solar blind ultraviolet electrochemical photodetector according to embodiments of the present invention, co-catalyst nanoparticles 850 may be modified on the surface of the protective layer 870 by a photo-deposition method, and 100 μ L of 20mg/mL ruthenium chloride (RuCl) is added to 20mL of deionized water3) Solution of a-TiO to be produced2the/n-AlGaN nanopore array is arranged in the same time as the a-TiO2And applying ultraviolet illumination corresponding to the band gap on the/n-AlGaN nanopore array. a-TiO due to the photoelectric effect of semiconductors2the/n-AlGaN nanopore array generates photo-generated electron-hole pairs after absorbing photons. Then photoproduced electrons are diffused to the surface of the nano hole, and the energy of the photoproduced electrons is larger than that of ruthenium ions Ru in the solution3+The photo-generated electrons diffused to the surface of the nano-pores are reduced and modified on the a-TiO2Ru on surface of/n-AlGaN nanopore array3+And forming nanometer Ru particles, wherein the nanometer particles can be selected to be 2 nm.
As an embodiment of the present invention, a method for fabricating a photodetector using an AlGaN nanopore array modified with promoter nanoparticles as a photo anode includes: forming a first area which is not covered with the protective layer on the surface of the AlGaN nanopore array, wherein the first area is arranged outside the nanopore area; a conductive region for spot welding indium balls to form a photo anode is provided on the first region for extracting the photo anode. The first area is formed on the surface of the nanopore array and is not overlapped with the area where the nanopore is located, so that the short circuit is prevented, and the extraction electrode can be more stable and effective. An ohmic contact conductive area can be formed on the first area 860 and the surface of the nanopore array by spot welding of indium balls, a square area with the size of 2mm multiplied by 2mm can be selected as the conductive area, better conductive characteristics and current stability can be achieved, and meanwhile, a lead extraction electrode can be fixed, namely, a photo-anode can be formed.
As an embodiment of the present invention, a photodetector is prepared by using an AlGaN nanopore array modified with promoter nanoparticles as a photo anode, and the method further includes: and arranging the reference electrode, the counter electrode and the photo-anode in an electrolyte solution at a certain interval to prepare a three-electrode system so as to form the photodetector. Therefore, the photoelectrochemical photodetector based on simple water oxidation reaction as a photoelectric reaction mechanism is basically formed, the preparation condition is simple, the purity requirement is low, and the working process has little influence on electrode materials.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (18)
1. A photoelectrochemical photodetector for solar blind uv applications, comprising a photoelectrode and an electrolyte solution in contact with the photoelectrode for water-based oxidation as a photoelectric reaction mechanism, the photoelectrode comprising:
a substrate, and
a GaN-based nanopore array formed on the substrate surface, wherein the GaN-based nanopore array comprises an n-type GaN-based nanopore array and a p-type GaN-based nanopore array.
2. The photodetector of claim 1, wherein the GaN-based nanopores have a diameter of 0.01-5 μ ι η and a depth of 5-6000 nm; the distance between adjacent nano holes in the GaN-based nano hole array is 0.01-5 mu m.
3. The photodetector according to claim 1, wherein the substrate comprises a sapphire substrate, a gallium nitride substrate, a gallium oxide substrate, a silicon carbide substrate, a silicon substrate, or a substrate provided with a GaN-based material thin film.
4. The photodetector of claim 1, wherein the photoelectrode comprises a photoanode formed of an n-type GaN-based nanohole array and a photocathode formed of a p-type GaN-based nanohole array.
5. The photodetector of claim 1, further comprising a buffer layer between the substrate and the GaN-based nanopore array;
the buffer layer comprises at least three intermediate layers; the buffer layer includes a first intermediate layer formed on a substrate; a second intermediate layer formed on the first intermediate layer; a third intermediate layer formed on the second intermediate layer.
6. The photodetector of claim 1, wherein the GaN-based nanopore array is an n-type GaN-based nanopore array, the GaN-based nanopore array surface of the photoelectrode further comprises a protective layer covering the nanopore array surface, the protective layer has a thickness of 10nm or less, and the protective layer comprises at least titanium dioxide.
7. The photodetector of claim 6, wherein the photoelectrode further comprises promoter nanoparticles distributed on the surface of the protective layer, wherein the promoter nanoparticles are metal particles active in oxidation or reduction of water.
8. The photodetector of claim 6, wherein the surface of the GaN-based nanohole array further comprises a first region uncovered by the protective layer, the first region being disposed outside the nanohole region, the first region comprising indium ball spot-bonded thereon for forming a conductive region of the photoelectrode for leading out the photoelectrode.
9. The photo-detector of claim 1, wherein the photo-electrochemical photo-detector further comprises:
a reference electrode and a counter electrode in contact with the electrolyte solution,
the distance between the reference electrode and the counter electrode and between the reference electrode and the photoelectrode is more than or equal to 0.01 mm;
the reference electrode, the counter electrode and the photoelectrode are respectively connected with an electrochemical workstation with a current monitoring function.
10. The light detector of claim 9,
the electrolyte solution comprises an acidic or neutral electrolyte solution, the neutral electrolyte solution is a sodium sulfate or phosphate buffer solution, the acidic electrolyte solution comprises hydrobromic acid, sulfuric acid, hydrochloric acid or perchloric acid, and the concentration of the electrolyte solution is 0.01-5 mol/L;
the reference electrode is a silver or silver chloride (Ag/AgCl) electrode;
the counter electrode includes a platinum (Pt) electrode or a carbon (C) electrode.
11. A method for preparing a solar-blind UV-photoelectrochemical photodetector for use in the preparation of a photodetector according to any one of claims 1 to 10,
forming a GaN-based nanopore array on the substrate;
modifying the nanopore with a promoter nanoparticle;
and preparing the photodetector by using the GaN-based nano-pore array modified with the cocatalyst nano-particles as a photoelectrode.
12. The method of claim 11, wherein forming a GaN-based nanopore array on the substrate comprises:
pre-annealing the substrate;
forming a buffer layer on the pre-annealed substrate;
and forming a GaN-based nano-pore array on the surface of the buffer layer.
13. The method of claim 12, wherein forming a buffer layer on the pre-annealed substrate comprises:
the buffer layer at least comprises two intermediate layers;
forming a first intermediate layer on the substrate in a first condition,
forming a second intermediate layer on the first intermediate layer in a second condition;
forming a third intermediate layer in a third condition on the second intermediate layer.
14. The method of claim 12, wherein forming the GaN-based nanopore array on the surface of the buffer layer of the substrate comprises:
forming a GaN-based thin film on the buffer layer in a fourth condition;
and etching the film to form the GaN-based nano-hole array.
15. The method of claim 12, wherein forming the GaN-based nanopore array on the surface of the buffer layer of the substrate comprises:
forming small islands on the surface of the buffer layer,
and forming the GaN-based nano-hole array on the surface of the buffer layer on which the island is formed.
16. The method of claim 11, wherein modifying the promoter nanoparticles on the nanopores of the GaN-based nanopore array comprises:
forming a protective layer covering the surface of the nanopore array on the surface of the GaN-based nanopore array;
and modifying the surface of the protective layer with cocatalyst nanoparticles.
17. The method of claim 16, wherein the fabricating the photodetector using the GaN-based nanopore array of modified promoter nanoparticles as a photoelectrode comprises:
forming a first region on the surface of the GaN-based nanopore array, wherein the first region is not covered by the protective layer and is arranged outside the nanopore region;
and arranging a spot welding indium ball on the first area to form a conductive area of the photoelectrode, and leading out the photoelectrode.
18. The method of claim 11, wherein the fabricating the photodetector using the GaN-based nanopore array of modified promoter nanoparticles as a photoelectrode further comprises:
arranging a reference electrode, a counter electrode and a photoelectrode in an electrolyte solution at a certain interval to prepare a three-electrode system to form the photodetector;
wherein the distance is greater than or equal to 0.01 mm.
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