Preparation method of Pd plasmon-Nb2C mixed colloidal solution and AlGaN-based ultraviolet photodetector

Abstract

The present invention discloses a method for preparing a Pd plasmon-Nb2C mixed colloidal solution, comprising the following steps: x Mix and stir for 1.5-2h; perform centrifugal washing, remove the turbid liquid layer, add deionized water, repeat several times to obtain a Pd plasmon-Nb2C mixed colloidal solution. The present invention also discloses a Schottky contact electrode of an AlGaN-based ultraviolet photodetector prepared by the above preparation method, an AlGaN-based ultraviolet photodetector comprising the above Schottky contact electrode, and a preparation method. The present invention covers a layer of plasmon array on the surface of the Schottky contact electrode structure, increases the photocurrent by enhancing the local electric field and light absorption; utilizes Nb2CT x The reducibility of the solution allows for the reduction and preparation of Pd plasmon structures, which is a simple process that is more economical and universal.

Description

Technical Field

[0001] The present invention relates to an ultraviolet photodetector, and in particular to a preparation method of a Pd plasmon-Nb2C mixed colloidal solution, a Schottky contact electrode of an AlGaN-based ultraviolet photodetector, an AlGaN-based ultraviolet photodetector and a preparation method thereof. Background Art

[0002] Ultraviolet photodetectors, as optoelectronic components that play an important role in missile warning, weather monitoring, and communications support, have attracted widespread attention. Traditional GaN-based ultraviolet photodetectors have shortcomings such as a narrow bandgap and low electron saturation mobility, resulting in narrow response bands, weak visible light filtering, severe device heating, and poor stability. These problems make it difficult to meet the growing demand for device miniaturization, integration, and shorter wavelengths. Therefore, there is an urgent need to develop a new generation of ultraviolet photoelectric devices that can be used under UVC (deep ultraviolet) band working conditions and meet the application requirements of device miniaturization and integration. As a result, research on III-nitride multi-compound ultraviolet photodetectors represented by AlGaN has emerged. Therefore, the exploration of deep ultraviolet AlGaN ultraviolet photodetectors and their implementation methods has groundbreaking revolutionary significance and social application value.

[0003] CN115566096A discloses an AlGaN / Nb2C-based ultraviolet photodetector and a preparation method thereof. Its Schottky contact electrode is prepared using a two-dimensional Nb2C material. However, the structure has insufficient stability and poor photoelectric response characteristics due to insufficient light absorption. The introduction of a plasmon structure can overcome the above problems to a certain extent, but the modification process based on the plasmon structure is currently more complicated, and the yield and morphology are poor. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, one of the objects of the present invention is to provide a method for preparing a Pd plasmon-Nb2C mixed colloidal solution, which is easy to operate when used to prepare Schottky contact electrodes for AlGaN-based ultraviolet photodetectors, and is economical and universal.

[0005] A second object of the present invention is to provide a Schottky contact electrode for an AlGaN-based ultraviolet photodetector.

[0006] A third object of the present invention is to provide an AlGaN-based ultraviolet photodetector, in which the surface of the Schottky contact electrode is covered with a layer of plasmon array, which can increase the photocurrent by enhancing the local electric field and light absorption.

[0007] A fourth object of the present invention is to provide a method for preparing the above-mentioned AlGaN-based ultraviolet photodetector.

[0008] The purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a Pd plasmon-Nb2C mixed colloidal solution comprises the following steps:

[0010] PdCl2 and Nb2CT x Mix and stir for 1.5-2h; Nb2CT x The concentration of the droplets is 0.05-0.08 mg / mL, and the concentration of the PdCl2 solution is 0.177-0.354 mg / ml; centrifugal washing is performed at a rate of 18000-20000 rpm for 10-15 minutes, the lower layer of turbid liquid is removed, deionized water is added, and the process is repeated multiple times to obtain a Pd plasmon-Nb2C mixed colloidal solution.

[0011] The Schottky contact electrode of the AlGaN-based ultraviolet photodetector is prepared by using the Pd plasmon-Nb2C mixed colloidal solution prepared by the preparation method of the Pd plasmon-Nb2C mixed colloidal solution.

[0012] An AlGaN-based ultraviolet photodetector comprises an ultraviolet photodetector epitaxial wafer and an insulating layer, an ohmic contact electrode and a Schottky contact electrode arranged on the ultraviolet photodetector epitaxial wafer;

[0013] The ultraviolet photodetector epitaxial wafer comprises a non-doped Ga polar surface AlN buffer layer and a non-doped Ga polar surface AlN buffer layer grown in sequence on a sapphire substrate. x Ga 1-x N layers, where x = 0.5 to 0.8;

[0014] The insulating layer covers the non-doped Ga polar surface Al x Ga 1-x On a portion of the surface on the N layer, the ohmic contact electrode is arranged on the insulating layer, the Schottky contact electrode covers the upper surface of the ohmic contact electrode, and the insulating layer, the side surface of the ohmic contact electrode and the non-doped Ga polar surface Al x Ga 1-x The ohmic contact electrode also covers the non-doped Ga polar surface Al x Ga 1-x On part of the surface of the N layer; the Schottky contact electrode includes a two-dimensional Nb2C and a Pd plasmon array structure covered on the two-dimensional Nb2C.

[0015] Preferably, the insulating layer is a patterned Al2O3 insulating layer with a thickness of 50 to 100 nm.

[0016] Preferably, the ohmic contact electrode is a patterned ohmic contact electrode, which is made by Ti / Al / Ni / Au evaporation and has a thickness of 50 to 100 nm.

[0017] Preferably, the substrate is a sapphire substrate.

[0018] Preferably, the non-doped Ga polar surface AlN buffer layer and the non-doped Ga polar surface Al x Ga 1-x The thickness of the N layer is 350-500 nm and 300-450 nm respectively.

[0019] Preferably, the non-doped Ga polar surface AlN buffer layer and the non-doped Ga polar surface Al x Ga 1-x The N layer has (0001) as the epitaxial direction.

[0020] The method for preparing the AlGaN-based ultraviolet photodetector comprises the following steps:

[0021] The non-doped Ga polar AlN buffer layer and the non-doped Ga polar AlN buffer layer are grown on the substrate in sequence. x Ga 1-x N layer, obtaining an ultraviolet photodetector epitaxial wafer and performing a cleaning process; wherein x = 0.5 to 0.8;

[0022] Performing photolithography on the cleaned ultraviolet photodetector epitaxial wafer to obtain an isolation pattern; etching the photolithographic ultraviolet photodetector epitaxial wafer to etch a groove along the isolation pattern;

[0023] Through mask alignment, the non-doped Ga polar surface Al x Ga 1-x Photolithography is performed on one side of the N layer, and Al x Ga 1-x An insulating layer pattern is prepared on the N layer; the ultraviolet photodetector epitaxial wafer prepared with the insulating layer pattern is placed in an electron beam evaporation device, an insulating layer is evaporated to obtain an insulating layer, and the ultraviolet photodetector epitaxial wafer prepared with the insulating layer is cleaned;

[0024] Through mask alignment, Al x Ga 1-x The other side of the N layer is photolithographically processed to obtain an ohmic contact electrode pattern; the ultraviolet photodetector epitaxial wafer with the ohmic contact electrode pattern is placed in an electron beam evaporation device to evaporate an ohmic contact electrode metal to obtain an ohmic contact electrode metal; and the ultraviolet photodetector epitaxial wafer with the ohmic contact electrode metal is cleaned;

[0025] Through mask alignment, on the ohmic contact electrode metal on one side of the insulating layer, and on the side of the insulating layer, the ohmic contact electrode and the non-doped Ga polar surface Al x Ga 1-x On the N layer, photolithography is performed to obtain a Schottky contact electrode pattern;

[0026] A Pd plasmon-Nb2C mixed colloidal solution is dropped onto the Schottky contact electrode pattern to evenly cover it. After heating and setting, a Schottky contact electrode prepared with a Pd plasmon-Nb2C mixed material is obtained to obtain a plasmon-enhanced AlGaN-based ultraviolet photodetector.

[0027] Preferably, the heating is specifically: heating at 50-70°C.

[0028] More specifically, the method for preparing the AlGaN-based ultraviolet photodetector includes the following steps:

[0029] (1) A non-doped Ga polar AlN buffer layer and a non-doped Ga polar AlN buffer layer are grown on a sapphire substrate. x Ga 1-x N layer (thin film), to obtain the ultraviolet photodetector epitaxial wafer;

[0030] (2) placing the AlGaN ultraviolet photodetector epitaxial wafer obtained in step (1) in acetone, deionized water, and anhydrous ethanol in sequence for ultrasonic treatment, taking it out and washing it with deionized water and then drying it with hot high-purity nitrogen;

[0031] (3) Preparation of mesa isolation pattern: The AlGaN rectifier epitaxial wafer obtained in step (2) is subjected to photolithographic preparation of insulating mesa isolation pattern: photoresist is evenly applied on the AlGaN rectifier epitaxial wafer obtained in step (2) by spin coating, the AlGaN rectifier epitaxial wafer coated with photoresist is pre-baked, and then placed in a photolithography machine for exposure, and finally the exposed epitaxial wafer is immersed in a developer for photolithographic development and cleaning;

[0032] (4) Mesa isolation: Reactive ion etching is performed on the AlGaN ultraviolet photodetector epitaxial wafer after photolithography. Grooves are etched along the boss pattern in the AlGaN ultraviolet photodetector epitaxial wafer to obtain separated and insulated bosses and then cleaned;

[0033] (5) performing photolithographic preparation of the insulating layer electrode pattern on the AlGaN rectifier epitaxial wafer obtained in step (4): aligning the AlGaN epitaxial wafer using the alignment marks in the mask, and repeating the process in step (3);

[0034] (6) preparing an insulating layer on the AlGaN rectifier epitaxial wafer, placing the AlGaN ultraviolet photodetector epitaxial wafer with the insulating layer pattern obtained by photolithography development in step (5) in an electron beam evaporation device, evacuating the evaporation chamber, and then evaporating an Al2O3 insulating layer;

[0035] (7) Immersing the AlGaN ultraviolet photodetector epitaxial wafer in a degumming solution and removing it, rinsing it with deionized water and using acetone to ultrasonically remove the photoresist and evaporated metal remaining on the surface of the AlGaN ultraviolet photodetector epitaxial wafer, then washing it with deionized water after ultrasonication, and then drying it with hot high-purity nitrogen;

[0036] (8) Aligning the AlGaN rectifier epitaxial wafer using the alignment marks in the mask, repeating the process in step (3), photolithography and development at the corresponding positions, preparing the device ohmic contact electrode pattern and cleaning;

[0037] (9) preparing an ohmic contact electrode on the AlGaN rectifier epitaxial wafer: placing the AlGaN rectifier epitaxial wafer with the ohmic contact electrode pattern developed by photolithography obtained in step (8) into an electron beam evaporation device, repeating the process of step (6) to evaporate the ohmic contact electrode metal on the AlGaN ultraviolet photodetector epitaxial wafer;

[0038] (10) Repeat step (7) to remove the residual photoresist and evaporated metal on the surface of the AlGaN epitaxial wafer by soaking in a degumming solution and ultrasonic cleaning;

[0039] (11) Place the AlGaN epitaxial wafer with the metal electrode evaporated into a rapid annealing device and perform rapid annealing in a flowing N2 atmosphere at a temperature of 600°C for 3 minutes;

[0040] (12) The annealed device was placed in a piranha wash solution for 5 minutes. The piranha wash solution was prepared by mixing concentrated sulfuric acid and 30% hydrogen peroxide in a ratio of 7:3.

[0041] (13) Aligning the AlGaN rectifier epitaxial wafer using the alignment marks in the mask, repeating the process in step (3), photolithography and development at the corresponding positions, preparing the device Schottky contact electrode pattern and cleaning;

[0042] (14) PdCl2 and Nb2CT x Mix and stir for 2h. x The droplet concentration was 0.05 mg / mL, and the PdCl2 solution concentration was 0.177 mg / ml. Centrifugal washing was performed at 18,000 rpm for 15 minutes. The lower turbid liquid layer was removed and deionized water was added. This was repeated three times to obtain a Pd plasmon-Nb2C mixed colloidal solution.

[0043] (15) Schottky contact electrodes are prepared on the AlGaN rectifier epitaxial wafer: the AlGaN ultraviolet detector epitaxial wafer with the Schottky contact electrode pattern developed by photolithography obtained in step (13) is placed on a glass slide, and the Pd plasmon-Nb2C mixed colloidal solution prepared in step (14) is dripped on it so that the mixed colloidal solution fully and evenly covers the surface of the AlGaN ultraviolet photodetector epitaxial wafer; after uniform coverage, it is heated and placed to be shaped to obtain a Schottky contact electrode; finally, an AlGaN-Nb2C-based ultraviolet photodetector is obtained.

[0044] Preferably, the non-doped Ga polar surface AlN buffer layer and the non-doped Ga polar surface Al x Ga 1-x The N films all have (0001) as the epitaxial direction.

[0045] Preferably, the ultrasonic treatment time in step (2) and step (7) is 3 to 15 minutes.

[0046] Preferably, the thickness of the photoresist in step (3) is 0.2 to 0.7 μm, the exposure time is 1 to 4 s, and the development time is 45 to 95 s.

[0047] Preferably, the depth of the groove in step (4) is 1 to 2.5 μm;

[0048] Preferably, the vacuum degree in step (6) is 1 to 5×10 -5 Pa;

[0049] The annealing temperature in step (11) is 450° C. to 800° C., and the annealing time is 3 to 5 minutes.

[0050] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0051] (1) The present invention utilizes Nb2CT x The reducibility of the solution allows for the reduction and preparation of Pd plasmon structures, which is more economical and universal in the preparation of Schottky contact electrodes compared to the current complex processes such as MBE or MOVCD.

[0052] (2) In the design of the Schottky contact electrode structure, the present invention covers the surface with a layer of plasmon array, which can increase the photocurrent by enhancing the local electric field and light absorption.

[0053] (3) The present invention uses Group III nitrides represented by AlGaN as the basic material of ultraviolet photodetectors. Group III nitrides have more excellent material properties than traditional Si chips and can better realize the miniaturization and integration of devices in shorter wavelength applications.

[0054] (4) The surface morphology of the epitaxial material of the present invention is better, which can greatly improve the contact quality of the metal electrode and the interface quality between the Schottky electrode and the epitaxial material.

[0055] (5) The present invention uses a transparent sapphire substrate material as the device epitaxial substrate to facilitate the collection and transmission of optical signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 Schematic diagram of the structure of a plasmon-enhanced AlGaN-based ultraviolet photodetector according to an embodiment of the present invention.

[0057] Figure 2 This is a SEM characterization image of the localized plasmon array according to an embodiment of the present invention.

[0058] Figure 3 This is a comparison diagram of IV curve tests of a plasmon-enhanced AlGaN-based ultraviolet photodetector according to an embodiment of the present invention. DETAILED DESCRIPTION

[0059] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0060] Example 1

[0061] This embodiment provides a method for preparing an AlGaN-Nb2C-based ultraviolet photodetector, which specifically includes:

[0062] (1) Growing an AlGaN ultraviolet photodetector epitaxial wafer on a sapphire substrate using a metal organic chemical vapor deposition technique: sequentially growing a Ga polar AlN buffer layer and a non-doped Ga polar AlGaN layer on the sapphire substrate; the AlN buffer layer has a thickness of 450 nm; and the non-doped Ga polar AlGaN layer has a thickness of 400 nm;

[0063] (2) The AlGaN ultraviolet photodetector epitaxial wafer was placed in acetone, deionized water, and anhydrous ethanol in sequence and ultrasonicated for 3 minutes each. After removal, it was rinsed with deionized water, and the rinsed AlGaN was blown dry with hot high-purity nitrogen;

[0064] (3) Preparation of mesa isolation pattern: The cleaned AlGaN ultraviolet photodetector epitaxial wafer is spin-coated with positive photoresist, model RZJ304, with a photoresist thickness of 0.2 μm, and the epitaxial wafer coated with photoresist is placed on a hot plate for pre-baking for 90 seconds. The epitaxial wafer coated with photoresist is then placed in a photolithography machine and aligned through the mask alignment mark. The development area size is 2 mm × 1 mm. The exposure is then performed for 15 seconds. The exposed epitaxial wafer is then immersed in a positive developer, model RZX3038, for 50 seconds. Finally, the developed epitaxial wafer is taken out, rinsed with deionized water, and blown dry with hot high-purity nitrogen gas. The film is then placed on a hot plate for baking for 90 seconds.

[0065] (4) Mesa isolation pattern etching: Place the AlGaN ultraviolet photodetector epitaxial wafer after photolithography in a reactive ion etcher to perform reactive ion etching on the isolation layer pattern exposed by photolithography, and etch out a groove corresponding to the pattern with a groove depth of 2 μm. After etching, rinse the epitaxial wafer surface with deionized water and blow dry with hot nitrogen;

[0066] (5) Preparation of insulating layer pattern: Align the AlGaN ultraviolet photodetector epitaxial wafer using the alignment marks on the mask, repeat the photolithography process in step (3), perform photolithography development at the corresponding position, and prepare an exposed device insulating layer pattern area on the AlGaN ultraviolet photodetector epitaxial wafer with a size of 0.3 mm × 1 mm;

[0067] (6) Preparation of insulating layer for AlGaN ultraviolet photodetector epitaxial wafer after photolithography: Place the AlGaN ultraviolet photodetector epitaxial wafer with insulating layer pattern into electron beam evaporation equipment, and pump the vacuum degree of the cavity to 1×10 -5 Pa, followed by evaporation of the insulating layer material Al2O34 with a thickness of 50nm;

[0068] (7) Immerse the AlGaN ultraviolet photodetector epitaxial wafer with the prepared insulating layer in the degumming solution for 10 minutes, remove it, rinse it with deionized water, and place it in acetone for 15 minutes of ultrasonic treatment. After taking it out, rinse it with deionized water and blow it dry with hot nitrogen;

[0069] (8) Preparation of ohmic contact electrode pattern: Align the AlGaN ultraviolet photodetector epitaxial wafer through the alignment mark in the mask plate, repeat the photolithography process in step (3), photolithography and development at the corresponding position, and prepare the device ohmic contact electrode pattern area exposed on the AlGaN ultraviolet photodetector epitaxial wafer, with a size of 2×0.2mm×1mm, located on the left and right sides of the etching table respectively;

[0070] (9) Preparation of ohmic contact electrodes for the AlGaN ultraviolet photodetector epitaxial wafer after photolithography: Place the AlGaN ultraviolet photodetector epitaxial wafer with the device ohmic contact pattern into the electron beam evaporation equipment, and pump the vacuum degree of the cavity to 1×10 -5 Pa, followed by evaporation of ohmic contact electrode materials Ti / Al / Ni / Au with a thickness of 50 nm;

[0071] (10) Repeat step (7) to remove the residual photoresist and evaporated metal on the surface of the AlGaN epitaxial wafer by soaking in a degumming solution and ultrasonic cleaning;

[0072] (11) Place the AlGaN epitaxial wafer with the metal electrode evaporated into a rapid annealing device and perform rapid annealing in a flowing N2 atmosphere at a temperature of 400°C for 4 minutes.

[0073] (12) The annealed device was placed in a piranha wash solution for 5 minutes. The piranha wash solution was prepared by mixing concentrated sulfuric acid and 30% hydrogen peroxide in a ratio of 7:3.

[0074] (13) Preparation of Schottky contact electrode pattern: Align the AlGaN UV photodetector epitaxial wafer using the alignment mark in the mask, repeat the photolithography process in step (3), perform photolithography and development on the corresponding position on the insulating layer pattern side, and prepare the device Schottky contact electrode pattern area exposed on the AlGaN UV photodetector epitaxial wafer with a size of 1.6 mm × 1 mm;

[0075] (14) PdCl2 and Nb2CT x Mix and stir for 2h. x The droplet concentration was 0.05 mg / mL, and the PdCl2 solution concentration was 0.177 mg / ml. Centrifugal washing was performed at 18,000 rpm for 15 minutes. The lower turbid liquid layer was removed and deionized water was added. This was repeated three times to obtain a Pd plasmon-Nb2C mixed colloidal solution.

[0076] (15) Prepare Schottky contact electrodes on the photolithographic AlGaN ultraviolet photodetector epitaxial wafer: Paste the AlGaN ultraviolet photodetector epitaxial wafer with the Schottky contact electrode pattern on a glass slide, use a syringe to draw a small amount of the mixed colloidal solution prepared in step (14) and drop it on the surface of the epitaxial wafer. Place the AlGaN ultraviolet photodetector epitaxial wafer in a vacuum oven to dry it to shape the plasmon structure. Finally, soak the AlGaN epitaxial wafer in acetone for 50 seconds to remove the residual photoresist and mixed colloidal material on the surface of the AlGaN epitaxial wafer. Finally, a plasmon-enhanced AlGaN-based ultraviolet photodetector is obtained.

[0077] The structure of the plasmon-enhanced AlGaN-based ultraviolet photodetector prepared in this embodiment is as follows: Figure 1 As shown, it includes an ultraviolet photodetector epitaxial wafer and an insulating layer, an ohmic contact electrode and a Schottky contact electrode arranged on the ultraviolet photodetector epitaxial wafer;

[0078] The ultraviolet photodetector epitaxial wafer comprises a non-doped Ga polar surface AlN buffer layer 2 and a non-doped Ga polar surface AlN buffer layer 3 grown in sequence on a sapphire substrate 1. x Ga 1-x N layer 3, where x = 0.5 to 0.8;

[0079] The insulating layer 4 covers the non-doped Ga polar surface Al x Ga 1-x On a portion of the surface of the N layer 3, the ohmic contact electrode 5 is provided on the insulating layer, and the Schottky contact electrode covers the upper surface of the ohmic contact electrode 5, as well as the insulating layer 4, the side surface of the ohmic contact electrode 5 and the non-doped Ga polar surface Al x Ga 1-x The ohmic contact electrode 5 also covers the non-doped Ga polar surface Al x Ga 1-x On a portion of the surface of the N layer 3 ; the Schottky contact electrode includes a two-dimensional Nb2C layer 6 and a Pd plasmon array structure 7 covering the two-dimensional ultra-thin Nb2C layer 6 .

[0080] The surface SEM characterization test results of plasmon are as follows Figure 2 As shown, the particle size is about 100 nm and the crystal quality is very good.

[0081] The performance test comparison results of plasmon-enhanced AlGaN-based ultraviolet photodetector devices are as follows: Figure 3 As shown in the figure, compared with the AlGaN / Nb2C-based ultraviolet photodetector, the ultraviolet detector modified with the plasmon structure has higher photocurrent response characteristics.

[0082] Example 2

[0083] This embodiment provides a method for preparing a plasmon-enhanced AlGaN-based ultraviolet photodetector, which specifically includes:

[0084] (1) An AlGaN ultraviolet photodetector epitaxial wafer is grown on a sapphire substrate using a metal organic chemical vapor deposition method, comprising a Ga polar AlN buffer layer grown on the sapphire substrate and a non-doped Ga polar AlGaN layer grown on the Ga polar AlN buffer layer; the AlN buffer layer has a thickness of 500 nm; and the non-doped Ga polar AlGaN layer has a thickness of 450 nm;

[0085] (2) The AlGaN ultraviolet photodetector epitaxial wafer was placed in acetone, deionized water, and anhydrous ethanol in sequence and ultrasonicated for 3 minutes each. After removal, it was rinsed with deionized water, and the rinsed AlGaN was blown dry with hot high-purity nitrogen;

[0086] (3) Preparation of mesa isolation pattern: The cleaned AlGaN ultraviolet photodetector epitaxial wafer is spin-coated with positive photoresist, model RZJ304, with a photoresist thickness of 0.3 μm, and the epitaxial wafer coated with photoresist is placed on a hot plate for pre-baking for 90 seconds. The epitaxial wafer coated with photoresist is then placed in a photolithography machine and aligned through the mask alignment mark. The development area size is 2 mm × 1 mm. The exposure is then performed for 15 seconds. The exposed epitaxial wafer is then immersed in a positive developer, model RZX3038, for 50 seconds. Finally, the developed epitaxial wafer is taken out, rinsed with deionized water, and blown dry with hot high-purity nitrogen gas. The film is then placed on a hot plate for baking for 90 seconds.

[0087] (4) Mesa isolation pattern etching: Place the AlGaN ultraviolet photodetector epitaxial wafer after photolithography in a reactive ion etcher to perform reactive ion etching on the isolation layer pattern exposed by photolithography, and etch out a groove corresponding to the pattern with a groove depth of 2.5 μm. After etching, rinse the epitaxial wafer surface with deionized water and blow dry with hot nitrogen;

[0088] (5) Preparation of insulating layer pattern: Align the AlGaN ultraviolet photodetector epitaxial wafer using the alignment marks on the mask, repeat the photolithography process in step (3), perform photolithography development at the corresponding position, and prepare an exposed device insulating layer pattern area on the AlGaN ultraviolet photodetector epitaxial wafer with a size of 0.3 mm × 1 mm;

[0089] (6) Preparation of insulating layer for AlGaN ultraviolet photodetector epitaxial wafer after photolithography: Place the AlGaN ultraviolet photodetector epitaxial wafer with insulating layer pattern into electron beam evaporation equipment, and pump the vacuum degree of the cavity to 1×10 -5 Pa, followed by evaporation of the insulating layer material Al2O3 with a thickness of 100nm;

[0090] (7) Immerse the AlGaN ultraviolet photodetector epitaxial wafer with the prepared insulating layer in the degumming solution for 5 minutes, remove it, rinse it with deionized water, and place it in acetone for 10 minutes of ultrasonic treatment. After taking it out, rinse it with deionized water and blow it dry with hot nitrogen;

[0091] (8) Preparation of ohmic contact electrode pattern: Align the AlGaN ultraviolet photodetector epitaxial wafer through the alignment mark in the mask plate, repeat the photolithography process in step (3), photolithography and development at the corresponding position, and prepare the device ohmic contact electrode pattern area exposed on the AlGaN ultraviolet photodetector epitaxial wafer, with a size of 2×0.2mm×1mm, located on the left and right sides of the etching table respectively;

[0092] (9) Preparation of ohmic contact electrodes for the AlGaN ultraviolet photodetector epitaxial wafer after photolithography: Place the AlGaN ultraviolet photodetector epitaxial wafer with the device ohmic contact pattern into the electron beam evaporation equipment, and pump the vacuum degree of the cavity to 1×10 -5 Pa, followed by evaporation of ohmic contact electrode materials Ti / Al / Ni / Au with a thickness of 100 nm;

[0093] (10) Repeat step (9) to remove the residual photoresist and evaporated metal on the surface of the AlGaN epitaxial wafer by soaking in a degumming solution and ultrasonic cleaning;

[0094] (11) Place the AlGaN epitaxial wafer with the metal electrode evaporated into a rapid annealing device and perform rapid annealing in a flowing N2 atmosphere at a temperature of 600°C for 3 minutes.

[0095] (12) The annealed device was placed in a piranha wash solution for 5 minutes. The piranha wash solution was prepared by mixing concentrated sulfuric acid and 30% hydrogen peroxide in a ratio of 7:3.

[0096] (13) Preparation of Schottky contact electrode pattern: Align the AlGaN UV photodetector epitaxial wafer using the alignment mark in the mask, repeat the photolithography process in step (3), perform photolithography and development on the corresponding position on the insulating layer pattern side, and prepare the device Schottky contact electrode pattern area exposed on the AlGaN UV photodetector epitaxial wafer with a size of 1.6 mm × 1 mm;

[0097] (14) PdCl2 and Nb2CT x Mix and stir for 2h. x The concentration of the droplets was 0.05 mg / mL, and the concentration of the PdCl2 solution was 0.354 mg / ml. Centrifugal washing was performed at a rate of 18000 rpm for 15 minutes. The lower layer of turbid liquid was removed and deionized water was added. This was repeated three times to obtain a Pd plasmon-Nb2C mixed colloidal solution.

[0098] (15) Prepare Schottky contact electrodes and plasmon array structures on the photolithographic AlGaN ultraviolet photodetector epitaxial wafer: Paste the AlGaN ultraviolet photodetector epitaxial wafer with the Schottky contact electrode pattern on a glass slide, use a syringe to draw a small amount of the mixed colloidal solution obtained in step (14) and drop it on the surface of the epitaxial wafer. Place the AlGaN ultraviolet photodetector epitaxial wafer in a vacuum oven and dry it to shape the Schottky electrode and plasmon array. Finally, soak the AlGaN epitaxial wafer in acetone for 50 seconds to remove the residual photoresist and colloidal solution on the surface of the AlGaN epitaxial wafer. Finally, a plasmon-enhanced AlGaN-based ultraviolet photodetector is obtained.

[0099] The plasmon crystals prepared in this embodiment have very good quality and have higher photocurrent response characteristics than AlGaN / Nb2C-based ultraviolet photodetectors.

[0100] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a Pd plasmon-Nb2C mixed colloidal solution, characterized in that: The following steps are involved: PdCl2 and Nb2CT x Mix and stir for 1.5-2h; Nb2CT x The concentration of the droplets is 0.05-0.08 mg / mL, and the concentration of the PdCl2 solution is 0.177-0.354 mg / ml. Centrifugal washing is performed at a rate of 18,000-20,000 rpm for 10-15 minutes. The lower layer of turbid liquid is removed, deionized water is added, and centrifugal washing is repeated multiple times to obtain a Pd plasmon-Nb2C mixed colloidal solution.

2. A Schottky contact electrode of an AlGaN-based ultraviolet photodetector, characterized in that: The Pd plasmon-Nb2C mixed colloidal solution is prepared by the preparation method of the Pd plasmon-Nb2C mixed colloidal solution according to claim 1; the Schottky contact electrode includes two-dimensional Nb2C and a Pd plasmon array structure covered on the two-dimensional Nb2C.

3. AlGaN-based ultraviolet photodetector, characterized in that: The device comprises an ultraviolet photodetector epitaxial wafer and an insulating layer, an ohmic contact electrode and a Schottky contact electrode of the AlGaN-based ultraviolet photodetector according to claim 2, which are arranged on the ultraviolet photodetector epitaxial wafer; The ultraviolet photodetector epitaxial wafer comprises a non-doped Ga polar surface AlN buffer layer and a non-doped Ga polar surface AlN buffer layer grown in sequence on a sapphire substrate. x Ga 1-x N layers, where x = 0.5 to 0.8; The insulating layer covers the non-doped Ga polar surface Al x Ga 1-x On a portion of the surface on the N layer, the ohmic contact electrode is arranged on the insulating layer, the Schottky contact electrode covers the upper surface of the ohmic contact electrode, and the insulating layer, the side surface of the ohmic contact electrode and the non-doped Ga polar surface Al x Ga 1-x The ohmic contact electrode also covers the non-doped Ga polar surface Al x Ga 1-x on the surface of part of the N layer.

4. The AlGaN-based ultraviolet photodetector according to claim 3, characterized in that: The insulating layer is a patterned Al2O3 insulating layer with a thickness of 50-100 nm.

5. The AlGaN-based ultraviolet photodetector according to claim 3, characterized in that: The ohmic contact electrode is a patterned ohmic contact electrode, which is made by Ti / Al / Ni / Au evaporation and has a thickness of 50-100 nm.

6. The AlGaN-based ultraviolet photodetector according to claim 3, characterized in that: The substrate is a sapphire substrate.

7. The AlGaN-based ultraviolet photodetector according to claim 3, characterized in that: The non-doped Ga polar surface AlN buffer layer and the non-doped Ga polar surface Al x Ga 1-x The thickness of the N layer is 350~500nm and 300~450nm respectively.

8. The AlGaN-based ultraviolet photodetector according to claim 3 or 7, characterized in that: The non-doped Ga polar surface AlN buffer layer and the non-doped Ga polar surface Al x Ga 1-x The N layer has (0001) as the epitaxial direction.

9. The method for preparing the AlGaN-based ultraviolet photodetector according to any one of claims 3 to 8, characterized in that: The following steps are involved: The non-doped Ga polar AlN buffer layer and the non-doped Ga polar AlN buffer layer are grown on the substrate in sequence. x Ga 1-x N layer, obtain ultraviolet photodetector epitaxial wafer and perform cleaning treatment; wherein x = 0.5~0.8; Performing photolithography on the cleaned ultraviolet photodetector epitaxial wafer to obtain an isolation pattern; etching the photolithographic ultraviolet photodetector epitaxial wafer to etch a groove along the isolation pattern; Through mask alignment, the non-doped Ga polar surface Al x Ga 1-x Photolithography is performed on one side of the N layer, and Al x Ga 1-x An insulating layer pattern is prepared on the N layer; the ultraviolet photodetector epitaxial wafer prepared with the insulating layer pattern is placed in an electron beam evaporation device, an insulating layer is evaporated to obtain an insulating layer, and the ultraviolet photodetector epitaxial wafer prepared with the insulating layer is cleaned; Through mask alignment, Al x Ga 1-x The other side of the N layer is photolithographically processed to obtain an ohmic contact electrode pattern; the ultraviolet photodetector epitaxial wafer with the ohmic contact electrode pattern is placed in an electron beam evaporation device to evaporate an ohmic contact electrode metal to obtain an ohmic contact electrode metal; and the ultraviolet photodetector epitaxial wafer with the ohmic contact electrode metal is cleaned; Through mask alignment, on the ohmic contact electrode metal on one side of the insulating layer, and on the side of the insulating layer, the ohmic contact electrode and the non-doped Ga polar surface Al x Ga 1-x On the N layer, photolithography is performed to obtain a Schottky contact electrode pattern; The Pd plasmon-Nb2C mixed colloidal solution is dropped onto the Schottky contact electrode pattern and evenly covered. After heating and setting, a Schottky contact electrode prepared by the Pd plasmon-Nb2C mixed material is obtained to obtain a plasmon-enhanced AlGaN-based ultraviolet photodetector.

10. The preparation method according to claim 9, characterized in that The heating is specifically: heating at 50-70°C.

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