Gallium-aluminum co-doped n-ZnO / p-GaN heterojunction and preparation and application thereof

Abstract

The invention discloses a gallium-aluminum co-doped n-ZnO / p-GaN heterojunction and preparation and application thereof, and belongs to the technical field of semiconductors. Comprising a sapphire substrate, a GaN buffer layer, a u-GaN layer, a p-GaN layer, a ZnO seed crystal layer and gallium-aluminum co-doped ZnO nanorods. According to the method, after growth of a p-GaN layer is finished, a high-temperature decomposition step is carried out to form porous GaN, a ZnO seed layer is spin-coated, then a high-temperature annealing step is carried out to grow ZnO nanorods, the properties that the GaN porous structure increases the contact area of heterojunctions and forms a three-dimensional heterostructure are utilized, and by means of application of the ZnO seed layer, the three-dimensional heterojunction structure is formed, so that the yield of the ZnO nanorods is improved. Compared with the prior art, the preparation method has the advantages that the requirement of nanorod growth on the lattice matching degree of the substrate is lowered, the energy band structure between n-ZnO and p-GaN is effectively regulated and controlled through gallium-aluminum doping, in addition, the GaN porous structure provides growth conditions for vertical arrangement growth of nanorods, the photosensitive area is increased, and high photoelectric conversion efficiency is achieved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to gallium-aluminum co-doped n-ZnO / p-GaN heterojunctions, their preparation, and applications. Background Technology

[0002] GaN is a wide bandgap semiconductor material with a direct bandgap of 3.39 eV at room temperature. It possesses characteristics such as a large bandgap, high saturated electron drift velocity, high thermal conductivity, low dielectric constant, and good chemical stability, making it widely used in power electronics, high-brightness LEDs, and detectors. Compared to two-dimensional thin-film GaN, three-dimensional porous GaN has a larger specific surface area. The porous structure of GaN increases the contact area of ​​the heterojunction, forming the properties of a three-dimensional heterostructure.

[0003] ZnO is a group II-VI direct bandgap compound semiconductor material with advantages such as environmental friendliness, non-toxicity, and good chemical stability. Its wide bandgap, high exciton binding energy, and significant piezoelectric properties make it a promising candidate material for applications in photodetectors, piezoelectric devices, gas sensors, and optoelectronic devices. It is also an important candidate material for display technology and solar cells. In particular, ZnO can form abundant nanostructures, with highly ordered ZnO nanorod arrays significantly increasing the interfacial contact area between the charge generation layer and the transport layer, thereby promoting efficient separation and transport of interfacial charges. Furthermore, this ordered nanostructure helps reduce the probability of electron scattering and recombination at grain boundaries and defects, providing continuous directional transport paths for photogenerated carriers. Therefore, applying ZnO nanorod arrays to ultraviolet photodetectors helps improve the device's photoelectric conversion efficiency and response performance.

[0004] PN junctions (the region near the interface between N-type and P-type semiconductors) are among the most fundamental components in modern electronics, widely used in diodes, transistors, photodetectors, photocatalysis, gas sensors, energy conservation, and emission reduction. By rationally selecting semiconductor materials and constructing corresponding heterostructures, the advantages of multiple components can be integrated, significantly improving the operating efficiency of related devices.

[0005] Due to the strong self-compensation effect of ZnO, it is difficult to obtain stable p-type doping. Therefore, combining zinc oxide with other p-type materials to prepare heterostructures has become a feasible solution. GaN and ZnO have similar crystal structures, close lattice constants, and low lattice mismatch. Furthermore, GaN has a mature fabrication process, allowing for reliable and controllable p-type doping. Therefore, the two can form high-quality heterostructures, which hold promise for applications in the fabrication of high-response ultraviolet photodetectors. Common methods for growing ZnO nanorods on GaN include hydrothermal methods, chemical vapor transport methods, sol-gel methods, and electrochemical methods.

[0006] However, the aforementioned methods often suffer from complex processes, demanding conditions for control, and difficulties in precisely controlling the morphology, orientation, and density of ZnO nanorods. This results in the prepared nanorods frequently exhibiting collapsed, agglomerated, or irregularly arranged states. This morphological disorder limits the interface quality and carrier transport efficiency of the heterojunction, thereby affecting device performance. Therefore, developing a ZnO / GaN heterojunction fabrication method that can effectively control the growth morphology of nanorods, is simple to implement, and can significantly improve the responsivity of ultraviolet photodetectors has significant research value and application potential. Summary of the Invention

[0007] The purpose of this invention is to provide gallium-aluminum co-doped n-ZnO / p-GaN heterojunctions, their preparation, and applications, overcoming the shortcomings of existing technologies such as the inability to precisely control the morphology of zinc oxide nanorods and the complexity of the preparation process. By utilizing the property of GaN decomposition at high temperatures to form a porous structure, the contact area of ​​the PN junction is increased, providing growth conditions for the vertically aligned growth of nanorods, improving the photosensitive area, and achieving high photoelectric conversion efficiency.

[0008] To achieve the above objectives, this invention provides a method for preparing a gallium-aluminum co-doped n-ZnO / p-GaN heterojunction, comprising the following steps: S1. Using an MOCVD system, GaN buffer layer, u-GaN layer and p-GaN layer are grown sequentially on a sapphire substrate to obtain a substrate; the gallium nitride substrate is then subjected to ultrasonic cleaning and nitrogen drying to obtain a pretreated gallium nitride substrate, the surface layer of which is a p-GaN layer. S2. In a mixture of hydrogen and nitrogen, the gallium nitride substrate is thermally decomposed to form porous GaN on the surface of the p-GaN layer. S3. A ZnO seed layer is formed on the p-GaN layer by spin-coating a seed layer solution; S4. Place the sample obtained in S3 in the reaction chamber for high-temperature annealing to form a ZnO seed crystal layer from the ZnO seed layer. S5. The sample obtained in S4 is placed in a reaction vessel containing the growth solution and grown in a low-temperature water bath for 90-120 min at a temperature of 80-95℃. Gallium-aluminum doped ZnO nanorod arrays are grown on the ZnO seed layer to obtain gallium-aluminum co-doped n-ZnO / p-GaN heterojunction.

[0009] Preferably, in S1, the gallium source of the GaN buffer layer is TMGa, the nitrogen source is NH3, the growth temperature of the GaN buffer layer is 500~570℃, and the thickness of the GaN buffer layer is 22~28nm.

[0010] Preferably, in S1, the gallium source of the u-GaN layer is TMGa, the nitrogen source is NH3, the growth temperature of the u-GaN layer is 1000~1100℃, and the thickness of the u-GaN layer is 1.8~2.7µm.

[0011] Preferably, in S1, the gallium source of the p-GaN layer is TMGa, the nitrogen source is NH3, the magnesium source is Cp2Mg, the growth temperature of the p-GaN layer is 930~990℃, and the thickness of the p-GaN layer is 1.7~2.4µm.

[0012] Preferably, in S2, the volume ratio of hydrogen to nitrogen is 1:9, the thermal decomposition temperature is 900~1100℃, and the time is 30~140min.

[0013] Preferably, in step S3, zinc acetate dihydrate is dissolved in ethylene glycol methyl ether to a concentration of 0.5-1 mol / L, and monoethanolamine is added as a stabilizer. The molar ratio of ethanolamine to zinc ions is 1:1-1.5:1, to prepare a seed layer solution with a concentration of 0.5-1 mol / L and a spin-coating thickness of 20-100 nm.

[0014] Preferably, in S4, the annealing temperature is 500~550℃ and the annealing time is 90~120min.

[0015] Preferably, in S5, the growth solution is an aqueous solution composed of zinc salt, gallium salt, aluminum salt and hexamethylenetetramine; the molar ratio of zinc salt and hexamethylenetetramine is 1:1 to 1:2; the growth solution is prepared by introducing gallium salt solution and aluminum salt solution of a specific concentration into a zinc salt solution of equal concentration, wherein the doping concentration of gallium and aluminum is controlled by adjusting the amount of gallium salt solution and aluminum nitrate solution added.

[0016] Specifically, Ga(NO3)3 and Al(NO3)3 solutions are added to zinc acetate solution to induce Al doping in the growth solution. 3 + / (Al 3+ +Zn 2+ The molar ratios of Ga in the Ga-doped growth solution were 1-6%;3+ / (Ga 3+ +Zn 2+ The molar ratio of Ga to Al in the co-doped growth solution is 1-6%; 3+ / (Ga 3+ +Al 3+ +Zn 2+ The molar ratio of Al is 1~6%. 3+ / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of ) is 1~6%, and then it is mixed with the same volume and concentration of C6H 12 N4 solution mixed.

[0017] Preferably, the zinc salt is Zn(NO3)2·6H2O; the gallium salt is Ga(NO3)3·9H2O; and the aluminum salt is Al(NO3)3·9H2O.

[0018] The present invention also provides a gallium-aluminum co-doped n-ZnO / p-GaN heterojunction prepared by the above-described preparation method, comprising a sapphire substrate, a GaN buffer layer of 22-28 nm, a u-GaN layer of 1.8-2.7 µm, a p-GaN layer with a porous structure of 1.7-2.4 µm, a ZnO seed layer of 20-100 nm, and a gallium-aluminum co-doped ZnO nanorod array with a diameter of 130-210 nm and a length of 500-1000 nm grown perpendicular to the p-GaN substrate layer on the ZnO seed layer.

[0019] This gallium-aluminum co-doped n-ZnO / p-GaN heterojunction is used in optoelectronic devices.

[0020] Therefore, the present invention has the following beneficial effects: 1. The present invention describes the preparation and application of a gallium-aluminum co-doped n-ZnO / p-GaN heterojunction, which ingeniously utilizes the characteristic of GaN decomposition at high temperatures. Thermal decomposition is carried out in a mixed gas environment of hydrogen and nitrogen, thereby successfully forming a porous GaN layer. By precisely controlling the heating time, the depth of the nanopores can be flexibly adjusted. The entire operation process is extremely simple and low-cost.

[0021] 2. In this invention, the Ga and Al doping concentrations in the gallium-aluminum co-doped n-type ZnO nanorods can be precisely controlled by adjusting the amount of gallium and aluminum salts added to the precursor growth solution. This doping method is simple to operate and the doping level can be flexibly adjusted, which is beneficial for systematically studying the influence of doping concentration on the electrical and optical properties of heterojunctions, and provides a reliable process route for preparing n-ZnO / p-GaN heterostructures with different doping concentration requirements.

[0022] 3. This invention effectively optimizes the crystallinity of ZnO nanorods by introducing Group IIIA donor elements (Ga, Al) for co-doping. Specifically, this results in increased grain size, more uniform distribution, and a significant reduction in grain boundary defect state density, thereby improving carrier transport performance. Furthermore, the specific surface area of ​​the constructed three-dimensional porous p-GaN framework is 3 to 5 times that of traditional two-dimensional planar p-GaN films, greatly increasing the heterojunction interface contact area. This not only promotes the effective separation and collection of photogenerated carriers and significantly improves photocurrent response, but also provides an excellent nucleation substrate for the vertically ordered growth of ZnO nanorods. This synergistic effect enhances the device's light absorption capacity and internal quantum efficiency, ultimately achieving high photoelectric conversion efficiency.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the preparation of gallium-aluminum co-doped n-ZnO nanorods / porous p-GaN heterojunctions prepared in Example 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the gallium-aluminum co-doped n-ZnO nanorod / porous p-GaN heterojunction prepared in Example 1 of the present invention; Figure 3 This is a planar SEM image of the porous GaN prepared in Example 1 of the present invention; Figure 4 The images shown are planar SEM images of the samples prepared in Example 1 and the comparative example of the present invention, wherein (a) is a SEM image of ZnO, (b) is a SEM image of GZO, (c) is a SEM image of AZO, and (d) is a SEM image of GAZO. Figure 5 The XRD patterns are those of the samples prepared in Example 1 and the comparative example of the present invention.

[0025] Figure 6 The PL spectra of the samples prepared in Example 1 and the comparative example of the present invention are shown.

[0026] Figure 7 The images show the ultraviolet absorption spectra of the samples prepared in Example 1 and the comparative example of this invention. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] like Figure 1 The fabrication process flow diagram shown illustrates a method for preparing gallium-aluminum co-doped n-ZnO / p-GaN heterojunctions, comprising the following steps: S1. Using an MOCVD system, GaN buffer layer, u-GaN layer and p-GaN layer are grown sequentially on a sapphire substrate to obtain a substrate; the gallium nitride substrate is then subjected to ultrasonic cleaning and nitrogen drying to obtain a pretreated gallium nitride substrate, the surface layer of which is a p-GaN layer.

[0029] S2. In a mixture of hydrogen and nitrogen, the gallium nitride substrate is thermally decomposed to form porous GaN on the surface of the p-GaN layer.

[0030] S3. A ZnO seed layer is formed on the p-GaN layer by spin-coating a seed layer solution.

[0031] S4. Place the sample obtained in S3 into the reaction chamber for high-temperature annealing to form a ZnO seed crystal layer.

[0032] S5. The sample obtained in S4 is placed in a reaction vessel containing the growth solution and grown in a low-temperature water bath for 90-120 min at a temperature of 80-95℃. Gallium-aluminum doped ZnO nanorod arrays are grown on the ZnO seed layer to obtain gallium-aluminum co-doped n-ZnO / p-GaN heterojunction.

[0033] In S1, the gallium source of the GaN buffer layer is TMGa, the nitrogen source is NH3, the growth temperature of the GaN buffer layer is 500~570℃, and the thickness of the GaN buffer layer is 22~28nm; the gallium source of the u-GaN layer is TMGa, the nitrogen source is NH3, the growth temperature of the u-GaN layer is 1000~1100℃, and the thickness of the u-GaN layer is 1.8~2.7µm; the gallium source of the p-GaN layer is TMGa, the magnesium source is Cp2Mg, the growth temperature of the p-GaN layer is 930~990℃, and the thickness of the p-GaN layer is 1.7~2.4µm.

[0034] Furthermore, in S2, the thermal decomposition temperature is 900~1100℃, and the thermal decomposition time is 30~140min.

[0035] Furthermore, in S3, zinc acetate dihydrate is dissolved in ethylene glycol methyl ether to a concentration of approximately 0.5–1 mol / L, and monoethanolamine is added as a stabilizer. The molar ratio of ethanolamine to zinc ions is 1:1–1.5:1, to prepare a seed layer solution with a concentration of 0.5–1 mol / L. The spin-coating thickness is 20–100 nm.

[0036] Furthermore, in S4, the annealing temperature is 500~550℃, and the annealing time is 90~120min.

[0037] Furthermore, in S5, the growth solution is an aqueous solution composed of zinc salt, gallium salt, aluminum salt and hexamethylenetetramine; the molar ratio of zinc salt to hexamethylenetetramine is 1:1 to 1:2.

[0038] The growth solution is prepared by adding Ga(NO3)3 and Al(NO3)3 solutions to a zinc acetate solution, thereby doping Al in the growth solution. 3+ / (Al 3+ +Zn 2+ The molar ratios of Ga in the Ga-doped growth solution were 1-6%; 3+ / (Ga 3+ +Zn 2+ The molar ratio of Ga to Al in the co-doped growth solution is 1-6%; 3+ / (Ga 3+ +Al 3+ +Zn 2+ The molar ratio of Al is 1~6%. 3+ / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of ) is 1~6%, and then it is mixed with the same volume and concentration of C6H 12 N4 solution mixed.

[0039] Furthermore, the zinc salt is Zn(NO3)2·6H2O; the gallium salt is Ga(NO3)3·9H2O; and the aluminum salt is Al(NO3)3·9H2O.

[0040] This invention also provides a gallium-aluminum co-doped n-ZnO / p-GaN heterojunction prepared by the above-described preparation method, with the results as follows: Figure 2 As shown, the structure includes a sapphire substrate, a GaN buffer layer of 22-28 nm, a u-GaN layer of 1.8-2.7 µm, a p-GaN layer with a porous structure of 1.7-2.4 µm, a ZnO seed layer of 20-100 nm, and a gallium-aluminum co-doped ZnO nanorod array with a diameter of 130-210 nm and a length of 500-1000 nm grown perpendicular to the p-GaN substrate layer on the ZnO seed layer.

[0041] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0042] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0043] Example 1 This embodiment provides a method for preparing gallium-aluminum co-doped n-ZnO / p-GaN heterojunctions, specifically including the following steps: S1. In an MOCVD system, a GaN buffer layer, a u-GaN layer, and a p-GaN layer are sequentially grown on a sapphire substrate to obtain a substrate; the gallium nitride substrate is then subjected to ultrasonic cleaning and nitrogen drying to obtain a pretreated gallium nitride substrate, the surface layer of which is a p-GaN layer; on the C-plane of the sapphire substrate (… <0001> A 25 nm thick GaN buffer layer, a 2.5 μm thick u-GaN layer, and a 2 μm thick p-GaN layer were sequentially stacked on the orientation plane to obtain a gallium nitride substrate. The growth temperature of the GaN buffer layer was 550 °C, the growth temperature of the u-GaN layer was 1080 °C, and the growth temperature of the p-GaN layer was 970 °C. The gallium nitride substrate was then subjected to ultrasonic treatment in acetone, ethanol, and deionized water for 15 min each, followed by drying with nitrogen gas to obtain a pretreated substrate.

[0044] S2. The pretreated gallium nitride substrate is placed in a tube furnace and thermally decomposed at 1000°C for 60 min in a mixture of hydrogen and nitrogen to obtain porous GaN; the volume ratio of hydrogen to nitrogen in the mixture of hydrogen and nitrogen is 1:9. Figure 3 Here are SEM images of porous GaN samples, from... Figure 3 As can be seen, Example 1 prepared a uniform and regularly arranged hexagonal hole structure, which showed that gallium nitride under high temperature annealing underwent thermal decomposition based on lattice symmetry. This proved that the gallium nitride template used had extremely high crystal quality and low defect density. At the same time, it showed that the temperature and atmosphere of the annealing process were very precisely controlled, and porous gallium nitride that can be used as an ideal nanopatterning substrate was successfully prepared.

[0045] S3. A 0.5 mol / L ZnO seed layer solution was spin-coated onto the surface of the sample obtained in S2 using both low-speed and high-speed spin coating. The seed layer solution was prepared by dissolving 2.195 g of zinc acetate dihydrate in 20 ml of ethylene glycol methyl ether and adding monoethanolamine as a stabilizer. The molar ratio of ethanolamine to zinc ions was 1:1. The spin coating thickness was 60 nm and the spin coating time was 30 s.

[0046] S4. Place the sample obtained in S3 in the reaction chamber for high-temperature annealing at 500℃ for 1 hour to form a ZnO seed crystal layer.

[0047] S5. Prepare the growth solution by adding a 0.05 mol / L Ga(NO3)3 and Al(NO3)3 solution to a 0.05 mol / L Zn(NO3)2 solution, followed by an equal volume and concentration of C6H4O2. 12The growth solution was obtained by mixing N4 solution, in which Ga-doped sample Ga 3+ / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of Al to Al in the Al-doped sample is 3%. 3 / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of Ga to Al is 1%; the Ga and Al co-doped sample makes Ga... 3+ / (Ga 3+ +Al 3+ +Zn 2+ The molar ratio of Al is 3%. 3+ / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of S4 to aluminum oxide was 3%. The sample obtained from S4 was vertically placed into a low-temperature water bath containing the growth solution. The temperature was 95℃ and the growth time was 3h, resulting in a gallium-aluminum co-doped zinc oxide nanorod / gallium nitride heterojunction, named GAZO.

[0048] Example 2 This embodiment prepares gallium-aluminum co-doped zinc oxide nanorods / gallium nitride heterojunctions according to the method of Example 1. The difference from Example 1 is that the thermal decomposition temperature in step S2 is 960℃, the thermal decomposition time is 80 min, and the Al content in the growth solution in step S5 is different. 3 / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of Ga is 6%. 3+ / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of the components was 6%, the water bath temperature was 90℃, and the hydrothermal time was 3h.

[0049] Example 3 This embodiment prepares a gallium-aluminum co-doped porous gallium nitride / zinc oxide heterojunction according to the method of Example 1. The difference from Example 1 is that the thermal decomposition temperature in step S2 is 1050℃, the thermal decomposition time is 80 min, and the Al content in the growth solution in step S5 is [not specified]. 3 / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of Ga is 6%. 3+ / (Al 3+ +Ga 3+ +Zn 2+ The molar ratio of ) is 3%, the water bath temperature is 90℃, and the hydrothermal time is 4h.

[0050] Comparative Example This comparative example provides a method for preparing gallium-aluminum co-doped n-ZnO / p-GaN heterojunctions, which is basically the same as the steps in Example 1. The only difference is that the proportions of each part in the growth solution in step S5 are different. 0% Ga(NO3)3 and Al(NO3)3 solutions, 0.05 mol / L Ga(NO3)3, and 0.05 mol / L Al(NO3)3 are added to a 0.05 mol / L zinc acetate dihydrate solution, respectively. These are named ZnO, GZO, and AZO, corresponding to the undoped sample, Ga-doped sample, and Al-doped sample, respectively.

[0051] Figure 4 SEM images of the sample from Example 1 and the three samples from the comparative examples, respectively. Figure 4 (d) Figure 4 (a) Figure 4 (b) and Figure 4 (c). By Figure 4 As can be seen, the gallium-aluminum co-doped zinc oxide nanorods prepared in Example 1 are uniformly and densely distributed on the surface of the gallium nitride substrate. The diameters of the ZnO, GZO, AZO and GAZO samples are approximately 210 nm, 170 nm, 140 nm and 130 nm, respectively, and the length is approximately 1 µm, exhibiting good crystal quality and regular morphology.

[0052] Figure 5 The XRD patterns are of the sample from Example 1 and three samples from the comparative example. Figure 5 It can be seen that all samples only have (002) and (004) diffraction peaks, indicating that the prepared ZnO NRs have good c-axis orientation and hexagonal wurtzite structure. Furthermore, in Figure 5 No other diffraction peaks belonging to Ga or Al were observed, indicating that Ga and Al are well dissolved in the ZnO lattice, suggesting that the gallium-aluminum co-doped zinc oxide nanorods have high crystal quality and form a good heterojunction structure with gallium nitride.

[0053] Figure 6 The PL spectra of the sample from Example 1 and the three samples from the comparative examples are shown below. Figure 6 It can be seen that all samples consist of two emission peaks: one is a strong ultraviolet emission peak at approximately 375 nm, and the other is a weak visible light emission peak. The relative intensity of the UV emission peak of the co-doped ZnO NRs is significantly reduced. This is because Ga 3+ And Al 3+When ions dissolve into the ZnO lattice, the radiative recombination of free excitons at the near edge of ZnO decreases, leading to a reduction in the intensity of the ultraviolet emission peak. Visible light emission in ZnO typically originates from oxygen vacancies, which can be attributed to the fact that oxygen vacancies act as radiative centers during luminescence. The visible light emission of the GZO sample is more pronounced than that of other samples, exhibiting the highest intensity of its visible light emission peak. This is likely due to the greater number of oxygen vacancies introduced into the ZnO crystal.

[0054] Figure 7 The UV absorption spectra of the sample from Example 1 and the three samples from the comparative examples are provided by [the relevant authority / organization]. Figure 7 It can be seen that all samples exhibit a relatively broad ultraviolet absorption peak at 365 nm, while almost no absorption peak is observed in the visible light region. This is likely due to interband transitions of electrons in ZnO. With the doping of Ga and Al, the absorption peak of the doped ZnO NRs shows a significant red shift, which can be attributed to the reduction of the ZnO band gap. The ultraviolet absorption efficiency of co-doped ZnO NRs is significantly improved, mainly due to the presence of Ga. 3+ And Al 3+ When ions are dissolved into the ZnO lattice, the high concentration of free electrons (mainly provided by Ga) enhances the material's interaction with incident light.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Preparation of gallium-aluminum co-doped n-ZnO / p-GaN heterojunction, characterized in that, Includes the following steps: S1. Using an MOCVD system, GaN buffer layer, u-GaN layer and p-GaN layer are grown sequentially on a sapphire substrate to obtain a gallium nitride substrate; the gallium nitride substrate is then subjected to ultrasonic cleaning and nitrogen drying to obtain a pretreated gallium nitride substrate, the surface layer of which is a p-GaN layer. S2. In a mixture of hydrogen and nitrogen, the gallium nitride substrate is thermally decomposed to form porous GaN with a nanoporous structure on the surface of the p-GaN layer. S3. A ZnO seed layer is formed on the p-GaN layer by spin-coating a seed layer solution; S4. Place the sample obtained in S3 in the reaction chamber for high-temperature annealing to form a ZnO seed crystal layer from the ZnO seed layer. S5. The sample obtained in S4 is placed in a reaction vessel containing the growth solution and grown in a low-temperature water bath for 90-120 min at a temperature of 80-95℃. Gallium-aluminum doped ZnO nanorod arrays are grown on the ZnO seed layer to obtain gallium-aluminum co-doped n-ZnO / p-GaN heterojunction.

2. The preparation of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction according to claim 1, characterized in that, In S1, the gallium source of the GaN buffer layer is TMGa, the nitrogen source is NH3, the growth temperature of the GaN buffer layer is 500~570℃, and the thickness of the GaN buffer layer is 22~28nm.

3. The preparation of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction according to claim 1, characterized in that, In S1, the gallium source of the u-GaN layer is TMGa, the nitrogen source is NH3, the growth temperature of the u-GaN layer is 1000~1100℃, and the thickness of the u-GaN layer is 1.8~2.7µm.

4. The preparation of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction according to claim 1, characterized in that, In S1, the gallium source of the p-GaN layer is TMGa, the nitrogen source is NH3, and the magnesium source is Cp2Mg. The growth temperature of the p-GaN layer is 930~990℃, and the thickness of the p-GaN layer is 1.7~2.4µm.

5. The preparation of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction according to claim 1, characterized in that, In S2, the volume ratio of hydrogen to nitrogen is 1:9, the thermal decomposition temperature is 900~1100℃, and the time is 30~140min.

6. The preparation of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction according to claim 1, characterized in that, In S3, zinc acetate dihydrate is dissolved in ethylene glycol methyl ether to a concentration of 0.5-1 mol / L, and monoethanolamine is added as a stabilizer. The molar ratio of monoethanolamine to zinc ions is 1:1-1.5:1 to prepare a seed layer solution with a concentration of 0.5-1 mol / L. The spin-coating thickness is 20-100 nm.

7. The preparation of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction according to claim 1, characterized in that, In S4, the annealing temperature is 500~550℃ and the annealing time is 90~120min.

8. The preparation of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction according to claim 1, characterized in that, In S5, the growth solution is an aqueous solution composed of zinc salt, gallium salt, aluminum salt and hexamethylenetetramine; the molar ratio of zinc salt and hexamethylenetetramine is 1:1 to 1:2; the growth solution is prepared by introducing gallium salt solution and aluminum salt solution into zinc salt solution of equal concentration, wherein the doping concentration of gallium and aluminum is controlled by adjusting the amount of gallium salt solution and aluminum nitrate solution added.

9. A gallium-aluminum co-doped n-ZnO / p-GaN heterojunction, characterized in that, The gallium-aluminum co-doped n-ZnO / p-GaN heterojunction prepared according to any one of claims 1-8 includes a sapphire substrate, a GaN buffer layer of 22-28 nm, a u-GaN layer of 1.8-2.7 µm, a p-GaN layer with a porous structure of 1.7-2.4 µm, a ZnO seed layer of 20-100 nm, and a gallium-aluminum co-doped ZnO nanorod array with a diameter of 130-210 nm and a length of 500-1000 nm grown perpendicular to the p-GaN layer on the ZnO seed layer.

10. An application of the gallium-aluminum co-doped n-ZnO / p-GaN heterojunction as described in claim 9, characterized in that, Gallium-aluminum co-doped n-ZnO / p-GaN heterojunctions are used in optoelectronic devices.

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