Vertical structure GaN-based p-i-n type ultraviolet detector on metal molybdenum substrate

Abstract

The application belongs to the technical field of wide band gap semiconductor photoelectric detection devices, and relates to a vertical structure GaN-based p-i-n type ultraviolet detector on a metal molybdenum substrate. Metal molybdenum is used as a substrate, there is a patterned back electrode layer on the upper surface of the metal molybdenum substrate, there is a molybdenum diffusion barrier layer on the upper surface of the metal molybdenum substrate which is not covered by the patterned back electrode layer, there are GaN buffer layer, n-type GaN layer, n-type Al x Ga 1‑x N layer, i-type Al y Ga 1‑y N layer and p-type Al z Ga 1‑z N layer are grown in sequence on the upper surface of the patterned back electrode layer and the molybdenum diffusion barrier layer in a lateral epitaxial growth mode, there is a passivation layer on the upper surface of the p-type Al z Ga 1‑z N layer, the passivation layer is slotted until the p-type Al z Ga 1‑z N layer is exposed, and a p-type electrode is arranged in the slot of the passivation layer. The application avoids cracks of each GaN-based film layer in the ultraviolet detector caused by thermal stress, increases spectral responsivity, and reduces response time.

Description

Technical Field

[0001] This invention belongs to the field of wide bandgap semiconductor photodetector technology, and relates to a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate. Background Technology

[0002] Ultraviolet (UV) detection technology has demonstrated immense application value in fields such as environmental monitoring, imaging technology, flame detection, missile early warning, spacecraft guidance, and space UV communication. Among the many materials used in fabricating UV detectors, gallium nitride (GaN)-based materials have attracted significant attention. GaN-based materials mainly include GaN and its alloys with indium nitride (InN) and aluminum nitride (AlN). The ternary alloy AlGaN material, in particular, allows for continuous variation of the bandgap between 3.39 eV (GaN) and 6.2 eV (AlN) by adjusting the Al composition, corresponding to a cutoff wavelength range of 365 nm (GaN) to 200 nm (AlN), covering the entire solar blind zone (200–280 nm). Because UV detectors operating in the solar blind zone are unaffected by solar background radiation, they possess a high signal-to-noise ratio. Corresponding UV detection and early warning systems can effectively track missile exhaust plumes, providing early warning for ground-based weapon systems. Furthermore, GaN-based materials exhibit advantages such as corrosion resistance and high-temperature resistance, enabling them to operate in harsh environments. Therefore, GaN-based materials have high application value in the field of ultraviolet detection. Current GaN-based ultraviolet detectors mainly include photoconductive, Schottky barrier, metal-semiconductor-metal (MSM), and pin-type device structures. Among them, pin-type GaN-based ultraviolet detectors have advantages such as low operating voltage, high input impedance, good linearity, low noise, and high ultraviolet / visible light suppression ratio. Furthermore, by adjusting the thickness of the i-layer and the alloy composition, different application requirements can be met, thus leading to their widespread use.

[0003] Due to the high cost of GaN and AlN single-crystal substrates, GaN-based ultraviolet detectors currently mostly use heterogeneous single-crystal substrates such as sapphire (α-Al₂O₃), silicon carbide (SiC), and silicon (Si). Compared to these single-crystal heterogeneous substrates, metal substrates offer advantages such as large area, low cost, electrical conductivity, thermal conductivity, and flexibility. They can be directly used as the back electrode of ultraviolet detectors, facilitating the fabrication of inexpensive, high-performance ultraviolet photodetectors with vertically conductive structures. Compared to most GaN-based detectors with laterally conductive structures on insulating substrates such as α-Al₂O₃, this saves electrode area on the ultraviolet light incident surface and increases spectral responsivity. Since photogenerated carriers in vertically conductive ultraviolet photodetectors migrate and collect in the short vertical direction of the device, the response time can be reduced.

[0004] Among many metals, molybdenum (Mo) has the highest coefficient of thermal expansion (5.2 × 10⁻⁶). -6The coefficient of thermal expansion ( / K) is very close to the α-axis thermal expansion coefficient of GaN (5.6 × 10⁻⁶). -6 Therefore, how to fabricate GaN-based devices with low thermal mismatch stress vertical conductive structures on molybdenum substrates has attracted the attention of researchers.

[0005] However, fabricating GaN-based thin films on molybdenum substrates presents significant challenges. It is well known that the most common growth method for GaN-based thin films is conventional metal-organic chemical vapor deposition (MOCVD) using ammonia (NH3) as the nitrogen source. While MOCVD offers fast growth rates and high-quality crystal films, researchers have found that the high growth temperature (approximately 1050°C) of MOCVD causes harmful high-temperature reactions between molybdenum and the GaN film, making it difficult to grow continuous GaN films on molybdenum substrates. Therefore, conventional MOCVD methods cannot be used to directly fabricate GaN-based ultraviolet detectors on molybdenum substrates.

[0006] Although there are reports that GaN thin films can be grown directly on molybdenum substrates at low temperatures using electron cyclotron resonance-plasma-enhanced metal-organic chemical vapor deposition (ECR-PEMOCVD) (≤600℃), the crystal quality of the GaN thin films is not high because the molybdenum substrate is not single-crystal. In addition, the growth rate of the ECR-PEMOCVD method is slow, which is very unfavorable for growing GaN-based thick film devices. Summary of the Invention

[0007] The present invention aims to provide a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate, which has a high spectral responsivity, fast response time, and can avoid cracking of each GaN-based film layer in the ultraviolet detector caused by thermal stress.

[0008] The technical solution for achieving the objective of this invention is as follows:

[0009] A vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate is disclosed. The molybdenum substrate has a partially covered patterned back electrode layer on its upper surface. A molybdenum diffusion barrier layer is located on the upper surface of the molybdenum substrate not covered by the patterned back electrode layer. From bottom to top, a GaN buffer layer, an n-type GaN layer, and an n-type Al layer are sequentially arranged on the upper surfaces of the patterned back electrode layer and the molybdenum diffusion barrier layer. x Ga 1-x N layer, i-type Al y Ga 1-y N-layer and p-type Al z Ga 1-z N layers, in p-type Al z Ga 1-zThe upper surface of layer N is a passivation layer, and grooves are cut into this passivation layer. The cutting involves selecting a centrally located square region within the passivation layer and creating multiple rectangular grooves parallel to the cell boundaries. All grooves are cut outside the square region, controlling the total projected area of ​​the grooved portion to be 30% to 65% of the original passivation layer area, until the p-type Al is exposed. z Ga 1-z N-layer, with p-type Al set within the passivation layer trench. z Ga 1-z N-layer contact p-type electrode; where: 0.1≤x≤0.7, 0.1≤y≤0.7, 0.1≤z≤0.7.

[0010] The molybdenum substrate is a single-layer molybdenum plate or molybdenum foil, and the thickness of the molybdenum substrate is 0.01 to 2 mm.

[0011] The patterned back electrode layer consists of a stacked structure of MoSi2 layer and Ga-doped ZnO layer from bottom to top. The patterned back electrode layer has a raised periodic pattern structure on the upper surface of the molybdenum substrate. The periodic pattern can be any one or a combination of two or more of the following: cylinder, elliptical cylinder, and polygonal cylinder. The period of the periodic pattern is 0.25 to 1.4 μm (the sum of the diameter of a pattern structure and the length of the side spacing of a pattern structure). The duty cycle of the periodic pattern is between 8% and 50%. The total thickness of the patterned back electrode layer is 50 to 150 nm, of which the thickness of the Ga-doped ZnO layer is 40 to 100 nm, and the Ga doping amount in the Ga-doped ZnO layer is 1 at% to 6.2 at. The back electrode layer is used to fabricate a vertically conductive ultraviolet detector. The upper surface of the back electrode layer provides the initial nucleation surface for subsequent GaN-based films. Using a patterned back electrode layer, in conjunction with a molybdenum diffusion barrier layer, enables lateral epitaxial overgrowth of each GaN-based film, improving the crystal growth quality of each GaN-based film. Furthermore, a appropriately periodized patterned back electrode layer can effectively scatter ultraviolet light, thereby improving the peak photoresponse of the ultraviolet detector. The periodic pattern of the back electrode layer can be achieved through techniques such as the fabrication of the required films, photolithography, and film etching.

[0012] The MoSi2 layer was chosen for the patterned back electrode stack structure because MoSi2 has good electrical conductivity and can form a good ohmic contact with the molybdenum substrate, thus making it suitable as a back electrode material. Due to the thermal expansion coefficient of MoSi2 (7.8 × 10⁻⁶), it is suitable for use as a back electrode material. -6The coefficient of thermal expansion ( / K) of MoSi2 is close to that of both the molybdenum substrate and GaN, which helps to avoid cracking of subsequent GaN-based films caused by thermal stress. Furthermore, the MoSi2 layer can be synthesized by the high-temperature reaction between the molybdenum substrate and the pre-fabricated Si layer (using rapid thermal annealing). In the reaction kinetics between the molybdenum substrate and the Si layer, it is almost entirely a diffusion of Si atoms through the interface to the molybdenum substrate side (e.g., at 1200℃, the diffusion coefficient of metallic Mo in MoSi2 is approximately 10). -16 cm 2 / s or lower (about 10,000 times slower than the diffusion coefficient of silicon in MoSi2), thus generating a MoSi2 layer of a certain thickness below the surface of the molybdenum substrate. That is, the MoSi2 layer has a certain effect of blocking the diffusion of molybdenum atoms into each GaN base film layer. By controlling the temperature and time of the high-temperature reaction, a thin layer of Si(111) layer that has not reacted with molybdenum and has been crystallized by annealing can be retained on the upper surface of the pre-placed Si layer. This crystallized Si(111) layer can be used as the epitaxial substrate for the subsequent Ga-doped ZnO layer. After the Ga-doped ZnO layer is further obtained by rapid thermal annealing, it can provide a good substrate for the subsequent epitaxial growth of GaN.

[0013] During the rapid thermal annealing of the Ga-doped ZnO layer, the vast majority of Si atoms in the crystallized Si(111) layer continue to diffuse towards the lower molybdenum substrate to form a MoSi2 layer. The remaining few Si atoms diffuse towards the upper Ga-doped ZnO layer, increasing the doping concentration near the MoSi2 side of the Ga-doped ZnO interface and resulting in a narrower interface barrier width. This allows for good ohmic contact between the MoSi2 and Ga-doped ZnO layers. In this way, the pre-fabricated Si layer can be depleted by rapidly annealing the temperature and time, thus creating a stacked back electrode structure of MoSi2 and Ga-doped ZnO layers from bottom to top on the molybdenum substrate.

[0014] The reason for choosing a Ga-doped ZnO layer in the stacked structure of the patterned back electrode layer is primarily to isolate the high-temperature reaction between the crystallized Si(111) film and GaN, as this reaction can generate a large number of voids at the Si-GaN interface. Additionally, ZnO and GaN have the same crystal structure, a small a-axis lattice mismatch (1.9%), and a low a-axis thermal expansion coefficient (6.5 × 10⁻⁶). -6The a-axis thermal expansion coefficient of GaN is very close to that of the molybdenum substrate and the MoSi2 layer, which helps to avoid cracking of subsequent GaN base films caused by thermal stress. In particular, compared to ZnO, using Ga-doped ZnO has the following advantages: 1) The a-axis lattice constant of Ga-doped ZnO is closer to that of GaN, which helps to further reduce the lattice mismatch between ZnO and GaN, thereby reducing the mismatch dislocation density in the GaN film; 2) Ga in Ga-doped ZnO is less likely to volatilize at high temperatures than Zn, which can improve the thermal stability of ZnO, and the addition of a certain concentration of Ga to ZnO can slow down the interfacial reaction between ZnO and GaN; 3) Ga-doped ZnO can achieve a thermal expansion coefficient as high as 10⁻⁶ K. 21 ~10 22 cm -3 The electron concentration is on the order of magnitude, which is beneficial for obtaining a very narrow interface barrier width, and achieving good ohmic contact between the Ga-doped ZnO layer and the GaN layer through carrier tunneling.

[0015] The molybdenum diffusion barrier layer is made of one or more of Si3N4, SiO2, and Si2N2O, and the thickness of the molybdenum diffusion barrier layer is 50-100 nm.

[0016] In this invention, the molybdenum diffusion barrier layer performs three important functions: first, it blocks the diffusion of Mo atoms from the molybdenum substrate to subsequent GaN-based films; second, it blocks the diffusion of gallium (Ga) atoms from subsequent GaN-based films to the molybdenum substrate; and third, it provides a masking layer for the lateral epitaxial overgrowth of GaN-based films on the upper surface of the patterned back electrode layer. This is because, during GaN film growth, due to differences in nucleation energy, the GaN-based film preferentially nucleates and grows on the upper surface of the patterned back electrode layer (i.e., the upper surface of the Ga-doped ZnO layer), and the lateral epitaxial overgrowth to the upper surface of the molybdenum diffusion barrier layer causes most vertical dislocations to gradually bend towards the surface of the molybdenum substrate, reducing the density of vertically penetrating dislocations. Utilizing these three functions of the molybdenum diffusion barrier layer can significantly improve the crystal growth quality of subsequent GaN-based films, thereby improving the performance of the ultraviolet detector. Compared to SiO2, the thermal expansion coefficient of Si3N4 films (2.8–3.2 × 10⁻⁶) is lower. -6 Si3N4 is closer to molybdenum substrates and GaN-based thin films, and its effect on blocking Ga atom diffusion is better than that of SiO2. Therefore, provided that the required wavelength of ultraviolet light can be transmitted, this invention recommends Si3N4 or Si2N2O (with a thermal expansion coefficient of 2.4 × 10⁻⁶) as the preferred materials. -6 / K) is used as a molybdenum diffusion barrier layer.

[0017] The thickness of the GaN buffer layer is 20–200 nm;

[0018] The thickness of the n-type GaN layer is 0.3–1 μm, and the Si doping concentration is 5 × 10⁻⁶. 17 ~5×10 20 cm -3 ;

[0019] The n-type Al x Ga 1-x The thickness of the N-layer is 30–150 nm, and the Si doping concentration is 5 × 10⁻⁶. 17 ~5×10 19 cm -3 ;

[0020] This invention sets n-type Al x Ga 1-x The purpose of the N-layer is to utilize n-type GaN layers and n-type Al. x Ga 1-x The valence band shift between N layers reduces the probability of holes crossing the potential barrier to reach the upper active region, which can improve the UV / Vis suppression ratio of the UV detector.

[0021] The i-type Al y Ga 1-y The thickness of the N layer is 120–200 nm;

[0022] The p-type Al z Ga 1-z The thickness of the N layer is 20–150 nm, and the Mg doping concentration is 5 × 10⁻⁶. 18 ~5×10 20 cm -3 ;

[0023] The passivation layer is made of Si3N4, SiO2 or Si2N2O, and has a thickness of 35-45 nm.

[0024] The passivation layer is set to passivate p-type Al. z Ga 1-z The surface dangling bonds and various defects in the N-layer reduce surface recombination of charge carriers and can prevent p-type Al z Ga 1-z Oxidation of the N-layer. In addition, by utilizing the principle of antireflection coating, the thickness of the passivation layer can be designed according to the peak response wavelength of the ultraviolet detector and the refractive index of the passivation layer, so that the passivation layer can also function as an antireflection coating.

[0025] The p-type electrode is made of one or more of Au, Ni, Pt, Pd, and Ru in a stack.

[0026] The beneficial effects of this invention are as follows: By setting GaN-based film layers on a molybdenum substrate with a relatively matched coefficient of thermal expansion, the thermal stress of the ultraviolet detector during fabrication and use is greatly reduced, avoiding cracking of the GaN-based film layers in the ultraviolet detector caused by thermal stress, increasing the thermal stability of the detector, and expanding the working environment of the detector; the detector has a high ultraviolet / visible light suppression ratio; compared with most GaN-based detectors with lateral conductive structures and front-incident light on insulating substrates such as α-Al2O3, the molybdenum substrate can be used as a back electrode, thus saving the p-type electrode area of ​​the ultraviolet light incident surface and increasing the spectral responsivity of the ultraviolet detector; since the photogenerated carriers in the vertically conductive structure ultraviolet detector migrate and collect in the short vertical direction of the device, the response time can be significantly reduced. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a device unit of a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate according to the present invention.

[0028] Figure 2 This is a top view of a device unit of a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate according to the present invention.

[0029] In the figure: 1. Molybdenum substrate, 2. Patterned back electrode layer, 3. Molybdenum diffusion barrier layer, 4. GaN buffer layer, 5. n-type GaN layer, 6. n-type Al x Ga 1-x N layer, 7, i-type Al y Ga 1-y N-layer, 8, p-type Al z Ga 1-z 9. N-layer, passivation layer, 10. p-type electrode. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0031] Example 1

[0032] In this embodiment, the cross-sectional pattern of one device unit of the ultraviolet detector is a square of 185μm×185μm. Within one device unit, upright cylinders made of MoSi2 / Ga-doped ZnO (30nm / 50nm) are periodically arranged in a square planar lattice structure within a 165μm×165μm square, thereby forming a periodic pattern of the patterned back electrode layer 2. The diameter of each MoSi2 / Ga-doped ZnO (30nm / 50nm) cylinder is controlled to be 200nm and the total thickness is 80nm. The axial spacing of the nearest neighbor MoSi2 / Ga-doped ZnO (30nm / 50nm) cylinder is 250nm, that is, the side spacing of the nearest neighbor MoSi2 / Ga-doped ZnO (30nm / 50nm) cylinder is 50nm. That is, the period of the patterned back electrode layer 2 is controlled to be 250nm. The area ratio of the patterned back electrode layer 2 to the molybdenum substrate 1, that is, the duty cycle, is controlled to be 50%.

[0033] Example 1 describes a method for fabricating a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate, comprising the following steps:

[0034] Step 1: Fabrication of the patterned back electrode layer 2: A single-layer molybdenum substrate with a polished upper surface is selected as the molybdenum substrate 1, and the thickness of the molybdenum substrate 1 is controlled to be 0.5 mm. Photoresist is spin-coated on the upper surface of the molybdenum substrate 1, and the area where the patterned back electrode layer 2 will be fabricated is exposed by photolithography. Other areas are masked with photoresist. The molybdenum substrate 1 is transferred to the sample stage in the vacuum chamber of the magnetron sputtering equipment. A Si target with a purity of 6N is used as the target material, and a 45 nm thick Si layer is sputtered and deposited at a sample stage heating temperature of 100 °C. Then, the sample was removed and the photoresist mask on the upper surface of the sample was removed to obtain a patterned Si layer on the molybdenum substrate 1. The molybdenum substrate 1 sample with the patterned Si layer was placed in a rapid thermal annealing furnace. In a high-purity argon (Ar) atmosphere with a purity of 6N at one atmosphere, the upper surface of the sample was subjected to rapid thermal annealing at 600℃, so that the patterned Si layer and the molybdenum substrate 1 react at the interface to generate a 27nm thick MoSi2 layer, and a 4nm thick crystallized Si (111) crystalline film was retained on the upper surface of the MoSi2 layer.

[0035] Next, photoresist was spin-coated onto the upper surface of the molybdenum substrate 1, and the area where the patterned back electrode layer 2 was to be fabricated was exposed by photolithography. Other areas were masked with photoresist. The molybdenum substrate 1 was transferred to the sample stage in the vacuum chamber of the magnetron sputtering equipment. Using a Ga-doped ZnO target as the target material, a 50 nm thick Ga-doped ZnO layer was sputtered and deposited at a sample stage heating temperature of 100 °C. The Ga doping content in the Ga-doped ZnO layer was controlled to be 5.5 at%. Then, the sample was removed and the photoresist mask on the upper surface of the sample was removed, resulting in a patterned MoSi2 / Si / Ga-doped ZnO (27 nm / 4 nm / 50 nm) on the molybdenum substrate 1. Then, the molybdenum substrate 1 sample with the patterned MoSi2 / Si / Ga-doped ZnO (27 nm / 4 nm / 50 nm) was placed in a rapid thermal annealing furnace. In a high-purity argon atmosphere with a purity of 6 N at one atmosphere, the upper surface of the sample was rapidly thermally annealed at 600 °C to achieve the desired effect. Most of the Si atoms in the 4nm thick Si layer continue to diffuse downwards to the interface between MoSi2 and the molybdenum substrate 1 to react and generate MoSi2. A very small number of Si atoms in the 4nm thick Si layer diffuse upwards to the lower surface of the Ga-doped ZnO layer (the diffusion coefficient of Si atoms in MoSi2 is much greater than that in ZnO, and the ZnO layer acts as a Si diffusion barrier layer) until the 4nm thick Si layer is completely exhausted, thereby obtaining a patterned back electrode layer 2 with a total thickness of 80nm, which is made of MoSi2 / Ga-doped ZnO (30nm / 50nm). From bottom to top, it is a stacked structure of a 30nm thick MoSi2 layer and a 50nm thick Ga-doped ZnO layer. The patterned back electrode layer 2 appears as a raised periodic cylindrical structure on the upper surface of the molybdenum substrate 1. The Ga doping amount in the Ga-doped ZnO layer is 5.5at%, and after rapid thermal annealing, an annealed crystallized Ga-doped ZnO layer with a preferred orientation (002) is obtained.

[0036] Step 2: Preparation of molybdenum diffusion barrier layer 3: Photoresist is spin-coated onto the upper surface of the sample after step 1, and the area where the molybdenum diffusion barrier layer 3 will be deposited is exposed by photolithography. The area of ​​the patterned back electrode layer 2 is masked with photoresist. A 60nm thick Si3N4 layer is deposited at a low temperature under the sample stage temperature of 90℃ using plasma-enhanced chemical deposition (PECVD). Then the sample is removed and the photoresist mask on the upper surface of the sample is removed, thus preparing a 60nm thick molybdenum diffusion barrier layer 3 made of Si3N4.

[0037] Steps 3 through 7 all employ the MOCVD method to sequentially grow the required GaN base films laterally on the upper surface of the patterned back electrode layer 2 and the molybdenum diffusion barrier layer 3, as detailed below:

[0038] Step 3, Low-temperature deposition of GaN buffer layer 4: The sample completed in step 2 is transferred to the graphite substrate in the reaction chamber of the MOCVD equipment. Then, the graphite substrate is heated to 520°C, and NH3 with a purity of 6N and TMGa are used as reaction gases to deposit a 30nm thick GaN buffer layer 4.

[0039] Step 4: Deposit n-type GaN layer 5: Next, heat the graphite substrate to 1050℃, and deposit a 0.5μm thick n-type GaN layer 5 using ammonia (NH3), trimethylgallium (TMGa), and silane (SiH4) with a purity of 6N as the N source, Ga source, and Si doping source, respectively. Control the Si doping concentration of the n-type GaN layer 5 to be 5×10⁻⁶. 18 cm -3 .

[0040] Step 5: Deposition of n-type Al x Ga 1-x N-layer 6: Next, the MOCVD graphite substrate was heated to 1080℃, and a 50nm thick n-type Al layer was deposited using NH3, TMGa, trimethylaluminum (TMAl), and SiH4 with a purity of 6N as the N source, Ga source, Al source, and Si doping source, respectively. x Ga 1-x Layer N, 6, controls the Al component value in the material to be x=0.51 (i.e., the product is n-type Al). 0.51 Ga 0.49 The doping concentrations of N and Si are 1×10⁻⁶. 18 cm -3 .

[0041] Step 6: Deposition of type i Al y Ga 1-y N-layer 7: Continue to stabilize the MOCVD graphite substrate temperature at 1150℃, turn off the SiH4 gas flow rate, and keep the flow rates of NH3, TMGa, and TMAl unchanged from step 5, to deposit a 150nm thick i-type Al layer. y Ga 1-y Layer N, 7, controls the Al component value in the material to be y=0.51 (i.e., the product is type i Al). 0.51 Ga 0.49 N).

[0042] Step 7: Deposition of p-type Al z Ga 1-z N-layer 8: Next, the MOCVD graphite substrate was heated to 1100℃, and a 30nm thick p-type Al layer was deposited using NH3, TMGa, TMAl and Mg(C5H5)2 with a purity of 6N as N source, Ga source, Al source and Mg doping source, respectively. z Ga 1-zN layers, 8, with the Al component value controlled at z=0.51 (i.e., the product is p-type Al). 0.51 Ga 0.49 The N and Mg doping concentrations are 8 × 10⁻⁶. 18 cm -3 Then, the sample was removed and placed in a rapid thermal annealing furnace. In a high-purity nitrogen (N2) atmosphere with a purity of 6N, the upper surface of the sample was subjected to rapid thermal annealing at 800℃ for 1 minute to activate p-type Al. z Ga 1-z Mg ions in N layer 8.

[0043] Step 8: Prepare the grooved passivation layer. Step 9: Transfer the sample from Step 7 to the sample stage inside the vacuum chamber of the PECVD equipment, and use the PECVD method to prepare the passivation layer on the p-type Al. z Ga 1-z A 35nm thick Si2N2O layer is deposited on layer N8 as a passivation layer 9. Photoresist is spin-coated onto the upper surface of passivation layer 9, and the passivation layer 9 to be etched is exposed by photolithography. Using inductively coupled plasma (ICP) dry etching with the photoresist as a mask, passivation layer 9 is etched. On the top surface of one device unit (185μm×185μm) of the ultraviolet detector in this embodiment, 40 elongated rectangular slots parallel to the unit boundary are centered within a 165μm×165μm square area. Slots are also made on the outer side of the 165μm×165μm square (i.e., the width of the slots around the perimeter is 10μm). The total projected area of ​​the slotted portion is controlled to occupy 30% of one device unit. The etching depth is 35nm until p-type Al is exposed. z Ga 1-z N layer 8, and a grooved passivation layer 9 is prepared.

[0044] Step 9: Transfer the sample from Step 8 to the sample stage in the vacuum chamber of the magnetron sputtering equipment. Using magnetron sputtering, sequentially prepare a 15nm thick Ni layer and a 25nm thick Au layer on the grooved passivation layer 9. Then, remove the sample and remove the photoresist mask from the upper surface of the sample to prepare the Ni / Au stacked p-type electrode 10. Next, place the sample in a rapid thermal annealing furnace and perform rapid thermal annealing treatment at 800℃ for 50s in a high-purity N2 atmosphere with a purity of 6N to achieve the Ni / Au stacked p-type electrode 10 and p-type Al z Ga 1-z N-layer 8 ohmic contacts.

[0045] Thus, the fabrication of a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate described in Example 1 is complete, and the overall structure is as follows: Figure 1 As shown, the structure of the p-type electrode 10 and the passivation layer 9 is as follows: Figure 2As shown, one device unit of this ultraviolet detector, under a -3V bias voltage, has a peak response wavelength of 270nm, a peak spectral responsivity of 133mA / W, and an ultraviolet / visible light suppression ratio greater than 4×10⁻⁶. 3 The response time is 25ns.

[0046] Example 2

[0047] In this embodiment, the cross-sectional pattern of one device unit of the ultraviolet detector is a square of 185μm × 185μm. Within one device unit, upright square prisms made of MoSi2 / Ga-doped ZnO (50nm / 100nm) are periodically arranged in a square planar lattice structure, thus forming the periodic pattern of the patterned back electrode layer 2. The base side length of the 50nm / 100nm regular square prism is 400nm, and the total thickness is 150nm. The axial spacing of the nearest neighbor MoSi2 / Ga-doped ZnO (50nm / 100nm) regular square prism is 1.4μm, which means that the side spacing of the nearest neighbor MoSi2 / Ga-doped ZnO (50nm / 100nm) regular square prism is 1.2μm. This means that the period of the patterned back electrode layer 2 is controlled to be 1.4μm, and the area ratio of the patterned back electrode layer 2 to the molybdenum substrate 1, i.e., the duty cycle, is controlled to be 8%.

[0048] Example 2 describes a method for fabricating a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate, comprising the following steps:

[0049] Step 1: Fabrication of the patterned back electrode layer 2: A polished molybdenum foil is selected as the molybdenum substrate 1, with a thickness of 2 mm. Photoresist is spin-coated onto the upper surface of the molybdenum substrate 1, and the area where the patterned back electrode layer 2 will be fabricated is exposed by photolithography. Other areas are masked with photoresist. The molybdenum substrate 1 is transferred to the sample stage in the vacuum chamber of the magnetron sputtering equipment. A 6N purity Si target is used as the target material, and a 75 nm thick Si layer is sputtered and deposited at a sample stage heating temperature of 100°C. The sample was removed and the photoresist mask on the upper surface of the sample was removed. A patterned Si layer was obtained on the molybdenum substrate 1. The molybdenum substrate 1 sample with the patterned Si layer was placed in a rapid thermal annealing furnace. In a high-purity argon (Ar) atmosphere with a purity of 6N at one atmosphere, the upper surface of the sample was subjected to rapid thermal annealing at 600℃. This caused the patterned Si layer and the molybdenum substrate 1 to react at the interface to form a 47nm thick MoSi2 layer. A 6nm thick crystallized Si (111) film was retained on the upper surface of the MoSi2 layer.

[0050] Next, photoresist was spin-coated onto the upper surface of the molybdenum substrate 1, and the area where the patterned back electrode layer 2 was to be fabricated was exposed by photolithography. Other areas were masked with photoresist. The molybdenum substrate 1 was then transferred to the sample stage in the vacuum chamber of the magnetron sputtering equipment. Using a Ga-doped ZnO target as the target material, a 100 nm thick Ga-doped ZnO layer was sputtered and deposited at a sample stage heating temperature of 100 °C. The Ga doping amount in the Ga-doped ZnO layer was controlled to be 1 at%. The sample was then removed, and the photoresist mask on the upper surface of the sample was removed, resulting in a patterned MoSi2 / Si / Ga-doped ZnO (47 nm / 6 nm / 100 nm) on the molybdenum substrate 1. The molybdenum substrate 1 sample with the patterned MoSi2 / Si / Ga-doped ZnO (47 nm / 6 nm / 100 nm) was then placed in a rapid thermal annealing furnace. In a high-purity argon atmosphere at one atmosphere, the upper surface of the sample was annealed. Rapid thermal annealing at 600℃ is performed, causing most of the Si atoms in the 6nm thick Si layer to continue to diffuse downwards to the interface between MoSi2 and the molybdenum substrate 1 to react and generate MoSi2. A very small portion of the Si atoms in the 6nm thick Si layer diffuse upwards to the lower surface of the Ga-doped ZnO layer until the 6nm thick Si layer is completely exhausted, thereby obtaining a patterned back electrode layer 2 with a total thickness of 150nm, made of MoSi2 / Ga-doped ZnO (50nm / 100nm). From bottom to top, it is a stacked structure of a 50nm thick MoSi2 layer and a 100nm thick Ga-doped ZnO layer. The patterned back electrode layer 2 exhibits a raised periodic square prism structure on the upper surface of the molybdenum substrate 1. The Ga doping amount in the Ga-doped ZnO layer is 1at%, and after rapid thermal annealing, an annealed crystallized Ga-doped ZnO layer with preferred orientation (002) is obtained.

[0051] Step 2: Preparation of molybdenum diffusion barrier layer 3: Photoresist is spin-coated onto the upper surface of the sample after step 1, and the area where the molybdenum diffusion barrier layer 3 will be deposited is exposed by photolithography. The area of ​​the patterned back electrode layer 2 is masked with photoresist. A 100 nm thick SiO2 layer is deposited at a low temperature under the sample stage temperature of 90 °C using plasma-enhanced chemical deposition (PECVD). Then the sample is removed and the photoresist mask on the upper surface of the sample is removed, thus preparing a 100 nm thick molybdenum diffusion barrier layer 3 made of SiO2.

[0052] Steps 3 through 7 all employ the MOCVD method to sequentially grow the required GaN base films laterally on the upper surface of the patterned back electrode layer 2 and the molybdenum diffusion barrier layer 3, as detailed below:

[0053] Step 3, Low-temperature deposition of GaN buffer layer 4: The sample completed in step 2 is transferred to the graphite substrate in the reaction chamber of the MOCVD equipment. Then, the graphite substrate is heated to 520°C, and NH3 with a purity of 6N and TMGa are used as reaction gases to deposit a 200nm thick GaN buffer layer 4.

[0054] Step 4: Deposit n-type GaN layer 5: Next, heat the graphite substrate to 1050℃, and deposit a 1μm thick n-type GaN layer 5 using NH3 (6N purity), trimethylgallium (TMGa), and silane (SiH4) as the N source, Ga source, and Si doping source, respectively. Control the Si doping concentration of the n-type GaN layer 5 to be 5×10⁻⁶. 17 cm -3 .

[0055] Step 5: Deposition of n-type Al x Ga 1-x N-layer 6: Next, the MOCVD graphite substrate was heated to 1080℃, and a 150nm thick n-type Al layer was deposited using NH3, TMGa, trimethylaluminum (TMAl), and SiH4 with a purity of 6N as the N source, Ga source, Al source, and Si doping source, respectively. x Ga 1-x Layer N, 6, with the Al component value controlled to x=0.1 (i.e., the product is n-type Al). 0.1 Ga 0.9 The N and Si doping concentrations are 5 × 10⁻⁶. 17 cm -3 .

[0056] Step 6: Deposition of type i Al y Ga 1-y N-layer 7: Continue to stabilize the MOCVD graphite substrate temperature at 1150℃, turn off the SiH4 gas flow rate, and keep the flow rates of NH3, TMGa, and TMAl unchanged from step 5, to deposit a 200nm thick i-type Al layer. y Ga 1-y Layer N, 7, controls the Al component value in the material to be y=0.1. (That is, the product is type i Al) 0.1 Ga 0.9 N)

[0057] Step 7: Deposition of p-type Al z Ga 1-z N-layer 8: Next, the MOCVD graphite substrate was heated to 1100℃, and a 150nm thick p-type Al layer was deposited using NH3, TMGa, TMAl and Mg(C5H5)2 with a purity of 6N as N source, Ga source, Al source and Mg doping source, respectively. z Ga 1-z N layers, 8, with the Al component value controlled at z=0.1 (i.e., the product is p-type Al).0.1 Ga 0.9 The doping concentrations of N and Mg are 5 × 10⁻⁶. 18 cm -3 Then, the sample was removed and placed in a rapid thermal annealing furnace. In a high-purity nitrogen (N2) atmosphere with a purity of 6N, the upper surface of the sample was subjected to rapid thermal annealing at 800℃ for 40 seconds to activate p-type Al. z Ga 1-z Mg ions in N layer 8.

[0058] Step 8: Prepare the grooved passivation layer. Step 9: Transfer the sample from Step 7 to the sample stage inside the vacuum chamber of the PECVD equipment, and use the PECVD method to prepare the passivation layer on the p-type Al. z Ga 1-z A 40nm thick Si3N4 layer is deposited on layer N8 as a passivation layer 9. Photoresist is spin-coated onto the upper surface of passivation layer 9, and the passivation layer 9 to be etched is exposed by photolithography. Using inductively coupled plasma (ICP) dry etching with the photoresist as a mask, passivation layer 9 is etched. On the top surface of one device unit (185μm×185μm) of the ultraviolet detector in this embodiment, 50 elongated rectangular slots parallel to the unit boundary are centered within a 165μm×165μm square area. Slots are also made on the outer side of the 165μm×165μm square (i.e., the width of the slots around the perimeter is 10μm). The total projected area of ​​the slotted portion is controlled to occupy 45% of one device unit. The etching depth is 40nm until p-type Al is exposed. z Ga 1-z N layer 8, and a grooved passivation layer 9 is prepared.

[0059] Step 9: Transfer the sample from Step 8 to the sample stage in the vacuum chamber of the magnetron sputtering equipment. Using magnetron sputtering, sequentially prepare a 15nm thick Pt layer and a 30nm thick Au layer on the grooved passivation layer 9. Then, remove the sample and remove the photoresist mask from the upper surface of the sample to prepare the Pt / Au stacked p-type electrode 10. Next, place the sample in a rapid thermal annealing furnace and perform rapid thermal annealing treatment at 800℃ for 40s in a nitrogen atmosphere with a purity of 6N to achieve the Pt / Au stacked p-type electrode 10 and p-type Al z Ga 1-z N-layer 8 ohmic contacts.

[0060] Thus, the fabrication of a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate, as described in Example 2, is complete. One device unit of this ultraviolet detector, under a -3V bias, exhibits a peak response wavelength of 340nm, a peak spectral responsivity of 162mA / W, and an ultraviolet / visible light suppression ratio greater than 1×10⁻⁶. 3 The response time is 36ns.

[0061] Example 3

[0062] In this embodiment, the cross-sectional pattern of one device unit of the ultraviolet detector is a square of 185μm × 185μm. Within one device unit, a planar lattice of square dots arranged in a centered 165μm × 165μm area contains alternating upright cylinders and square prisms made of MoSi2 / Ga-doped ZnO (10nm / 40nm), forming a periodic pattern of the patterned back electrode layer 2. The diameter / side length of each MoSi2 / Ga-doped ZnO (10nm / 40nm) cylinder or square prism is controlled to be 200nm, and the total thickness is 50nm. The axial spacing of the nearest neighbor MoSi2 / Ga-doped ZnO (10nm / 40nm) cylinder or square prism is 400nm, i.e., the nearest neighbor MoSi2 / Ga-doped ZnO (10nm / 40nm) cylinder or square prism. The side spacing of the cylinder or regular square prism is 200nm, that is, the period of the patterned back electrode layer 2 is controlled to be 400nm, and the area ratio of the patterned back electrode layer 2 to the metal molybdenum substrate 1, that is, the duty cycle, is controlled to be 22%.

[0063] Example 3 describes a method for fabricating a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate, comprising the following steps:

[0064] Step 1: Fabrication of the patterned back electrode layer 2: A polished molybdenum foil is selected as the molybdenum substrate 1, and the thickness of the molybdenum substrate 1 is controlled to be 0.01 mm. Photoresist is spin-coated on the upper surface of the molybdenum substrate 1, and the area where the patterned back electrode layer 2 will be fabricated is exposed by photolithography. Other areas are masked with photoresist. The molybdenum substrate 1 is transferred to the sample stage in the vacuum chamber of the magnetron sputtering equipment. A Si target with a purity of 6N is used as the target material, and a 16 nm thick Si layer is sputtered and deposited at a sample stage heating temperature of 100 °C. Then, the sample was removed and the photoresist mask on the upper surface of the sample was removed to obtain a patterned Si layer on the molybdenum substrate 1. The molybdenum substrate 1 sample with the patterned Si layer was placed in a rapid thermal annealing furnace and subjected to rapid thermal annealing at 600°C in a high-purity argon (Ar) atmosphere with a purity of 6N at one atmosphere. This caused the patterned Si layer to react with the molybdenum substrate 1 at the interface to generate an 8nm thick MoSi2 layer, and a 3nm thick crystallized Si (111) crystalline film was retained on the upper surface of the MoSi2 layer.

[0065] Next, photoresist was spin-coated onto the upper surface of the molybdenum substrate 1, and the area where the patterned back electrode layer 2 would be fabricated was exposed by photolithography. Other areas were masked with photoresist. The molybdenum substrate 1 was then transferred to the sample stage in the vacuum chamber of the magnetron sputtering equipment. Using a Ga-doped ZnO target as the target material, a 40 nm thick Ga-doped ZnO layer was sputtered and deposited at a sample stage heating temperature of 100 °C. The Ga doping content in the Ga-doped ZnO layer was controlled to be 6.2 at%. The sample was then removed, and the photoresist mask on the upper surface of the sample was removed, resulting in a patterned MoSi2 / Si / Ga-doped ZnO (8 nm / 3 nm / 40 nm) on the molybdenum substrate 1. The molybdenum substrate 1 sample with the patterned MoSi2 / Si / Ga-doped ZnO (8 nm / 3 nm / 40 nm) was then placed in a rapid thermal annealing furnace. The upper surface of the sample was annealed at 600 °C in a high-purity argon atmosphere at one atmosphere. Rapid thermal annealing at ℃ causes most of the Si atoms in the 3nm thick Si layer to continue to diffuse downwards to the interface between MoSi2 and the molybdenum substrate 1 to react and generate MoSi2. A very small portion of the Si atoms in the 3nm thick Si layer diffuse upwards to the lower surface of the Ga-doped ZnO layer until the 3nm thick Si layer is completely exhausted, thereby obtaining a patterned back electrode layer 2 with a total thickness of 50nm, made of MoSi2 / Ga-doped ZnO (10nm / 40nm). From bottom to top, it is a stacked structure of a 10nm thick MoSi2 layer and a 40nm thick Ga-doped ZnO layer. The patterned back electrode layer 2 on the upper surface of the molybdenum substrate 1 is a structure of alternating raised periodic cylinders and regular square prisms. The Ga doping amount in the Ga-doped ZnO layer is 6.2at%, and after rapid thermal annealing, an annealed crystallized Ga-doped ZnO layer with a preferred orientation of (002) is obtained.

[0066] Step 2: Preparation of molybdenum diffusion barrier layer 3: Photoresist is spin-coated onto the upper surface of the sample after step 1, and the area where the molybdenum diffusion barrier layer 3 will be deposited is exposed by photolithography. The area of ​​the patterned back electrode layer 2 is masked with photoresist. A 50nm thick Si2N2O layer is deposited at a low temperature under the sample stage temperature of 90℃ using plasma-enhanced chemical deposition (PECVD). Then the sample is removed and the photoresist mask on the upper surface of the sample is removed, thus preparing a 50nm thick molybdenum diffusion barrier layer 3 made of Si2N2O.

[0067] Steps 3 through 7 all employ the MOCVD method to sequentially grow the required GaN base films laterally on the upper surface of the patterned back electrode layer 2 and the molybdenum diffusion barrier layer 3, as detailed below:

[0068] Step 3, Low-temperature deposition of GaN buffer layer 4: The sample completed in step 2 is transferred to the graphite substrate in the reaction chamber of the MOCVD equipment. Then, the graphite substrate is heated to 520°C, and NH3 with a purity of 6N and TMGa are used as reaction gases to deposit a 20nm thick GaN buffer layer 4.

[0069] Step 4: Deposit n-type GaN layer 5: Next, heat the graphite substrate to 1050℃, and deposit a 0.3μm thick n-type GaN layer 5 using NH3 (6N purity), trimethylgallium (TMGa), and silane (SiH4) as the N source, Ga source, and Si doping source, respectively. Control the Si doping concentration of the n-type GaN layer 5 to be 5×10⁻⁶. 20 cm -3 .

[0070] Step 5: Deposition of n-type Al x Ga 1-x N-layer 6: Next, the MOCVD graphite substrate was heated to 1080℃, and a 30nm thick n-type Al layer was deposited using NH3, TMGa, trimethylaluminum (TMAl), and SiH4 with a purity of 6N as the N source, Ga source, Al source, and Si doping source, respectively. x Ga 1-x N-layer 6, controlling the Al component value in the material to be x=0.7 (i.e., the product is n-type Al). 0.7 Ga 0.3 The N and Si doping concentrations are 5 × 10⁻⁶. 19 cm -3 .

[0071] Step 6: Deposition of type i Al y Ga 1-y N-layer 7: Continue to stabilize the MOCVD graphite substrate temperature at 1150℃, turn off the SiH4 gas flow rate, and keep the flow rates of NH3, TMGa, and TMAl unchanged from step 5, to deposit a 120nm thick i-type Al layer. y Ga 1-y Layer N, 7, controls the Al component value in the material to be y=0.7. (That is, the product is type i Al) 0.7 Ga 0.3 N)

[0072] Step 7: Deposition of p-type Al z Ga 1-z N-layer 8: Next, the graphite substrate of MOCVD was heated to 1100℃, and a 20nm thick p-type Al layer was deposited using NH3, TMGa, TMAl and Mg(C5H5)2 with a purity of 6N as N source, Ga source, Al source and Mg doping source, respectively. z Ga 1-z N layers, 8, with the Al component value controlled at z=0.7 (i.e., the product is p-type Al).0.7 Ga 0.3 The doping concentrations of N and Mg are 5 × 10⁻⁶. 20 cm -3 Then, the sample was removed and placed in a rapid thermal annealing furnace. Under a nitrogen (N2) atmosphere, the upper surface of the sample was subjected to rapid thermal annealing at 800°C for 2 minutes to activate p-type Al. z Ga 1-z Mg ions in N layer 8.

[0073] Step 8: Prepare the grooved passivation layer. Step 9: Transfer the sample from Step 7 to the sample stage inside the vacuum chamber of the PECVD equipment, and use the PECVD method to prepare the passivation layer on the p-type Al. z Ga 1-z A 45nm thick SiO2 layer is deposited on layer N8 as a passivation layer 9. Photoresist is spin-coated onto the upper surface of passivation layer 9, and the passivation layer 9 to be etched is exposed by photolithography. Using inductively coupled plasma (ICP) dry etching with the photoresist as a mask, the passivation layer 9 is etched. On the top surface of one device unit (185μm×185μm) of the ultraviolet detector in this embodiment, 60 elongated rectangular slots parallel to the unit boundary are centered within a 165μm×165μm square area. Slots are also made on the outer side of the 165μm×165μm square (i.e., the width of the slots around the perimeter is 10μm). The total projected area of ​​the slotted portion is controlled to occupy 65% ​​of one device unit. The etching depth is 45nm until the p-type Al is exposed. z Ga 1-z N layer 8, and a grooved passivation layer 9 is prepared.

[0074] Step 9: Transfer the sample from Step 8 to the sample stage in the vacuum chamber of the magnetron sputtering equipment. Using magnetron sputtering, sequentially prepare a 20 nm thick Pd layer and a 30 nm thick Au layer on the grooved passivation layer 9. Then, remove the sample and remove the photoresist mask from the upper surface of the sample to prepare the Pd / Au stacked p-type electrode 10. Next, place the sample in a rapid thermal annealing furnace and perform rapid thermal annealing treatment at 800°C for 2 min in a N2 atmosphere with a purity of 6N to achieve the Pd / Au stacked p-type electrode 10 and p-type Al z Ga 1-z N-layer 8 ohmic contacts.

[0075] Thus, the fabrication of a vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate, as described in Example 3, is complete. One device unit of this ultraviolet detector, under a -3V bias, exhibits a peak response wavelength of 240nm, a peak spectral responsivity of 10⁶ mA / W, and an ultraviolet / visible light suppression ratio greater than 1×10⁻⁶. 4 The response time is 19ns.

[0076] In Examples 1, 2, and 3, none of the GaN-based film layers in the ultraviolet detector exhibited cracks caused by thermal stress, indicating that using a molybdenum substrate in a vertical GaN-based pin-type ultraviolet detector yielded beneficial results and achieved the original intent of the present invention.

Claims

1. A vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate, characterized in that, The vertical GaN-based pin-type ultraviolet detector uses molybdenum as a substrate. On the upper surface of the molybdenum substrate is a partially covered patterned back electrode layer. This patterned back electrode layer consists of a stack of MoSi2 layers and Ga-doped ZnO layers from bottom to top. The patterned back electrode layer on the upper surface of the molybdenum substrate has a raised, periodic patterned structure. On the upper surface of the molybdenum substrate not covered by the patterned back electrode layer is a molybdenum diffusion barrier layer. On the upper surfaces of the patterned back electrode layer and the molybdenum diffusion barrier layer, from bottom to top, are sequentially arranged a GaN buffer layer, an n-type GaN layer, and an n-type Al layer. x Ga 1-x N layer, i-type Al y Ga 1-y N-layer and p-type Al z Ga 1-z N layers, in p-type Al z Ga 1-z The upper surface of layer N is a passivation layer, and grooves are cut into this passivation layer. The cutting involves selecting a centrally located square region within the passivation layer and creating multiple rectangular grooves parallel to the cell boundaries. All grooves are cut outside the square region, controlling the total projected area of ​​the grooved portion to be 30% to 65% of the original passivation layer area, until the p-type Al is exposed. z Ga 1-z N-layer, with p-type Al set within the passivation layer trench. z Ga 1-z N-layer contact p-type electrode; where: 0.1≤x≤0.7, 0.1≤y≤0.7, 0.1≤z≤0.

7.

2. The vertical structure GaN-based pin-type ultraviolet detector on a molybdenum substrate according to claim 1, characterized in that, The molybdenum substrate is a single-layer molybdenum plate or molybdenum foil, and the thickness of the molybdenum substrate is 0.01 to 2 mm.

3. The vertical structure GaN-based pin-type ultraviolet detector on a molybdenum substrate according to claim 1, characterized in that, The periodic pattern structure is a combination of any one or more of cylinders, elliptical cylinders, and polygonal cylinders. The period of the periodic pattern is 0.25 to 1.4 μm, and the duty cycle of the periodic pattern is between 8% and 50%. The total thickness of the patterned back electrode layer is 50 to 150 nm, of which the thickness of the Ga-doped ZnO layer is 40 to 100 nm, and the Ga doping amount in the Ga-doped ZnO layer is 1 at% to 6.2 at.

4. The vertical structure GaN-based pin-type ultraviolet detector on a molybdenum substrate according to claim 1, characterized in that, The molybdenum diffusion barrier layer is made of one or more of Si3N4, SiO2, and Si2N2O, and the thickness of the molybdenum diffusion barrier layer is 50-100 nm.

5. A vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate according to claim 1, characterized in that, The thickness of the GaN buffer layer is 20–200 nm; The thickness of the n-type GaN layer is 0.3–1 μm, and the Si doping concentration is 5 × 10⁻⁶. 17 ~5×10 20 cm -3 ; The n-type Al x Ga 1-x The thickness of the N-layer is 30–150 nm, and the Si doping concentration is 5 × 10⁻⁶. 17 ~5×10 19 cm -3 ; The i-type Al y Ga 1-y The thickness of the N layer is 120–200 nm; The p-type Al z Ga 1-z The thickness of the N layer is 20–150 nm, and the Mg doping concentration is 5 × 10⁻⁶. 18 ~5×10 20 cm -3 .

6. A vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate according to claim 1, characterized in that, The passivation layer is made of Si3N4, SiO2 or Si2N2O, and has a thickness of 35-45 nm.

7. A vertical GaN-based pin-type ultraviolet detector on a molybdenum substrate according to claim 1, characterized in that, The p-type electrode is made of one or more of Au, Ni, Pt, Pd, and Ru in a stack.

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