A double p-layer silicon carbide PIN ultraviolet photodetector and preparation method thereof

Abstract

A double p-layer silicon carbide p-i-n ultraviolet photodetector and a preparation method thereof, relating to an ultraviolet photodetector. The detector is provided with a silicon carbide highly doped n+ type substrate, a silicon carbide n-type buffer layer, a cylindrical silicon carbide low doped n-type absorption layer, a cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer, a cylindrical silicon carbide low doped p-type absorption layer, a passivation isolation dielectric layer, and a passivation isolation layer from bottom to top; the entire device has two p-i-n structures in the longitudinal direction and the transverse direction, and the depletion layer electric fields of the two p-i-n structures are interconnected and coupled, and the photogenerated carriers generated in the longitudinal p-i-n are accelerated by the electric field to drift to the p+ type ohmic contact layer in the transverse and longitudinal combined p-i-n structure. An n+ type ohmic contact electrode is provided on the back of the n+ type substrate, and a p+ type ohmic contact electrode is provided on the upper surface of the p+ type ohmic contact layer to avoid the problem of photogenerated carrier recombination, improve the efficiency of collecting photogenerated carriers, and obtain a higher device responsiveness.

Description

Technical Field

[0001] The invention relates to an ultraviolet photoelectric detector, in particular to a double-p-layer silicon carbide PIN ultraviolet photoelectric detector capable of improving the absorption and responsiveness of extreme ultraviolet and deep ultraviolet band signals and a preparation method thereof. Background Art

[0002] As ultraviolet light has been increasingly widely used in defense, industrial manufacturing, photolithography, medical disinfection, and environmental monitoring, the detection technology of ultraviolet light band signals, especially extreme ultraviolet and deep ultraviolet band (wavelength 10-280nm) signals has gradually become a research hotspot in the field of optoelectronic devices. Ultraviolet photodetectors of different types and working principles have gradually been developed, among which semiconductor material ultraviolet photodetectors with excellent characteristics such as low voltage, small size, and long life have become the research focus.

[0003] At present, the mainstream semiconductor detection technology for ultraviolet band signals mainly adopts silicon-based detectors. However, in harsh working environments such as high-energy photon radiation and high temperature, the performance of silicon-based detectors will be greatly reduced, and the device may be damaged. In addition, the single-crystal silicon bandgap width is small, and the silicon-based detector will be affected by visible light when working. It is necessary to use a filter to filter signals in other bands, which increases the cost and volume of the detector. Wide-bandgap semiconductor photodetectors can accurately detect ultraviolet signals. Silicon carbide, as the main material of the third-generation wide-bandgap semiconductor, has excellent characteristics such as wide bandgap, high breakdown electric field, high carrier saturation rate, and high thermal conductivity (Jiafa Cai, Xiaping Chen, Rongdun Hong, Weifeng Yang, Zhengyun Wu, High-performance 4H-SiC-based pin ultraviolet photodiode and investigation of its capacitance characteristics [J]. Optics Communications, 2014, 333: 182-186.), so silicon carbide-based ultraviolet photodetectors have excellent properties such as high quantum efficiency, visible blindness, radiation resistance, and high temperature resistance. Since the absorption coefficient of ultraviolet signals inside semiconductors is large, that is, the absorption length (i.e., propagation distance) is short, the highly doped p+ ohmic contact layer of commonly used pn junction and pin structure ultraviolet photodetectors has very strong absorption of ultraviolet signals, especially signals in the extreme ultraviolet and deep ultraviolet bands, and converts them into photogenerated carriers. However, since the spatial depletion layer of the p+ ohmic contact layer is very thin, the photogenerated carriers in its region cannot be separated and collected by the electric field to form a response current, but disappear due to the carrier recombination effect, reducing the device responsivity (Zhang M, Wang KL, Jiang H, Hong R, Wu Z, High performance silicon carbide avalanche-pi-n ultraviolet photodiode with dual operation models [J]. Electronics Letters, 2016, 52 (17): 1474-1476.). Therefore, overcoming the inhibition of the device responsivity by the absorption recombination effect of the p+ ohmic contact layer on the extreme ultraviolet and deep ultraviolet band signals has become a difficulty and focus in the research of silicon carbide ultraviolet photodetectors. Summary of the invention

[0004] The purpose of the present invention is to provide a double p-layer silicon carbide pin ultraviolet photodetector that can improve the absorption of extreme ultraviolet and deep ultraviolet signals and thus improve the detection efficiency, in order to address the shortcomings of traditional silicon carbide pin ultraviolet photodetectors, that is, the absorption of signals in the extreme ultraviolet and deep ultraviolet bands by the p+ layer leads to reduced responsiveness and quantum efficiency.

[0005] Another object of the present invention is to provide a method for preparing a double p-layer silicon carbide pin ultraviolet photodetector.

[0006] The double p-layer silicon carbide pin ultraviolet photodetector is provided with a silicon carbide highly doped n+ type substrate, a silicon carbide n-type buffer layer, a cylindrical silicon carbide low doped n-type absorption layer, a cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer, a cylindrical silicon carbide low doped p-type absorption layer, a passivation isolation dielectric layer, and a passivation isolation layer from bottom to top;

[0007] A homogeneous silicon carbide n-type buffer layer is epitaxially grown on the silicon surface of a silicon carbide highly doped n+ type substrate, a cylindrical silicon carbide low-doped n-type absorption layer is arranged upward from the center of the silicon carbide n-type buffer layer, a small-area cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer is arranged outwardly with the axis of the cylindrical silicon carbide low-doped n-type absorption layer as the center, a large-area cylindrical silicon carbide low-doped p-type absorption layer is arranged upward with the axis of the cylindrical silicon carbide low-doped n-type absorption layer as the center, a passivation isolation dielectric layer is arranged between the cylindrical silicon carbide low-doped p-type absorption layer and the p+ type ohmic contact layer, and a passivation isolation layer is arranged on the surface of the cylindrical silicon carbide low-doped p-type absorption layer; an n+ type electrode is arranged on the back of the silicon carbide highly doped n+ type substrate, and a p+ type electrode is arranged on the upper surface of the cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer.

[0008] The entire device has two pin structures, one is a small-area horizontal and vertical combined pin structure formed by a cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer, a cylindrical silicon carbide low-doped n-type absorption layer and a silicon carbide n-type buffer layer, and the other is a large-area vertical pin structure formed by a cylindrical silicon carbide low-doped p-type absorption layer, a cylindrical silicon carbide low-doped n-type absorption layer and a silicon carbide n-type buffer layer. The depletion layer electric fields of the two pin structures are interconnected and coupled, so that the photogenerated carriers generated in the vertical pin can be accelerated by the electric field and drifted to the p+ type ohmic contact layer in the horizontal and vertical combined pin structure.

[0009] The longitudinal section width of the double p-layer silicon carbide pin ultraviolet photodetector can be 50μm to 800μm; the diameter of the cylindrical silicon carbide low-doped p-type absorption layer and the width of the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer are 48μm to 798μm and 100nm to 5μm respectively; the width of the passivation isolation dielectric layer between the cylindrical silicon carbide low-doped p-type absorption layer and the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer is 1μm to 10μm; the silicon carbide high-doped n+ type substrate can adopt a commercial n+ conductive substrate, and the doping concentration of the silicon carbide high-doped n+ type substrate can be 10 18 / cm 3 ~10 19 / cm 3 The thickness may be 50 μm to 500 μm; the doping concentrations of the silicon carbide n-type buffer layer, the cylindrical silicon carbide low-doped n-type absorption layer, the cylindrical silicon carbide low-doped p-type absorption layer and the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer may be 10 18 / cm 3 ~10 19 / cm 3 , 10 14 / cm 3 ~10 16 / cm 3 , 10 15 / cm 3 ~10 17 / cm 3 and 10 18 / cm 3 ~10 19 / cm 3 The thickness can be 100nm~1μm, 200nm~5μm, 100nm~1μm and 200nm~1μm respectively. The passivation isolation dielectric layer between the cylindrical silicon carbide low-doped p-type absorption layer and the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer and the passivation isolation layer on the surface of the cylindrical silicon carbide low-doped p-type absorption layer can be a passivation isolation dielectric material such as silicon dioxide, hafnium oxide or silicon nitride, with a thickness of 100nm~1μm and less than 10nm respectively.

[0010] The method for preparing a double p-layer silicon carbide pin ultraviolet photodetector comprises the following steps:

[0011] 1) RCA standard cleaning of silicon carbide highly doped n+ type substrate;

[0012] 2) homoepitaxially growing a silicon carbide n-type buffer layer on the Si surface of the n+ type substrate;

[0013] 3) epitaxially growing a cylindrical low-doped n-type absorption layer on the silicon carbide n-type buffer layer;

[0014] 4) forming a small-area cylindrical tubular silicon carbide highly doped p+-type ohmic contact layer on the outside of the n-type absorption layer by using deposition, photolithography, etching, ion implantation and high-temperature annealing techniques;

[0015] 5) using deposition, photolithography, etching, ion implantation and high temperature annealing techniques to form a large-area cylindrical low-doped p-type absorption layer centered on the surface of the n-type absorption layer;

[0016] 6) forming a passivation isolation dielectric layer between the p-type absorption layer and the p+ type ohmic contact layer by using photolithography, etching and deposition techniques;

[0017] 7) forming a passivation isolation layer less than 10 nm thick on the p-type absorption layer using thermal oxidation technology;

[0018] 8) A p+ type ohmic contact electrode and an n+ type ohmic contact electrode are prepared on the surface of the highly doped p+ type ohmic contact layer and on the bottom of the n+ type substrate, respectively, using photolithography, magnetron sputtering and annealing techniques.

[0019] The conventional vertical pin sandwich structure of silicon carbide ultraviolet photodetectors in the prior art must simultaneously meet the requirements of complete depletion of the i-layer and good p-type ohmic contact to achieve high-performance ultraviolet detection, so a highly doped p+ type ohmic contact layer is required on the surface. However, the highly doped p+ type ohmic contact layer on the surface of the detector has almost no spatial depletion layer. According to the exponential decay absorption principle of light in semiconductors, most of the incident extreme ultraviolet and deep ultraviolet signals are absorbed in the p+ type ohmic contact layer and converted into photogenerated carriers. Due to the separation of the electric field in the spatial depletion layer, the photogenerated carriers cannot be effectively separated to form current, but randomly diffuse in the p+ type ohmic contact layer and are annihilated by recombination, resulting in low detection quantum efficiency of the conventional vertical pin sandwich structure of silicon carbide ultraviolet photodetectors for extreme ultraviolet and deep ultraviolet signals.

[0020] Compared with the prior art, the present invention has the following outstanding advantages: the double p-layer silicon carbide pin ultraviolet photodetector designed by the present invention has two pin structures, a small-area pin structure formed by a p+-type ohmic contact layer, an n-type absorption layer and an n-type buffer layer in a horizontal and vertical combination, and the other is a large-area vertical pin structure formed by a p-type absorption layer, an n-type absorption layer and an n-type buffer layer. According to the semiconductor pn junction energy band theory, a pn junction with low doping concentration at both ends, the space depletion layer will extend to both ends of the p-type absorption layer and the n-type absorption layer at the same time, and the p-type absorption layer and the n-type absorption layer can be completely depleted at the same time under appropriate thickness conditions. Most of the incident extreme ultraviolet and deep ultraviolet signals are incident into the device through the p-type absorption layer, and are absorbed and converted into photogenerated carriers in the p-type absorption layer and the n-type absorption layer and separated by the electric field of the space depletion layer. Since the p-type absorption layer cannot form an effective ohmic contact electrode with the metal, the present invention designs a double p-layer structure for the silicon carbide pin ultraviolet photodetector, and designs a small-area silicon carbide highly doped p+ type ohmic contact layer at one end of the low-doped n-type absorption layer surface of the device for collecting photogenerated carriers, and designs a large-area silicon carbide low-doped p-type absorption layer at the other end for generating and separating photogenerated carriers. The photogenerated carriers formed in the p-type absorption layer and the n-type absorption layer are separated by the weak electric field of the spatial depletion layer in the large-area pin structure, and then collected by the strong electric field of the depletion layer in the small-area pin structure with the p+ type ohmic contact layer and exported to the external circuit for testing and analysis. Therefore, the double p-layer silicon carbide pin ultraviolet photodetector designed by the present invention can significantly improve the detection efficiency of signals in the extreme ultraviolet and deep ultraviolet bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a two-dimensional cross-sectional schematic diagram of the double p-layer silicon carbide pin ultraviolet photodetector described in an embodiment of the present invention.

[0022] Figure 2 It is a three-dimensional cross-sectional schematic diagram of the double p-layer silicon carbide PIN ultraviolet photodetector described in an embodiment of the present invention.

[0023] Figure 3 The absolute spectral response curves of the double p-layer silicon carbide pin ultraviolet photodetector described in the embodiment of the present invention and the conventional longitudinal sandwich pin structure ultraviolet photodetector. DETAILED DESCRIPTION

[0024] In order to make the structure of the present invention more clear and understandable, the following embodiments will further illustrate the present invention in conjunction with the accompanying drawings.

[0025] See also Figure 1 and 2The double p-layer silicon carbide PIN ultraviolet photodetector of the embodiment of the present invention is provided with a commercial grade silicon carbide highly doped n+ type substrate (1) from bottom to top, the thickness of the substrate can be 50 μm to 500 μm, and the doping concentration can be 10 18 / cm 3 ~10 19 / cm 3 , the longitudinal section width can be 50μm~800μm, that is, the device area can be 625πμm 2 ~160000μm 2 A homogeneous silicon carbide n-type buffer layer (2) is epitaxially grown on the silicon surface of a silicon carbide highly doped n+ type substrate (1), the thickness of which can be 100 nm to 1 μm, and the doping concentration can be on the order of 10 18 / cm 3 ~10 19 / cm 3 A cylindrical silicon carbide low-doped n-type absorption layer (3) is arranged upward from the center of the n-type buffer layer, with a diameter of 50 μm to 800 μm and a thickness of 200 nm to 5 μm, and a doping concentration of 10 14 / cm 3 ~10 16 / cm 3 A small-area cylindrical tubular silicon carbide high-doped p+-type ohmic contact layer (4) is arranged outwardly with the axis of the cylindrical silicon carbide low-doped n-type absorption layer (3) as the center, and the width can be 100nm to 5μm, the thickness can be 200nm to 1μm, and the doping concentration can be 10 18 / cm 3 ~10 19 / cm 3 A large-area cylindrical silicon carbide low-doped p-type absorption layer (5) is arranged upward from the axis of the cylindrical silicon carbide low-doped n-type absorption layer (3), the diameter of which can be 48 μm to 798 μm, the thickness of which can be 100 nm to 1 μm, and the doping concentration of which can be 10 15 / cm 3 ~10 17 / cm 3; A passivation isolation dielectric layer (6) is provided between the cylindrical silicon carbide low-doped p-type absorption layer (5) and the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer (4), and the passivation isolation dielectric layer material can be silicon dioxide, hafnium oxide and silicon nitride, etc., and the thickness can be 100nm to 1μm; a silicon dioxide passivation isolation layer (9) is provided on the surface of the cylindrical silicon carbide low-doped p-type absorption layer (5), and the thickness is less than 10nm. The whole device has two pin structures, one is a small-area horizontal and vertical combined pin structure formed by the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer (4), the cylindrical silicon carbide low-doped n-type absorption layer (3) and the n-type buffer layer, and the other is a large-area vertical pin structure formed by the cylindrical silicon carbide low-doped p-type absorption layer (5), the cylindrical silicon carbide low-doped n-type absorption layer (3) and the n-type buffer layer. A p+ type ohmic contact electrode (7) is provided on the upper surface of the cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer (4), and an n+ type ohmic contact electrode (8) is provided on the back surface of the silicon carbide highly doped n+ type substrate (1).

[0026] The method for preparing the double p-layer silicon carbide pin ultraviolet photodetector comprises the following steps:

[0027] 1) performing RCA standard cleaning on the silicon carbide n+ type substrate (1);

[0028] 2) homoepitaxially growing a silicon carbide n-type buffer layer (2) on the Si surface of the silicon carbide highly doped n+ type substrate (1);

[0029] 3) epitaxially growing a cylindrical low-doped n-type absorption layer (3) on the silicon carbide n-type buffer layer;

[0030] 4) forming a small-area cylindrical tubular silicon carbide highly doped p+-type ohmic contact layer (4) on the outside of the cylindrical silicon carbide low-doped n-type absorption layer (3) by using deposition, photolithography, etching, ion implantation and high-temperature annealing technology;

[0031] 5) using deposition, photolithography, etching, ion implantation and high temperature annealing techniques to form a large-area cylindrical silicon carbide low-doped p-type absorption layer (5) centered on the surface of the cylindrical silicon carbide low-doped n-type absorption layer (3);

[0032] 6) using photolithography, etching and deposition techniques to form a passivation isolation dielectric layer (6) between the cylindrical silicon carbide low-doped p-type absorption layer (5) and the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer (4), wherein the dielectric layer material may be silicon dioxide, hafnium oxide and silicon nitride, etc.;

[0033] 7) forming a silicon dioxide passivation isolation layer (9) on the cylindrical silicon carbide low-doped p-type absorption layer (5) by using thermal oxidation and deposition technology;

[0034] 8) A p+ type ohmic contact electrode (7) and an n+ type ohmic contact electrode (8) are prepared on the surface of a cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer (4) and on the bottom of a silicon carbide highly doped n+ type substrate (1) respectively by using photolithography, magnetron sputtering and annealing techniques.

[0035] Specific examples are given below.

[0036] 1) Perform RCA standard cleaning on the silicon carbide highly doped n+ type substrate (1) sample, the steps are as follows:

[0037] a. Ultrasonic cleaning with toluene, acetone and ethanol at least twice, then rinse with deionized water.

[0038] b. Use liquid No. 3 to boil at 250°C for 20 minutes, and rinse with hot and cold deionized water. The volume ratio of the liquid No. 3 is H2SO4:H2O2=4:1.

[0039] c. Soak the sample in diluted hydrofluoric acid (hydrogen fluoride: deionized water = 1:10 by volume) for 3 minutes or more, and then rinse with hot and cold deionized water.

[0040] d. Boil the sample in liquid No. 1 for 10 minutes or more, and rinse with hot and cold deionized water. The liquid No. 1 has a volume ratio of NH3·H2O:H2O2:H2O=1:1:4.

[0041] e. Boil the sample in liquid No. 2 for 10 minutes or more, and rinse with hot and cold deionized water. The volume ratio of liquid No. 1 is HCl: H2O2: H2O = 1:1:4.

[0042] f. Soak the sample in diluted hydrofluoric acid (hydrogen fluoride: deionized water = 1:10 by volume) for 3 minutes or more, then rinse with hot and cold deionized water, blow dry the substrate with nitrogen gas, and set aside.

[0043] 2) After RCA standard cleaning, the (0001) Si surface of the highly doped n+ type silicon carbide substrate (1) was homoepitaxially grown with a doping concentration of 10 18 / cm 3 ~10 19 / cm 3 , a silicon carbide n-type buffer layer (2) with a thickness of 100nm to 1μm.

[0044] 3) The doping concentration of epitaxial growth on the silicon carbide n-type buffer layer is on the order of 10 14 / cm 3 ~10 16 / cm 3A cylindrical silicon carbide n-type absorption layer (3) with a diameter of 50 μm to 800 μm and a thickness of 200 nm to 5 μm.

[0045] 4) using photolithography, etching and deposition techniques to form a mask, on this basis, Al ions are implanted into the cylindrical silicon carbide low-doped n-type absorption layer (3), high temperature annealing is performed to activate the Al ions, and a small-area cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer (4) is formed on the outside of the cylindrical silicon carbide low-doped n-type absorption layer (3), the width of which can be 100nm to 5μm, the thickness of which can be 200nm to 1μm, and the doping concentration of which can be 10 18 / cm 3 ~10 19 / cm 3 .

[0046] 5) A mask is formed by photolithography, etching and deposition techniques, and Al ions are implanted into the cylindrical silicon carbide low-doped n-type absorption layer (3) on this basis. High temperature annealing is performed to activate the Al ions, and a large-area cylindrical silicon carbide low-doped p-type absorption layer (5) is formed in the center of the surface of the cylindrical silicon carbide low-doped n-type absorption layer (3). The diameter of the cylindrical silicon carbide low-doped p-type absorption layer (5) can be 48 μm to 798 μm, the thickness can be 100 nm to 1 μm, and the doping concentration can be 10 15 / cm 3 ~10 17 / cm 3 .

[0047] 6) A mask is formed by photolithography, etching and deposition techniques, and a passivation isolation dielectric layer (6) is formed between the cylindrical silicon carbide low-doped p-type absorption layer (5) and the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer (4) by chemical vapor deposition. The passivation isolation dielectric layer can be made of silicon dioxide, hafnium oxide and silicon nitride, etc., and can have a thickness of 100 nm to 1 μm.

[0048] 7) The sample is cleaned according to the RCA standard to remove impurities on the sample surface, and dry oxygen, wet oxygen and dry oxygen are used for alternating oxidation to grow a layer of oxide on the positive surface of the sample (towards the upper surface of the i-type absorption layer) as a sacrificial layer; the sample with the grown sacrificial layer is placed in buffered hydrofluoric acid for etching to remove the sacrificial layer; dry oxygen, wet oxygen, dry oxygen and nitrogen are used for alternating oxidation to grow a thermally oxidized silicon dioxide passivation isolation layer (9) with a thickness of less than 10 nm.

[0049] 8) using a photolithography process to expose and develop the photoresist, using buffered hydrofluoric acid to etch the oxide layer on the upper part of the cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer (4) to form an electrode window, using a magnetron sputtering process to prepare a layer of alloy, a p+ type ohmic contact electrode (7), preparing a layer of photoresist on the front side of the sample for protection and isolation, using buffered hydrofluoric acid to etch the oxide layer on the bottom side of the substrate, using magnetron sputtering to prepare an alloy layer to form an n+ type ohmic contact electrode (8), and annealing the two electrodes so that the p+ type electrode and n+ type electrode of the sample form good ohmic contacts with the cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer (4) and the silicon carbide highly doped n+ type substrate (1), respectively.

[0050] Figure 3 The absolute spectral response curves of the double p-layer silicon carbide pin ultraviolet photodetector described in the embodiment of the present invention and the conventional longitudinal sandwich pin structure ultraviolet photodetector are given. Figure 3 It can be seen that the double p-layer silicon carbide pin ultraviolet photodetector designed by the present invention can significantly improve the detection efficiency of signals in the extreme ultraviolet and deep ultraviolet bands. The present invention effectively avoids the problem of photogenerated carrier recombination caused by surface defects of the p+ type ohmic contact layer in the traditional silicon carbide pin photodetector in the extreme ultraviolet and deep ultraviolet bands, improves the efficiency of collecting photogenerated carriers, and obtains a higher device responsivity.

Claims

1. A double p-layer silicon carbide pin ultraviolet photodetector, characterized in that The invention is provided with a silicon carbide highly doped n+ type substrate, a silicon carbide n-type buffer layer, a cylindrical silicon carbide low doped n-type absorption layer, a cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer, a cylindrical silicon carbide low doped p-type absorption layer, a passivation isolation dielectric layer, and a passivation isolation layer; a homogeneous silicon carbide n-type buffer layer is epitaxially grown on the silicon surface of the silicon carbide highly doped n+ type substrate, a cylindrical silicon carbide low doped n-type absorption layer is arranged upward from the center of the silicon carbide n-type buffer layer, and a small area is arranged outward with the axis of the cylindrical silicon carbide low doped n-type absorption layer as the center. A cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer is provided, with a large area cylindrical silicon carbide low-doped p-type absorption layer being provided upwardly with the axis of the cylindrical silicon carbide low-doped n-type absorption layer as the center, a passivation isolation dielectric layer is provided between the cylindrical silicon carbide low-doped p-type absorption layer and the p+ type ohmic contact layer, and a passivation isolation layer is provided on the surface of the cylindrical silicon carbide low-doped p-type absorption layer; an n+ type electrode is provided on the back side of the silicon carbide high-doped n+ type substrate, and a p+ type electrode is provided on the upper surface of the cylindrical tubular silicon carbide high-doped p+ type ohmic contact layer; It has two pin structures, one is a small-area horizontal and vertical combined pin structure formed by a cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer, a cylindrical silicon carbide low-doped n-type absorption layer and a silicon carbide n-type buffer layer, and the other is a large-area vertical pin structure formed by a cylindrical silicon carbide low-doped p-type absorption layer, a cylindrical silicon carbide low-doped n-type absorption layer and a silicon carbide n-type buffer layer. The depletion layer electric fields of the two pin structures are interconnected and coupled, so that the photogenerated carriers generated in the vertical pin can be accelerated by the electric field and drifted to the p+ type ohmic contact layer in the horizontal and vertical combined pin structure.

2. A double p-layer silicon carbide pin ultraviolet photodetector as claimed in claim 1, characterized in that The cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer has a width of 100nm to 5μm, a thickness of 200nm to 1μm, and a doping concentration of 10 18 / cm 3 ~10 19 / cm 3 .

3. A double p-layer silicon carbide pin ultraviolet photodetector as claimed in claim 1, characterized in that The cylindrical silicon carbide low-doped p-type absorption layer has a diameter of 48 μm to 798 μm, a thickness of 100 nm to 1 μm, and a doping concentration of 10 15 / cm 3 ~10 17 / cm 3 .

4. A double p-layer silicon carbide pin ultraviolet photodetector as claimed in claim 1, characterized in that The passivation isolation dielectric layer between the cylindrical silicon carbide low-doped p-type absorption layer and the cylindrical tubular silicon carbide highly-doped p+-type ohmic contact layer and the passivation isolation layer on the upper surface of the cylindrical silicon carbide low-doped p-type absorption layer can be passivation isolation dielectric materials such as silicon dioxide, hafnium oxide or silicon nitride, and the thicknesses are 100nm to 1μm and less than 10nm respectively.

5. A double p-layer silicon carbide pin ultraviolet photodetector as claimed in claim 1, characterized in that The thickness of the silicon carbide highly doped n+ type substrate is 50 μm to 500 μm, and the doping concentration is on the order of 10 18 / cm 3 ~10 19 / cm 3 .

6. A double p-layer silicon carbide pin ultraviolet photodetector as claimed in claim 1, characterized in that The thickness of the n-type buffer layer is 100 nm to 1 μm, and the doping concentration is on the order of 10 18 / cm 3 ~10 19 / cm 3 .

7. A double p-layer silicon carbide pin ultraviolet photodetector as claimed in claim 1, characterized in that The diameter of the n-type absorption layer is 50 μm to 800 μm, the thickness is 200 nm to 5 μm, and the doping concentration is 10 14 / cm 3 ~10 16 / cm 3 .

8. A method for preparing a double p-layer silicon carbide pin ultraviolet photodetector, characterized in that The preparation method is used to prepare a double p-layer silicon carbide pin ultraviolet photodetector as claimed in any one of claims 1 to 7, and the preparation method comprises the following steps: 1) RCA standard cleaning of silicon carbide highly doped n+ type substrate; 2) Homoepitaxially growing a silicon carbide n-type buffer layer on the Si surface of an n+ type substrate; 3) epitaxially growing a cylindrical low-doped n-type absorption layer on the silicon carbide n-type buffer layer; 4) Using deposition, photolithography, etching, ion implantation and high temperature annealing technology to form a small area of ​​cylindrical tubular silicon carbide highly doped p+ type ohmic contact layer on the outside of the n-type absorption layer; 5) Using deposition, photolithography, etching, ion implantation and high temperature annealing technology to form a large-area cylindrical low-doped p-type absorption layer centered on the surface of the n-type absorption layer; 6) using photolithography, etching and deposition techniques to form a passivation isolation dielectric layer between the p-type absorption layer and the p+ type ohmic contact layer; 7) Forming a silicon dioxide passivation isolation layer on the p-type absorption layer using thermal oxidation technology; 8) Photolithography, magnetron sputtering and annealing techniques are used to prepare p+ type ohmic contact electrodes and n+ type ohmic contact electrodes on the surface of the highly doped p+ type ohmic contact layer and on the bottom of the n+ type substrate, respectively.

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