Pocket-doped 4H-SiC-based avalanche photodiode device

Abstract

The invention discloses a Pocket doped 4H-SiC-based avalanche photodiode device. The Pocket doped 4H-SiC-based avalanche photodiode device comprises a substrate layer, a multiplication layer, a passivation layer, a PAD layer, a metal electrode region and a photosensitive window region. A Pocket highly-doped region is introduced into a multiplication layer of the 4H-SiC avalanche photodiode, so that the electric field distribution condition at the edge of a boss surface of the multiplication layer is optimized, the breakdown probability of the boss surface is reduced, the available carrier concentration of the multiplication region is increased, the light current is increased while the lower dark current is kept, the threshold voltage of the device is increased, and the device performance is improved. The current gain and the signal-to-noise ratio are increased, and good photoelectric amplification performance is shown.

Description

Technical Field

[0001] The invention belongs to the field of wide bandgap semiconductor devices, and in particular relates to a pocket-doped 4H-SiC-based avalanche photodiode device. Background Art

[0002] Sunlight is the main source of ultraviolet radiation on the earth's surface. The intensity of solar background radiation in the 240-280nm band is almost zero, which is the "solar-blind" ultraviolet band. Since the radiation in this band is evenly distributed in the space within the atmosphere, ultraviolet detectors have broad potential application prospects in ultraviolet detection technologies such as ultraviolet communications and ultraviolet alarm technologies. Semiconductor ultraviolet photodetectors are semiconductor sensors developed based on the photoelectric effect.

[0003] Existing optoelectronic devices can be divided into vacuum type and solid type according to their structure. Vacuum photomultiplier tubes (PMT) are widely used in the industry. For example, the commercial UV PMT model R6836 of Hamamatsu Corporation in Japan has a spectral response range of 115 to 320nm, a dark current of the order of 0.1nA, and a photocurrent gain greater than 105. Solid-state avalanche photodiodes (APDs) solve the shortcomings of PMTs such as large size, easy breakage, short life, operating voltage higher than 1000V, and quantum efficiency lower than 30% with lower dark current and greater photocurrent gain, and can achieve higher sensitivity detection, showing broad application prospects.

[0004] Existing Si-based APDs are difficult to meet the requirements of biochemical detection, corona detection, and missile warning, where the radiation intensity is less than pW / cm 2 Since SiC materials have a wider bandgap and higher thermal stability, and the developed 4H-SiC-based APD has single-photon detection capability, it has unique advantages in the field of low-intensity signal detection in extreme environments.

[0005] However, due to the limitations of APD device structure design and process conditions, the existing 4H-SiC APD still has shortcomings such as large table edge electric field and easy breakdown, uneven avalanche breakdown, small device fill factor, low single-photon detection efficiency, and high dark count value. It is necessary to optimize the structural design to improve the device's service stability and enhance its performance indicators. Summary of the invention

[0006] The object of the present invention is to provide a pocket-doped 4H-SiC-based avalanche photodiode device in view of the deficiencies in the prior art.

[0007] The object of the present invention is achieved through the following technical solutions: A pocket-doped 4H-SiC-based avalanche photodiode device, comprising: a substrate layer, a multiplication layer, a passivation layer, a PAD layer, a metal electrode region and a photosensitive window region;

[0008] The substrate layer is cylindrical and is located at the bottom layer of the pocket-doped 4H-SiC-based avalanche photodiode device;

[0009] The multiplication layer is in the form of a convex truncated cone, shares a central axis with the substrate layer, and contacts the substrate layer along a first direction, wherein the first direction is from the central axis of the substrate layer upwards;

[0010] The multiplication layer is divided into five multiplication zones along the first direction, which are respectively recorded as the first multiplication zone, the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone. The five multiplication zones share a central axis along the first direction and are in contact with each other in sequence. The first multiplication zone is in the form of a convex truncated cone, and the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone are in the form of a truncated cone. The inclination angles of the truncated cone part of the first multiplication zone, the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone are consistent.

[0011] The contact surfaces between the substrate layer and the first multiplication region, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region are all circular surfaces whose outer normals are along the first direction;

[0012] The passivation layer is a hollow truncated cone shell, having a common central axis with the multiplication layer and in contact with its upper surface, covering the outer surface of the multiplication layer, and the contact surface is a fan-shaped curved surface, having the same inclination angle as the truncated cone of the multiplication layer;

[0013] The PAD layer is a hollow truncated cone shell, having a common central axis with the passivation layer and in contact with its upper surface, covering the outer surface of the passivation layer, and the contact surface is a fan-shaped curved surface with the same inclination angle as the truncated cone of the passivation layer;

[0014] The photosensitive window area is in a circular ring shape and is located on the upper surface of the fifth multiplication area;

[0015] The metal electrode area includes an anode area and a cathode area, wherein the anode area is a cylindrical ring body, contacts with the first multiplication area along a first direction, covers the upper surface of the convex cone of the first multiplication area, and the contact surface is a circular ring; the cathode area is a cylinder, shares the same central axis with the photosensitive window area and contacts along the first direction, covers the photosensitive window area, and the contact surface is a circle.

[0016] Furthermore, the substrate layer and the multiplication layer are made of the same material.

[0017] Furthermore, the bandgap width of the multiplication layer is greater than the bandgap width of the substrate layer.

[0018] Furthermore, the first multiplication region and the other multiplication regions have a different doping type; the substrate layer, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region have the same doping type.

[0019] Furthermore, the doping concentration of the third multiplication zone is higher than that of the second multiplication zone and the fourth multiplication zone, and the second multiplication zone, the third multiplication zone and the fourth multiplication zone adopt Pocket doping.

[0020] The beneficial effects of the present invention are as follows: by introducing a Pocket high-doping region into the multiplication layer of a 4H-SiC avalanche photodiode, the electric field distribution at the edge of the convex table of the multiplication layer is optimized, the table breakdown probability is reduced, the available carrier concentration in the multiplication region is increased, the photocurrent is increased while maintaining a low dark current, the threshold voltage of the device is increased, the current gain and the signal-to-noise ratio are increased, and good photoelectric amplification performance is exhibited. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the structure of a pocket-doped 4H-SiC-based avalanche photodiode device along a first direction;

[0022] Figure 2 The present invention is a process flow chart of preparing a pocket-doped 4H-SiC-based avalanche photodiode device;

[0023] Figure 3 is a schematic diagram of doping concentration, where Figure 3 (a) is a schematic diagram of the doping concentration of a 4H-SiC APD device structure along the first direction in Comparative Example 1; Figure 3 (b) is a schematic diagram of the doping concentration of the structure of the pocket-doped 4H-SiC-based avalanche photodiode device along the first direction in Example 2;

[0024] Figure 4 is the volt-ampere characteristic curve, where Figure 4 (a) is the forward volt-ampere characteristic curve. Figure 4 (b) is a reverse voltammetric characteristic curve;

[0025] Figure 5 is the current gain curve under 280nm monochromatic light;

[0026] Figure 6 It is the response spectrum in the ultraviolet and visible light range of 200-450nm. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The invention provides a pocket-doped 4H-SiC-based avalanche photodiode device, comprising a substrate layer, a multiplication layer, a passivation layer, a PAD layer, a metal electrode region and a photosensitive window region.

[0029] The substrate layer is cylindrical and is located at the bottom layer of the pocket-doped 4H-SiC-based avalanche photodiode device.

[0030] The multiplication layer is in the form of a convex frustum, shares a common central axis with the substrate layer, and contacts the substrate layer along a first direction, wherein the first direction is from the central axis of the substrate layer upward.

[0031] The multiplication layer is divided into five multiplication zones along the first direction, which are respectively recorded as the first multiplication zone, the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone. The five multiplication zones share a central axis along the first direction and are in contact with each other in sequence. The first multiplication zone is in the form of a convex truncated cone, and the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone are in the form of a truncated cone. The inclination angles of the truncated cone part of the first multiplication zone, the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone are consistent.

[0032] The contact surfaces between the substrate layer and the first multiplication region, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region are all circular surfaces whose outer normals are along the first direction.

[0033] The passivation layer is a hollow truncated cone shell, which has the same central axis as the multiplication layer and contacts with its upper surface, covers the outer surface of the multiplication layer, and the contact surface is a fan-shaped surface with the same inclination angle as the truncated cone of the multiplication layer.

[0034] The PAD layer is a hollow truncated cone shell, which shares the same central axis with the passivation layer and contacts with its upper surface, covers the outer surface of the passivation layer, and the contact surface is a fan-shaped surface with the same inclination angle as the truncated cone of the passivation layer.

[0035] The photosensitive window area is in a circular ring shape and is located in the upper surface area of ​​the fifth multiplication zone.

[0036] The metal electrode region includes an anode region and a cathode region, wherein the anode region is a cylindrical ring body, contacts the first multiplication region along a first direction, covers the upper surface of the convex truncated cone of the first multiplication region, and the contact surface is a circular ring. The cathode region is a cylinder, shares a central axis with the photosensitive window region and contacts along a first direction, covers the photosensitive window region, and the contact surface is a circle.

[0037] The substrate layer and the multiplication layer are made of the same material.

[0038] The bandgap width of the multiplication layer is greater than the bandgap width of the substrate layer.

[0039] The first multiplication region has a different doping type from the other multiplication regions, and the substrate layer, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region have the same doping type.

[0040] The doping concentration of the third multiplication zone is higher than that of the second multiplication zone and the fourth multiplication zone, and the second multiplication zone, the third multiplication zone and the fourth multiplication zone adopt Pocket doping.

[0041] Example 1

[0042] Figure 1 It is a schematic diagram of the structure of a pocket-doped 4H-SiC-based avalanche photodiode device along the first direction.

[0043] like Figure 1 As shown, a pocket-doped 4H-SiC-based avalanche photodiode device includes: a substrate layer 101, a multiplication layer, a passivation layer 107, a PAD layer 108, a metal electrode region 109 and a photosensitive window region.

[0044] In this embodiment, the materials of the substrate layer 101 and the multiplication layer are both 4H-SiC. The material of the passivation layer 107 is SiN x , the PAD layer 108 is a high-quality metal conductive material, and the metal electrode region 109 is a metal contact electrode.

[0045] The element nitrogen is uniformly used for n-type doping, and the element aluminum is uniformly used for p-type doping.

[0046] The device is grown on the substrate layer 101 by using a chemical vapor deposition (CVD) method, and the doping concentration of each layer at a specified depth is achieved by using ion implantation.

[0047] The substrate layer 101 is uniformly doped with n-type and is located at the bottom of the pocket-doped 4H-SiC-based avalanche photodiode device, with a doping concentration of 1*10 19 cm -3The axis is along the 0001 crystal direction of 4H-SiC, that is, the first direction in which the central axis of the cylinder of the substrate layer 101 is upward; the substrate layer 101 is cylindrical, the cylinder thickness is 10 μm, and the bottom diameter is 1000 μm.

[0048] The multiplication layer is in the form of a convex frustum, which is grown on the substrate layer 101 and has a common central axis with the substrate layer 101 and is in contact with the substrate layer 101 along a first direction, where the first direction is the central axis of the substrate layer 101 pointing upwards.

[0049] The multiplication layer is divided into five multiplication zones along the first direction, which are respectively denoted as the first multiplication zone 102, the second multiplication zone 103, the third multiplication zone 104, the fourth multiplication zone 105 and the fifth multiplication zone 106. The five multiplication zones share a central axis along the first direction and are in contact with each other in sequence; the first multiplication zone 102 is a convex frustum, and the second multiplication zone 103, the third multiplication zone 104, the fourth multiplication zone 105 and the fifth multiplication zone 106 are frustum; the inclination angles of the first multiplication zone 102, the second multiplication zone 103, the third multiplication zone 104, the fourth multiplication zone 105 and the fifth multiplication zone 106 are consistent.

[0050] The first multiplication zone 102 is in the shape of a convex truncated cone with an inclination angle of 6 to 10° and a thickness of 3.0 μm; the second multiplication zone 103, the third multiplication zone 104, the fourth multiplication zone 105 and the fifth multiplication zone 106 are respectively in the shape of a truncated cone with an inclination angle of 6 to 10°, a thickness between 0.1 and 0.5 μm, and a diameter of the truncated cone surface of 800 μm.

[0051] The first multiplication region 102 is p-type doped, with a doping concentration between 1*10 15 ~1*10 19 cm -3 The second multiplication region 103, the third multiplication region 104 and the fourth multiplication region 105 are n-type doped, using Pocket high doping, and the doping concentration is between 1*10 15 ~5*10 18 cm -3 The five-fold increase region 106 is n-type doped, with a doping concentration of 1*10 19 cm -3 .

[0052] The contact surfaces between the substrate layer 101 and the first multiplication zone 102 , the second multiplication zone 103 , the third multiplication zone 104 , the fourth multiplication zone 105 and the fifth multiplication zone 106 are all circular surfaces whose outer normals are along the first direction.

[0053] The passivation layer 107 covers the upper surface of the multiplication layer and is in the shape of a hollow truncated cone shell with an inclination angle of 6 to 10 degrees and a thickness of 400 to 600 nm.

[0054] The passivation layer 107 is a hollow truncated cone shell, which has the same central axis as the multiplication layer and contacts with its upper surface, covers the outer surface of the multiplication layer, and the contact surface is a fan-shaped surface with the same inclination angle as the truncated cone of the multiplication layer.

[0055] The PAD layer 108 can be made of a metal material with good conductive properties, and is grown on the upper surface of the passivation layer 107 , in the shape of a hollow truncated cone shell with an inclination angle of 6 to 10°, and a thickness of 100 to 500 nm.

[0056] The PAD layer is a hollow truncated cone shell, which is coaxial with the passivation layer 107 and contacts with its upper surface, covers the outer surface of the passivation layer 107, and the contact surface is a fan-shaped surface with the same inclination angle as the truncated cone of the passivation layer.

[0057] The metal electrode region 109 includes an anode region and a cathode region, wherein the anode region is a cylindrical ring body, contacts the first multiplication region 102 along the first direction, covers the upper surface of the convex truncated cone of the first multiplication region 102, and the contact surface is annular. The cathode region is a cylinder, shares the same central axis with the photosensitive window region and contacts along the first direction, covers the photosensitive window region, and the contact surface is circular. The thickness is between 300 and 800 nm; the ring width / cylinder diameter is between 40 and 80 nm; the metal electrode region 109 is a Ti metal electrode.

[0058] The photosensitive window area is in a circular shape and is located on the upper surface area of ​​the truncated cone of the fifth multiplication area after the top layer of the passivation layer 107 and the PAD layer 108 is etched. The outer ring diameter is between 400 and 750 nm; the inner ring diameter is the cylinder diameter of the cathode area of ​​the metal electrode area 109.

[0059] The preparation process of a pocket-doped 4H-SiC-based avalanche photodiode device is as follows: Figure 2 As shown, it includes five parts: layer-by-layer growth and layer-by-layer ion doping, device table etching, device surface passivation, photosensitive window etching, and ohmic electrode preparation.

[0060] The first multiplication region 102, the second multiplication region 103, the third multiplication region 104, the fourth multiplication region 105, the fifth multiplication region 106, the passivation layer 107, the PAD layer 108 and the metal electrode region 109 are grown sequentially on the substrate layer 101 by chemical vapor deposition; particles of specified type and concentration are doped layer by layer by ion implantation.

[0061] Mesa etching is the process of preparing low-damage mesas with specified tilt angles using photoresist reflow technology and dry cycle etching process in a variable temperature environment to ensure that the electric field is evenly distributed in the depletion region when the device is operating, and to effectively electrically isolate the device from adjacent devices on the integrated circuit.

[0062] Surface passivation is to pre-treat the table surface and then deposit a 200-300nm passivation layer 107 using PECVD. The passivation layer 107 can reduce the contamination, damage, defects and electric field distribution on the surface of the device structure and prevent the device from breaking down prematurely.

[0063] PECVD deposition and a 200-300 nm PAD layer 108 are used, and the PAD layer 108 connects the device pins with the external circuit while further protecting the device surface structure.

[0064] The photosensitive window etching is based on a dry-wet two-step etching process with a sacrificial layer protection method to achieve low-damage photosensitive window etching.

[0065] The metal electrode region 109 is prepared by adopting a low-resistance ohmic contact process and high-temperature annealing in a nitrogen atmosphere.

[0066] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0067] Comparative Example 1:

[0068] like Figure 3 (a) shows a schematic diagram of the doping concentration of a 4H-SiC APD device along the first direction. The thicknesses of the substrate layer 101, the first multiplication region 102, the second multiplication region 103, the third multiplication region 104, the fourth multiplication region 105 and the fifth multiplication region 106 are 3.0, 3.0, 0.5, 0.2, 0.5 and 0.3 μm, respectively. The first multiplication region 102 is p-type doped, and the substrate layer, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region are all n-type doped, and the doping concentrations are 1*10 19 、-1*10 19 , 1*10 15 , 5*10 18 , 1*10 15 and 1*10 19 cm -3 (The negative sign indicates p-type doping only).

[0069] Embodiment 2:

[0070] like Figure 3(b) shows a schematic diagram of the doping concentration of a pocket-doped 4H-SiC-based avalanche photodiode device along the first direction. The thicknesses of the substrate layer 101, the first multiplication region 102, the second multiplication region 103, the third multiplication region 104, the fourth multiplication region 105 and the fifth multiplication region 106 are 3.0, 3.0, 0.5, 0.2, 0.5 and 0.3 μm, respectively. The first multiplication region 102 is p-type doped, and the substrate layer, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region are all n-type doped; the substrate layer 101 is uniformly doped, and the doping concentration is 1*10 19 cm -3 The first multiplication region 102 is Gaussian doped, and the doping concentration is -1*10 19 ~-1*10 15 cm -3 Uniform decreasing distribution (negative sign indicates p-type doping only); the second multiplication region 103, the third multiplication region 104, the fourth multiplication region 105 and the fifth multiplication region 106 are Gaussian doped, and the doping concentration is 5*10 from the third multiplication region 104 to the second multiplication region 103. 18 ~1*10 15 cm -3 Evenly distributed decreasingly, and upward the fourth doubling zone 105 is 5*10 18 ~1*10 15 cm -3 The fifth multiplication zone 106 is uniformly doped, and the doping concentration is 1*10 19 cm -3 .

[0071] The epitaxial structure of Example 2 is exactly the same as that of Control Example 1, except for the doping type and doping concentration of each layer.

[0072] Figure 3 (a) and Figure 3 Compared with the device structure in (b), the advantage of Example 2 over the traditional SiCAPD device in Control Example 1 is that the introduction of the Pocket high doping concentration region makes the electric field distribution in the multiplication region more uniform, and the possibility of premature breakdown of the device surface is smaller; in addition, the Pocket high doping is more consistent with the physical doping concentration distribution formed by the ion implantation process.

[0073] The advantages of the pocket-doped 4H-SiC-based avalanche photodiode device will be further illustrated below by simulating the device electrical performance data using the Sentaurus TCAD simulation tool.

[0074] like Figure 4As shown, the spherical scatter plot represents the volt-ampere characteristic curve of the comparative example 1, and the straight line, line segment, and dotted line respectively represent the maximum doping concentration value of 5*10 in the Gaussian doping distribution of the second multiplication region 103, the third multiplication region 104, and the fourth multiplication region 105 in the embodiment 2. 18 , 1*10 18 , 1*10 17 cm -3 (The minimum doping concentration is 1*10 15 cm -3 , the same below) is the volt-ampere characteristic curve, where: Figure 4 (a) is the forward voltage, Figure 4 (b) is the reverse voltage. It is obvious that the leakage current of Example 2 is smaller at 0V voltage, and the maximum doping concentration of Gaussian doping is 1*10 17 cm -3 The device has the smallest leakage current magnitude and the largest breakdown voltage. At the same time, the maximum doping concentration is 5*10 18 cm -3 In the case of Example 2, compared with Control Example 1, Example 2 has a smaller breakdown voltage, which is manifested as smaller energy loss and power consumption, and is more advantageous in actual engineering applications.

[0075] like Figure 5 As shown, the spherical scatter plot represents the current gain curve of the comparative example 1, and the straight line represents the maximum doping concentration value of 5*10 in the Gaussian doping distribution of the second multiplication region 103, the third multiplication region 104, and the fourth multiplication region 105 in the embodiment 2. 18 , 1*10 18 , 1*10 17 cm -3 Current gain curve under 280nm monochromatic light. Compared with control example 1, the doping concentration in Example 2 has a larger current gain at the same voltage before the breakdown voltage; and Example 2 shows a current gain significantly greater than 1*10 5 The current gain is significantly improved.

[0076] like Figure 6 As shown in FIG. 1 , the maximum doping concentration value in the Gaussian doping distribution of the second multiplication region 103, the third multiplication region 104, and the fourth multiplication region 105 in the pocket-doped 4H-SiC-based avalanche photodiode device of Example 2 is 5*10 18 cm -3 The response spectrum in the range of 200-450nm ultraviolet and visible light. The quantum efficiency peak of Example 1 under 275nm monochromatic light is 62%, and the ultraviolet-visible light suppression ratio is as high as 2816.5, with an extremely high signal-to-noise ratio, reaching the current industry-leading level.

[0077] The 4H-SiC APD device structure design with the introduction of the Pocket high-doping region exhibits excellent performance: extremely low leakage current, fast photoresponse, high current signal gain, excellent signal-to-noise ratio, and low table breakdown probability. These characteristics make it have a wide range of application potentials for ultraviolet detection in extreme environments and provide guidance for the fabrication of high-performance 4H-SiC APD devices.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A pocket-doped 4H-SiC-based avalanche photodiode device, characterized in that: include: Substrate layer, multiplication layer, passivation layer, PAD layer, metal electrode region and photosensitive window region; The substrate layer is cylindrical and is located at the bottom layer of the pocket-doped 4H-SiC-based avalanche photodiode device; The multiplication layer is in the form of a convex truncated cone, shares a central axis with the substrate layer, and contacts the substrate layer along a first direction, wherein the first direction is from the central axis of the substrate layer upwards; The multiplication layer is divided into five multiplication zones along the first direction, which are respectively recorded as the first multiplication zone, the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone. The five multiplication zones share a central axis along the first direction and are in contact with each other in sequence. The first multiplication zone is in the form of a convex truncated cone, and the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone are in the form of a truncated cone. The inclination angles of the truncated cone part of the first multiplication zone, the second multiplication zone, the third multiplication zone, the fourth multiplication zone and the fifth multiplication zone are consistent. The contact surfaces between the substrate layer and the first multiplication region, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region are all circular surfaces whose outer normals are along the first direction; The passivation layer is a hollow truncated cone shell, having a common central axis with the multiplication layer and in contact with its upper surface, covering the outer surface of the multiplication layer, and the contact surface is a fan-shaped curved surface, having the same inclination angle as the truncated cone of the multiplication layer; The PAD layer is a hollow truncated cone shell, having a common central axis with the passivation layer and in contact with its upper surface, covering the outer surface of the passivation layer, and the contact surface is a fan-shaped curved surface with the same inclination angle as the truncated cone of the passivation layer; The photosensitive window area is in a circular ring shape and is located on the upper surface of the fifth multiplication area; The metal electrode area includes an anode area and a cathode area, wherein the anode area is a cylindrical ring body, contacts with the first multiplication area along a first direction, covers the upper surface of the convex cone of the first multiplication area, and the contact surface is a circular ring; the cathode area is a cylinder, shares the same central axis with the photosensitive window area and contacts along the first direction, covers the photosensitive window area, and the contact surface is a circle.

2. A pocket-doped 4H-SiC-based avalanche photodiode device according to claim 1, characterized in that: The substrate layer and the multiplication layer are made of the same material.

3. A pocket-doped 4H-SiC-based avalanche photodiode device according to claim 2, characterized in that: The bandgap width of the multiplication layer is greater than the bandgap width of the substrate layer.

4. The pocket-doped 4H-SiC-based avalanche photodiode device according to claim 1, characterized in that: The first multiplication region has a different doping type from the other multiplication regions; the substrate layer, the second multiplication region, the third multiplication region, the fourth multiplication region and the fifth multiplication region have the same doping type.

5. The pocket-doped 4H-SiC-based avalanche photodiode device according to claim 1, characterized in that: The doping concentration of the third multiplication zone is higher than that of the second multiplication zone and the fourth multiplication zone, and the second multiplication zone, the third multiplication zone and the fourth multiplication zone adopt Pocket doping.

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