A single photon avalanche diode unit, a detector and a method of manufacturing thereof

Abstract

The application provides a single photon avalanche diode unit, a detector and a preparation method thereof. The SPAD unit comprises a substrate, an epitaxial layer arranged on the upper surface of the substrate and a first well region arranged in the epitaxial layer. Two avalanche multiplication regions are formed by arranging a forward second well region and a reverse second well region on the upper and lower surfaces of the first well region, so as to improve the detection efficiency of the SPAD for different wavelengths. The avalanche region close to the surface is more sensitive to short wavelengths. The collision ionization intensity of the avalanche multiplication region formed by the first well region and the two adjacent forward second well region and reverse second well region is large, so that the detection efficiency of the SPAD is improved. By designing the superimposed PN junction in the longitudinal direction, the area of the SPAD is fully utilized, and a new idea is provided for the wide spectral response, high detection efficiency and miniaturization of the SPAD array.

Description

Technical Field

[0001] This application relates to the field of lidar ranging, and in particular to a single-photon avalanche diode unit, a detector, and a method for fabricating the same. Background Technology

[0002] In optoelectronic technology research, detection is a crucial component of semiconductor optoelectronics. Single-photon avalanche diodes (SPADs) possess advantages such as fast response speed, high avalanche gain, light weight, low power consumption, and a wide spectral range. SPAD detectors have become an important means of realizing optical signal detection and can perform dynamic imaging of targets. They are suitable for laser imaging and play a vital supporting role in a wide range of applications, including biological genetics, national defense and security, deep space exploration, high-energy physics, and quantum communication, making them a hot research topic in scientific research.

[0003] A single-photon avalanche diode (SPAD) is an avalanche photodiode operating in Geiger mode (i.e., operating voltage greater than breakdown voltage). When the energy of a photon transmitted into the SPAD exceeds the bandgap of silicon, some electrons absorb the photon energy and transition to the conduction band, forming photogenerated electrons. In operation, a reverse bias voltage is applied to the cathode (N+) and anode (P+) of the SPAD. Photogenerated electrons generated in the P-region outside the depletion region are called minority carriers. Due to the concentration gradient, they diffuse into the depletion region. Photogenerated electrons and holes generated and diffused into the depletion region are directly separated by the electric field and enter the cathode and anode respectively, thus achieving spectral detection. Traditional SPADs have high response efficiency for blue and green light, but their photon detection efficiency is relatively low for the wavelengths required for imaging in consumer electronics and lidar, which to some extent restricts the large-scale application of SPADs. Therefore, improving the photon detection efficiency in the near-infrared band is a promising research direction. To address the aforementioned issues, this invention proposes a SPAD structure with multiple avalanche regions, achieving both a wide spectral response and high detection efficiency. Summary of the Invention

[0004] To address these challenges, this invention provides a single-photon avalanche diode (SPAD) unit, detector, and its fabrication method, solving the significant technical problems of low photon detection efficiency (PDE) and narrow response spectral range inherent in conventional SPAD structures. The SPAD unit structure provided by this invention combines a first well region with two avalanche multiplication regions: a first well region and two adjacent forward-facing second well regions. Due to the different depths of the avalanche regions, the absorption effects vary across these regions, improving the SPAD unit's response efficiency to photons across different wavelength ranges. Simultaneously, multiple parallel avalanche multiplication regions are formed. The first and second high-voltage well regions act as a connecting circuit, linking the avalanche regions to the anode and cathode, thereby increasing the unit's detection efficiency without increasing the chip area.

[0005] In a first aspect, embodiments of this application provide a single-photon avalanche diode unit, the single-photon avalanche diode unit comprising a plurality of single-photon avalanche diode units, each of the single-photon avalanche diode units comprising, in a longitudinal section: a substrate; an epitaxial layer disposed on the upper surface of the substrate, wherein a first well region is disposed in the epitaxial layer; a forward second well region and a reverse second well region respectively located on the upper surface and the lower surface of the first well region; wherein the first well region, the forward second well region, and the reverse second well region are longitudinally flush; a PN junction structure is formed between the first well region and the forward second well region and the reverse second well region; a first high-voltage well region extending longitudinally from the lower surface of the first well region to the upper surface of the epitaxial layer on the second side of the first well region; a first electrode contact disposed on the top of the first high-voltage well region; a second high-voltage well region extending longitudinally from the lower surface of the reverse second well region to the upper surface of the epitaxial layer on the first side of the reverse second well region; and a second electrode contact disposed on the top of the second high-voltage well region.

[0006] In some embodiments, the positive second well region and the negative second well region have the same doping type, and the doping type of the first well region is opposite to that of the positive second well region and the negative second well region; the doping type of the first high-voltage well region is the same as that of the first well region, and the doping type of the second high-voltage well region is the same as that of the positive second well region and the negative second well region.

[0007] In some embodiments, the lateral widths of both the forward second well region and the reverse second well region are smaller than those of the first well region.

[0008] In some embodiments, the substrate is any one of silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide semiconductor substrates.

[0009] In some embodiments, the single-photon avalanche diode unit further includes a deep isolation trench structure located around each single-photon avalanche diode unit, the deep isolation trench structure being disposed through the epitaxial layer and the substrate.

[0010] In some embodiments, the cross-sectional shape of the single-photon avalanche diode unit is square, circular, or polygonal.

[0011] Secondly, embodiments of this application provide a single-photon avalanche diode detector, comprising a plurality of single-photon avalanche diode units as described above, wherein the plurality of single-photon avalanche diode units are arranged in an array.

[0012] In some embodiments, the single-photon avalanche diode detector has four single-photon avalanche diode detector units, which are arranged in a 2×2 array.

[0013] Thirdly, embodiments of this application provide a method for fabricating a single-photon avalanche diode unit. The method includes: depositing an epitaxial layer on a substrate; implanting a first well region in the epitaxial layer; implanting a forward second well region and a reverse second well region on the upper and lower surfaces of the first well region, respectively, such that a first side and a third side of the first well region are flush with the forward second well region and the reverse second well region; implanting a first high-voltage well region longitudinally from the lower surface of the first well region to the upper surface of the epitaxial layer, the first high-voltage well region surrounding a second side and a fourth side of the first well region; implanting a second high-voltage well region longitudinally from the lower surface of the reverse second well region to the upper surface of the epitaxial layer, the second high-voltage well region surrounding the first side and the third side of the forward second well region, the first well region, and the reverse second well region; and providing a first electrode contact and a second electrode contact on the top of the first high-voltage well region and the second high-voltage well region, respectively.

[0014] Fourthly, embodiments of this application provide a method for fabricating a single-photon avalanche diode detector, wherein the single-photon avalanche diode detector includes a plurality of single-photon avalanche diode units obtained by the fabrication method described above, and the method includes: etching around each single-photon avalanche diode unit to form a deep isolation trench structure penetrating the epitaxial layer and the substrate.

[0015] The single-photon avalanche diode (SPAD) cell structure provided by this invention combines a first well region with two avalanche multiplication regions between an upper forward second well region and a lower reverse second well region. Due to the different depths of the avalanche regions, the absorption effects of different regions vary, improving the response efficiency of the SPAD cell to photons in different wavelength ranges. Furthermore, without increasing the cell area, it provides more avalanche area, improving the detection efficiency of the SPAD cell for near-infrared photons. The two avalanche multiplication regions between the forward and reverse second well regions and the first well region are far from the cell surface, reducing the impact of silicon surface defects and ionic impurities on the avalanche multiplication regions during the manufacturing process, effectively improving the cell's dark count. The forward and reverse second well regions are connected to the second electrode via a shared second high-voltage well region, connecting to external circuitry, effectively reducing the area for large-scale array integration and improving the integration density of chip products. In addition, the fabrication process of the SPAD cell provided by this invention is compatible with CMOS (Complementary Metal Oxide Semiconductor) processes, enabling large-scale mass production and applications. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the longitudinal section structure of the single-photon avalanche diode unit provided in Embodiment 1 of this application;

[0017] Figures 2A-2B This is a schematic diagram of the cross-sectional structure of the single-photon avalanche diode unit provided in Embodiment 1 of this application;

[0018] Figure 3 This is a schematic diagram of the cross-sectional structure of the single-photon avalanche diode detector provided in Embodiment 2 of this application;

[0019] Figures 4 to 8 This is a schematic diagram of the longitudinal section structure during the fabrication process of the single-photon avalanche diode unit provided in Embodiment 3 of this application;

[0020] Figure 9 This is a schematic diagram of the longitudinal section structure during the fabrication process of the single-photon avalanche diode detector provided in Embodiment 4 of this application. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0022] Example 1

[0023] Embodiment 1 of this application provides a single-photon avalanche diode unit. Figure 1 This is a schematic diagram of the longitudinal section of the single-photon avalanche diode unit 100 provided in Embodiment 1 of this application, as shown below. Figure 1 As shown, the single-photon avalanche diode unit 100 includes the following in its longitudinal section:

[0024] Substrate 101; an epitaxial layer 102 disposed on the upper surface of the substrate 101, wherein a first well region 103 is disposed in the epitaxial layer 102; here, the substrate 101 can be a P-type substrate or an N-type substrate, and the substrate 101 can be any one of silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide semiconductor substrates. Correspondingly, the epitaxial layer 102 on the upper surface of the substrate 101 can be a P-type epitaxial layer or an N-type epitaxial layer. The first well region 103 is located in the middle of the epitaxial layer, away from the upper and lower surfaces of the epitaxial layer, and extends along the lateral X direction. Its doping type can be P-type or N-type.

[0025] A forward second well region 114 and a reverse second well region 124 are respectively located on the upper surface and lower surface of the first well region 103. The first sides S1 of the first well region 103, the forward second well region 114, and the reverse second well region 124 are longitudinally aligned. A PN junction structure is formed between the first well region 103, the forward second well region 114, and the reverse second well region 124. In this embodiment, the widths of the forward second well region 114 and the reverse second well region 124 are both smaller than the width of the first well region 103. That is, the first well region 103 is longitudinally aligned with the forward second well region 114 and the reverse second well region 124 on the first side S1, and the first well region 103 protrudes from the forward second well region 114 and the reverse second well region 124 on the second side S2. The forward second well region 114 and the reverse second well region 124 have the same doping type, and both are opposite to the doping type of the first well region 103. Therefore, a PN junction structure is formed between the forward second well region 114 and the first well region 103, and a PN junction structure is formed between the first well region 103 and the reverse second well region 124. Thus, in the single-photon avalanche diode unit structure provided in this embodiment, two avalanche multiplication regions are combined between the first well region 103 and the upper forward second well region 114 and the lower reverse second well region 124. Since the depths of the avalanche regions are different, the absorption effects of different regions are also different, which improves the response efficiency of the SPAD unit to photons in different wavelength ranges. In addition, since the two avalanche multiplication regions between the first well region 103 and the forward and reverse second well regions are far from the surface of the unit, the influence of silicon surface defects and ionic impurities on the avalanche multiplication regions during the process is reduced, effectively improving the dark count of the unit.

[0026] On the second side S2 of the first well region 103, a first high-voltage well region 105 extends longitudinally from the lower surface of the first well region 103 to the upper surface of the epitaxial layer 102. A first electrode contact 107 is provided on the top of the first high-voltage well region 105 for extracting the electrical signal of the first well region 103. The doping type of the first high-voltage well region 105 is the same as that of the first well region. For example, the doping type of both the first well region and the first high-voltage well region is N-type. In this case, the first electrode contact is a cathode contact. On the first side S1 of the reverse second well region 124, a second high-voltage well region 106 extends longitudinally from the lower surface of the reverse second well region 124 to the upper surface of the epitaxial layer 102. A second electrode contact 108 is provided on the top of the second high-voltage well region 106 for extracting the electrical signals of the forward second well region 114 and the reverse second well region 124. The doping type of the second high-voltage well region 106 is the same as that of the forward and reverse second well regions. For example, the doping type of the second high-voltage well region is P-type. In this case, the second electrode contact is an anode contact. For example, the upper surfaces of the first electrode contact 107 and the second electrode contact 108 are flush with the upper surface of the epitaxial layer 102.

[0027] In this embodiment, the first high-pressure well region 105 extends along the Z-direction, and its depth in the Z-direction is much greater than that of the first well region 103 in the Z-direction, while the width of the first well region 103 in the X-direction is much greater than that of the first high-pressure well region 105. Similarly, the second high-pressure well region 106 extends along the Z-direction, and its depth in the Z-direction is much greater than that of the forward second well region 114 and the reverse second well region 124, while the width of the forward second well region 114 and the reverse second well region 124 in the X-direction is much greater than that of the second high-pressure well region 106. The doping type of the first high-pressure well region 105 is the same as that of the first well region 103, and its doping concentration is greater than that of the first well region 103. The doping type of the second high-pressure well region 106 is the same as that of the forward second well region and the reverse second well region, and its doping concentration is greater than that of the forward second well region and the reverse second well region. The first well region 103 forms two avalanche multiplication regions with the upper positive second well region 114 and the lower negative second well region 124. The positive second well region 114 and the negative second well region 124 share a second high-voltage well region 106 connected to the second electrode contact 108, which is connected to the external circuit, effectively reducing the area of ​​large-scale array integration and improving the integration of chip products.

[0028] Figure 2A This is a schematic diagram of the cross-sectional structure of the top surface of the photonic avalanche diode unit provided in Embodiment 1 of this application. Figure 2B This is a schematic diagram of the cross-sectional structure of the photonic avalanche diode unit along the AA plane provided in Embodiment 1 of this application, wherein 114' represents the positional relationship of the forward second well region 114 on the upper surface of 103, as shown in the reference diagram. Figures 1 to 2B As can be seen, the SPAD unit in this embodiment has a square cross-section. In space, the first electrode contact 107 is surrounded by the first high-pressure trap region 105, and the second electrode contact 108 is surrounded by the second high-pressure trap region 106. The first high-pressure trap region 105 includes a V-shaped structure composed of the second side S2 and the fourth side S4. Correspondingly, the second high-pressure trap region 106 includes a V-shaped structure composed of the first side S1 and the third side S3. The first high-pressure trap region 105 and the second high-pressure trap region 106 are not in contact with each other in terms of spatial structure. The cross-sectional area of ​​the first well region 103 is larger than that of the forward first well region 114 and the reverse second well region 124. That is, the first well region 103 is aligned with the forward second well region 114 and the reverse second well region 124 on the first side S1 and the third side S3. The first well region 103 protrudes from the forward second well region 114 and the reverse second well region 124 on the second side S2 and the fourth side S4, so that the first high-pressure well region 105 is directly connected to the first well region 103 on both the second side S2 and the fourth side S4. The forward second well region 114 and the reverse second well region 124 share the second high-pressure well region 106 on the first side S1 and the third side S3.

[0029] In some embodiments, the single-photon avalanche diode unit 100 further includes a deep isolation trench structure (DTI) 109 located around each of the single-photon avalanche diode units 100, the DTI 109 extending through the epitaxial layer 102 and the substrate 101. The DTI serves to shield between SPADs, preventing signals from one SPAD from entering adjacent SPADs to reduce crosstalk. It should be understood that in this embodiment, the DTI is shared by SPADs on either side of its edge along a given edge; that is, the epitaxial layer on one side of the DTI is part of the SPAD on that side, and the epitaxial layer on the other side of the DTI is part of the SPAD on the other side.

[0030] In some embodiments, the cross-sectional shape of the single-photon avalanche diode unit can also be one of a variety of shapes such as circular or polygonal.

[0031] The single-photon avalanche diode (SPAD) cell structure provided in this application combines a first well region with two avalanche multiplication regions between the upper forward second well region and the lower reverse second well region. Due to the different depths of the avalanche regions, the absorption effects of different regions vary, improving the response efficiency of the SPAD cell to photons in different wavelength ranges. Furthermore, without increasing the cell area, it provides more avalanche area, improving the detection efficiency of the SPAD cell for near-infrared photons. The two avalanche multiplication regions between the forward and reverse second well regions and the first well region are far from the cell surface, reducing the impact of silicon surface defects and ionic impurities on the avalanche multiplication regions during the manufacturing process, effectively improving the cell's dark count. The forward and reverse second well regions are connected to the second electrode via a shared second high-voltage well region, connecting to external circuitry, effectively reducing the area of ​​large-scale array integration and improving the integration density of chip products. In addition, the fabrication process of the SPAD cell provided in this application is compatible with CMOS processes, enabling large-scale mass production and application.

[0032] Example 2

[0033] This application provides a single-photon avalanche diode detector. Figure 3 This is a schematic diagram of the cross-sectional structure of the single-photon avalanche diode detector provided in Example 2, with reference to... Figure 3The single-photon avalanche diode detector 200 includes a plurality of single-photon avalanche diode units 100 as described above. The plurality of single-photon avalanche diode units 100 are arranged in an array. In this embodiment, the structure of the single-photon avalanche diode unit 100 is the same as that in Embodiment 1. The single-photon avalanche diode detector 200 includes 4 SPAD units 100, and the 4 SPAD units are arranged in a 2×2 array. In some embodiments, the number of SPAD units can be other numbers, such as 6, 8, 10, etc., which are not limited here.

[0034] Example 3

[0035] Embodiment 3 of this application provides a method for fabricating a single-photon avalanche diode unit. Figures 4 to 9 This is a schematic diagram of the fabrication process of the single-photon avalanche diode unit 100 provided in Embodiment 3 of this application. The fabrication method includes:

[0036] Step S1, as follows Figure 4 As shown, an epitaxial layer is deposited on a substrate, and a first well region is implanted in the epitaxial layer. The substrate 101 can be a P-type or N-type substrate, and can be any semiconductor substrate selected from silicon, germanium-silicon, gallium arsenide, gallium nitride, or indium gallium arsenide. The epitaxial layer 102 deposited on the substrate 101 can be a P-type or N-type epitaxial layer with the same doping type as the substrate 110. The first well region is formed in the epitaxial layer 201 by ion implantation. Here, the first well region is located in the middle of the epitaxial layer, away from the upper and lower surfaces of the epitaxial layer, and extends along the lateral X direction. The doping type of the first well region can be P-type or N-type, and is not limited here.

[0037] Step S2: Inject a forward-oriented second well region and a reverse-oriented second well region into the upper and lower surfaces of the first well region, respectively, so that the first and third sides of the first well region are flush with the forward-oriented and reverse-oriented second well regions; see [link to previous steps]. Figure 5 A forward second well region 114 and a reverse second well region 124 are formed by ion implantation on the upper and lower surfaces of the first well region 103, respectively. Here, the lateral width of the first well region 103 is greater than that of the forward second well region 114 and the reverse second well region 124, and in the XZ plane, the first side of the first well region 103 is flush with the forward second well region 114 and the reverse second well region 124. It should be understood that in space, the first side S1 is opposite to the second side S2, and the third side S3 is opposite to the fourth side S4. That is to say, in space, the first well region 103 is flush with the forward second well region 114 and the reverse second well region 124 on the first and third sides, while the forward second well region 114 and the reverse second well region 124 protrude from the second and fourth sides.

[0038] Step S3: Inject a first high-pressure well region longitudinally from the lower surface of the first well region to the upper surface of the epitaxial layer, wherein the first high-pressure well region surrounds the second and fourth sides of the first well region; see also Figure 6 A first high-pressure well region 105 is formed around the first well region 103 by ion implantation on the second side S2 and the fourth side. The lower surface of the first high-pressure well region 105 is flush with the lower surface of the first well region 103, and extends longitudinally Z to the upper surface of the epitaxial layer 102, with its longitudinal depth being much greater than its lateral width. The doping type of the first high-pressure well region 105 is the same as that of the first well region 103, but the doping concentration is higher than that of the first well region 103.

[0039] Step S4: Inject a second high-pressure well region longitudinally from the lower surface of the reverse second well region to the upper surface of the epitaxial layer. The second high-pressure well region surrounds the first and third sides of the forward second well region, the first well region, and the reverse second well region; see also Figure 7 A second high-pressure well region 106 is formed around the forward second well region 114, the first well region, and the reverse second well region by ion implantation on the first side S1 and the third side of the reverse second well region 124. The lower surface of the second high-pressure well region 106 is flush with the lower surface of the reverse second well region 124 and extends longitudinally to the upper surface of the epitaxial layer 102. Its longitudinal depth is much greater than its lateral width. The doping type of the second high-pressure well region 106 is the same as that of the forward second well region and the reverse second well region, but the doping concentration is higher than that of the forward second well region and the reverse second well region.

[0040] Step S5: A first electrode contact and a second electrode contact are respectively disposed on the top of the first high-pressure trap region and the second high-pressure trap region. (See also...) Figure 8 A first electrode contact 107 is provided at the top of the first high-voltage well region 105, and the first electrode contact 107 surrounds the first high-voltage well region 107 for extracting the electrical signal of the first well region 103. A second electrode contact 108 is provided at the top of the second high-voltage well region 106, and the second electrode contact 108 surrounds the second high-voltage well region 106 for extracting the electrical signals of the forward second well region 114 and the reverse second well region 124.

[0041] Example 4

[0042] Embodiment 4 of this application provides a method for fabricating a single-photon avalanche diode detector, wherein the single-photon avalanche diode detector 200 includes a plurality of single-photon avalanche diode units 100 obtained by the fabrication method as described in Embodiment 3. See [link to Embodiment 4]. Figure 9 The methods include:

[0043] The periphery of each of the single-photon avalanche diode units 100 is etched to form a deep isolation trench 109 structure that penetrates the epitaxial layer 102 and the substrate 101.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any person skilled in the art can make various changes, modifications, substitutions and variations to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A single-photon avalanche diode unit, characterized in that, The single-photon avalanche diode unit comprises, in its longitudinal section: Substrate; An epitaxial layer is disposed on the upper surface of the substrate, and a first well region is disposed in the epitaxial layer; A positive second well region and a negative second well region are respectively located on the upper surface of the first well region and the lower surface of the first well region; wherein, the first side of the first well region, the positive second well region, and the negative second well region are longitudinally flush; a PN junction structure is formed between the first well region and the positive second well region and the negative second well region, respectively; A first high-voltage well region extends longitudinally from the lower surface of the first well region to the upper surface of the epitaxial layer on the second side of the first well region; a first electrode contact is provided at the top of the first high-voltage well region; A second high-voltage well region extends longitudinally from the lower surface of the reverse second well region to the upper surface of the epitaxial layer on the first side of the reverse second well region; a second electrode contact is provided at the top of the second high-voltage well region; The first high-pressure well region forms a V-shaped structure around the second and fourth sides of the first well region; the second high-pressure well region forms a V-shaped structure around the first and third sides of the positive second well region, the first well region, and the reverse second well region. The width of the first high-pressure well region in the X direction is much greater than that of the first high-pressure well region; the second high-pressure well region extends along the Z direction, and its depth in the Z direction is much greater than that of the forward second well region and the reverse second well region, while the width of the forward second well region and the reverse second well region in the X direction is much greater than that of the second high-pressure well region.

2. The single-photon avalanche diode unit according to claim 1, characterized in that: The positive second well region and the negative second well region have the same doping type, and the doping type of the first well region is opposite to that of the positive second well region and the negative second well region. The doping type of the first high-voltage well region is the same as that of the first well region, and the doping type of the second high-voltage well region is the same as that of the forward second well region and the reverse second well region.

3. The single-photon avalanche diode unit according to claim 2, characterized in that, The lateral widths of both the forward second well region and the reverse second well region are smaller than those of the first well region.

4. The single-photon avalanche diode unit according to claim 3, characterized in that, The substrate is any one of silicon, germanium silicon, gallium arsenide, gallium nitride, or indium gallium arsenide semiconductor substrates.

5. The single-photon avalanche diode unit according to claim 4, characterized in that, The single-photon avalanche diode unit further includes a deep isolation trench structure located around each single-photon avalanche diode unit, the deep isolation trench structure being disposed through the epitaxial layer and the substrate.

6. The single-photon avalanche diode unit according to claim 5, characterized in that, The cross-sectional shape of the single-photon avalanche diode unit is square, circular, or polygonal.

7. A single-photon avalanche diode detector, characterized in that, The single-photon avalanche diode detector includes a plurality of single-photon avalanche diode units as described in claim 1, and the plurality of single-photon avalanche diode units are arranged in an array.

8. The single-photon avalanche diode detector according to claim 7, characterized in that, The single-photon avalanche diode detector contains four single-photon avalanche diode detector units, which are arranged in a 2×2 array.

9. A method for fabricating a single-photon avalanche diode unit, characterized in that, The method includes: An epitaxial layer is deposited on a substrate, and a first well region is implanted in the epitaxial layer; A forward second well region and a reverse second well region are injected into the upper and lower surfaces of the first well region, respectively, so that the first and third sides of the first well region are flush with the forward and reverse second well regions; a PN junction structure is formed between the first well region and the forward and reverse second well regions, respectively. The first high-pressure well region is injected longitudinally from the lower surface of the first well region to the upper surface of the epitaxial layer, and the first high-pressure well region forms a V-shaped structure around the second and fourth sides of the first well region. The second high-pressure well region is injected longitudinally from the lower surface of the reverse second well region to the upper surface of the epitaxial layer. The second high-pressure well region forms a V-shaped structure around the first side and the third side of the forward second well region, the first well region, and the reverse second well region. A first electrode contact and a second electrode contact are respectively provided on the top of the first high-pressure trap region and the second high-pressure trap region; The width of the first high-pressure well region in the X direction is much greater than that of the first high-pressure well region; the second high-pressure well region extends along the Z direction, and its depth in the Z direction is much greater than that of the forward second well region and the reverse second well region, while the width of the forward second well region and the reverse second well region in the X direction is much greater than that of the second high-pressure well region.

10. A method for fabricating a single-photon avalanche diode detector, wherein, The single-photon avalanche diode detector comprises a plurality of single-photon avalanche diode units obtained by the fabrication method as described in claim 9, characterized in that the method comprises: The periphery of each of the single-photon avalanche diode units is etched to form a deep isolation trench structure that penetrates the epitaxial layer and the substrate.

Images