Multi-mesa silicon-germanium spad photodetector with shield ring and preparation method

Abstract

The application discloses a kind of multiple mesa with shield ring silicon germanium SPAD photoelectric detector and preparation method, it is related to microelectronic technology field, the detector includes from bottom to top sequentially arranged N-type silicon substrate, intrinsic silicon epitaxial layer, intrinsic germanium epitaxial layer and P-type germanium epitaxial layer;Intrinsic silicon epitaxial layer upper surface is formed with shield ring and charge layer, shield ring is surrounded in the outer periphery of charge layer;Detector has at least two mesa structures, wherein P-type germanium epitaxial layer forms first mesa, intrinsic germanium epitaxial layer, charge layer and shield ring form second mesa;The horizontal projection of first mesa is located in second mesa, and first mesa is not overlapped with shield ring in vertical direction.The application is by making P-type germanium mesa and shield ring vertical dislocation, avoid the early breakdown caused by electric field concentration below shield ring, improve avalanche gain and single-photon detection efficiency, and compatible with silicon-based CMOS technology.

Description

Technical Field

[0001] This invention belongs to the field of microelectronics technology, specifically relating to a multi-shielded silicon-germanium SPAD (Single-Photon Avalanche Diode) photodetector and its fabrication method. Background Technology

[0002] Near-infrared photodetectors have wide applications in fiber optic communication, lidar, 3D imaging, and biomedical detection. Detectors operating in the 1550 nm communication band, in particular, have extremely high requirements for performance indicators such as responsivity, dark current, and avalanche gain. Currently, high-performance near-infrared single-photon detectors mainly use indium gallium arsenide (InGaAs) materials, which exhibit excellent absorption coefficients and carrier transport properties in this band. However, InGaAs materials require heteroepitaxial growth on InP substrates, resulting in high fabrication costs and incompatibility with mainstream silicon-based CMOS processes, making large-scale, low-cost optoelectronic integration difficult.

[0003] In recent years, colloidal quantum dot (such as PbS) detectors have attracted attention due to their solution processing and low-cost potential. However, they suffer from problems such as poor stability, low carrier mobility, and high defect state density, which cannot yet meet the reliability requirements of commercial systems.

[0004] Germanium (Ge) materials exhibit high absorption coefficients in the near-infrared band (especially at 1600 nm), and its epitaxial growth process is highly compatible with silicon-based CMOS processes, making it an ideal candidate material for realizing silicon-based integrated near-infrared detectors. Silicon-based germanium avalanche photodetectors (APDs) and single-photon avalanche diodes (SPADs) have been extensively studied. The traditional absorption multiplication separation (SACM) structure separates the light-absorbing region (Ge) from the avalanche multiplication region (Si), effectively reducing dark current. However, during mesa etching, dry etching introduces defects into the Ge sidewalls, leading to increased sidewall leakage current.

[0005] A 2024 Nature paper proposed a shielding ring structure that effectively reduces the peak electric field at the mesa edge by introducing a P-type shielding ring into the Si layer. Although this structure effectively reduces the electric field at the etching interface by introducing the shielding ring, the electric field concentration phenomenon below the shielding ring causes the IV curve to break down prematurely, resulting in a decrease in device avalanche gain. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a multi-shielded silicon-germanium SPAD photodetector with a shielding ring and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a multi-shielded silicon-germanium SPAD photodetector, comprising: The N-type silicon substrate, intrinsic silicon epitaxial layer, intrinsic germanium epitaxial layer, and P-type germanium epitaxial layer are arranged sequentially from bottom to top. The upper surface of the intrinsic silicon epitaxial layer is formed with a shielding ring and a charge layer by photolithography and implantation processes, and the shielding ring is disposed around the outer periphery of the charge layer. A first ohmic contact electrode is disposed on the upper surface of the P-type germanium epitaxial layer, and a second ohmic contact electrode is disposed on the N-type silicon substrate. The silicon-germanium SPAD photodetector includes at least two mesa structures, with the P-type germanium epitaxial layer forming the first mesa and the intrinsic germanium epitaxial layer, the charge layer, and the shielding ring forming the second mesa. The horizontal projection of the first platform lies within the horizontal projection of the second platform; the first platform does not overlap with the area of ​​the shielding ring in the vertical direction.

[0007] In one embodiment of the present invention, both the shielding ring and the charge layer are P-type doped, and the doping concentration of the shielding ring is 1×10⁻⁶. 18 cm -3 -5×10 19 cm -3 The doping concentration of the charge layer is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .

[0008] In one embodiment of the present invention, the thickness of the intrinsic silicon epitaxial layer is 0.1-2 μm, and the thickness of the intrinsic germanium epitaxial layer is 0.1-2 μm.

[0009] In one embodiment of the present invention, the doping concentration of the p-type germanium epitaxial layer is 5 × 10⁻⁶. 18 cm -3 -5×10 19 cm -3 The thickness is 10-200nm.

[0010] In one embodiment of the present invention, the distance between the shielding ring and the overall boundary of the silicon-germanium SPAD photodetector is 1%-50% of the inner diameter of the shielding ring.

[0011] In one embodiment of the present invention, the resistivity of the N-type silicon substrate is no more than 0.005 Ω·cm and the thickness is 300-500 μm.

[0012] In one embodiment of the present invention, a passivation layer is further included, which covers the surface of the mesa structure; the material of the passivation layer is one or more combinations of SiO2, Al2O3, and SiN, and the thickness is 10-500 nm.

[0013] In one embodiment of the present invention, the P-type germanium epitaxial layer is formed by epitaxial growth or ion implantation, and the ion implantation depth is 100-200 nm.

[0014] This invention provides a method for fabricating multiple silicon-germanium SPAD photodetectors with surface shielding rings, applicable to the fabrication of multiple silicon-germanium SPAD photodetectors with surface shielding rings as described in any of the above embodiments, comprising the following steps: Provide N-type silicon substrates; An intrinsic silicon epitaxial layer is epitaxially grown on the N-type silicon substrate; A shielding ring and a charge layer are formed on the upper surface of the intrinsic silicon epitaxial layer by photolithography and implantation processes, wherein the shielding ring surrounds the outer periphery of the charge layer. Intrinsic germanium epitaxial layer and P-type germanium epitaxial layer are grown sequentially; The second mesa of the entire germanium material region is defined and formed through the first photolithography and etching process. The P-type germanium epitaxial layer is etched into a mesa by a second photolithography and etching process to form a first mesa, wherein the horizontal projection of the first mesa is located within the horizontal projection of the second mesa; the first mesa does not overlap with the area of ​​the shielding ring in the vertical direction. Deposit a passivation layer on the device surface; Photolithography defines P-type and N-type contact regions, and etching removes the passivation layer in the corresponding regions; Metal is deposited in the P-type contact region and the N-type contact region to form a first ohmic contact electrode and a second ohmic contact electrode.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The multi-mesa shielded ring silicon-germanium SPAD photodetector of the present invention effectively reduces the electric field intensity at the edge of the mesa by setting the shielding ring, thereby reducing sidewall tunneling current and generation-recombination current caused by etching defects. In addition, by performing secondary mesa etching on the P-type germanium epitaxial layer to form an independent first mesa, and ensuring that it does not overlap with the shielding ring in the vertical direction, the additional electric field concentration region below the shielding ring is eliminated, so that the maximum peak electric field is precisely located below the charge layer.

[0016] 2. The multi-mesh shielded ring silicon-germanium SPAD photodetector of the present invention is fabricated using CMOS-compatible silicon-based epitaxy, photolithography, ion implantation, and etching processes, requiring no heterogeneous substrates or expensive materials. Both mesh etching operations can be performed using standard dry etching equipment, passivation, and metallization processes, exhibiting strong process compatibility and suitability for optoelectronic integration.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a multi-faceted shielded ring silicon-germanium SPAD photodetector provided in an embodiment of the present invention; Figure 2 This is a flowchart illustrating a method for fabricating multiple silicon-germanium SPAD photodetectors with shielding rings, as provided in an embodiment of the present invention.

[0019] Icons: 1-N-type silicon substrate; 2-Intrinsic silicon epitaxial layer; 3-Intrinsic germanium epitaxial layer; 4-P-type germanium epitaxial layer; 5-Shielding ring; 6-Charge layer; 7-First ohmic contact electrode; 8-Second ohmic contact electrode; 9-Passivation layer. Detailed Implementation

[0020] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for preparing a multi-faceted shielded ring silicon-germanium SPAD photodetector based on the present invention.

[0021] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0022] In a first aspect, embodiments of the present invention provide a multi-stage silicon-germanium SPAD photodetector with a shielded ring on each surface. Please refer to... Figure 1 , Figure 1 This is a schematic diagram of the structure of a multi-faceted silicon-germanium SPAD photodetector with shielding rings provided in an embodiment of the present invention.

[0023] like Figure 1As shown, the multi-shielded silicon-germanium SPAD photodetector of this embodiment includes: an N-type silicon substrate 1, an intrinsic silicon epitaxial layer 2, an intrinsic germanium epitaxial layer 3, and a P-type germanium epitaxial layer 4 arranged sequentially from bottom to top; a shielding ring 5 and a charge layer 6 are formed on the upper surface of the intrinsic silicon epitaxial layer 2 through photolithography and implantation processes, and the shielding ring 5 surrounds the outer periphery of the charge layer 6; a first ohmic contact electrode 7 is disposed on the upper surface of the P-type germanium epitaxial layer 4, and a second ohmic contact electrode 8 is disposed on the N-type silicon substrate 1; The silicon-germanium SPAD photodetector of this embodiment includes at least two mesa structures. The first mesa is formed by a P-type germanium epitaxial layer 4, and the second mesa is formed by an intrinsic germanium epitaxial layer 3, a charge layer 6, and a shielding ring 5. The horizontal projection of the first mesa is located within the horizontal projection of the second mesa. The area of ​​the first mesa does not overlap with the area of ​​the shielding ring 5 in the vertical direction.

[0024] In this embodiment, the N-type silicon substrate 1 can be an N-type heavily doped silicon wafer with a resistivity not exceeding 0.005 Ω·cm and a thickness of 300-500 μm. This substrate serves as the bottom contact layer and mechanical support layer of the device.

[0025] In this embodiment, the thickness of the intrinsic silicon epitaxial layer 2 is 0.1-2 μm. This layer serves as an avalanche multiplication region to withstand collisional ionization under high electric fields.

[0026] In this embodiment, both the shielding ring 5 and the charge layer 6 are P-type doped, and optionally, the doping element is boron. The doping concentration of the shielding ring 5 is 1×10⁻⁶. 18 cm -3 -5×10 19 cm -3 For example, it could be 1×10 19 cm -3 The doping concentration of charge layer 6 is 1×10⁶. 16 cm -3 -1×10 19 cm -3 For example, it could be 1×10 17 cm -3 The distance between the shielding ring 5 and the overall boundary of the silicon-germanium SPAD photodetector is 1%-50% of the inner diameter of the shielding ring 5.

[0027] Understandably, in this embodiment, by adjusting the ratio (1% to 50%) of the width of the shielding ring 5 to the device boundary distance, dark current and responsivity can be flexibly balanced. Increasing the width of the shielding ring 5 can further suppress edge leakage current, making it suitable for high-sensitivity detection; decreasing the width of the shielding ring 5 and increasing the area of ​​the first mesa can improve light absorption efficiency, making it suitable for high-responsivity scenarios.

[0028] In this embodiment, the thickness of the intrinsic germanium epitaxial layer 3 is 0.1-2 μm. This layer serves as the absorption region for near-infrared light.

[0029] It should be noted that when the detector is pursuing a large bandwidth, the thickness of the intrinsic germanium epitaxial layer 3 needs to be reduced in order to reduce the carrier transit time. The thickness is generally around 100-500 nm. However, when the detector is pursuing high absorption efficiency, the thickness of the intrinsic germanium epitaxial layer 3 needs to be increased to improve the detector responsivity. The thickness is generally around 1-2 μm.

[0030] In this embodiment, the doping concentration of the p-type germanium epitaxial layer 4 is 5 × 10⁻⁶. 18 cm -3 -5×10 19 cm -3 The thickness is 10-200 nm. This layer is formed by epitaxial growth or by ion implantation, with an implantation depth of 100-200 nm.

[0031] In this embodiment, the first ohmic contact electrode 7 disposed on the upper surface of the P-type germanium epitaxial layer 4 is a P-type electrode. The second ohmic contact electrode 8 disposed on the N-type silicon substrate 1 is an N-type electrode. In other optional embodiments, the second ohmic contact electrode 8 may be disposed on the back side of the N-type silicon substrate 1.

[0032] In this embodiment, the second mesa is formed by the intrinsic germanium epitaxial layer 3, the charge layer 6 and the shielding ring 5 through a first etching, and the first mesa is formed by the P-type germanium epitaxial layer 4 through a second etching.

[0033] For example, the second mesa has a diameter of 50 μm, the first mesa has a diameter of 30 μm, and the horizontal distance between the P-type germanium mesa and the shielding ring 5 is 5 μm to ensure no overlap in the vertical direction.

[0034] In an optional embodiment, the multi-mesh silicon-germanium SPAD photodetector with shielding ring further includes a passivation layer 9, which covers the surface of the mesh structure; the material of the passivation layer 9 is one or more combinations of SiO2, Al2O3, and SiN, and the thickness is 10-500 nm.

[0035] In this embodiment, the multi-mesa shielded ring silicon-germanium SPAD photodetector effectively reduces the electric field intensity at the mesa edge through the shielding ring 5, thereby reducing sidewall tunneling current and generation-recombination current caused by etching defects. Furthermore, by performing secondary mesa etching on the P-type germanium epitaxial layer 4 to form an independent first mesa that does not overlap with the shielding ring 5 in the vertical direction, the additional electric field concentration region below the shielding ring 5 is eliminated, ensuring that the maximum electric field peak is precisely located below the charge layer 6.

[0036] Secondly, embodiments of the present invention provide a method for fabricating multiple silicon-germanium SPAD photodetectors with shielding rings, applicable to the fabrication of the multiple silicon-germanium SPAD photodetectors with shielding rings provided in the first aspect.

[0037] Please see Figure 2 , Figure 2 This is a flowchart illustrating a method for fabricating multiple silicon-germanium SPAD photodetectors with shielding rings, as provided in an embodiment of the present invention. Figure 2 As shown, the fabrication method of multiple silicon-germanium SPAD photodetectors with shielding rings in this embodiment includes the following steps: Step 1: Provide an N-type silicon substrate.

[0038] Specifically, an N-type silicon wafer with a resistivity ≤0.005 Ω·cm and a thickness of 400μm was selected and subjected to standard RCA cleaning to remove surface organic contaminants and metal ions.

[0039] Step 2: Epitaxially grow an intrinsic silicon epitaxial layer on an N-type silicon substrate.

[0040] Specifically, an intrinsic silicon layer with a thickness of 1 μm is epitaxially grown on an N-type silicon substrate using ultra-high vacuum chemical vapor deposition (UHV-CVD) or atmospheric pressure chemical vapor deposition (APCVD).

[0041] Step 3: A shielding ring and a charge layer are formed on the upper surface of the intrinsic silicon epitaxial layer through photolithography and implantation processes. The shielding ring is disposed around the outer periphery of the charge layer.

[0042] Specifically, the patterns of the shielding ring and charge layer are defined using photolithography. Boron ions (B2O3) are implanted using an ion implanter. + Following this, rapid thermal annealing activates the doped atoms, forming a shielding ring and a charge layer. The doping concentration of the shielding ring is 1×10⁻⁶. 19 cm -3 The doping concentration of charge layer 6 is 1×10⁶. 17 cm -3 The distance between the shielding ring and the overall boundary of the silicon-germanium SPAD photodetector is 30% of the inner diameter of the shielding ring.

[0043] Step 4: Sequentially grow an intrinsic germanium epitaxial layer and a P-type germanium epitaxial layer.

[0044] After implantation and annealing, an intrinsic germanium epitaxial layer and a p-type germanium epitaxial layer were sequentially grown epitaxially. The intrinsic germanium epitaxial layer had a thickness of 0.8 μm, and the p-type germanium epitaxial layer was achieved by in-situ doping with B₂H₆ at a doping concentration of 1 × 10⁻⁶. 19 cm -3 Thickness 50nm.

[0045] Step 5: Define and form the second mesa of the entire germanium material region through the first photolithography and etching process; Specifically, photoresist is spin-coated, and exposure and development define the entire area of ​​germanium material (second mesa, 50 μm in diameter). Inductively coupled plasma (ICP) etching is used, with the etching depth penetrating the intrinsic germanium epitaxial layer and part of the intrinsic silicon epitaxial layer (approximately 0.5 μm) to form the second mesa. The photoresist is then removed.

[0046] Step 6: The P-type germanium epitaxial layer is etched to form the first mesa by a second photolithography and etching process.

[0047] The horizontal projection of the first platform is located within the horizontal projection of the second platform; the first platform does not overlap with the area of ​​the shielding ring in the vertical direction.

[0048] Specifically, photoresist is spin-coated again, and exposure and development are performed to define the P-type germanium mesa region (first mesa, 30 μm in diameter), ensuring its horizontal projection lies within the second mesa and does not overlap with the shielding ring in the vertical direction. The P-type germanium epitaxial layer can be etched using a gentle dry etching method (such as RIE, SF6 / CHF3 gas), stopping at the surface of the intrinsic germanium epitaxial layer. The photoresist is then removed.

[0049] Step 7: Deposit a passivation layer on the device surface.

[0050] Specifically, plasma-enhanced chemical vapor deposition (PECVD) can be used to deposit SiO2 on the device surface with a thickness of 200 nm to cover all mesa sidewalls and top, passivating surface defects.

[0051] Step 8: Define the P-type contact area and N-type contact area by photolithography, and etch away the passivation layer in the corresponding area.

[0052] Specifically, photolithography defines P-type contact regions (located on top of the first mesa) and N-type contact regions (located on the back or front of the substrate). Wet etching with buffered hydrofluoric acid (BHF) solution removes SiO2 from the corresponding regions, forming contact holes.

[0053] Step 9: Deposit metal in the P-type contact region and the N-type contact region to form the first ohmic contact electrode and the second ohmic contact electrode.

[0054] Specifically, without removing the photoresist, a metal layer is directly deposited using electron beam evaporation or magnetron sputtering: first, a Ti / Au stacked metal is deposited as a P-type electrode, and Al is deposited on the back side of the substrate as an N-type electrode. Subsequently, the photoresist and the metal on it are removed through a lift-off process to form a patterned electrode. Finally, alloying is performed to form a good ohmic contact.

[0055] The fabrication method of the multi-mesa silicon-germanium SPAD photodetector with shielding ring in this embodiment achieves vertical misalignment between the P-type germanium mesa and the shielding ring through two photolithography-etching processes, avoiding the electric field concentration below the shielding ring caused by photolithography alignment errors in traditional processes. Simultaneously, the use of a "no-resist direct metal deposition" stripping process simplifies the procedure and reduces photoresist residue contamination of the contact interface.

[0056] For details regarding the fabrication method of the multiple surface-shielded ring silicon-germanium SPAD photodetectors and their corresponding beneficial effects, please refer to the relevant content on the multiple surface-shielded ring silicon-germanium SPAD photodetectors provided in the first aspect; it will not be repeated here.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0058] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0059] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A multi-unit silicon-germanium SPAD photodetector with shielding rings on its surface, characterized in that, include: The N-type silicon substrate, intrinsic silicon epitaxial layer, intrinsic germanium epitaxial layer, and P-type germanium epitaxial layer are arranged sequentially from bottom to top. The upper surface of the intrinsic silicon epitaxial layer is formed with a shielding ring and a charge layer by photolithography and implantation processes, and the shielding ring is disposed around the outer periphery of the charge layer. A first ohmic contact electrode is disposed on the upper surface of the P-type germanium epitaxial layer, and a second ohmic contact electrode is disposed on the N-type silicon substrate. The silicon-germanium SPAD photodetector includes at least two mesa structures, with the P-type germanium epitaxial layer forming the first mesa and the intrinsic germanium epitaxial layer, the charge layer, and the shielding ring forming the second mesa. The horizontal projection of the first platform lies within the horizontal projection of the second platform; the first platform does not overlap with the area of ​​the shielding ring in the vertical direction.

2. The multi-shielded silicon-germanium SPAD photodetector according to claim 1, characterized in that, Both the shielding ring and the charge layer are P-type doped, and the doping concentration of the shielding ring is 1×10⁻⁶. 18 cm -3 -5×10 19 cm -3 The doping concentration of the charge layer is 1×10⁻⁶. 16 cm -3 -1×10 19 cm -3 .

3. The multi-shielded silicon-germanium SPAD photodetector according to claim 1, characterized in that, The thickness of the intrinsic silicon epitaxial layer is 0.1-2 μm, and the thickness of the intrinsic germanium epitaxial layer is 0.1-2 μm.

4. The multi-shielded silicon-germanium SPAD photodetector according to claim 1, characterized in that, The doping concentration of the p-type germanium epitaxial layer is 5 × 10⁻⁶. 18 cm -3 -5×10 19 cm -3 The thickness is 10-200nm.

5. The multi-shielded silicon-germanium SPAD photodetector according to claim 1, characterized in that, The distance between the shielding ring and the overall boundary of the silicon-germanium SPAD photodetector is 1%-50% of the inner diameter of the shielding ring.

6. The multi-shielded silicon-germanium SPAD photodetector according to claim 1, characterized in that, The resistivity of the N-type silicon substrate does not exceed 0.005 Ω·cm, and the thickness is 300-500μm.

7. The multi-shielded silicon-germanium SPAD photodetector according to claim 1, characterized in that, It also includes a passivation layer, which covers the surface of the mesa structure; the material of the passivation layer is one or more combinations of SiO2, Al2O3, and SiN, and the thickness is 10-500 nm.

8. The multi-shielded silicon-germanium SPAD photodetector according to claim 1, characterized in that, The P-type germanium epitaxial layer is formed by epitaxial growth or ion implantation, with the ion implantation depth being 100-200 nm.

9. A method for fabricating multiple silicon-germanium SPAD photodetectors with shielding rings on their surfaces, characterized in that, The method for preparing multiple silicon-germanium SPAD photodetectors with shielding rings as described in any one of claims 1-8 includes the following steps: Provide N-type silicon substrates; An intrinsic silicon epitaxial layer is epitaxially grown on the N-type silicon substrate; A shielding ring and a charge layer are formed on the upper surface of the intrinsic silicon epitaxial layer by photolithography and implantation processes, wherein the shielding ring surrounds the outer periphery of the charge layer. Intrinsic germanium epitaxial layer and P-type germanium epitaxial layer are grown sequentially; The second mesa of the entire germanium material region is defined and formed through the first photolithography and etching process. The P-type germanium epitaxial layer is etched into a mesa by a second photolithography and etching process to form a first mesa, wherein the horizontal projection of the first mesa is located within the horizontal projection of the second mesa; the first mesa does not overlap with the area of ​​the shielding ring in the vertical direction. Deposit a passivation layer on the device surface; Photolithography defines P-type and N-type contact regions, and etching removes the passivation layer in the corresponding regions; Metal is deposited in the P-type contact region and the N-type contact region to form a first ohmic contact electrode and a second ohmic contact electrode.

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