A silicon germanium spad with compensation doping under a shielding ring and a preparation method thereof
By introducing a compensating doping design below the shielding ring in a silicon-based germanium avalanche photodiode, the problem of premature breakdown caused by electric field enhancement is solved, achieving a balance between low dark current and high gain, and improving the detection performance and stability of the device.
Patent Information
- Application Number
- CN202610763868.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-29
- Publication Date
- 2026-08-25
AI Technical Summary
Traditional silicon-based germanium avalanche photodiodes have insufficient detection performance in the 1550nm band, and the enhanced electric field caused by the shielding ring structure leads to premature breakdown and reduced avalanche gain, affecting device stability and detection capability.
The design employs a compensation doping below the shielding ring, which includes a high-concentration P-type doped shielding ring and a low-concentration N-type compensation doped region, forming an effective barrier to block leakage current and balance the electric field distribution, thereby restoring avalanche gain.
It significantly reduces dark current, improves detection sensitivity and operational stability, and retains high gain characteristics, making it suitable for applications such as optical communication and lidar.
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Figure CN122641111A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor optoelectronic device technology, specifically relating to a silicon-based germanium SPAD (Single-Photon Avalanche Diode) with compensating doping below a shielding ring and its preparation method. Background Technology
[0002] In fiber optic communication, the 1550nm band is the core operating band for long-distance trunk communication due to its extremely low transmission loss. Avalanche photodiodes, with their internal gain characteristics, can achieve efficient detection of weak light signals and are core optical receiving devices in applications such as optical communication and lidar. However, traditional silicon-based avalanche photodiodes cannot effectively detect the 1550nm band, while III-V compound semiconductor devices, although having excellent performance, are incompatible with complementary metal-oxide-semiconductor (CMOS) processes and are expensive. Silicon-based germanium materials provide a feasible solution to these contradictions. Germanium can efficiently absorb 1550nm light signals and can be epitaxially grown on silicon substrates, making it compatible with CMOS processes. At the same time, silicon has excellent impact ionization characteristics. Therefore, silicon-based germanium avalanche photodiodes maintain the advantages of high integration and low cost while also possessing good detection performance.
[0003] In existing silicon-based germanium avalanche photodiode technology, to reduce the dark current caused by sidewall defects introduced by etching in mesa-type devices, a dual-mesa structure is proposed. This structure makes the diameter of the germanium absorption region mesa smaller than the diameter of the silicon multiplication region mesa. By spatially separating the germanium and silicon sidewalls, the leakage current problem at the sidewall surface is alleviated, and the edge electric field concentration effect is reduced. Furthermore, by introducing a shielding ring structure into the device, the defective region of the germanium sidewall is effectively isolated, preventing high electric fields from penetrating to the sidewall surface and significantly reducing the device's dark current.
[0004] However, while the double-mesa structure helps reduce leakage current, surface defects caused by etching cannot be completely eliminated, and sidewall surface recombination current remains an important component of dark current. Introducing a shielding ring can effectively suppress sidewall leakage current, but because the shielding ring uses a high concentration of P-type doping, the PN junction formed between it and the underlying N-type silicon substrate significantly enhances the electric field below the shielding ring. This causes premature avalanche breakdown in this region below the design breakdown voltage, resulting in a substantial reduction in device avalanche gain, weakening weak light amplification capabilities, shortening the linear avalanche operating region, and deteriorating operational stability. Summary of the Invention
[0005] To address the aforementioned problems in the prior art, this invention provides a silicon-based germanium SPAD with compensating doping below a shielding ring. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a silicon-based germanium SPAD with compensating doping below a shielding ring, comprising: The layers arranged from bottom to top are: an N-type doped silicon substrate, an intrinsic silicon layer, a P-type doped silicon layer, an intrinsic germanium layer, and a P-type doped germanium layer. A shielding ring is disposed around the outer periphery of the P-type doped silicon layer. The shielding ring is a P-type doped silicon ring, and the doping concentration of the shielding ring is higher than the doping concentration of the P-type doped silicon layer. An N-type doped region is disposed on the back side of the N-type doped silicon substrate; An anode electrode is disposed on the P-type doped germanium layer and forms an ohmic contact with it; A cathode electrode is disposed on the back side of the N-type doped region and forms an ohmic contact with it; The silicon-based germanium SPAD has a single mesa structure, wherein the mesa edges of the intrinsic silicon layer, the P-type doped silicon layer, the intrinsic germanium layer, and the P-type doped germanium layer are flush. A compensation doping region is provided in the region directly below the shielding ring in the N-type doped silicon substrate. The compensation doping region is an N-type doped region, and the doping concentration of the compensation doping region is lower than the doping concentration of the N-type doped silicon substrate.
[0006] In one embodiment of the present invention, the doping concentration of the P-type doped silicon layer is 1×10⁻⁶. 16 cm -3 -1×10 17 cm -3 The doping concentration of the shielding ring is 1×10⁻⁶. 18 cm -3 -1×10 19 cm -3 .
[0007] In one embodiment of the present invention, the doping concentration of the compensation doped region is 1×10⁻⁶. 18 cm -3 -1×10 20 cm -3 The depth of the compensation doped region is greater than or equal to the junction depth of the shielding ring.
[0008] In one embodiment of the present invention, the horizontal projected area of the compensation doping region is greater than or equal to the horizontal projected area of the shielding ring.
[0009] In one embodiment of the present invention, the depth of the compensation doped region is 100-300 nm and the width is 50-200 μm.
[0010] In one embodiment of the present invention, a silicon-germanium alloy transition layer is provided between the intrinsic germanium layer and the p-type doped germanium layer.
[0011] In one embodiment of the present invention, the upper surface of the shielding ring is flush with the upper surface of the P-type doped silicon layer.
[0012] In one embodiment of the present invention, the doping concentration of the N-type doped region is higher than the doping concentration of the N-type doped silicon substrate.
[0013] This invention provides a method for preparing a silicon-based germanium SPAD with compensating doping below a shielding ring, applicable to the silicon-based germanium SPAD with compensating doping below a shielding ring described in any of the above embodiments, comprising the following steps: Provides N-type doped silicon substrates; A compensation doped region is formed in the silicon substrate by ion implantation. The compensation doped region is an N-type doped region and the doping concentration is lower than that of the silicon substrate. An intrinsic silicon layer is epitaxially grown on the silicon substrate as a multiplication layer; A P-type doped silicon layer is formed on the intrinsic silicon layer by ion implantation as a charge layer; A P-type doped shielding ring is formed by ion implantation in the peripheral region of the P-type doped silicon layer, and the doping concentration of the shielding ring is higher than that of the P-type doped silicon layer. An intrinsic germanium layer is epitaxially grown on the P-type doped silicon layer and the shielding ring as an absorption layer; A P-type doped germanium layer is formed on the intrinsic germanium layer by ion implantation or in-situ doping as an anode contact layer; A single mesa structure is formed by dry etching, making the mesa edges of the intrinsic silicon layer, the P-type doped silicon layer, the intrinsic germanium layer, and the P-type doped germanium layer flush. An N-type doped region is formed on the back side of the silicon substrate as a cathode contact region; An anode electrode is formed on the P-type doped germanium layer, and a cathode electrode is formed on the back side of the N-type doped region.
[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The silicon-based germanium SPAD with compensating doping below the shielding ring of the present invention forms an effective potential barrier below the germanium sidewall by setting a high-concentration P-type doped shielding ring, blocking leakage current injected into the active region from the sidewall defect region, significantly reducing the device's dark current and improving detection sensitivity. A compensating doped region is set in the N-type doped silicon substrate directly below the shielding ring, solving the problems of electric field concentration and premature breakdown caused by the introduction of the shielding ring. The compensating doped region reduces the net doping concentration of the N-type region below the shielding ring, widens the depletion layer, effectively balances the electric field enhancement caused by the high-concentration P-type doping of the shielding ring, restores avalanche gain, and significantly widens the linear avalanche operating region, improving the device's operational stability.
[0015] 2. The silicon-based germanium SPAD with compensating doping below the shielding ring of the present invention effectively suppresses dark current and improves weak light detection capability, while perfectly preserving the high gain characteristics of the device and enhancing the weak light amplification capability, making the device have significant advantages in application scenarios such as optical communication and lidar that require high sensitivity and high gain.
[0016] 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
[0017] Figure 1 This is a schematic diagram of a silicon-based germanium SPAD with compensating doping below a shielding ring provided in an embodiment of the present invention; Figure 2 This is a flowchart of a method for preparing a silicon-based germanium SPAD with compensating doping below a shielding ring, provided in an embodiment of the present invention. Figure 3 These are structural simulation diagrams of the control group device in the embodiments of the present invention, wherein the left diagram is a schematic diagram of the structure without shielding ring and without compensation doping, and the right diagram is a schematic diagram of the structure with shielding ring and without compensation doping; Figure 4 This is a structural simulation diagram of the experimental group devices in the embodiments of the present invention; Figure 5 The figures shown are simulation comparison experiment results from embodiments of the present invention.
[0018] Icons: 1-N-type doped silicon substrate; 2-Intrinsic silicon layer; 3-P-type doped silicon layer; 4-Shielding ring; 5-Intrinsic germanium layer; 6-P-type doped germanium layer; 7-N-type doped region; 8-Anode electrode; 9-Cathode electrode; 10-Compensation doped region. Detailed Implementation
[0019] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following, in conjunction with the accompanying drawings and specific embodiments, provides a detailed description of a silicon-based germanium SPAD with compensating doping below a shielding ring and its preparation method according to the present invention.
[0020] 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.
[0021] In a first aspect, embodiments of the present invention provide a silicon-based germanium SPAD with compensating doping below a shielding ring, which aims to solve the problem of difficulty in balancing low dark current and high gain through the synergistic design of the shielding ring and the compensating doping region.
[0022] Please see Figure 1 , Figure 1 This is a schematic diagram of a silicon-based germanium SPAD with compensating doping below a shielding ring, provided in an embodiment of the present invention. Figure 1 As shown, the silicon-based germanium SPAD with compensating doping below the shielding ring in this embodiment includes: an N-type doped silicon substrate 1, an intrinsic silicon layer 2, a P-type doped silicon layer 3, a shielding ring 4, an intrinsic germanium layer 5, a P-type doped germanium layer 6, an N-type doped region 7, an anode electrode 8, and a cathode electrode 9.
[0023] Specifically, the N-type doped silicon substrate 1 serves as the device substrate, and its doping concentration can be selected according to the device's operating voltage requirements, typically lightly or moderately doped. The intrinsic silicon layer 2, acting as a multiplication layer, is disposed on the N-type doped silicon substrate 1. This multiplication layer is the main region where avalanche multiplication occurs, and its thickness and doping concentration have a decisive influence on the device's breakdown voltage and gain characteristics. In this embodiment, the thickness of the multiplication layer is preferably 0.3 μm-2 μm.
[0024] The p-type doped silicon layer 3, serving as a charge layer, is disposed on top of the intrinsic silicon layer 2. This charge layer is used to precisely control the electric field distribution in the absorption and multiplication regions, ensuring that the multiplication region reaches the avalanche critical electric field while the absorption region maintains a low saturation drift electric field. In this embodiment, the doping concentration of the p-type doped silicon layer 3 is preferably 1 × 10⁻⁶. 16 cm -3 -1×10 17 cm -3 A shielding ring 4 is disposed around the outer periphery of the P-type doped silicon layer 3. The shielding ring 4 is a P-type doped silicon ring, and its doping concentration is higher than that of the charge layer. The main function of the shielding ring 4 is to block the leakage current injected into the active region from the germanium sidewall defect region, significantly reducing the dark current of the device. In this embodiment, the doping concentration of the shielding ring 4 is preferably 1×10⁻⁶. 18 cm -3 -1×10 19 cm -3 In this embodiment, the upper surface of the shielding ring 4 is flush with the upper surface of the P-type doped silicon layer 3 to ensure full coverage of the sidewall defect region.
[0025] The intrinsic germanium layer 5, serving as an absorption layer, is disposed above the p-type doped silicon layer 3 and the shielding ring 4. Germanium material exhibits highly efficient absorption of optical signals at a wavelength of 1550 nm, which is crucial for the device to achieve communication band detection. The thickness of the absorption layer is preferably 0.3 μm-2 μm to ensure sufficient light absorption efficiency. As a preferred embodiment, a silicon-germanium alloy transition layer can also be disposed between the intrinsic germanium layer 5 and the p-type doped silicon layer 3 to improve the lattice matching of the heterojunction interface and reduce interface defects.
[0026] The P-type doped germanium layer 6 serves as the anode contact layer, disposed on top of the intrinsic germanium layer 5. This anode contact layer is used to form a good ohmic contact and reduce contact resistance. The N-type doped region 7 serves as the cathode contact region, disposed on the back side of the N-type doped silicon substrate 1. The doping concentration of this cathode contact region is typically higher than that of the N-type doped silicon substrate 1 to ensure low-resistance contact.
[0027] The anode electrode 8 is disposed on the P-type doped germanium layer 6 and forms an ohmic contact with it; the cathode electrode 9 is disposed on the back side of the N-type doped region 7 and forms an ohmic contact with it.
[0028] The silicon-based germanium SPAD of this embodiment has a single mesa structure, wherein the mesa edges of the intrinsic silicon layer 2, the P-type doped silicon layer 3, the intrinsic germanium layer 5, and the P-type doped germanium layer 6 are flush. This single mesa structure simplifies the etching process and effectively suppresses sidewall leakage current through the sidewall protection of the shielding ring 4.
[0029] In this embodiment, a compensation doping region 10 is disposed in the region directly below the shielding ring 4 within the N-type doped silicon substrate 1. The compensation doping region 10 is N-type doped, and its doping concentration is lower than that of the N-type doped silicon substrate 1. The introduction of the compensation doping region 10 aims to balance the additional electric field caused by the high concentration of P-type doping in the shielding ring 4, and suppress premature breakdown below the shielding ring 4. In this embodiment, the preferred doping concentration of the compensation doping region 10 is 1×10⁻⁶. 18 cm -3 -1×10 20 cm -3 Its depth is greater than or equal to the junction depth of the shielding ring 4, and its horizontal projected area is greater than or equal to the horizontal projected area of the shielding ring 4, so as to ensure effective modulation of the electric field below the shielding ring 4.
[0030] Optionally, the depth of the compensation doped region 10 is 100-300 nm and the width is 50-200 μm.
[0031] In an optional embodiment, a silicon-germanium alloy transition layer is provided between the intrinsic germanium layer 5 and the p-type doped germanium layer 6.
[0032] The silicon-based germanium SPAD with compensating doping below the shielding ring in this embodiment of the invention forms an effective barrier below the germanium sidewall by setting a high-concentration P-type doped shielding ring, blocking leakage current injected into the active region from the sidewall defect region, significantly reducing the device's dark current and improving detection sensitivity. Simultaneously, by setting a compensating doped region in the N-type silicon substrate directly below the shielding ring, the problems of electric field concentration and premature breakdown caused by the introduction of the shielding ring are solved. The compensating doped region reduces the net doping concentration of the N-type region below the shielding ring, widens the depletion layer, effectively balances the electric field enhancement caused by the high-concentration P-type doping of the shielding ring, restores avalanche gain, and significantly widens the linear avalanche operating region, improving the device's operational stability.
[0033] Secondly, embodiments of the present invention provide a method for preparing a silicon-based germanium SPAD with compensating doping below a shielding ring, applicable to the silicon-based germanium SPAD with compensating doping below a shielding ring provided in the first aspect.
[0034] Please see Figure 2 , Figure 2 This is a flowchart illustrating a method for preparing a silicon-based germanium SPAD with compensating doping below a shielding ring, as provided in an embodiment of the present invention. Figure 2 As shown, the preparation method of the silicon-based germanium SPAD with compensating doping below the shielding ring in this embodiment includes the following steps: Step 1: Provide an N-type doped silicon substrate. Perform standard cleaning on the silicon substrate to remove surface contaminants.
[0035] Step 2: Form a compensation doped region in the silicon substrate by ion implantation.
[0036] Optionally, a photolithography process is used to define the pattern of the compensation doped region, which is positioned directly below the subsequent shielding ring. N-type ion implantation is then performed, with the implantation dose and energy optimized according to the required doping concentration and depth, forming a compensation doped region with a doping concentration lower than that of the silicon substrate. Annealing activation is then performed after implantation.
[0037] Optionally, the depth of the compensation doped region 10 is 100-300 nm and the width is 50-200 μm.
[0038] Step 3: Epitaxially grow an intrinsic silicon layer on a silicon substrate as a multiplication layer.
[0039] Alternatively, processes such as chemical vapor deposition or molecular beam epitaxy can be used to grow an intrinsic silicon layer with uniform thickness and good crystal quality.
[0040] Step 4: Form a P-type doped silicon layer as a charge layer on the intrinsic silicon layer by ion implantation.
[0041] Specifically, a photolithography process is used to define the charge layer region, and P-type ion implantation is performed to form a charge layer with a specific doping concentration.
[0042] Step 5: Form a P-type doped shielding ring in the peripheral region of the P-type doped silicon layer by ion implantation.
[0043] Specifically, a photolithography process is used to define the shielding ring pattern, and a high dose of P-type ion implantation is performed to form a shielding ring with a doping concentration higher than that of the charge layer.
[0044] Step 6: Epitaxially grow an intrinsic germanium layer as an absorption layer on the P-type doped silicon layer and the shielding ring.
[0045] Considering the lattice mismatch between silicon and germanium, it is preferable to first epitaxially grow a silicon-germanium alloy transition layer, and then epitaxially grow an intrinsic germanium layer to obtain a high-quality heterostructure interface.
[0046] Step 7: Form a P-type doped germanium layer on the intrinsic germanium layer by ion implantation or in-situ doping as the anode contact layer.
[0047] Step 8: Form a single mesa structure by dry etching, making the mesa edges of the intrinsic silicon layer, P-type doped silicon layer, intrinsic germanium layer, and P-type doped germanium layer flush.
[0048] It should be noted that the etching process needs to be precisely controlled to ensure the size of the mesa and the shape of the sidewalls.
[0049] Step 9: Form an N-type doped region on the back side of the silicon substrate as a cathode contact region. Alternatively, highly doped N-type regions can be formed by backside ion implantation or laser annealing.
[0050] Step 10: Form an anode electrode on the P-type doped germanium layer and a cathode electrode on the back side of the N-type doped region.
[0051] Alternatively, a metal layer can be deposited by sputtering or evaporation, and electrode patterns can be formed by photolithography and etching processes, followed by alloying annealing to form a good ohmic contact.
[0052] Furthermore, the performance of the silicon-based germanium SPAD structure with compensating doping below the shielding ring proposed in this invention was verified using Silvaco TCAD simulation software. Three control groups were specifically set up for comparative analysis.
[0053] Control group 1: No shielding ring, no compensation doping structure, i.e., traditional single-mesa silicon-based germanium SPAD.
[0054] Control group 2: Devices with shielding rings but no compensation doping structure, i.e., devices that introduce shielding rings into traditional single-mesa silicon-based germanium SPADs but do not perform compensation doping.
[0055] Experimental group: The silicon-based germanium SPAD with shielding ring and compensation doping proposed in this invention.
[0056] The simulation conditions were set as follows: A 3D device model was created using the Silvaco TCAD simulation tool. The same material parameters, boundary conditions, and temperature conditions were set. A scanning voltage was applied to the anode of the device, and key performance indicators such as dark current, gain, and breakdown voltage were monitored.
[0057] Please see Figure 3 and Figure 4 , Figure 3 The diagram shows a structural simulation of the control group device in this embodiment of the invention. The left diagram shows a structure without a shielding ring and without compensation doping, while the right diagram shows a structure with a shielding ring and without compensation doping. Figure 4 This is a structural simulation diagram of the experimental group devices in the embodiments of the present invention.
[0058] like Figure 4 As shown, the device has a vertical structure, consisting of a Si substrate and a Ge epitaxial layer, with a PIPIN structure from top to bottom. The P on the surface of the Ge layer... + The charge layer is used to eliminate the potential barrier and form an ohmic contact; the intrinsic region in Ge is the main part that absorbs infrared light and has a low electric field; photogenerated electrons enter the highly doped Si charge region and are accelerated under the electric field of the charge region. After reaching the intrinsic Si multiplication region, they undergo collisional ionization under the influence of a strong electric field, thus triggering the avalanche multiplication effect. This structure in which the absorption region and the multiplication region are separated makes photon absorption and multiplication independent, thereby reducing device noise. The introduction of the charge layer can precisely control the electric field of the absorption region and the multiplication region. On the one hand, it makes the electric field of the multiplication region large enough to cause avalanche breakdown; on the other hand, it makes the charge carriers in the absorption region drift at a saturation velocity. The large number of charge carriers generated by avalanche multiplication are absorbed by the N in Si. + The electrodes in the region are collected and drawn out from the surface.
[0059] Understandably, for mesa-type devices, etching processes inevitably cause damage to the etched surface. If immature processes are used for multiple etching operations, the damage may be even greater. Ge has a narrow bandgap, and due to surface defects, its sidewalls are more prone to surface recombination. While Si has a wider bandgap, the Si multiplication layer is where the electric field strength is strongest, making its sidewalls also susceptible to surface recombination. Leakage current from the etched sidewall surfaces is a major component of the dark current in mesa-type APDs. Multiple etching operations introduce greater manufacturing challenges for multi-mesa structures; therefore, using a single etching operation to form a single mesa structure is beneficial for stable and repeatable device performance and for further optimization and development.
[0060] In the SACM structure of the APD, the Si multiplication region needs to reach the avalanche critical electric field (3e5V / cm), while the Ge absorption region only needs to reach the carrier saturation drift electric field (1e4V / cm). The distribution of the electric field will be precisely controlled by the injection concentration of P-Si. Therefore, the shielding ring is designed on the outer ring of P-Si and is P-type doped. To achieve a more ideal surface leakage current suppression effect, the doping concentration is designed to be higher than that of the charge layer (P-Si).
[0061] Because a higher shielding ring concentration will cause the electric field in the absorption-multiplication region to concentrate more in the multiplication region, the intrinsic Si below the shielding ring will reach the avalanche critical field strength earlier than the intrinsic Si in the bulk, resulting in premature breakdown. Therefore, this invention employs selective compensatory doping in the N-Si region below the shielding ring to reduce the doping concentration at the N-end, thereby balancing the high doping caused by the P-end shielding ring, reducing the electric field, and suppressing premature breakdown. Theoretically, a good design can completely avoid premature breakdown caused by the shielding ring. Both in simulation and manufacturing processes, the concentration, depth, and width of the compensatory doping can be optimized to suppress premature breakdown. A reasonable parameter design can completely balance the premature breakdown caused by the shielding ring. To address the suppression of premature breakdown, the parameters of the compensatory doping were optimized using Silvaco TCAD simulation software.
[0062] Please see Figure 5 , Figure 5 These are simulation comparison experimental results from embodiments of the present invention, used to demonstrate the impact of shielding rings and compensating doping on the dark current and gain of the device. Figure 5 As shown, with a shielding ring and without compensating doping, the breakdown voltage is advanced (approximately 19.5V), leading to a decrease in gain. Compensating doping balances the strong field below the shielding ring, causing the Si bulk to break down earlier than the Si below the shielding ring, effectively suppressing the premature breakdown effect (breakdown voltage approximately 23.0V) and preserving high gain. Simultaneously, it widens the linear avalanche region by 3.5V, significantly improving the device's operational stability. This invention innovatively proposes a simpler process involving single-mesa etching, shielding ring implantation, and compensating doping, achieving both low dark current and high gain. Theoretically, it can achieve zero gain loss, completely suppressing the premature breakdown effect caused by the shielding ring, and this has been verified through simulation. Furthermore, the process method of introducing compensating doping into the SiGe system proposed in this invention is groundbreaking and technologically feasible.
[0063] 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.
[0064] 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.
[0065] 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 silicon-based germanium SPAD with compensating doping below a shielding ring, characterized in that, include: The layers arranged from bottom to top are: an N-type doped silicon substrate, an intrinsic silicon layer, a P-type doped silicon layer, an intrinsic germanium layer, and a P-type doped germanium layer. A shielding ring is disposed around the outer periphery of the P-type doped silicon layer. The shielding ring is a P-type doped silicon ring, and the doping concentration of the shielding ring is higher than the doping concentration of the P-type doped silicon layer. An N-type doped region is disposed on the back side of the N-type doped silicon substrate; An anode electrode is disposed on the P-type doped germanium layer and forms an ohmic contact with it; A cathode electrode is disposed on the back side of the N-type doped region and forms an ohmic contact with it; The silicon-based germanium SPAD has a single mesa structure, wherein the mesa edges of the intrinsic silicon layer, the P-type doped silicon layer, the intrinsic germanium layer, and the P-type doped germanium layer are flush. A compensation doping region is provided in the region directly below the shielding ring in the N-type doped silicon substrate. The compensation doping region is an N-type doped region, and the doping concentration of the compensation doping region is lower than the doping concentration of the N-type doped silicon substrate.
2. The silicon-based germanium SPAD with compensating doping below the shielding ring according to claim 1, characterized in that, The doping concentration of the P-type doped silicon layer is 1×10⁻⁶. 16 cm -3 -1×10 17 cm -3 The doping concentration of the shielding ring is 1×10⁻⁶. 18 cm -3 -1×10 19 cm -3 .
3. The silicon-based germanium SPAD with compensating doping below the shielding ring according to claim 1, characterized in that, The doping concentration of the compensation doping region is 1×10⁻⁶. 18 cm -3 -1×10 20 cm -3 The depth of the compensation doped region is greater than or equal to the junction depth of the shielding ring.
4. The silicon-based germanium SPAD with compensating doping below the shielding ring according to claim 1, characterized in that, The horizontal projected area of the compensation doping region is greater than or equal to the horizontal projected area of the shielding ring.
5. The silicon-based germanium SPAD with compensating doping below the shielding ring according to claim 1, characterized in that, The depth of the compensation doped region is 100-300 nm and the width is 50-200 μm.
6. The silicon-based germanium SPAD with compensating doping below the shielding ring according to claim 1, characterized in that, A silicon-germanium alloy transition layer is provided between the intrinsic germanium layer and the p-type doped germanium layer.
7. The silicon-based germanium SPAD with compensating doping below the shielding ring according to claim 1, characterized in that, The upper surface of the shielding ring is flush with the upper surface of the P-type doped silicon layer.
8. The silicon-based germanium SPAD with compensating doping below the shielding ring according to claim 1, characterized in that, The doping concentration of the N-type doped region is higher than that of the N-type doped silicon substrate.
9. A method for preparing a silicon-based germanium SPAD with compensating doping below a shielding ring, characterized in that, The silicon-based germanium SPAD with compensating doping below the shielding ring as described in any one of claims 1-8 comprises the following steps: Provides N-type doped silicon substrates; A compensation doped region is formed in the silicon substrate by ion implantation. The compensation doped region is an N-type doped region and the doping concentration is lower than that of the silicon substrate. An intrinsic silicon layer is epitaxially grown on the silicon substrate as a multiplication layer; A P-type doped silicon layer is formed on the intrinsic silicon layer by ion implantation as a charge layer; A P-type doped shielding ring is formed by ion implantation in the peripheral region of the P-type doped silicon layer, and the doping concentration of the shielding ring is higher than that of the P-type doped silicon layer. An intrinsic germanium layer is epitaxially grown on the P-type doped silicon layer and the shielding ring as an absorption layer; A P-type doped germanium layer is formed on the intrinsic germanium layer by ion implantation or in-situ doping as an anode contact layer; A single mesa structure is formed by dry etching, making the mesa edges of the intrinsic silicon layer, the P-type doped silicon layer, the intrinsic germanium layer, and the P-type doped germanium layer flush. An N-type doped region is formed on the back side of the silicon substrate as a cathode contact region; An anode electrode is formed on the P-type doped germanium layer, and a cathode electrode is formed on the back side of the N-type doped region.