A photoelectric detector and a preparation method thereof

Abstract

This invention discloses a photodetector and its fabrication method. The photodetector includes: a substrate; a first groove formed on the substrate; a first conductivity type doped region and a second conductivity type doped region, spaced apart on one side of the substrate; the first and second conductivity type doped regions are respectively formed within the substrate on both sides of the first groove; a wavelength extension region located within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the upper limit of the infrared wavelength of the photodetector's response; a first electrode and a second electrode, the first electrode being located on the side of the first conductivity type doped region away from the substrate and in contact with the first conductivity type doped region; the second electrode being located on the side of the second conductivity type doped region away from the substrate and in contact with the second conductivity type doped region. This invention can extend the response wavelength of the device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a photodetector and its fabrication method. Background Technology

[0002] In traditional short-wave infrared (SWIR) photodetectors, germanium (Ge) material, with its band gap of approximately 0.66 eV, can achieve detection in the 0.9 μm-1.7 μm wavelength range when used as the absorption layer. Furthermore, the process is mature and compatible with silicon-based complementary metal-oxide-semiconductor (CMOS), making it advantageous for low-cost, high-integration applications. However, the upper limit of the wavelength response of photodetectors using germanium as the absorption layer is limited, making it difficult to cover the longer-wavelength SWIR region, thus restricting the application of these devices in longer-wavelength imaging and spectral analysis. Summary of the Invention

[0003] This invention provides a photodetector and its fabrication method to solve the problem of limited wavelength response limits in current photodetectors.

[0004] In a first aspect, the present invention provides a photodetector, the photodetector comprising: Substrate; the substrate has a first groove; the bandgap of the substrate on the side with the first groove is less than or equal to the bandgap of germanium; A first conductivity type doped region and a second conductivity type doped region are located on one side of the substrate, separated by a gap; the first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of a first groove, the first groove is spaced apart from the first conductivity type doped region, and the first groove is spaced apart from the second conductivity type doped region; the first conductivity type and the second conductivity type are different. The wavelength extension region is located within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the upper limit of the wavelength of the infrared light responded by the photodetector. The first electrode is located on the side of the first conductivity type doped region away from the substrate and is in contact with the first conductivity type doped region; the second electrode is located on the side of the second conductivity type doped region away from the substrate and is in contact with the second conductivity type doped region.

[0005] Optionally, the substrate includes a germanium substrate or a germanium-on-insulator substrate; The germanium substrate on an insulator includes a silicon substrate layer, an insulating substrate layer, and a germanium substrate layer. The insulating substrate layer is located on one side of the silicon substrate layer, and the germanium substrate layer is located on the side of the insulating substrate layer away from the silicon substrate layer. The germanium substrate layer has a first groove.

[0006] Optionally, the first conductivity type doped region includes a first conductivity type germanium doped region; the second conductivity type doped region includes a second conductivity type germanium doped region. The doping concentration of the first conductivity type doped region is 10. 17 cm -3 -10 19 cm -3 The doping concentration of the second conductivity type doped region is 10. 17 cm -3 -10 19 cm -3 .

[0007] Optionally, the thickness of the germanium substrate layer ranges from 500nm to 1000nm; the depth of the first groove ranges from 200nm to 500nm; and the width of the first groove ranges from 1um to 5um.

[0008] Optionally, the wavelength extension region also includes the same elements as the substrate material on the side where the first groove is located.

[0009] Optionally, the wavelength extension region includes a germanium-tin wavelength extension region and / or a germanium-lead wavelength extension region; wherein the tin element in the germanium-tin wavelength extension region is used as a bandgap element, and the lead element in the germanium-lead wavelength extension region is used as a bandgap element. Tin has an atomic percentage of 5%-20%, and lead has an atomic percentage of 5%-20%.

[0010] Optionally, the photodetector further includes: a passivation layer; The passivation layer is located on one side of the substrate, and also on the side of the first conductivity type doped region, the second conductivity type doped region, and the wavelength extension region away from the substrate; along the direction parallel to the substrate, the passivation layer is provided with a first through-slot and a second through-slot at intervals on both sides, the vertical projection of the first through-slot on the substrate is located within the vertical projection of the first conductivity type doped region on the substrate, and the vertical projection of the second through-slot on the substrate is located within the vertical projection of the second conductivity type doped region on the substrate. The first electrode is located on the side of the passivation layer corresponding to the first conductivity type doped region away from the substrate and is located in the first through-groove; the second electrode is located on the side of the passivation layer corresponding to the second conductivity type doped region away from the substrate and is located in the second through-groove.

[0011] Secondly, the present invention provides a method for fabricating a photodetector, the method comprising: A substrate is provided; the substrate has a first groove; the bandgap width of the substrate on the side with the first groove is less than or equal to the bandgap width of germanium; A wavelength extension region is formed within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the wavelength range of the infrared light responded by the photodetector. A first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate. The first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of the first groove. The first groove is spaced apart from the first conductivity type doped region and the second conductivity type doped region is spaced apart. The first conductivity type and the second conductivity type are different. A first electrode is formed on the side of the first conductivity type doped region away from the substrate; the first electrode is in contact with the first conductivity type doped region; A second electrode is formed on the side of the second conductivity type doped region away from the substrate; the second electrode is in contact with the second conductivity type doped region.

[0012] Optionally, a substrate is provided, comprising: Germanium substrates are provided; The first groove is formed by etching a germanium substrate using photolithography and etching processes; Alternatively, a substrate may be provided, including: A germanium-on-insulator substrate is provided; the germanium-on-insulator substrate includes a silicon substrate layer, an insulating substrate layer and a germanium substrate layer, wherein the insulating substrate layer is located on one side of the silicon substrate layer and the germanium substrate layer is located on the side of the insulating substrate layer away from the silicon substrate layer; The first groove is formed by etching the germanium substrate using photolithography and etching processes.

[0013] Optionally, a wavelength extension region is formed within the first groove, including: A wavelength extension region is formed in the first groove using molecular beam epitaxy and / or chemical vapor deposition processes; the wavelength extension region includes a germanium-tin wavelength extension region and / or a germanium-lead wavelength extension region; wherein the tin element in the germanium-tin wavelength extension region is used as a bandgap element, and the lead element in the germanium-lead wavelength extension region is used as a bandgap element.

[0014] Optionally, a first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate, including: The germanium substrates on both sides of the first groove are doped using ion implantation and / or solid-state diffusion processes to form a first conductivity type germanium doped region and a second conductivity type germanium doped region. Alternatively, ion implantation and / or solid-state diffusion processes can be used to dope the germanium substrate layers on both sides of the first groove to form a first conductivity type germanium doped region and a second conductivity type germanium doped region. Alternatively, the second groove can be formed by etching the germanium substrate on both sides of the first groove using photolithography and etching processes; Using epitaxial doping technology, a first conductivity type germanium doped region and a second conductivity type germanium doped region are formed in the two second grooves, respectively; Alternatively, the second groove can be formed by etching the germanium substrate layer on both sides of the first groove using photolithography and etching processes; Using epitaxial doping technology, germanium doped regions of the first conductivity type and germanium doped regions of the second conductivity type are formed in the two second grooves, respectively.

[0015] Optionally, after forming a first conductivity type doped region and a second conductivity type doped region at intervals on one side of the substrate, the method further includes: A passivation layer is formed on one side of the substrate, and on the side of the first conductivity type doped region, the second conductivity type doped region, and the wavelength extension region away from the substrate; along a direction parallel to the substrate, a first through-groove and a second through-groove are provided on both sides of the passivation layer at intervals, the vertical projection of the first through-groove onto the substrate is located within the vertical projection of the first conductivity type doped region onto the substrate, and the vertical projection of the second through-groove onto the substrate is located within the vertical projection of the second conductivity type doped region onto the substrate. A first electrode is formed on the side of the first conductivity type doped region away from the substrate, including: A first electrode is formed on the side of the passivation layer away from the substrate corresponding to the doped region of the first conductivity type, and in the first through-hole. A second electrode is formed on the side of the second conductivity type doped region away from the substrate, including: A second electrode is formed on the side of the passivation layer away from the substrate corresponding to the doped region of the second conductivity type, and within the second through-hole.

[0016] In this embodiment, the first conductivity type doped region, the second conductivity type doped region, the substrate between the first conductivity type doped region and the second conductivity type doped region, and the wavelength extension region can form a PIN structure. Region I adopts a composite structure of the substrate between the first conductivity type doped region and the second conductivity type doped region and the wavelength extension region. By utilizing the tunable bandgap characteristics of the bandgap control elements in the wavelength extension region, the cutoff wavelength of the photodetector response can be effectively extended by adjusting the content ratio of the bandgap control elements, thereby effectively improving the applicability of the SWIR photodetector in long-wavelength imaging, spectral analysis, and night vision surveillance.

[0017] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1This is a schematic diagram of the structure of a photodetector provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another photodetector provided in an embodiment of the present invention; Figure 3 This is a flowchart of a method for fabricating a photodetector provided in an embodiment of the present invention; Figures 4-6 This is a schematic diagram of some steps in the fabrication method of a photodetector provided in an embodiment of the present invention; Figure 7 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention; Figures 8-9 This is a schematic diagram of some steps in another method for fabricating a photodetector provided in an embodiment of the present invention. Figure 10 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention; Figure 11 This is a schematic diagram of some steps in a method for fabricating a photodetector provided in an embodiment of the present invention. Figure 12 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention; Figure 13 This is a schematic diagram of some steps in a method for fabricating a photodetector provided in an embodiment of the present invention. Figure 14 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] Figure 1 This is a schematic diagram of the structure of a photodetector provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the photodetector includes: a substrate 1; the substrate 1 has a first groove 10. The bandgap of the substrate 1 on the side with the first groove 10 is less than or equal to the bandgap of germanium. A first conductivity type doped region 21 and a second conductivity type doped region 22 are spaced apart on one side of the substrate 1, and are respectively formed in the substrate 1 on both sides of the first groove 10. The first groove 10 is spaced apart from the first conductivity type doped region 21, and the first groove 10 is spaced apart from the second conductivity type doped region 22; the first conductivity type and the second conductivity type are different. A wavelength extension region 3 is located in the first groove 10. The wavelength extension region 3 includes bandgap control elements, the content of which is related to the upper limit of the wavelength of the infrared light responded by the photodetector. A first electrode 41 and a second electrode 42 are also included. The first electrode 41 is located on the side of the first conductivity type doped region 21 away from the substrate 1, and is in contact with the first conductivity type doped region 21. The second electrode 42 is located on the side of the second conductivity type doped region 22 away from the substrate 1, and the second electrode 42 is in contact with the second conductivity type doped region 22.

[0023] Specifically, the photodetector may include a substrate 1, which may be a single-layer substrate made of a single material. For example, substrate 1 may include a germanium substrate. Substrate 1 may also be a multilayer substrate formed by bonding two or more different materials through a specific process. For example, substrate 1 may include a germanium-on-insulator (GOI) substrate. A first groove 10 is provided on one side of substrate 1. The side of substrate 1 with the first groove 10 may be an intrinsic semiconductor layer. The side of substrate 1 with the first groove 10 may serve as an absorption layer, absorbing photons when the photodetector is operating. For example, the material of the side of substrate 1 with the first groove 10 may include germanium. Germanium, as an absorption layer, can respond to infrared light with a wavelength range of approximately 0.9µm-1.7µm.

[0024] The photodetector may further include a first conductivity type doped region 21 and a second conductivity type doped region 22. The conductivity type of the first conductivity type doped region 21 may include N-type or P-type, and the doping type of the second conductivity type doped region 22 may include P-type or N-type. When the doping type of the first conductivity type doped region 21 is N-type, the doping type of the second conductivity type doped region 22 is P-type; when the doping type of the first conductivity type doped region 21 is P-type, the doping type of the second conductivity type doped region 22 is N-type.

[0025] The first conductivity type doped region 21 and the second conductivity type doped region 22 can be disposed at intervals on one side of the substrate 1, and the first conductivity type doped region 21 and the second conductivity type doped region 22 can be formed within the substrate 1. For example, selective doping treatment can be performed on the substrate 1 on both sides of the first groove 10 using processes such as photolithography to prepare the first conductivity type doped region 21 and the second conductivity type doped region 22.

[0026] The photodetector may further include a wavelength extension region 3, which may be disposed within the first groove 10. The wavelength extension region 3 may include an intrinsic semiconductor compound, and the semiconductor compound may include a bandgap element. A bandgap element is an element that can adjust the band gap of the semiconductor compound, thereby extending the infrared response wavelength of the photodetector. The band gap of the semiconductor compound is related to the content ratio of the bandgap element. For example, the bandgap element may include tin (Sn). In this embodiment of the invention, the upper limit of the infrared wavelength of the photodetector response can be adjusted by regulating the content ratio of the bandgap element in the semiconductor compound.

[0027] The first conductivity type doped region 21, the second conductivity type doped region 22, the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 can constitute a PIN structure. The I region includes the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3. For example, the substrate 1 of the I region can be made of germanium, and the wavelength extension region 3 can include tin. When the photodetector is working, the germanium material in the I region can absorb infrared light with a wavelength range of approximately 0.9µm-1.7µm. By adjusting the tin content in the wavelength extension region 3, the cutoff wavelength of the photodetector's response wavelength can be extended to approximately 3µm. That is, in this embodiment of the invention, the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 are set as the I region of the PIN structure. The content of the bandgap control element in the wavelength extension region 3 is adjustable, allowing the photodetector to respond to infrared light with a wavelength range of approximately 0.9µm-3µm, thus enabling the photodetector to detect shorter-wave infrared light in a longer wavelength band.

[0028] A first electrode 31 may be provided on the side of the first conductivity type doped region 21 away from the substrate 1. The first electrode 31 may be electrically connected to the first conductivity type doped region 21. A second electrode 32 may be provided on the side of the second conductivity type doped region 22 away from the substrate 1. The second electrode 32 may be electrically connected to the second conductivity type doped region 22. When the photodetector is working, the first electrode 31 and the second electrode 32 can be externally connected to a reverse bias voltage. The substrate 1 of region I and the wavelength extension region 3 can absorb short-wave infrared light. Photons penetrate into the interior of the substrate 1 of region I and the wavelength extension region 3, thereby generating electron-hole pairs inside the substrate 1 of region I and the wavelength extension region 3. Under the action of the strong electric field established by the external reverse bias voltage, electrons and holes are pulled towards the N-type doped region and the P-type doped region, respectively. For example, the first conductivity type doped region 21 is P-type doped and the second conductivity type doped region 22 is N-type doped. At this time, electrons are pulled towards the second conductivity type doped region 22 and holes are pulled towards the first conductivity type doped region 21, so that holes and electrons are collected by the first electrode 31 and the second electrode 32, respectively, thereby forming a detectable photocurrent in the external circuit.

[0029] In this embodiment, the first conductivity type doped region 21, the second conductivity type doped region 22, the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 can form a PIN structure. Region I adopts a composite structure of the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22 and the wavelength extension region 3. By utilizing the tunable bandgap characteristics of the bandgap control element in the wavelength extension region 3, the cutoff wavelength of the photodetector response can be effectively extended by adjusting the content ratio of the bandgap control element, thereby effectively improving the applicability of the SWIR photodetector in long-wavelength imaging, spectral analysis, and night vision surveillance.

[0030] In related technologies, to extend the cutoff wavelength of photodetectors, a vertical PIN structure is formed by epitaxially growing germanium-tin (GeSn) on a germanium or silicon substrate. While this design can extend the cutoff wavelength, the thick epitaxial film easily introduces stress and defects, increasing dark current, and the process is complex with poor compatibility with CMOS integration. In contrast, the technical solution of this invention sets the wavelength extension region 3 within the first groove 10 of the substrate 1. The first conductivity type doped region 21, the second conductivity type doped region 22, the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 can form a horizontal PIN structure. This effectively alleviates lattice mismatch and stress concentration problems, reduces defect density, thereby reducing dark current and improving device performance and stability. Simultaneously, the planar design of the horizontal PIN structure facilitates optical coupling and chip-level integration, has good compatibility with CMOS processes, and reduces fabrication difficulty and cost.

[0031] Optionally, based on the above embodiments, Figure 2 This is a schematic diagram of another photodetector provided in an embodiment of the present invention, as shown below. Figure 1 and Figure 2 As shown, substrate 1 includes a germanium substrate or a germanium-on-insulator substrate 20. The germanium-on-insulator substrate 20 includes a silicon substrate layer 11, an insulating substrate layer 12, and a germanium substrate layer 13. The insulating substrate layer 12 is located on one side of the silicon substrate layer 11, and the germanium substrate layer 13 is located on the side of the insulating substrate layer 12 away from the silicon substrate layer 11. The germanium substrate layer 13 is provided with a first groove 10.

[0032] Specifically, the substrate 1 of the photodetector provided in this embodiment of the invention can be a single-layer germanium substrate, or it can be a germanium-on-insulator (GOI) substrate 20. The GOI substrate 20 can include a silicon substrate layer 11, an insulating substrate layer 12, and a germanium substrate layer 13. The insulating substrate layer 12 can include a silicon dioxide substrate layer. The germanium substrate layer 13 in the GOI substrate 20 can serve as an absorption layer. The germanium substrate layer 13 can be provided with a first groove 10. The first conductivity type doped region 21, the second conductivity type doped region 22, the germanium substrate layer 13 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 can form a horizontal PIN structure.

[0033] The substrate 1 of the photodetector provided in this embodiment of the invention may include a germanium-on-insulator substrate 20, which can provide effective electrical and thermal isolation for the device, significantly reduce the parasitic current of the device, improve the signal-to-noise ratio, and provide a basis for high-sensitivity detection.

[0034] Optionally, based on the above embodiments, refer to... Figure 1 and Figure 2 The first conductivity type doped region 21 includes a first conductivity type germanium doped region; the second conductivity type doped region 22 includes a second conductivity type germanium doped region. The doping concentration of the first conductivity type doped region 21 is 10. 17 cm -3 -10 19 cm -3 The doping concentration of the second conductivity type doped region 22 is 10. 17 cm -3 -10 19 cm -3 .

[0035] Specifically, substrate 1 can be a single-layer germanium substrate or a germanium-on-insulator (GOI) substrate 20. The semiconductor material of the first conductivity type doped region 21 and the second conductivity type doped region 22 can both be germanium. For example, selective doping of substrate 1 on both sides of the first groove 10 can be performed using photolithography or other processes to prepare the first conductivity type doped region 21 and the second conductivity type doped region 22. In this embodiment of the invention, both the first conductivity type doped region 21 and the second conductivity type doped region 22 use mature germanium materials. At the same time, substrate 1 can be a single-layer germanium substrate or a germanium-on-insulator (GOI) substrate 20, which takes into account both mature processes and low defect characteristics, ensuring the stability of the device.

[0036] The doping concentration of the first conductivity type doped region 21 and the second conductivity type doped region 22 can be set to 10. 17 cm -3 -10 19 cm -3The first conductivity type doped region 21 and the second conductivity type doped region 22, formed by doping, together with the intermediate substrate 1 and the wavelength extension region 3, constitute the I region, forming a horizontal PIN structure. This ensures effective carrier separation and collection after light incidence, improving photoelectric conversion efficiency. The size, position, and depth design of the first conductivity type doped region 21 and the second conductivity type doped region 22 must take into account device response speed, dark current control, and subsequent metallization processes to achieve the fabrication of a high-performance SWIR detector.

[0037] In some embodiments of the present invention, the doping concentration of the first conductivity type doped region 21 and the second conductivity type doped region 22 can be arbitrarily set, and can be less than 10. 17 cm -3 or greater than 10 19 cm -3 No specific limitations are made here.

[0038] Optionally, based on the above embodiments, refer to... Figure 2 The thickness of the germanium substrate 13 ranges from 500nm to 1000nm. The depth of the first groove 10 ranges from 200nm to 500nm, and the width of the first groove 10 ranges from 1um to 5um.

[0039] Specifically, the substrate 1 of the photodetector provided in this embodiment of the invention can be a germanium-on-insulator (GOI) substrate 20. The germanium substrate layer 13 of the germanium-on-insulator substrate 10 can serve as an absorption layer, and the thickness of the germanium substrate layer 13 can range from 500 nm to 1000 nm. This thickness design balances light absorption efficiency and device structure controllability. Optically, the above thickness ensures that short-wave infrared light is fully absorbed within the germanium absorption layer, thereby improving photoelectric conversion efficiency. In terms of process, the above thickness ensures the mechanical stability and controllability of the wafer during subsequent processing, reducing the risk of breakage or warping. The GOI substrate provides a high-quality insulating substrate layer 12, effectively reducing device parasitic capacitance. Furthermore, the GOI substrate is compatible with CMOS processes, laying the foundation for realizing high-performance, low-dark-current short-wave infrared photodetectors. In some embodiments of the invention, the thickness of the germanium substrate layer 13 can be arbitrarily set according to actual conditions, and can be less than 500 nm or greater than 1000 nm; no specific limitation is made here.

[0040] The depth of the first groove 10 can range from 200 nm to 500 nm, ensuring sufficient growth of the wavelength extension region 3 in region I, while avoiding excessive depth that could lead to excessive lattice stress or difficulties in the subsequent fabrication of the first conductivity type doped region 21 and the second conductivity type doped region 22. The width of the first groove 10 can range from 1 μm to 5 μm to ensure sufficient light incident area and facilitate uniform epitaxial growth and horizontal PIN layout. In some embodiments of the present invention, the depth and width of the first groove 10 can be arbitrarily set according to actual conditions. The depth of the first groove 10 can be less than 200 nm or greater than 500 nm, and the width of the first groove 10 can be less than 1 μm or greater than 5 μm; no specific limitation is made here.

[0041] Optionally, based on the above embodiments, the first groove 10 can adopt a rectangular or trapezoidal cross-section design, and the edge flatness can be controlled within ±10nm to ensure that the sidewalls and bottom surface of the first groove 10 are flat surfaces, thereby reducing epitaxial stress concentration and defect generation. The size design of the first groove 10 needs to ensure that the thickness of the wavelength extension region 3 in region I is within the range of 200nm–500nm, which can effectively absorb longer-wavelength short-wave infrared light (such as extending to about 3μm band) and ensure the stability of the device structure. The processing of the first groove 10 should take into account the mechanical stability of the substrate 1 to avoid warping or breakage, and the design should facilitate the subsequent formation of the first conductivity type doped region 21 and the second conductivity type doped region 22 as well as the integration of the horizontal PIN structure.

[0042] Through the above parameter design, the first groove 10 of this invention can not only define the selective epitaxial region of the wavelength extension region 3 of region I, improving light absorption efficiency and lattice quality, but also ensure the process controllability and CMOS compatibility of the horizontal PIN structure photodetector, thus providing a reliable foundation for the realization of high-performance, low dark current SWIR detectors.

[0043] Optionally, based on the above embodiments, refer to... Figure 1 and Figure 2 The wavelength extension region 3 also includes the same elements as the substrate 1 material on the side where the first groove 10 is provided.

[0044] Specifically, the wavelength extension region 3 may include an intrinsic semiconductor compound, which may include bandgap elements and elements identical to those on the side of the substrate 1 where the first groove 10 is located. For example, the substrate 1 may be a single-layer germanium substrate or a germanium-on-insulator (GOI) substrate 20. The GOI substrate 20 may include a silicon substrate layer 11, an insulating substrate layer 12, and a germanium substrate layer 13. The germanium substrate layer 13 has the first groove 10 located, meaning the material of the substrate 1 on the side where the first groove 10 is located can be germanium. Simultaneously, the bandgap elements may include tin, in which case the wavelength extension region 3 may include a germanium-tin (GeSn) wavelength extension region.

[0045] In this embodiment of the invention, the wavelength extension region 3 containing bandgap elements also includes the same matrix elements as the substrate 1 on the side where the first groove 10 is located. This enables better lattice matching and interface compatibility between the wavelength extension region 3 and the substrate 1, reducing interface defects, lattice mismatch stress, and dislocation density caused by excessive material differences. This effectively reduces the device's dark current and improves carrier collection efficiency. Simultaneously, it facilitates epitaxial growth compatibility, ensures the crystal quality of the wavelength extension region 3, allows for uniform doping of bandgap elements and stable bandgap control, ultimately improving the photodetector's responsivity, detectivity, and operational stability.

[0046] Optionally, based on the above embodiments, refer to... Figure 1 and Figure 2 Wavelength extension region 3 includes the germanium-tin wavelength extension region and / or the germanium-lead wavelength extension region. Tin in the germanium-tin wavelength extension region is used as the bandgap element, and lead in the germanium-lead wavelength extension region is used as the bandgap element. The atomic percentage of tin is 5%-20%, and the atomic percentage of lead is 5%-20%.

[0047] Specifically, the material in wavelength extension region 3 may include germanium-tin semiconductor compounds and / or germanium-lead semiconductor compounds. Tin in the germanium-tin semiconductor compound can act as a bandgap modulator, and lead in the germanium-lead semiconductor compound can act as a bandgap modulator. Tin and lead can reduce the bandgap of the semiconductor alloy, causing a redshift in the light absorption cutoff wavelength, thereby extending the upper limit of the infrared wavelength of the photodetector response. Simultaneously, it can transform the alloy from an indirect bandgap to a direct bandgap, improving light absorption efficiency. For example, the short-wave infrared cutoff wavelength of the photodetector response may be positively correlated with the content ratio of tin and lead.

[0048] In this embodiment of the invention, the atomic percentages of tin and lead can be set to 5%-20%, which can significantly reduce the bandgap of the material and effectively extend the upper limit of the infrared response wavelength of the photodetector. It can also avoid problems such as insignificant wavelength extension due to too low tin or lead content, and lattice mismatch, increased defects, and increased dark current caused by too high tin or lead content. While achieving short-wave infrared detection in a longer wavelength range, it ensures the quality of the material crystal and the optoelectronic performance of the device.

[0049] Optionally, based on the above embodiments, refer to... Figure 1 and Figure 2 The photodetector also includes a passivation layer 5. The passivation layer 5 is located on one side of the substrate 1, and also on the side of the first conductivity type doped region 21, the second conductivity type doped region 22, and the wavelength extension region 3 away from the substrate 1. Along a direction parallel to the substrate 1, a first through-groove 51 and a second through-groove 52 are spaced apart on both sides of the passivation layer 5. The vertical projection of the first through-groove 51 onto the substrate 1 lies within the vertical projection of the first conductivity type doped region 21 onto the substrate 1, and the vertical projection of the second through-groove 52 onto the substrate 1 lies within the vertical projection of the second conductivity type doped region 22 onto the substrate 1. A first electrode 41 is located on the side of the passivation layer 5 corresponding to the first conductivity type doped region 21 away from the substrate 1, and is located within the first through-groove 51. A second electrode 42 is located on the side of the passivation layer 5 corresponding to the second conductivity type doped region 22 away from the substrate 1, and is located within the second through-groove 52.

[0050] Specifically, the photodetector may further include a passivation layer 5, which may cover the substrate 1, the first conductivity type doped region 21, the second conductivity type doped region 22, and the wavelength extension region 3. For example, the passivation layer 5 may include a silicon dioxide passivation layer and / or a silicon nitride passivation layer. The thickness of the passivation layer 5 may be set to 100nm-300nm. In some embodiments of the present invention, the thickness of the passivation layer 5 may be arbitrarily set according to actual conditions, and may be less than 100nm or greater than 300nm; no specific limitation is made here. The passivation layer 5 can protect the device surface, reduce surface recombination centers, reduce dark current, and ensure an unobstructed light incident path.

[0051] The passivation layer 5 corresponding to the first conductivity type doped region 21 can be provided with a first through-groove 51, and the passivation layer 5 corresponding to the second conductivity type doped region 22 can be provided with a second through-groove 52. The first electrode 41 can be located on the side of the passivation layer 5 corresponding to the first conductivity type doped region 21 away from the substrate 1 and is located in the first through-groove 51 to achieve electrical connection with the first conductivity type doped region 21. The second electrode 42 can be located on the side of the passivation layer 5 corresponding to the second conductivity type doped region 22 away from the substrate 1 and is located in the second through-groove 52 to achieve electrical connection with the second conductivity type doped region 22. The materials of the first electrode 41 and the second electrode 42 can include titanium-gold alloy, aluminum and / or nickel-gold alloy, and the thickness can be 100nm-300nm to ensure low contact resistance and reliable conductivity, while not blocking the light incident area.

[0052] This invention provides an innovative solution for constructing a horizontal PIN structure on a GOI substrate. This structure, where region I can be composed of germanium and germanium-tin / germanium-lead materials, and the first conductivity type doped region 21 and the second conductivity type doped region 22 are both made of germanium, achieves a comprehensive technical goal of wavelength extension, low defects, low dark current, high signal-to-noise ratio, and integrable fabrication. Through innovative material selection, structural design, and selective epitaxial processes, this invention specifically addresses the bottlenecks of existing technologies in wavelength response, dark current, lattice defects, and CMOS compatibility, providing a feasible technical route for high-performance, integrable long-wavelength SWIR photodetectors.

[0053] Figure 3 This is a flowchart of a method for fabricating a photodetector according to an embodiment of the present invention. Figures 4-6 This is a schematic diagram of some steps in a method for fabricating a photodetector provided in an embodiment of the present invention, as shown below. Figure 3 As shown, the preparation method includes: S100: Provide a substrate; the substrate is provided with a first groove; the bandgap width of the substrate on the side where the first groove is provided is less than or equal to the bandgap width of germanium.

[0054] Specifically, such as Figure 4As shown, a substrate 1 is first provided. Substrate 1 can be a single-layer substrate made of a single material; for example, substrate 1 may include a germanium substrate. Substrate 1 can also be a multilayer substrate formed by bonding two or more different materials through a specific process; for example, substrate 1 may include a germanium-on-insulator (GOI) substrate. A first groove 10 is provided on one side of substrate 1. The side of substrate 1 with the first groove 10 can be an intrinsic semiconductor layer. The side of substrate 1 with the first groove 10 can serve as an absorption layer, absorbing photons when the photodetector is working. For example, the material of substrate 1 with the first groove 10 can include germanium. Germanium material, as an absorption layer, can respond to infrared light with a wavelength range of approximately 0.9µm-1.7µm.

[0055] S110: A wavelength extension region is formed within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the wavelength range of the infrared light responded by the photodetector.

[0056] Specifically, such as Figure 5 As shown, a wavelength extension region 3 is formed within the first groove 10. The wavelength extension region 3 may include an intrinsic semiconductor compound, which may include a bandgap element. A bandgap element is an element that can adjust the band gap of the semiconductor compound, thereby extending the infrared response wavelength of the photodetector. The band gap of the semiconductor compound is related to the content ratio of the bandgap element. For example, the bandgap element may include tin (Sn). In this embodiment of the invention, the upper limit of the infrared wavelength response of the photodetector can be adjusted by regulating the content ratio of the bandgap element in the semiconductor compound.

[0057] S120: A first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate. The first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of the first groove. The first groove is spaced apart from the first conductivity type doped region and the second conductivity type doped region is spaced apart. The first conductivity type and the second conductivity type are different.

[0058] Specifically, such as Figure 6As shown, a first conductivity type doped region 21 and a second conductivity type doped region 22 are formed in the substrate 1 on both sides of the first groove 10. For example, selective doping of the substrate 1 on both sides of the first groove 10 can be performed using photolithography or other processes to fabricate the first conductivity type doped region 21 and the second conductivity type doped region 22. The conductivity type of the first conductivity type doped region 21 can include N-type or P-type, and the doping type of the second conductivity type doped region 22 can include P-type or N-type. When the doping type of the first conductivity type doped region 21 is N-type, the doping type of the second conductivity type doped region 22 is P-type; when the doping type of the first conductivity type doped region 21 is P-type, the doping type of the second conductivity type doped region 22 is N-type.

[0059] The first conductivity type doped region 21, the second conductivity type doped region 22, the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 can constitute a PIN structure. The I region includes the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3. For example, the substrate 1 of the I region can be made of germanium, and the wavelength extension region 3 can include tin. When the photodetector is working, the germanium material in the I region can absorb infrared light with a wavelength range of approximately 0.9µm-1.7µm. By adjusting the tin content in the wavelength extension region 3, the cutoff wavelength of the photodetector's response wavelength can be extended to approximately 3µm. That is, in this embodiment of the invention, the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 are set as the I region of the PIN structure. The content of the bandgap control element in the wavelength extension region 3 is adjustable, allowing the photodetector to respond to infrared light with a wavelength range of approximately 0.9µm-3µm, thus enabling the photodetector to detect shorter-wave infrared light in a longer wavelength band.

[0060] S130: A first electrode is formed on the side of the first conductivity type doped region away from the substrate; the first electrode is in contact with the first conductivity type doped region.

[0061] Specifically, such as Figure 1 As shown, a first electrode 41 is formed on the side of the first conductivity type doped region 21 away from the substrate 1, and the first electrode 31 can be electrically connected to the first conductivity type doped region 21.

[0062] S140: A second electrode is formed on the side of the second conductivity type doped region away from the substrate; the second electrode is in contact with the second conductivity type doped region.

[0063] Specifically, such as Figure 1 As shown, a second electrode 42 is formed on the side of the second conductivity type doped region 22 away from the substrate 1, and the second electrode 32 can be electrically connected to the second conductivity type doped region 22.

[0064] In this embodiment, the first conductivity type doped region 21, the second conductivity type doped region 22, the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22, and the wavelength extension region 3 can form a PIN structure. Region I adopts a composite structure of the substrate 1 between the first conductivity type doped region 21 and the second conductivity type doped region 22 and the wavelength extension region 3. By utilizing the tunable bandgap characteristics of the bandgap control element in the wavelength extension region 3, the cutoff wavelength of the photodetector response can be effectively extended by adjusting the content ratio of the bandgap control element, thereby effectively improving the applicability of the SWIR photodetector in long-wavelength imaging, spectral analysis, and night vision surveillance.

[0065] Optionally, based on the above embodiments, Figure 7 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention. Figures 8-9 This is a schematic diagram of some steps in another method for fabricating a photodetector provided in this embodiment of the invention, as shown below. Figure 7 As shown, the preparation method includes: S200: Provides a germanium substrate; or, provides a germanium-on-insulator substrate; the germanium-on-insulator substrate includes a silicon substrate layer, an insulating substrate layer and a germanium substrate layer, the insulating substrate layer being located on one side of the silicon substrate layer and the germanium substrate layer being located on the side of the insulating substrate layer away from the silicon substrate layer.

[0066] Specifically, such as Figure 4 and Figure 8 As shown, in fabricating a photodetector, a single-layer germanium substrate can be provided, or a germanium-on-insulator (GOI) substrate 20 can be provided. The GOI substrate 20 may include a silicon substrate layer 11, an insulating substrate layer 12, and a germanium substrate layer 13. The insulating substrate layer 12 may include a silicon dioxide substrate layer. The germanium substrate layer 13 in the GOI substrate 20 can serve as an absorption layer. The substrate 1 of the photodetector provided in this embodiment of the invention may include the germanium-on-insulator substrate 20, which can provide effective electrical and thermal isolation for the device, significantly reduce parasitic current, improve the signal-to-noise ratio, and provide a basis for high-sensitivity detection.

[0067] The thickness of the germanium substrate layer 13 can range from 500nm to 1000nm, a thickness design that balances light absorption efficiency and device structural controllability. Optically, this thickness ensures sufficient absorption of short-wave infrared light within the germanium absorption layer, thereby improving photoelectric conversion efficiency. In terms of process technology, this thickness guarantees the mechanical stability and controllability of the wafer during subsequent processing, reducing the risk of breakage or warpage. The GOI substrate provides a high-quality insulating substrate layer 12, effectively reducing device parasitic capacitance. Furthermore, the GOI substrate is compatible with CMOS processes, laying the foundation for achieving high-performance, low-dark-current short-wave infrared photodetectors.

[0068] S210: Using photolithography and etching processes, the germanium substrate is etched to form the first groove; or, using photolithography and etching processes, the germanium substrate layer is etched to form the first groove.

[0069] Specifically, such as Figure 4 and Figure 9 As shown, after providing a single-layer germanium substrate, a mask layer can be formed on the entire side of the germanium substrate. For example, the mask layer may include silicon oxide, silicon nitride, and / or photoresist, etc. Then, the mask layer is patterned using photolithography or other processes. The patterned mask layer can expose the area corresponding to the first groove 10. Then, the germanium substrate is etched using the mask layer as a mask to form the first groove 10. Alternatively, after providing a GOI substrate, a mask layer can be formed on the entire side of the germanium substrate layer 13 away from the silicon substrate layer 11. For example, the mask layer may include a silicon oxide layer, a silicon nitride layer, and / or a photoresist layer, etc. Then, the mask layer is patterned using photolithography or other processes. The patterned mask layer can expose the area corresponding to the first groove 10. Then, the germanium substrate layer 13 is etched using the mask layer as a mask to form the first groove 10.

[0070] In this embodiment of the invention, a first groove 10 of predetermined shape and size is formed through processes such as photolithography and etching for selective epitaxy of the subsequent wavelength extension region. The first groove 10 defines the boundary of the I-region growth region, which is beneficial for controlling the position and thickness of the wavelength extension region. During the processing of the first groove 10, the surface flatness of the substrate 1 is maintained to ensure lattice matching and epitaxial quality of the subsequent epitaxial layer. This step provides a structural basis for forming the horizontal PIN I-region, and also facilitates the formation of the subsequent first conductivity type doped region and second conductivity type doped region and device integration. The depth of the first groove 10 can be 200nm-500nm, the width can be 1um-5um, and the edge flatness can be ±10nm to control the epitaxial region and improve light absorption efficiency.

[0071] S220: A wavelength extension region is formed within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the wavelength range of the infrared light responded by the photodetector.

[0072] S230: A first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate. The first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of the first groove. The first groove is spaced apart from the first conductivity type doped region and the second conductivity type doped region is spaced apart. The first conductivity type and the second conductivity type are different.

[0073] S240: A first electrode is formed on the side of the first conductivity type doped region away from the substrate; the first electrode is in contact with the first conductivity type doped region.

[0074] S250: A second electrode is formed on the side of the second conductivity type doped region away from the substrate; the second electrode is in contact with the second conductivity type doped region.

[0075] Optionally, based on the above embodiments, Figure 10 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention. Figure 11 This is a schematic diagram of some steps in a method for fabricating a photodetector provided in another embodiment of the present invention, as shown below. Figure 10 As shown, the preparation method includes: S300: Provides a substrate; the substrate has a first groove; the bandgap of the substrate on the side with the first groove is less than or equal to the bandgap of germanium.

[0076] S310: A wavelength extension region is formed in the first groove using molecular beam epitaxy and / or chemical vapor deposition processes; the wavelength extension region includes bandgap elements, the content of which is related to the wavelength range of the infrared light responded by the photodetector; the wavelength extension region includes a germanium-tin wavelength extension region and / or a germanium-lead wavelength extension region; wherein the tin element in the germanium-tin wavelength extension region is used as a bandgap element, and the lead element in the germanium-lead wavelength extension region is used as a bandgap element.

[0077] Specifically, such as Figure 11 As shown, a wavelength extension region 3 is formed within the first groove 10 using molecular beam epitaxy (MBE) and / or chemical vapor deposition (CVD) processes. For example, a mask layer can be first formed on the side of the germanium substrate 13 away from the silicon substrate 11 and across the entire surface of the first groove 10. The mask layer may include a photoresist layer, a silicon oxide layer, and / or a silicon nitride layer, etc. Then, the mask layer is patterned using photolithography or similar processes to remove the mask layer within the first groove 10. The wavelength extension region 3 is then epitaxially formed inside and outside the first groove 10 using the mask layer as a mask; that is, the wavelength extension region 3 is grown through selected area epitaxy.

[0078] In this embodiment of the invention, region I forms a composite absorption layer of substrate 1 and wavelength extension region 3. Utilizing its tunable bandgap characteristics, wavelength extension region 3 can extend the light absorption range of the device from 0.9µm-1.7µm in traditional germanium absorption layers to approximately 3µm, achieving efficient absorption of long-wavelength short-wavelength infrared light. Selective epitaxy ensures that wavelength extension region 3 grows only in the first groove 10 region, reducing lattice defects and stress concentration, and improving device performance. The thickness and bandgap element content of wavelength extension region 3 can be optimized according to design requirements to balance absorption efficiency and device stability. Combined with surrounding first and second conductivity type doped regions, it lays the foundation for the subsequent construction of a horizontal PIN structure photodetector.

[0079] The material in wavelength extension region 3 may include germanium-tin semiconductor compounds and / or germanium-lead semiconductor compounds. Tin in the germanium-tin semiconductor compound can act as a bandgap modulator, and lead in the germanium-lead semiconductor compound can act as a bandgap modulator. Tin and lead can reduce the bandgap of the semiconductor alloy, causing a redshift in the light absorption cutoff wavelength, thereby extending the upper limit of the infrared wavelength of the photodetector response. Simultaneously, it can transform the alloy from an indirect bandgap to a direct bandgap, improving light absorption efficiency. For example, the short-wave infrared cutoff wavelength of the photodetector response can be positively correlated with the content ratio of tin and lead.

[0080] S320: A first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate. The first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of the first groove. The first groove is spaced apart from the first conductivity type doped region and the second conductivity type doped region is spaced apart. The first conductivity type and the second conductivity type are different.

[0081] S330: A first electrode is formed on the side of the first conductivity type doped region away from the substrate; the first electrode is in contact with the first conductivity type doped region.

[0082] S340: A second electrode is formed on the side of the second conductivity type doped region away from the substrate; the second electrode is in contact with the second conductivity type doped region.

[0083] Optionally, based on the above embodiments, Figure 12 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention. Figure 13 This is a schematic diagram of some steps in a method for fabricating a photodetector provided in another embodiment of the present invention, as shown below. Figure 12 As shown, the preparation method includes: S400: Provides a germanium substrate; or, provides a germanium-on-insulator substrate; the germanium-on-insulator substrate includes a silicon substrate layer, an insulating substrate layer and a germanium substrate layer, the insulating substrate layer being located on one side of the silicon substrate layer and the germanium substrate layer being located on the side of the insulating substrate layer away from the silicon substrate layer.

[0084] S410: The first groove is formed by etching the germanium substrate using photolithography and etching processes; or, the first groove is formed by etching the germanium substrate layer using photolithography and etching processes.

[0085] S420: A wavelength extension region is formed within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the wavelength range of the infrared light responded by the photodetector.

[0086] S430: Using ion implantation and / or solid-state diffusion processes, the germanium substrates on both sides of the first groove are doped to form a first conductivity type germanium doped region and a second conductivity type germanium doped region; or, using ion implantation and / or solid-state diffusion processes, the germanium substrate layers on both sides of the first groove are doped to form a first conductivity type germanium doped region and a second conductivity type germanium doped region; or, using photolithography and etching processes, the germanium substrates on both sides of the first groove are etched to form a second groove; using epitaxial doping processes, a first conductivity type germanium doped region and a second conductivity type germanium doped region are formed in the two second grooves respectively; or, using photolithography and etching processes, the germanium substrate layers on both sides of the first groove are etched to form a second groove; using epitaxial doping processes, a first conductivity type germanium doped region and a second conductivity type germanium doped region are formed in the two second grooves respectively.

[0087] Specifically, such as Figure 6 As shown, substrate 1 may include a single-layer germanium substrate. A mask layer may be formed on one entire side of the germanium substrate. The mask layer may include silicon oxide, silicon nitride, and / or photoresist, etc. Then, the mask layer is patterned using photolithography or other processes. The patterned mask layer can expose the regions corresponding to the first conductivity type doped region 21 and the second conductivity type doped region 22. Using the mask layer as a mask, ion implantation and / or solid-state diffusion processes can be used to dope the germanium substrate exposed by the mask layer to form the first conductivity type germanium doped region 21 and the second conductivity type germanium doped region 22. Alternatively, using the mask layer as a mask, an etching process can be used to etch the germanium substrate exposed by the mask layer to form second grooves 30. Then, an epitaxial doping process can be used to form the first conductivity type germanium doped region 21 and the second conductivity type germanium doped region 22 in the two second grooves 30, respectively.

[0088] like Figure 13 As shown, substrate 1 may include germanium-on-insulator substrate 20. A mask layer may be formed on the entire side of germanium substrate layer 13 away from silicon substrate layer 11. The mask layer may include silicon oxide, silicon nitride, and / or photoresist, etc. Then, the mask layer is patterned using photolithography or other processes. The patterned mask layer can expose the regions corresponding to the first conductivity type doped region 21 and the second conductivity type doped region 22. Using the mask layer as a mask, ion implantation and / or solid-state diffusion processes can be used to dope the exposed germanium substrate layer 13 to form the first conductivity type germanium doped region 21 and the second conductivity type germanium doped region 22. Alternatively, using the mask layer as a mask, an etching process can be used to etch the exposed germanium substrate layer 13 to form second grooves 30. Then, an epitaxial doping process can be used to form the first conductivity type germanium doped region 21 and the second conductivity type germanium doped region 22 in the two second grooves 30, respectively.

[0089] In this embodiment of the invention, P-type or N-type doping can be sequentially performed on specific regions of the top germanium substrate layer 13 of the GOI substrate on both sides of the formed composite absorption layer to form a first conductivity type doped region 21 and a second conductivity type doped region 22 of a horizontal PIN structure photodetector. Doping methods can employ ion implantation, epitaxial doping, or solid-state diffusion processes, and the doping concentration can be up to 10⁻⁶. 18 cm -3 -10 19 cm -3 Within the specified range, optimization is performed based on device performance requirements. Both the first conductivity type doped region 21 and the second conductivity type doped region 22 utilize germanium material, maintaining the advantages of mature processes and low defect characteristics. The first conductivity type doped region 21 and the second conductivity type doped region 22, together with the intermediate composite I region, constitute a horizontal PIN structure, ensuring effective carrier separation and collection after light incidence, thus improving photoelectric conversion efficiency. The design of the doped region size, location, and depth must consider device response speed, dark current control, and subsequent metallization processes to achieve the fabrication of a high-performance SWIR detector. After this step, the horizontal PIN structure is essentially formed, providing a foundation for subsequent metallization contacts, electrode formation, and device packaging, realizing a short-wavelength infrared photodetector with high sensitivity, long-wavelength response, and low dark current.

[0090] S440: A first electrode is formed on the side of the first conductivity type doped region away from the substrate; the first electrode is in contact with the first conductivity type doped region.

[0091] S450: A second electrode is formed on the side of the second conductivity type doped region away from the substrate; the second electrode is in contact with the second conductivity type doped region.

[0092] Optionally, based on the above embodiments, Figure 14 This is a flowchart of another method for fabricating a photodetector provided in an embodiment of the present invention, as shown below. Figure 14 As shown, the preparation method includes: S500: Provides a substrate; the substrate has a first groove; the bandgap of the substrate on the side with the first groove is less than or equal to the bandgap of germanium.

[0093] S510: A wavelength extension region is formed within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the wavelength range of the infrared light responded by the photodetector.

[0094] S520: A first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate. The first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of the first groove. The first groove is spaced apart from the first conductivity type doped region and the first groove is spaced apart from the second conductivity type doped region. The first conductivity type and the second conductivity type are different.

[0095] S530: A passivation layer is formed on one side of the substrate, and on the side of the first conductivity type doped region, the second conductivity type doped region, and the wavelength extension region away from the substrate; along a direction parallel to the substrate, a first through-groove and a second through-groove are provided on both sides of the passivation layer at intervals, the vertical projection of the first through-groove onto the substrate is located within the vertical projection of the first conductivity type doped region onto the substrate, and the vertical projection of the second through-groove onto the substrate is located within the vertical projection of the second conductivity type doped region onto the substrate.

[0096] Specifically, such as Figure 1 and Figure 2 As shown, a passivation layer 5 is formed on one side of the substrate 1, and on the side of the first conductivity type doped region 21, the second conductivity type doped region 22, and the wavelength extension region 3 away from the substrate 1. For example, the passivation layer 5 may include a silicon dioxide passivation layer and / or a silicon nitride passivation layer. The thickness of the passivation layer 5 can be set to 100nm-300nm. The passivation layer 5 can protect the device surface, reduce surface recombination centers, reduce dark current, and ensure an unobstructed light incident path. The passivation layer 5 corresponding to the first conductivity type doped region 21 may have a first through-groove 51, and the passivation layer 5 corresponding to the second conductivity type doped region 22 may have a second through-groove 52.

[0097] S540: A first electrode is formed on the side of the passivation layer corresponding to the first conductivity type doped region away from the substrate, and a first through-hole is formed therein.

[0098] Specifically, such as Figure 1 and Figure 2 As shown, a first electrode 41 is formed in the passivation layer 5 on the side away from the substrate 1 corresponding to the first conductivity type doped region 21, and in the first through-hole 51.

[0099] S550: A second electrode is formed on the side of the passivation layer away from the substrate corresponding to the doped region of the second conductivity type, and in the second through-hole.

[0100] Specifically, such as Figure 1 and Figure 2 As shown, a second electrode 42 is formed in the passivation layer 5 on the side away from the substrate 1 corresponding to the doped region 22 of the second conductivity type, and in the second through groove 52.

[0101] The materials of the first electrode 41 and the second electrode 42 may include titanium-gold alloy, aluminum and / or nickel-gold alloy, with a thickness of 100nm-300nm, ensuring low contact resistance and reliable conductivity while not obstructing the light incident area. Metal deposition can be performed using electron beam evaporation, sputtering, or CVD methods.

[0102] Through the above steps, the photodetector with a horizontal PIN structure formed in this embodiment of the invention has the following characteristics: the materials of the first conductivity type doped region 21 and the second conductivity type doped region 22 can be germanium, the I region can be a germanium + germanium-tin / germanium-lead composite layer, and the wavelength can be extended to about 3 μm or even longer. The horizontal PIN structure facilitates planar optical coupling and chip-level integration, the GOI substrate provides electrical insulation and CMOS compatibility, and the device achieves high photoelectric conversion efficiency, low dark current, and high signal-to-noise ratio short-wave infrared detection performance.

[0103] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and no limitation is imposed herein.

[0104] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A photodetector, characterized in that, include: Substrate; the substrate is provided with a first groove; the bandgap width of the substrate on the side where the first groove is provided is less than or equal to the bandgap width of germanium; A first conductivity type doped region and a second conductivity type doped region are located on one side of the substrate, spaced apart; the first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of the first groove, the first groove is spaced apart from the first conductivity type doped region, and the first groove is spaced apart from the second conductivity type doped region; the first conductivity type and the second conductivity type are different. A wavelength extension region is located within the first groove; the wavelength extension region includes bandgap control elements, the content of which is related to the upper limit of the wavelength of the infrared light responded to by the photodetector. A first electrode and a second electrode, wherein the first electrode is located on the side of the first conductivity type doped region away from the substrate and is in contact with the first conductivity type doped region; and the second electrode is located on the side of the second conductivity type doped region away from the substrate and is in contact with the second conductivity type doped region.

2. The photodetector according to claim 1, characterized in that, The substrate includes a germanium substrate or a germanium-on-insulator substrate; The germanium substrate on an insulator includes a silicon substrate layer, an insulating substrate layer, and a germanium substrate layer. The insulating substrate layer is located on one side of the silicon substrate layer, and the germanium substrate layer is located on the side of the insulating substrate layer away from the silicon substrate layer. The germanium substrate layer is provided with the first groove.

3. The photodetector according to claim 2, characterized in that, The first conductivity type doped region includes a first conductivity type germanium doped region; the second conductivity type doped region includes a second conductivity type germanium doped region. The doping concentration of the first conductivity type doped region is 10. 17 cm -3 -10 19 cm -3 The doping concentration of the second conductivity type doped region is 10. 17 cm -3 -10 19 cm -3 .

4. The photodetector according to claim 2, characterized in that, The thickness of the germanium substrate layer ranges from 500nm to 1000nm; the depth of the first groove ranges from 200nm to 500nm; and the width of the first groove ranges from 1um to 5um.

5. The photodetector according to claim 1, characterized in that, The wavelength extension region also includes the same elements as the substrate material on the side where the first groove is located.

6. The photodetector according to claim 1, characterized in that, The wavelength extension region includes a germanium-tin wavelength extension region and / or a germanium-lead wavelength extension region; wherein the tin element in the germanium-tin wavelength extension region is used as a bandgap element, and the lead element in the germanium-lead wavelength extension region is used as a bandgap element. The atomic percentage of tin is 5%-20%, and the atomic percentage of lead is 5%-20%.

7. The photodetector according to claim 1, characterized in that, Also includes: passivation layer; The passivation layer is located on one side of the substrate, and also on the side of the first conductivity type doped region, the second conductivity type doped region, and the wavelength extension region away from the substrate; along a direction parallel to the substrate, a first through-slot and a second through-slot are provided at intervals on both sides of the passivation layer, the vertical projection of the first through-slot on the substrate is located within the vertical projection of the first conductivity type doped region on the substrate, and the vertical projection of the second through-slot on the substrate is located within the vertical projection of the second conductivity type doped region on the substrate. The first electrode is located on the side of the passivation layer corresponding to the first conductivity type doped region away from the substrate and is located in the first through-hole; the second electrode is located on the side of the passivation layer corresponding to the second conductivity type doped region away from the substrate and is located in the second through-hole.

8. A method for fabricating a photodetector, characterized in that, include: A substrate is provided; the substrate is provided with a first groove; the bandgap width of the substrate on the side provided with the first groove is less than or equal to the bandgap width of germanium; A wavelength extension region is formed within the first groove; the wavelength extension region includes bandgap elements, the content of which is related to the wavelength range of the infrared light responded to by the photodetector. A first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate. The first conductivity type doped region and the second conductivity type doped region are respectively formed in the substrate on both sides of the first groove. The first groove is spaced apart from the first conductivity type doped region and the second conductivity type doped region is spaced apart. The first conductivity type and the second conductivity type are different. A first electrode is formed on the side of the first conductivity type doped region away from the substrate; the first electrode is in contact with the first conductivity type doped region; A second electrode is formed on the side of the second conductivity type doped region away from the substrate; the second electrode is in contact with the second conductivity type doped region.

9. The method for fabricating a photodetector according to claim 8, characterized in that, Provide a substrate, including: Germanium substrates are provided; The first groove is formed by etching the germanium substrate using photolithography and etching processes; Alternatively, a substrate may be provided, including: A germanium-on-insulator substrate is provided; the germanium-on-insulator substrate includes a silicon substrate layer, an insulating substrate layer and a germanium substrate layer, wherein the insulating substrate layer is located on one side of the silicon substrate layer and the germanium substrate layer is located on the side of the insulating substrate layer away from the silicon substrate layer; The first groove is formed by etching the germanium substrate using photolithography and etching processes.

10. The method for fabricating a photodetector according to claim 8, characterized in that, A wavelength extension region is formed within the first groove, including: The wavelength extension region is formed in the first groove using molecular beam epitaxy and / or chemical vapor deposition processes; the wavelength extension region includes a germanium-tin wavelength extension region and / or a germanium-lead wavelength extension region; wherein the tin element in the germanium-tin wavelength extension region is used as a bandgap element, and the lead element in the germanium-lead wavelength extension region is used as a bandgap element.

11. The method for fabricating a photodetector according to claim 9, characterized in that, A first conductivity type doped region and a second conductivity type doped region are formed at intervals on one side of the substrate, including: The germanium substrates on both sides of the first groove are doped using ion implantation and / or solid-state diffusion processes to form a first conductivity type germanium doped region and a second conductivity type germanium doped region. Alternatively, ion implantation and / or solid-state diffusion processes can be used to dope the germanium substrate layers on both sides of the first groove to form a first conductivity type germanium doped region and a second conductivity type germanium doped region. Alternatively, the germanium substrate on both sides of the first groove can be etched using photolithography and etching processes to form a second groove; Using epitaxial doping technology, a first conductivity type germanium doped region and a second conductivity type germanium doped region are formed in the two second grooves, respectively; Alternatively, the germanium substrate layer on both sides of the first groove can be etched using photolithography and etching processes to form a second groove; Using an epitaxial doping process, a first conductivity type germanium doped region and a second conductivity type germanium doped region are formed in the two second grooves, respectively.

12. The method for fabricating a photodetector according to claim 8, characterized in that, After forming a first conductivity type doped region and a second conductivity type doped region at intervals on one side of the substrate, the method further includes: A passivation layer is formed on one side of the substrate, and on the side of the first conductivity type doped region, the second conductivity type doped region, and the wavelength extension region away from the substrate; along a direction parallel to the substrate, a first through-slot and a second through-slot are provided at intervals on both sides of the passivation layer, the vertical projection of the first through-slot on the substrate is located within the vertical projection of the first conductivity type doped region on the substrate, and the vertical projection of the second through-slot on the substrate is located within the vertical projection of the second conductivity type doped region on the substrate. A first electrode is formed on the side of the first conductivity type doped region away from the substrate, including: The passivation layer corresponding to the first conductivity type doped region is located on the side away from the substrate, and the first electrode is formed in the first through-hole; A second electrode is formed on the side of the second conductivity type doped region away from the substrate, including: The passivation layer corresponding to the doped region of the second conductivity type is located on the side away from the substrate, and the second electrode is formed in the second through-hole.

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