Avalanche photodetector and preparation method thereof

Abstract

The embodiment of the present application provides an avalanche photodetector and a method for preparing the same. The avalanche photodetector includes an avalanche photodiode and an extraction structure. The avalanche photodiode includes a first contact layer, a charge layer, a light absorption layer, and a second contact layer arranged in sequence; the first contact layer and the extraction structure have a first doping type, the charge layer and the light absorption layer have a second doping type, the first doping type is different from the second doping type, and the first contact layer, the charge layer, the light absorption layer, and the second contact layer jointly form a first electric field; the extraction structure is located outside the avalanche photodiode along the second direction, the extraction structure and the light absorption layer jointly form a second electric field, the first direction intersects with the second direction; the first electric field does not contact the second electric field. By introducing the extraction structure outside the electric field region of the original avalanche photodetector, the extraction structure can attract carriers on the outside, reduce the diffusion of carriers into the electric field region to introduce additional diffusion current, and thus reduce device noise.

Description

Technical Field

[0001] The present application relates to the field of photoelectric detection technology, and in particular to an avalanche photoelectric detector and a method for preparing the same. Background Art

[0002] Semiconductor avalanche photodetector is a solid-state photodetector with internal high gain and is widely used in laser radar, unmanned driving, aerospace and other fields.

[0003] Since the measured signal is extremely weak, in order to avoid the signal being submerged, the avalanche photodetector is required to have characteristics such as low noise.

[0004] However, in the above-mentioned avalanche photodetector, carriers outside the photosensitive surface of the device will be collected by the electrode through diffusion or drift motion, introducing noise such as dark current, thereby affecting the detection accuracy of the detector. Summary of the invention

[0005] The embodiment of the present application provides an avalanche photodetector and a method for preparing the same, which reduces device noise by setting an extraction structure to attract carriers outside the electric field region, reduce the diffusion of carriers into the electric field region, and introduce additional diffusion current.

[0006] In a first aspect, an embodiment of the present application provides an avalanche photodetector, comprising an avalanche photodiode and an extraction structure.

[0007] The avalanche photodiode comprises a first contact layer, a charge layer, a light absorption layer and a second contact layer arranged in sequence along a first direction;

[0008] The first contact layer has a first doping type, the charge layer, the light absorption layer and the second contact layer have a second doping type, the first doping type is different from the second doping type, and the first contact layer, the charge layer, the light absorption layer and the second contact layer jointly form a first electric field;

[0009] The extraction structure has the first doping type, the extraction structure is located outside the avalanche photodiode along a second direction, the extraction structure and the light absorption layer jointly form a second electric field, and the first direction intersects the second direction;

[0010] The first electric field does not contact the second electric field.

[0011] In a possible implementation manner, along the second direction, an orthographic projection of the first contact layer on the extraction structure overlaps with the extraction structure.

[0012] In a possible implementation, along the first direction, the bottom end of the extraction structure is lower than, flush with, or higher than the bottom end of the first contact layer, and the top end of the extraction structure is flush with or higher than the top end of the first contact layer.

[0013] In a possible implementation manner, part of the electric lines of force between the first electric field and the second electric field extend along the first direction.

[0014] In a possible implementation, the avalanche photodiode further includes a first electrode and a second electrode, the first electrode is connected to the first contact layer, the second electrode is connected to the second contact layer, and the first electrode and the second electrode are respectively used for electrical connection;

[0015] The extraction structure includes an extraction electrode and an extraction portion, wherein the extraction portion is located outside the first contact layer along the second direction, the extraction electrode is located on a side of the extraction portion away from the second contact layer, and the extraction electrode is connected to the extraction portion.

[0016] In a possible implementation manner, the extraction portion is annular in shape and is located on the outer peripheral side of the first contact layer;

[0017] and / or,

[0018] The avalanche photodiode further includes a protection member, which is in a ring shape, is located between the first contact layer and the extraction portion, is connected to the first contact layer, and has the first doping type.

[0019] In a possible implementation, the avalanche photodiode further includes a first light absorbing layer and an anti-reflection layer, the first light absorbing layer has the second doping type, and the anti-reflection layer is located on a side of the first contact layer away from the second contact layer;

[0020] Along the first direction, the first light absorbing layer is located between the charge layer and the second contact layer.

[0021] In a possible implementation, the avalanche photodiode further includes a second light absorption layer and a passivation layer.

[0022] The second light absorbing layer is located outside the first light absorbing layer, the first light absorbing layer and the second light absorbing layer are an integral piece, and the extraction structure is located on the second light absorbing layer;

[0023] The passivation layer is located on a side of the second light absorbing layer away from the second contact layer.

[0024] The avalanche photodetector provided in the embodiment of the present application can effectively control the carrier transport path by introducing an independent first electric field and a second electric field and ensuring no contact, thereby reducing unnecessary carrier diffusion and drift, thereby reducing dark current and other noise sources and improving the signal-to-noise ratio of the avalanche photodetector.

[0025] The photogenerated carrier multiplication process is more controlled due to the optimized configuration of the electric field. This stable multiplication mechanism helps improve the gain stability of the detector, making it perform consistently under different operating conditions.

[0026] By optimizing the electric field and carrier path, carriers can be collected and multiplied faster, thereby improving the response speed of the avalanche photodetector.

[0027] In a second aspect, an embodiment of the present application provides a method for preparing an avalanche photodetector, comprising:

[0028] providing a substrate;

[0029] A charge layer, an extraction structure, a first contact layer, a light absorption layer and a second contact layer are sequentially formed on the substrate.

[0030] In a possible implementation, when the avalanche photodetector includes a first electrode, a second electrode, an extraction electrode, and an extraction portion, sequentially forming the charge layer, the extraction structure, the first contact layer, the light absorption layer, and the second contact layer on the substrate includes:

[0031] Photolithography and doping second doping ions on the light absorbing layer to form the charge layer;

[0032] Photolithography and doping the first doping ions on the second light absorbing layer to form the extraction portion;

[0033] Photolithography and doping first doping ions on the first light absorbing layer to form the first contact layer;

[0034] Performing photolithography on the first contact layer and the second light absorbing layer to form the first electrode and the extraction electrode respectively;

[0035] Photolithography and doping the second doping ions on the other side of the first light absorbing layer and the second light absorbing layer to form the second contact layer;

[0036] The second electrode is formed on the second contact layer by photolithography to form the avalanche photodetector.

[0037] The method for preparing the avalanche photodetector provided in the embodiment of the present application ensures the uniformity and strength of the electric field through precise photolithography and doping processes, and the formation of each layer and electrode enhances the separation and transport efficiency of photogenerated carriers. The design and position of the extraction part and the extraction electrode can optimize the control of peripheral dark carriers, reduce dark current, and improve the signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the implementation methods in the embodiments of the present application or the related technologies, the following is a brief introduction to the drawings required for use in the embodiments or the related technology descriptions. Obviously, the drawings described below are some embodiments of the present application, and a person skilled in the art can also obtain other drawings based on these drawings.

[0039] Figure 1 A schematic diagram of the first structure of the avalanche photodetector provided in this application;

[0040] Figure 2 A schematic diagram of the first electric field distribution of the avalanche photodetector provided in this application;

[0041] Figure 3 A schematic diagram of the electric field distribution of an avalanche photodetector in the prior art;

[0042] Figure 4 A schematic diagram of the second electric field distribution of the avalanche photodetector provided in this application;

[0043] Figure 5 A schematic diagram of the third electric field distribution of the avalanche photodetector provided in this application;

[0044] Figure 6 A second structural schematic diagram of the avalanche photodetector provided in this application;

[0045] Figure 7 A schematic diagram of a first process of a method for preparing an avalanche photodetector provided in the present application;

[0046] Figure 8 A schematic diagram of a first intermediate structure of an avalanche photodetector provided in this application;

[0047] Fig. 9 A second schematic flow chart of the method for preparing an avalanche photodetector provided in the present application;

[0048] Fig.10 A schematic diagram of a second intermediate structure of the avalanche photodetector provided in this application;

[0049] Fig.11 A schematic diagram of a part of the preparation process of the avalanche photodetector provided in this application;

[0050] Fig.12 A schematic diagram of a third intermediate structure of the avalanche photodetector provided in this application;

[0051] Fig.13 A schematic diagram of a fourth intermediate structure of the avalanche photodetector provided in this application;

[0052] Fig.14 A schematic diagram of the fifth intermediate structure of the avalanche photodetector provided in this application.

[0053] Description of reference numerals:

[0054] 10. Avalanche photodetector; Y, first direction; X, second direction;

[0055] 100, avalanche photodiode; 101, first electric field; 102, second electric field; 103, neutral region;

[0056] 110, first contact layer; 120, charge layer; 140, second contact layer; 150, first electrode; 160, second electrode; 170, protective member; 130, light absorbing layer; 130A, first light absorbing layer; 130B, second light absorbing layer; 180, anti-reflection layer; 190, passivation layer;

[0057] 200, extraction structure; 210, extraction electrode; 220, extraction part;

[0058] 300. Substrate.

[0059] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0060] Dark current is one of the main noises of avalanche photodetectors, which mainly includes diffusion current, generation-recombination current, direct tunneling current, trap-assisted tunneling current and surface leakage current.

[0061] Related technologies can reduce dark current components such as generation-recombination current, direct tunneling current, trap-assisted tunneling current, and surface leakage current by improving material lattice quality, optimizing preparation processes, and improving surface passivation. Alternatively, by introducing a shallow trench isolation (STI) structure, the diffusion of peripheral carriers into the electric field region can be blocked, thereby reducing the diffusion current.

[0062] However, the etching process will introduce lattice defects, etc., which will also cause generation-recombination current, trap-assisted tunneling current and surface leakage current.

[0063] In response to the above problems, an embodiment of the present application provides an avalanche photodetector and a method for preparing the same. By introducing an extraction structure outside the electric field region of the original avalanche photodetector, the extraction structure can attract carriers on the outside, reduce the diffusion of carriers into the electric field region to introduce additional diffusion current, and thus reduce device noise.

[0064] In order to make the purpose, implementation mode and advantages of the present application clearer, the exemplary implementation mode of the present application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0065] It should be noted that the brief description of terms in this application is only for the convenience of understanding the embodiments described below, and is not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their common and usual meanings.

[0066] In addition, the terms "include" and "have" and any variations thereof are intended to cover but not exclude inclusion, for example, a product or device comprising a list of components is not necessarily limited to those components expressly listed but may include other components not expressly listed or inherent to such products or devices.

[0067] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0068] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0069] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0070] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0071] Reference Figure 1 In a first aspect, an embodiment of the present application provides an avalanche photodetector 10 , comprising an avalanche photodiode 100 and an extraction structure 200 .

[0072] Specifically, the avalanche photodiode 100 includes a first contact layer 110, a charge layer 120, a light absorption layer 130, and a second contact layer 140 arranged in sequence along a first direction Y. The first contact layer 110 has a first doping type, and the charge layer 120, the light absorption layer 130, and the second contact layer 140 have a second doping type, and the first doping type is different from the second doping type.

[0073] It should be noted that the first doping type is different from the second doping type. Exemplarily, the first doping type is N-type and the second doping type is P-type; another exemplary embodiment, the first doping type is P-type and the second doping type is N-type. The embodiments of the present application are not limited to this and are not limited to the above examples.

[0074] It is understood that the first doping type is doping with a first doping ion, and the second doping type is doping with a second doping ion. Exemplarily, the first doping ion may be a phosphorus ion, and the second doping ion may be a boron ion. Another exemplary embodiment, the first doping ion may be a boron ion, and the second doping ion may be a phosphorus ion. The embodiments of the present application are not limited to this, nor are they limited to the above examples.

[0075] Correspondingly, depending on the doping ions, the avalanche photodetector 10 can be a top-down n-on-p photodetection structure or a top-down p-on-n photodetection structure.

[0076] The following description is made by taking the case where the first doping ions are phosphorus ions and the second doping ions are boron ions as an example, that is, the avalanche photodetector 10 is a top-down n-on-p photodetection structure.

[0077] Reference Figure 2 The first contact layer 110 , the charge layer 120 , the light absorption layer 130 and the second contact layer 140 jointly form a first electric field 101 .

[0078] Under the action of the reverse bias voltage, the central avalanche high field of the first electric field 101 is mainly concentrated between the first contact layer 110 and the charge layer 120 of different doping types, and the electric field area gradually expands from the charge layer to the light absorption layer 130. Photogenerated carriers (electrons and holes) are accelerated and energized under the action of the first electric field 101, triggering an avalanche to achieve carrier multiplication. In addition, the peripheral electric field of the first electric field 101 is mainly concentrated between the first contact layer 110 and the light absorption layer 130 of different doping types, and the dark carriers generated in the periphery will also be collected by the first electrode 150 through diffusion or drift motion, which will additionally increase the noise of the avalanche photodiode.

[0079] The extraction structure 200 has a first doping type. The extraction structure 200 is located outside the avalanche photodiode 100 along the second direction X. The extraction structure 200 is connected to the light absorption layer 130 and forms a second electric field 102 together with the light absorption layer 130. The first direction Y intersects with the second direction X; the first electric field 101 does not contact the second electric field 102.

[0080] Refer to the attached Figure 2 It can be seen that the first direction is the Y direction, and the second direction is the X direction.

[0081] The extraction structure 200 and the light absorbing layer 130 have opposite doping types. A second electric field 102 is formed between the extraction structure 200 and the light absorbing layer 130 due to the difference in doping types or an external bias voltage.

[0082] The function of the second electric field 102 is to guide and remove peripheral dark carriers and prevent peripheral dark carriers from diffusing into the central electric field region, thereby reducing dark current.

[0083] In the avalanche photodetector 10 provided in the embodiment of the present application, incident light is absorbed by the avalanche photodetector 10 to generate photogenerated electrons and holes, which are collided and ionized under the action of the electric field to achieve multiplication and signal amplification.

[0084] It is worth noting that in the structure of the avalanche photodetector 10 without the extraction structure 200, Figure 3 The dark carriers outside the first contact layer 110 may also be collected by the connected electrodes through diffusion or drift motion, introducing additional noise such as dark current.

[0085] It is understood that a neutral region 103 may be formed between the first electric field 101 and the second electric field 102. Figure 2 , Figure 4 and Figure 5 In any of the figures, along the second direction X, as the distances between the first contact layer 110 and the extraction structure 200 and the neutral region 103 decrease, the electric field gradually decreases until the neutral region 103, at which time the electric field approaches 0. The electrons in the neutral region 103 may diffuse into the first electric field 101, and then be collected by the connected electrodes through drift motion, introducing additional dark current; or even diffuse into the avalanche high field region to trigger avalanche amplification, introducing amplified dark current.

[0086] After the aforementioned extraction structure 200 is provided, part of the dark carriers generated outside the first contact layer can be directly collected by the extraction structure 200 without increasing the dark current of the avalanche photodetector 10, which helps to reduce device noise.

[0087] Reference Figure 2 and Figure 3 After the extraction structure 200 is set, the size of the neutral region 103 is reduced, that is, the number of electrons that may enter the first electric field 101 is reduced. By introducing the independent second electric field 102 and ensuring that it does not contact the first electric field 101, the movement path of the carriers can be effectively controlled, and unnecessary carrier diffusion and drift can be reduced, thereby reducing dark current and other noise sources, and improving the signal-to-noise ratio of the avalanche photodetector 10.

[0088] The photogenerated carrier multiplication process is more controlled due to the optimized configuration of the electric field. This stable multiplication mechanism helps improve the gain stability of the detector, making it perform consistently under different operating conditions.

[0089] By optimizing the electric field and the carrier path, the carriers can be collected and multiplied faster, thereby improving the response speed of the avalanche photodetector 10 .

[0090] In addition, due to the reduction of noise and the stabilization of gain, the overall detection accuracy of the avalanche photodetector 10 is improved, and the avalanche photodetector 10 can detect weak optical signals more accurately.

[0091] It should be noted that the doping concentrations of the first contact layer 110 and the extraction structure 200 can be selected according to actual conditions. For example, the doping concentration of the first contact layer 110 can be 10 19 cm -3 ; The doping concentration of the extraction structure 200 can be 10 18 cm -3 .

[0092] As an optional implementation, there are many factors that affect the neutral zone 103 .

[0093] In some embodiments, different voltages input to the extraction structure 200 may also affect the size of the neutral region 103. Figure 2 , the extraction structure 200 inputs a bias voltage of 0V, referring to Figure 4 , the extraction structure 200 inputs a bias voltage of 5V. Figure 2 and Figure 4 It can be seen that when the voltage input to the extraction structure 200 increases, the intensity of the second electric field 102 increases, and the size of the neutral zone 103 decreases. Therefore, under the premise of ensuring that the first electric field 101 and the second electric field 102 do not contact each other and the avalanche photodetector 10 works normally, the voltage input to the extraction structure 200 is as large as possible.

[0094] In some embodiments, the distance between the extraction structure 200 and the first contact layer 110 will affect the size of the neutral zone 103. Therefore, on the premise of ensuring that the first electric field 101 and the second electric field 102 do not contact each other and that the avalanche photodetector 10 operates normally, the distance between the extraction structure 200 and the first contact layer 110 is as small as possible.

[0095] Combination Figure 4 and Figure 5 It can be seen that, when the input voltage remains unchanged, the size of the neutral region 103 is reduced when the extraction structure 200 is close to the first contact layer 110. Therefore, under the premise of ensuring that the first electric field 101 and the second electric field 102 do not contact each other, the input voltage of the extraction structure 200 remains unchanged, and the avalanche photodetector 10 works normally, the distance between the extraction structure 200 and the first contact layer 110 is as small as possible.

[0096] As an optional implementation, there are different corresponding relationships between the first contact layer 110 and the extraction structure 200 .

[0097] In some embodiments, along the second direction X, an orthographic projection of the first contact layer 110 on the extraction structure 200 overlaps with the extraction structure 200 .

[0098] The extraction structure 200 is a structure located outside the avalanche photodiode 100 , has the same doping type as the first contact layer 110 , and is used to form the second electric field 102 .

[0099] Overlapping means that the orthographic projection of the first contact layer 110 and the extraction structure 200 have a common area in space in the second direction X. This layout can optimize the electric field distribution, so that the second electric field 102 can effectively guide and remove peripheral dark carriers.

[0100] By optimizing the electric field configuration and carrier paths, the overlapping area helps reduce the dark carriers entering the central electric field area, thereby reducing the dark current and improving the signal-to-noise ratio.

[0101] Due to the optimized configuration of the electric field, the overlapping region can effectively guide the peripheral dark carriers to move toward the extraction structure 200, thereby preventing the dark carriers from entering the central multiplication region.

[0102] By reducing the diffusion of dark carriers, the overlapping region effectively suppresses the generation of dark current, thereby reducing noise and improving the performance of the avalanche photodetector 10 .

[0103] In some embodiments, along the first direction Y, the bottom of the extraction structure 200 is lower than, flush with, or higher than the bottom of the first contact layer 110 , and the top of the extraction structure 200 is flush with or higher than the top of the first contact layer 110 .

[0104] The bottom end of the extraction structure 200 is higher than the bottom end of the first contact layer 110, which means that the extraction structure 200 overlaps with the first contact layer 110 in the first direction Y. When the extraction structure 200 is lower than the bottom end of the first contact layer 110, the depth of the extraction structure 200 in the first direction Y gradually increases. Through the above arrangement, it can be ensured that the extraction structure 200 can effectively contact and guide dark carriers diffused from deeper levels. By forming an electric field in a deeper area, the extraction structure 200 can capture and remove carriers diffused from the deep area to the electric field area, thereby reducing the source of dark current.

[0105] The top of the extraction structure 200 is flush with or higher than the top of the first contact layer 110 , which means that the extraction structure 200 extends higher in the first direction Y.

[0106] Through the above arrangement, it is possible to ensure that the extraction structure 200 forms an electric field in a wider vertical range, and can capture and remove dark carriers diffused from the upper layer. By forming an electric field in a higher area, the extraction structure 200 can effectively prevent carriers from diffusing from the surface or upper structure to the electric field area, thereby further reducing dark current.

[0107] By extending the range of the extraction structure 200 in the first direction Y, the extraction structure 200 can form an electric field in a larger spatial range to comprehensively capture and remove dark carriers that may enter the central electric field region. By effectively controlling and guiding the path of dark carriers, the number of dark carriers entering the multiplication region is reduced, thereby reducing the dark current. Due to the reduction of dark current, the signal-to-noise ratio is improved, thereby improving the overall performance and accuracy of the avalanche photodetector 10.

[0108] Reference Figure 2 In some embodiments, part of the electric lines between the first electric field 101 and the second electric field 102 extend along the first direction Y.

[0109] By designing the electric lines to extend along the first direction Y, an effective electric field gradient can be formed in the first direction Y, and ensuring that the first electric field 101 and the second electric field 102 are not in contact helps control the transport path of carriers and ensure that they move in the expected direction.

[0110] The presence of the electric field gradient makes the transport of carriers in the first direction Y more controlled. As can be seen from the foregoing, the first electric field 101 accelerates the multiplication of photogenerated carriers, and the second electric field 102 effectively guides peripheral carriers away from the central area. This transport path reduces unnecessary carrier diffusion, thereby reducing dark current.

[0111] By ensuring that the electric lines of force extend in the first direction Y, the coverage and intensity of the electric field are optimized, which can reduce the noise caused by carrier diffusion and improve the signal-to-noise ratio of the avalanche photodetector 10 .

[0112] The optimized electric field configuration can improve the stability of the gain, accelerate the collection and multiplication process of carriers, and thus increase the response speed of the avalanche photodetector 10 .

[0113] By means of the above-mentioned setting of the first electric field 101 and the second electric field 102, the effectiveness of the electric field and the controlled movement of carriers can be ensured. The avalanche photodetector 10 can exhibit high stability and sensitivity under different operating conditions and is suitable for application scenarios requiring high precision and low noise.

[0114] Reference Figure 6 In some embodiments, the avalanche photodiode 100 further includes a first electrode 150 and a second electrode 160, the first electrode 150 is connected to the first contact layer 110, the second contact layer 140 is located on the side of the light absorbing layer 130 away from the first contact layer 110; the second electrode 160 is connected to the second contact layer 140, and the first electrode 150 and the second electrode 160 are respectively used for electrical connection;

[0115] By connecting the first electrode 150 and the second electrode 160 to the positive and negative electrodes of the power supply respectively, a complete circuit is formed, so that an electric field can be formed in the avalanche photodiode 100. The electric field is the basis for multiplication of photogenerated carriers, ensuring the normal operation of the photodetector.

[0116] The extraction structure 200 includes an extraction electrode 210 and an extraction portion 220 . The extraction portion 220 is located outside the first contact layer 110 along the second direction X, so that the extraction portion 220 can effectively guide and remove peripheral dark carriers outside the electric field region.

[0117] By arranging the extraction portion 220 outside the electric field region, the peripheral carriers entering the central electric field region can be reduced, thereby reducing the dark current.

[0118] The extraction electrode 210 is located on the side of the extraction portion 220 away from the second contact layer 140, and the extraction electrode 210 is connected to the extraction portion 220. The extraction electrode 210 enables the extraction portion 220 to be connected to an external circuit, thereby establishing an auxiliary electric field in the extraction portion 220 region, namely, the second electric field 102. The second electric field 102 helps to attract and remove dark carriers, further reducing dark current.

[0119] The connection between the first electrode 150 and the second electrode 160 ensures that an electric field is formed and maintained within the avalanche photodiode 100 .

[0120] The extraction structure 200 can effectively guide and remove peripheral dark carriers through the above structure, reduce the number of carriers entering the central electric field region, and thus reduce dark current.

[0121] By reducing the dark current and optimizing the electric field configuration, the signal-to-noise ratio of the avalanche photodetector 10 is improved, thereby improving the overall detection performance and accuracy.

[0122] It should be noted that different bias voltages can be applied to the extraction electrode 210, which can be selected according to actual conditions. For example, the extraction electrode 210 can apply a zero bias voltage or a positive bias voltage.

[0123] Reference Figure 6 In some embodiments, the extraction portion 220 is ring-shaped.

[0124] The ring structure can uniformly surround the first contact layer 110 in space to form a symmetrical electric field distribution. The symmetrical distribution helps to uniformly guide and remove dark carriers diffused from all directions, avoiding electric field non-uniformity caused by structural asymmetry, thereby improving the removal efficiency of dark carriers.

[0125] The extraction portion 220 is located at the outer peripheral side of the first contact layer 110 , that is, surrounds the outer periphery of the first contact layer 110 .

[0126] By placing the extraction portion 220 on the outer peripheral side of the first contact layer 110, the peripheral area can be effectively covered and controlled. The above layout ensures that dark carriers in part of the peripheral area are captured and removed by the extraction portion 220 before diffusing into the central electric field region, thereby reducing the number of dark carriers entering the multiplication region.

[0127] Through the above arrangement, the annular extraction portion 220 surrounds the outer peripheral side of the first contact layer 110 to form a complete barrier, which can effectively capture and remove dark carriers diffused from all directions. In addition, the extraction portion 220 can effectively reduce the peripheral dark carriers from entering the central electric field area, thereby significantly reducing the dark current. Due to the reduction of dark current and the uniformity of the electric field, the signal-to-noise ratio of the avalanche photodetector 10 is improved, thereby improving the overall detection performance and accuracy.

[0128] Reference Figure 6 In some embodiments, the avalanche photodiode 100 further includes a first light absorbing layer 130A and an anti-reflection layer 180 . The first light absorbing layer 130A has a second doping type, and the first light absorbing layer 130A adopts a second doping type different from that of the first contact layer 110 .

[0129] By using the second doping type, the first contact layer 110, the charge layer 120, the first light absorption layer 130A and the first light absorption layer 130A form an effective electric field distribution along the first direction Y, which can effectively separate photogenerated electrons and holes and improve the photoelectric conversion efficiency.

[0130] The anti-reflection layer 180 is located on a side of the first contact layer 110 away from the second contact layer 140 .

[0131] The provision of the anti-reflection layer 180 helps to improve the light absorption efficiency. The anti-reflection layer 180 can be used to optimize the incident path of light, increase the transmittance of light in the light absorption layer, and thus improve the photoelectric conversion efficiency.

[0132] It is understandable that the material for preparing the anti-reflection layer 180 can be selected according to actual conditions. For example, the material for preparing the anti-reflection layer can be SiO 2 , or Si 3 N 4 , or SiO 2 / Si 3 N 4 Composite structure.

[0133] Along the first direction Y, the first light absorbing layer 130A is located between the charge layer 120 and the second contact layer 140 .

[0134] The above arrangement can ensure that the photogenerated carriers can be quickly accelerated and collected by the electric field after being generated. The existence of the charge layer 120 helps to optimize the electric field distribution and ensure that the photogenerated carriers are effectively separated and collected in the first light absorption layer 130A, thereby improving the response speed and efficiency of the device.

[0135] Reference Figure 6 In some embodiments, the avalanche photodiode 100 further includes a second light absorbing layer 130B and a passivation layer 190 .

[0136] Specifically, the second light absorbing layer 130B is located outside the first light absorbing layer 130A. By adding the second light absorbing layer 130B outside the first light absorbing layer 130A,

[0137] The first light absorbing layer 130A and the second light absorbing layer 130B are an integrated piece. The integrated design can reduce defects and discontinuities at the interface, reduce carrier recombination losses, improve carrier transmission efficiency, and help improve the photoelectric conversion efficiency and response speed of the device.

[0138] In a possible implementation, the light absorbing layer may be made of any material. For example, the light absorbing layer may be made of silicon material, or semiconductor materials such as InGaAs, SiC, GaN, or two-dimensional materials such as graphene, molybdenum disulfide, and black phosphorus, wherein the silicon material may be an epitaxial high-resistance silicon material, or may be formed by thinning a bulk silicon material.

[0139] It can be understood that the light absorbing layer is the substrate 300 .

[0140] Reference Figure 6 In some embodiments, the extraction structure 200 is located on the second light absorbing layer 130B. The extraction structure 200 can effectively form an electric field to help guide and remove peripheral dark carriers and prevent them from entering the multiplication region, thereby helping to reduce dark current and improve the signal-to-noise ratio.

[0141] The passivation layer 190 is located on the side of the second light absorbing layer 130B away from the second contact layer 140. The passivation layer 190 helps to reduce the surface state density, reduce the surface recombination velocity, thereby reducing the surface leakage current, and helps to improve the stability and performance of the device, especially in reducing dark current and noise.

[0142] In some embodiments, the avalanche photodiode 100 further includes a protective member 170, which is in the shape of a ring. The ring structure can evenly surround the first contact layer 110 and provide a symmetrical electric field distribution. The above symmetrical distribution helps to evenly distribute the electric field stress, reduce the risk of premature breakdown that may be caused by electric field concentration at the edge of the first contact layer 110, and thus improve the reliability of the device.

[0143] The protection member 170 is located between the first contact layer 110 and the extraction portion 220, and the protection member 170 can effectively prevent edge breakdown, which helps to stabilize the electric field distribution, ensure that the first electric field 101 and the second electric field 102 work independently, thereby optimizing the control and removal of carriers.

[0144] The protection member 170 is connected to the first contact layer 110. Thus, a stable fringe electric field is established, which helps to further control the electric field distribution and enhance the management of carriers.

[0145] The protection member 170 has a first doping type, that is, the protection member 170 has the same doping type as the first contact layer 110 and the extraction structure 200. Using the same doping type ensures that the electric field between the protection member 170 and the first contact layer 110 changes gradually, avoids the electric field at the edge of the first contact layer 110 being too concentrated and causing premature edge breakdown, helps to ensure efficient avalanche of the central electric field, and improves the reliability of the device.

[0146] In a possible implementation, there may be multiple protective members 170 .

[0147] The control and distribution of the electric field can be further enhanced by using multiple protection members 170. Multiple protection members 170 can provide better electric field uniformity, reduce electric field concentration, and thus reduce the breakdown risk of the device, which helps to improve the voltage resistance and reliability of the device.

[0148] A plurality of protection members 170 may be disposed at intervals between the first contact layer 110 and the extraction structure 200 .

[0149] The protective member 170 disposed at intervals can form a plurality of transition regions between the first contact layer 110 and the extraction structure 200. The transition region helps to gradually adjust the intensity and direction of the electric field, slow down the electric field gradient, and thus reduce the possibility of carrier tunneling and leakage current. In addition, the interval arrangement can effectively buffer and disperse the electric field stress, further improving the stability and performance of the device.

[0150] In a possible implementation, the avalanche photodetector 10 can be incident from the front or from the back according to actual conditions.

[0151] Frontal incidence means that light is incident from the front side of the device (i.e., usually the front side of the substrate 300). The frontal incidence structure is classic and has stable performance, but light is easily affected by absorption, reflection, scattering, etc. of the surface layer structure before reaching the photosensitive area (i.e., the first contact layer 110), resulting in loss. It is suitable for applications that require direct light incidence.

[0152] Back-incident means that light is incident from the back side of the device (i.e., the back side of the substrate 300). When back-incident, light directly irradiates the photosensitive area, avoiding interference and loss of the structural layer, which helps to improve the spectral response. It is suitable for applications where complex electrode arrangements or integration of other functions are required on the front side.

[0153] In a possible implementation, according to actual conditions, the avalanche photodetector 10 can work independently or be integrated with other unit devices as a basic structure.

[0154] Exemplarily, the avalanche photodetector 10 can operate as a single device to independently perform photoelectric conversion and signal detection tasks.

[0155] As another example, the avalanche photodetector 10 can be used as a basic structure and integrated with other unit devices (such as amplifiers, filters, processors, etc.) to form a complex optoelectronic system.

[0156] Second, refer to Figure 7 The present application embodiment provides a method for preparing an avalanche photodetector 10, comprising:

[0157] Reference Figure 8 , S100, providing a substrate.

[0158] The substrate 300 is usually a semiconductor material, such as silicon, gallium arsenide or other III-V compounds. Selecting a suitable substrate 300 material is the basis for ensuring device performance. A high-quality substrate 300 can provide good lattice matching, reduce lattice defects, thereby reducing dark current and improving device reliability.

[0159] Reference Figure 1 , S200, forming a charge layer, an extraction structure, a first contact layer, a light absorption layer and a second contact layer in sequence on the substrate.

[0160] The charge layer 120 is usually formed by ion implantation, diffusion or epitaxial growth. The charge layer 120 can help separate, transport and multiply photogenerated carriers. The quality and doping distribution of the charge layer 120 directly affect the uniformity and intensity of the electric field, thereby affecting the gain and response speed of the device.

[0161] The extraction structure 200 is used to guide and remove peripheral dark carriers. By optimizing the position and shape of the extraction structure 200, the dark current can be effectively reduced and the signal-to-noise ratio can be improved.

[0162] The first contact layer 110 is used to provide an electrode connection point to ensure the establishment and maintenance of the electric field. A good contact layer design can reduce contact resistance and improve carrier collection efficiency, thereby improving the response speed and gain of the device.

[0163] The remaining portion of the substrate 300 is the light absorbing layer 130 .

[0164] Reference Fig. 9 and Fig.10 In some embodiments, when the avalanche photodetector 10 includes a first electrode 150, a second electrode 160, an extraction electrode 210, and an extraction portion 220, the charge layer 120, the extraction structure 200, the first contact layer 110, the light absorption layer 130, and the second contact layer are sequentially formed on the substrate 300, including:

[0165] S210, photolithography and doping second doping ions on the substrate to form a charge layer.

[0166] The pattern of the charge layer 120 is formed on the substrate 300 by photolithography, and silicon dioxide is etched. Then, a doping process such as boron ion implantation and diffusion is performed and the p-type charge layer 120 is formed after the photoresist is removed.

[0167] The region of the charge layer 120 is defined on the substrate 300 using photolithography technology, and the charge layer 120 is formed by doping a second doping ion (such as N-type or P-type). The substrate 300 after photolithography is the light absorption layer 130. As can be seen from the foregoing, the light absorption layer 130 includes a first light absorption layer 130A and a second light absorption layer 130B.

[0168] Reference Figure 1 and Fig.10 In some embodiments, when the avalanche photodiode 100 includes the passivation layer 190, before photolithography and doping of the second doping ions on the substrate 300 to form the charge layer 120, after providing the substrate 300, the method further includes:

[0169] S205, pre-treating the substrate and depositing silicon dioxide on the substrate to form a passivation layer;

[0170] For ease of explanation, the p-type substrate 300 is taken as an example. First, the p-type substrate 300 is pre-treated by cleaning, and then silicon dioxide and other materials are deposited on the p-type substrate 300 by dry method, wet method or magnetron sputtering to form a passivation layer 190.

[0171] S220 , photolithography and doping of first doping ions on the second light absorbing layer to form an extraction portion.

[0172] The pattern of the extraction part 220 is formed on the second light absorption layer 130B by photolithography, and the silicon dioxide passivation layer 190 is etched. The extraction part 220 is formed by a doping process such as phosphorus ion implantation and diffusion, and then the photoresist is removed. The doping concentration of phosphorus ions can be 10 18 cm -3 Annealing is performed, during which a silicon dioxide passivation layer 190 is deposited.

[0173] In the second light absorbing layer 130B, the extraction portion 220 is formed by photolithography and doping with first doping ions (opposite to the doping type of the charge layer 120). Through precise photolithography and doping, the shape and position of the extraction portion 220 can be optimized, thereby effectively reducing dark current and improving signal-to-noise ratio.

[0174] Reference Fig.11 In some embodiments, when the avalanche photodiode 100 further includes the protection member 170, before the first doping ions are photolithographically doped to form the extraction portion 220, after the second doping ions are photolithographically doped to form the charge layer 120 on the substrate 300, the method further includes:

[0175] S215 , photolithography and doping of first doping ions on the second light absorbing layer to form a protective member.

[0176] The pattern of the protective member 170 is formed on the second light absorbing layer 130B by photolithography, and the silicon dioxide passivation layer 190 is etched. The protective member 170 is formed by a doping process such as phosphorus ion implantation and diffusion, and then the photoresist is removed. The doping concentration of phosphorus ions can be 10 17 ~10 18 cm -3 .

[0177] Reference Fig.12 , S230, on the first light absorbing layer, perform photolithography and doping with first doping ions to form a first contact layer.

[0178] The pattern of the first contact layer 110 is formed on the first light absorption layer 130A by photolithography, and the silicon dioxide passivation layer 190 is etched. The first contact layer 110 is formed by a doping process such as phosphorus ion implantation and diffusion, and then the photoresist is removed. The doping concentration of phosphorus ions can be 10 19 cm -3 . Annealing, during which silicon dioxide is deposited as an anti-reflection layer.

[0179] On the first light absorbing layer 130A, the first contact layer 110 is formed by photolithography and doping with first doping ions. Through precise photolithography and doping, the contact resistance can be reduced, the carrier collection efficiency can be improved, and thus the response speed and gain of the device can be improved.

[0180] Reference Fig.13 , S240, photolithography is performed on the first contact layer and the second light absorption layer to form a first electrode and an extraction electrode, respectively.

[0181] The front electrode is formed by magnetron sputtering or electron beam evaporation, the first electrode 150 and the extraction electrode 210 are patterned by photolithography, the first electrode 150 and the extraction electrode 210 are etched, and then the photoresist is removed, thereby obtaining the first electrode 150 and the extraction electrode 210. The first electrode 150 and the extraction electrode 210 may include one or more metals of gold, silver, titanium or aluminum, which is not limited in this embodiment.

[0182] The precise positioning and formation of the first electrode 150 and the extraction electrode 210 help optimize the electric field distribution, enhance the control of photogenerated carriers and the removal of peripheral dark carriers.

[0183] Reference Fig.14 , S250, photolithography and doping second doping ions on the other side of the first light absorbing layer and the second light absorbing layer to form a second contact layer.

[0184] The p-type second contact layer 140 is formed on the back of the first light absorbing layer 130A and the second light absorbing layer 130B by a doping process such as boron ion implantation and diffusion. The doping concentration of the boron ions can be 10 18 cm -3 .

[0185] The formation of the second contact layer 140 provides another electrode connection point to ensure the integrity and stability of the electric field. Through precise photolithography and doping, the uniformity and strength of the electric field can be optimized.

[0186] Reference Figure 6 , S260, photolithographically forming a second electrode on the second contact layer to form an avalanche photodetector.

[0187] The second electrode 160 is formed on the back side of the substrate 300 by magnetron sputtering or electron beam evaporation, wherein the second electrode 160 may include one or more metals of gold, silver, titanium or aluminum, which is not limited in this embodiment.

[0188] The formation of the second electrode 160 completes the electrode structure and ensures the establishment and maintenance of the electric field. Through precise photolithography, the shape and position of the electrode can be optimized to further improve the performance of the device.

[0189] The method for preparing the avalanche photodetector 10 provided in the embodiment of the present application ensures the uniformity and strength of the electric field through precise photolithography and doping processes, and the formation of each layer and electrode enhances the separation and transport efficiency of photogenerated carriers. The design and position of the extraction part 220 and the extraction electrode 210 can optimize the control of peripheral dark carriers, reduce dark current, and improve the signal-to-noise ratio.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0191] For the convenience of explanation, the above description has been made in conjunction with specific embodiments. However, the above exemplary discussion is not intended to be exhaustive or limit the embodiments to the specific forms disclosed above. Based on the above teachings, various modifications and variations can be obtained. The selection and description of the above embodiments are to better explain the principles and practical applications, so that those skilled in the art can better use the embodiments and various different variations of the embodiments suitable for specific use considerations.

Claims

1. An avalanche photodetector, characterized in that: comprising an avalanche photodiode (100) and an extraction structure (200), The avalanche photodiode (100) comprises a first contact layer (110), a charge layer (120), a light absorption layer (130) and a second contact layer (140) which are sequentially arranged along a first direction (Y); The first contact layer (110) has a first doping type, the charge layer (120), the light absorption layer (130) and the second contact layer (140) have a second doping type, the first doping type is different from the second doping type, and the first contact layer (110), the charge layer (120), the light absorption layer (130) and the second contact layer (140) jointly form a first electric field (101); The extraction structure (200) has the first doping type, the extraction structure (200) is located outside the avalanche photodiode (100) along the second direction (X), the extraction structure (200) is connected to the light absorption layer (130) and forms a second electric field (102) together with the light absorption layer (130), and the first direction (Y) intersects with the second direction (X); the extraction structure (200) comprises an extraction electrode (210) and an extraction portion (220), the extraction portion (220) is located outside the first contact layer (110) along the second direction (X), the extraction electrode (210) is located on a side of the extraction portion (220) away from the second contact layer (140), and the extraction electrode (210) is connected to the extraction portion (220); The first electric field (101) and the second electric field (102) are not in contact; A neutral zone (103) is formed between the first electric field (101) and the second electric field (102); when the voltage input to the extraction structure (200) increases, the size of the neutral zone (103) decreases; and / or when the distance between the extraction structure (200) and the first contact layer (110) decreases, the size of the neutral zone (103) decreases.

2. The avalanche photodetector according to claim 1, characterized in that: Along the second direction (X), the orthographic projection of the first contact layer (110) on the extraction structure (200) overlaps with the extraction structure (200).

3. The avalanche photodetector according to claim 2, characterized in that: Along the first direction (Y), the bottom end of the extraction structure (200) is lower than, flush with, or higher than the bottom end of the first contact layer (110), and the top end of the extraction structure (200) is flush with or higher than the top end of the first contact layer (110).

4. The avalanche photodetector according to any one of claims 1 to 3, characterized in that: Part of the electric lines of force between the first electric field (101) and the second electric field (102) extend along the first direction (Y).

5. The avalanche photodetector according to claim 4, characterized in that: The avalanche photodiode (100) further comprises a first electrode (150) and a second electrode (160), wherein the first electrode (150) is connected to the first contact layer (110), and the second electrode (160) is connected to the second contact layer (140), and the first electrode (150) and the second electrode (160) are respectively used for electrical connection.

6. The avalanche photodetector according to claim 5, characterized in that: The extraction portion (220) is in a ring shape and is located on the outer peripheral side of the first contact layer (110); and / or, The avalanche photodiode (100) further comprises a protection member (170), the protection member (170) being in a ring shape, the protection member (170) being located between the first contact layer (110) and the extraction portion (220), the protection member (170) being connected to the first contact layer (110), and the protection member (170) having the first doping type.

7. The avalanche photodetector according to claim 6, characterized in that: The avalanche photodiode (100) further comprises a first light absorbing layer (130A) and an anti-reflection layer (180), wherein the first light absorbing layer (130A) has the second doping type, and the anti-reflection layer (180) is located on a side of the first contact layer (110) away from the second contact layer (140); Along the first direction (Y), the first light absorbing layer (130A) is located between the charge layer (120) and the second contact layer (140).

8. The avalanche photodetector according to claim 7, characterized in that: The avalanche photodiode (100) further comprises a second light absorbing layer (130B) and a passivation layer (190). The second light absorbing layer (130B) is located outside the first light absorbing layer (130A), the first light absorbing layer (130A) and the second light absorbing layer (130B) are an integral piece, and the extraction structure (200) is located on the second light absorbing layer (130B); The passivation layer (190) is located on a side of the second light absorbing layer (130B) away from the second contact layer (140).

9. A method for preparing an avalanche photodetector according to any one of claims 1 to 8, characterized in that: include: Providing a substrate (300); A charge layer (120), an extraction structure (200), a first contact layer (110), a light absorption layer (130), and a second contact layer (140) are sequentially formed on the substrate (300); When the avalanche photodetector (10) comprises a first electrode (150), a second electrode (160), an extraction electrode (210), and an extraction portion (220), the charge layer (120), the extraction structure (200), the first contact layer (110), the light absorption layer (130), and the second contact layer (140) are sequentially formed on the substrate (300) and include: Photolithography and doping second doping ions on the substrate (300) to form the charge layer (120); Photolithography and doping first doping ions on the second light absorbing layer (130B) to form the extraction portion (220); Photolithography and doping first doping ions on the first light absorbing layer (130A) to form the first contact layer (110); Performing photolithography on the first contact layer (110) and the second light absorbing layer (130B) to form the first electrode (150) and the extraction electrode (210) respectively; Photolithography and doping the second doping ions on the other side of the first light absorbing layer (130A) and the second light absorbing layer (130B) to form the second contact layer (140); The second electrode (160) is formed on the second contact layer (140) by photolithography to form the avalanche photodetector (10).

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