Single photon avalanche diode, preparation method thereof and photoelectric detector

Abstract

The invention discloses a single-photon avalanche diode and a preparation method thereof and a photoelectric detector, the single-photon avalanche diode comprises a device main body and a reflection structure, the device main body forms a light-in surface and a light-out surface which are oppositely arranged, and a photosensitive area is also formed at the center position in the device main body; the photosensitive area is provided with a first semiconductor area and a second semiconductor area which are stacked downwards from the light emitting surface, the device body further comprises an edge area annularly arranged on the outer side of the center position, and an isolation area is further formed between the photosensitive area and the edge area; the reflection structure comprises a light-transmitting layer and a reflection layer which cover the light-emitting surface, a plane and an inclined plane which are connected are formed on the surface of the light-transmitting layer, the inclined plane is located above the isolation area and the third semiconductor area, and the areas, corresponding to the inclined plane, of the light-transmitting layer and the reflection layer form a light condensation area; the light gathering area is used for gathering light rays emitted from the outer side of the photosensitive area into the photosensitive area. According to the technical scheme, the light utilization rate of the single photon avalanche diode is improved, and the detection efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor regions, and in particular to a single-photon avalanche diode and a preparation method thereof, and a photoelectric detector having the single-photon avalanche diode. Background Art

[0002] A single photon avalanche diode (SPAD) is a semiconductor region photodetector with single-photon detection sensitivity. It uses the avalanche effect that occurs when a PN junction operates above the reverse breakdown voltage. It can multiply the carriers generated by the absorbed light and generate a large current that is detected by an external circuit, thereby realizing the photoelectric detection process.

[0003] In the existing photodiode structure, the avalanche breakdown generally occurs in the middle region, and an isolation region is usually set between the peripheral edge region and the edge of the main junction in the center to reduce the breakdown in the edge region. In order to improve the utilization rate of light, a reflective layer is usually set on the internal surface of the photodiode to reflect the light into the device to increase the amount of light absorbed by the middle region, thereby increasing the capture rate of photogenerated carriers in the middle region. In the existing scheme, the reflective layer of the photodiode is a planar structure, and the light is reflected by the reflective layer and reflected back to various regions inside the device in parallel and uniformly. In this way, a large amount of light is reflected to the isolation region outside the avalanche breakdown region and the peripheral edge region, resulting in a waste of light source, and the photogenerated carriers in the middle region cannot be completely captured, which leads to a low photon detection efficiency (PDE, Photon Detection Efficiency), thereby affecting the detection efficiency. Summary of the invention

[0004] The main purpose of the present invention is to provide a single-photon avalanche diode and a photodetector, aiming to improve the light utilization rate of the single-photon avalanche diode and improve the detection efficiency.

[0005] To achieve the above object, the single photon avalanche diode proposed in the present invention comprises:

[0006] A device body is formed with a light incident surface and a light emitting surface which are arranged opposite to each other, a photosensitive area is further formed in the device body, the photosensitive area is extended from the light emitting surface toward the light incident surface, the photosensitive area is located at the center of the device body, the photosensitive area is provided with a first semiconductor area and a second semiconductor area which are stacked downward from the light emitting surface, the device body further includes an edge area which is arranged outside the center, the edge area is provided with a third semiconductor area, and an isolation area is further formed between the photosensitive area and the edge area; and

[0007] A reflective structure, wherein the reflective structure comprises a light-transmitting layer and a reflective layer, wherein the light-transmitting layer covers the light-emitting surface, wherein a surface of the light-transmitting layer away from the light surface is formed with a plane and an inclined surface connected to each other, wherein the plane is located above the first semiconductor region, and the inclined surface is located above the isolation region and the third semiconductor region, wherein the reflective layer covers a side of the light-transmitting layer away from the light-emitting surface, and the light-transmitting layer and the reflective layer form a light-collecting area in an area corresponding to the inclined surface,

[0008] Light enters from the light incident surface and exits through the light exiting surface. The reflective structure reflects the light back to the inner side of the device body. The focusing area is used to focus the light emitted from the outer side of the photosensitive area into the photosensitive area.

[0009] In one embodiment of the present invention, the angle formed by the inclined surface and the light emitting surface is θ, and 15°≤θ≤45°.

[0010] In one embodiment of the present invention, a projection of the plane of the light-transmitting layer on the light-emitting surface extends to the outside of the photosensitive area.

[0011] In one embodiment of the present invention, the material of the light-transmitting layer includes one or more of silicon oxide, silicon nitride, and transparent glue;

[0012] The reflective layer is made of metal.

[0013] In one embodiment of the present invention, the device body comprises:

[0014] A substrate, wherein the light incident surface and the light emitting surface are respectively formed on two opposite surfaces of the substrate;

[0015] A portion of the structure of the first semiconductor region is exposed on the light emitting surface and extends from the light emitting surface to the light incident surface, and the first semiconductor region is located at the center of the substrate;

[0016] The second semiconductor region is arranged on a side of the first semiconductor region away from the light emitting surface, the second semiconductor region is extended from the light emitting surface to the light incident surface, a first PN junction is formed between the first semiconductor region and the second semiconductor region, and the first semiconductor region and the second semiconductor region form the photosensitive region;

[0017] Part of the structure of the third semiconductor region is exposed on the light emitting surface and extends from the light emitting surface to the light incident surface, and the third semiconductor region is located in the edge area of ​​the substrate;

[0018] The isolation region is disposed between the first semiconductor region and the third semiconductor region, and the light focusing region covers surfaces of the isolation region and the third semiconductor region.

[0019] In one embodiment of the present invention, the first semiconductor region includes a first doped region and a second doped region, the surface of the first doped region is exposed on the light emitting surface and extends toward the light incident surface, the second doped region is arranged around the first doped region, and a part of the structure of the second doped region is exposed on the light emitting surface, the second doped region is extended from the light emitting surface to the light incident surface, and the second doped region is in contact with the second semiconductor region.

[0020] In one embodiment of the present invention, the third semiconductor region includes a third doped region and a fourth doped region, the third doped region is partially exposed on the light emitting surface from the third doped region, the third doped region extends from the light emitting surface to the light incident surface, the fourth doped region is partially exposed on the light emitting surface, the fourth doped region is arranged around the third doped region, and the fourth doped region extends from the light emitting surface toward the light incident surface.

[0021] In one embodiment of the present invention, the single photon avalanche diode further includes a first electrode and a second electrode disposed on the light emitting surface, the first electrode being connected to the first semiconductor region, and the second electrode being connected to the third semiconductor region.

[0022] The present invention also proposes a method for preparing a single photon avalanche diode, comprising the following steps:

[0023] Depositing an insulating light-transmitting layer on the light-emitting surface of the device body;

[0024] Etching the surface of the insulating light-transmitting layer so that the insulating light-transmitting layer above the first semiconductor region is formed into a flat surface, and the insulating light-transmitting layer above the third semiconductor region and the isolation region is formed into an inclined surface;

[0025] A metal reflective layer is deposited on the surface of the insulating light-transmitting layer, and the metal reflective layer and the insulating light-transmitting layer form a light-focusing area in the area corresponding to the inclined surface.

[0026] The present invention also invents a photoelectric detector, which also includes the single-photon avalanche diode.

[0027] The single-photon avalanche diode of the technical solution of the present invention includes a device body and a reflective structure, wherein a photosensitive area is formed inside the device body, the photosensitive area is located at the center of the device body, the photosensitive area is provided with a first semiconductor area and a second semiconductor area stacked from the light-emitting surface downward, an isolation area is provided around the outside of the photosensitive area to prevent edge breakdown, and an edge area is also provided outside the isolation area, and the edge area includes a semiconductor area. The reflective structure covers the light-emitting surface, and the reflective structure includes a light-transmitting layer and a reflective layer covering the light-emitting surface. The surface of the light-transmitting layer is formed with a connected plane and an inclined surface, and the inclined surface is located above the isolation area and the third semiconductor area. The area of ​​the light-transmitting layer and the reflective layer corresponding to the inclined surface forms a light-collecting area. When the single-photon avalanche diode is used, the light emitted by the light source enters the device body from the light-incident surface, and the reflective structure arranged on the light-emitting surface of the device body can reflect the light to enter the device body again, so that the first semiconductor area and the second semiconductor area in the photosensitive area can be exposed to more light, and the light absorption efficiency inside the device body is improved, so that the number of carriers generated is doubled, and a large current is generated to be detected by the external circuit, thereby realizing the process of photoelectric detection. The reflective structure is also provided with a light-gathering area, which can also reflect the light emitted from the isolation area and the edge area, and gather the reflected light to the photosensitive area, effectively utilizing the light originally reflected to the outside of the photosensitive area, further increasing the amount of light in the photosensitive area, and further multiplying the number of carriers generated in the photosensitive area, thereby further improving the photon detection efficiency. In addition, the light-transmitting layer and the reflective layer are both located at the top layer of the device body, which does not affect the metal wiring at the bottom of the device body, and improves the convenience of wiring. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0029] Figure 1 This is a schematic diagram of the structure of a single photon avalanche diode of the present invention;

[0030] Figure 2 This is an effect diagram of the pixel reflection simulation of the single-photon avalanche diode of the present invention.

[0031] Description of Figure Numbers:

[0032]

[0033]

[0034] 100, device body; 15, third semiconductor region; 10, substrate; 151, third doped region; 101, light incident surface; 153, fourth doped region; 103, light emitting surface; 20, reflective structure; 11, first semiconductor region; 21, light-transmitting layer; 111, first doped region; 211, plane; 113, second doped region; 213, inclined surface; 13, second semiconductor region; 23, reflective layer.

[0035] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0038] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the meaning of "and / or" appearing in the full text is to include three parallel solutions. Taking "A and / or B as an example", it includes solution A, or solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] The single-photon avalanche photodiode operates above the breakdown voltage of the PN junction and can be used in a highly sensitive photon capture environment. In the existing single-photon avalanche diode, the central region is avalanche-broken, and an edge region is provided on the periphery of the central region, and an ISO isolation region is formed between the edge region and the central region to reduce the breakdown of the edge region. The surface inside the photodiode is also provided with a reflective layer 23 in a plane 211 structure to reflect light to the inside of the photodiode to increase the amount of light absorbed by the central region, thereby increasing the capture rate of photogenerated carriers in the central region. However, in addition to the light reflected into the avalanche breakdown region being utilized, the photogenerated carriers generated by the light reflected to the isolation region and the peripheral edge region cannot be completely captured, resulting in a waste of light, and the photogenerated carriers in the central region cannot be completely captured, which leads to a low photon detection efficiency (PDE, Photon Detection Efficiency), thereby affecting the detection efficiency.

[0041] Please refer to Figure 1 and Figure 2The present invention proposes a single-photon avalanche diode, which includes: a device body 100 and a reflective structure 20, forming a light incident surface 101 and a light emitting surface 103 arranged opposite to each other, a photosensitive area is also formed in the device body 100, the photosensitive area extends from the light emitting surface 103 to the light incident surface 101, the photosensitive area is located at the center of the device body 100, the photosensitive area is provided with a first semiconductor area 11 and a second semiconductor area 13 stacked downward from the light emitting surface 103, the device body 100 also includes an edge area arranged outside the center, the edge area is provided with a third semiconductor area 15, and an isolation area is formed between the photosensitive area and the edge area; the reflective structure 20 includes a light-transmitting layer 21 and a reflective layer, the light-transmitting layer 21 covers the light-emitting surface 103, the surface of the light-transmitting layer 21 away from the light surface is formed with a plane 211 and an inclined surface 213 connected to each other, the plane 211 is located above the first semiconductor region 11, and the inclined surface 213 is located above the isolation region and the third semiconductor region 15, the reflective layer covers the side of the light-transmitting layer 21 away from the light-emitting surface 103, the light-transmitting layer 21 and the reflective layer form a focusing area in the area corresponding to the inclined surface 213, the light enters from the light-incident surface and is emitted through the light-emitting surface 103, the reflective structure 20 reflects the light back to the inner side of the device body 100, and the focusing area is used to converge the light emitted from the outside of the photosensitive area into the photosensitive area.

[0042] The single-photon avalanche diode of the technical solution of the present invention comprises a device body 100 and a reflective structure 20, wherein a photosensitive region is formed inside the device body 100, the photosensitive region is located at the center of the device body 100, the photosensitive region is provided with a first semiconductor region 11 and a second semiconductor region 13 stacked downward from a light-emitting surface 103, an isolation region is provided around the photosensitive region to prevent edge breakdown, an edge region is also provided outside the isolation region, and the edge region includes a semiconductor region. The reflective structure 20 covers the light-emitting surface 103, and the reflective structure 20 comprises a light-transmitting layer 21 and a reflective layer covering the light-emitting surface 103, a surface of the light-transmitting layer 21 is formed with a plane 211 and an inclined surface 213 connected to each other, the inclined surface 213 is located above the isolation region and the third semiconductor region 15, and the light-transmitting layer 21 and the reflective layer form a light-focusing region in the region corresponding to the inclined surface 213. When the single-photon avalanche diode is in use, the light emitted by the light source enters the device body 100 from the light incident surface, and the reflective structure 20 arranged on the light emitting surface 103 of the device body 100 can reflect the light to enter the device body 100 again, so that the first semiconductor region 11 and the second semiconductor region 13 in the photosensitive area can receive more light, improve the light absorption efficiency inside the device body 100, double the number of carriers generated, generate a large current detected by the external circuit, and thus realize the process of photoelectric detection. Among them, the reflective structure 20 is also provided with a focusing area, which can also reflect the light emitted from the isolation area and the edge area, and gather the reflected light to the photosensitive area, effectively utilizing the light originally reflected to the outside of the photosensitive area, further increasing the amount of light in the photosensitive area, and can further double the number of carriers generated in the photosensitive area, thereby further improving the photon detection efficiency. Furthermore, the light-transmitting layer 21 and the reflective layer 23 of the reflective structure 20 are both located at the top layer of the device body 100 , which does not affect the metal wiring at the bottom, thereby improving the convenience of the metal wiring of the device body 100 .

[0043] It should be noted that the structure inside the device body 100 of the single-photon avalanche diode in the embodiment of the present invention can adopt the existing structure. By optimizing the reflective structure 20 on the surface of the device body 100, the light reflected by the reflective structure 20 is not uniformly emitted to the interior of the device, but the light emitted from the edge area and the isolation area is converged to the photosensitive area in the center, so that the photosensitive area can receive more light, effectively utilizing the light wasted in the existing scheme, increasing the utilization rate of light, doubling the number of carriers generated, and improving the photon detection efficiency.

[0044] Reference Figure 2 , Figure 2 This is a simulation result diagram of the single-photon avalanche diode (SPAD pixel device) of the present invention. It can be seen from the figure that its reflection effect is significant.

[0045] It can be understood that the reflective structure 20 may include various types, such as a reflective film, a light-transmitting film, and a light-focusing area formed by a light-focusing structure.

[0046] In one embodiment, the reflective structure 20 specifically includes a light-transmitting layer 21 and a reflective layer 23. The light-transmitting layer 21 covers the surface of the light-emitting surface 103, and the surface of the light-transmitting layer 21 facing away from the light surface is formed with a connected plane 211 and an inclined surface 213, and the inclined surface 213 is located on the outer peripheral side of the plane 211, and the end of the inclined surface 213 away from the plane 211 is connected to the light-emitting surface 103 so that the thickness of the edge of the light-transmitting layer 21 gradually decreases; the reflective layer 23 covers the surface of the light-transmitting layer 21, and the area where the reflective layer 23 covers the inclined surface 213 forms the focusing area.

[0047] In this embodiment, the light-transmitting layer 21 is made of a transparent material, and the light-transmitting material includes one or more of silicon oxide, silicon nitride, and transparent glue. The light-transmitting material is usually made of insulating material to avoid affecting the electrode. The light-transmitting material can form a film layer of a certain thickness on the light-emitting surface 103, thereby increasing the travel of the light and providing the necessary distance for reflecting and converging the light. Among them, the thickness of each position in the light-transmitting layer 21 is not the same, and the thickness of the plane 211 is greater than the thickness of the inclined surface 213. In addition, the thickness of the inclined surface 213 changes uniformly, which can make the converged light also change uniformly, so that the light change in the photosensitive area is also relatively uniform, avoiding the appearance of bright and dark spots.

[0048] In this embodiment, the preparation process of the light-transmitting layer 21 can be to first deposit one or more layers of light-transmitting material with uniform thickness by vapor deposition, and then etch the deposited transparent material by etching above the edge area and the isolation area by etching, so that an inclined slope appears on the outer edge of the transparent material. Among them, the inclined surface 213 surrounds the outer periphery of the plane 211 structure. It can be understood that in order to reflect as much light as possible to the photosensitive area in the middle, one end of the inclined surface 213 is directly connected to the light-emitting surface 103, so that the angle θ formed by the inclined surface 213 and the light-emitting surface 103 is between 15° and 45°, so that the reflection range of the focusing area can be improved to avoid wasting light in the edge area.

[0049] The material of the reflective layer 23 can be a metal material, and the reflective layer 23 is directly deposited on the side of the light-transmitting layer 21 away from the light-emitting surface 103 by vapor deposition. It can be understood that the reflective layer is opaque and can reflect light. Since the light-transmitting layer 21 is formed with a plane 211 and an inclined surface 213, the reflective surface of the reflective layer is also formed with a plane 211 and an inclined surface consistent with the light-transmitting layer 21. The plane 211 can reflect the light emitted from the photosensitive area, and the inclined surface can reflect and converge the light emitted from the edge area and the isolation area, so that the reflected light converges to the photosensitive area, thereby improving the utilization rate of the light. It should be noted that the projection of the plane 211 of the light-transmitting layer 21 on the light-emitting surface 103 can extend to the outside of the photosensitive area, and is slightly larger than the width of the photosensitive area, so as to ensure that the light emitted through the photosensitive area can be evenly reflected by the plane 211 of the reflective layer 23.

[0050] Please refer to Figure 1 In one embodiment of the present invention, the device body 100 includes:

[0051] A substrate 10, wherein the light incident surface 101 and the light emitting surface 103 are respectively formed on two opposite surfaces of the substrate 10;

[0052] A first semiconductor region 11, wherein a portion of the structure of the first semiconductor region 11 is exposed on the light emitting surface 103 and extends from the light emitting surface 103 to the light incident surface 101, and the first semiconductor region 11 is located at the center of the substrate 10;

[0053] a second semiconductor region 13, the second semiconductor region 13 being disposed on a side of the first semiconductor region 11 away from the light emitting surface 103, the second semiconductor region 13 extending from the light emitting surface 103 toward the light incident surface 101, a first PN junction being formed between the first semiconductor region 11 and the second semiconductor region 13, and the first semiconductor region 11 and the second semiconductor region 13 forming the photosensitive region;

[0054] A third semiconductor region 15, wherein a portion of the structure of the third semiconductor region 15 is exposed on the light emitting surface 103 and extends from the light emitting surface 103 to the light incident surface 101, and the third semiconductor region 15 is located at an edge region of the substrate 10;

[0055] The isolation region is disposed between the first semiconductor region 11 and the third semiconductor region 15 , and the light focusing region covers surfaces of the isolation region and the third semiconductor region 15 .

[0056] In this embodiment, the material of the substrate 10 can be a silicon wafer, or a germanium substrate 10, a germanium silicon substrate 10, an indium gallium arsenide substrate 10, a gallium arsenide substrate 10, a silicon carbide substrate 10, etc., which is not limited here.

[0057] The substrate 10 includes a light incident surface 101 and a light emitting surface 103 which are arranged oppositely and in parallel. Of course, the light incident surface 101 and the light emitting surface 103 can be understood to be basically parallel, that is, the two surfaces are arranged in parallel, and the two surfaces may be partially non-parallel due to processing errors. Light can enter from the light incident surface, pass through the substrate 10, and then exit from the light emitting surface. The depth direction of the avalanche photodiode is defined as the direction from the light incident surface 101 to the light emitting surface 103, and the direction parallel to the light incident surface 101 is the lateral direction.

[0058] The doping type of the substrate 10 is formed by doping impurity elements into the substrate 10, for example, the conductive type of the doped elements is N-type or P-type. The doping concentration of each position of the substrate 10 can be the same, or a gradient design can be performed, which is not limited here. In this embodiment, the doping types of the substrate 10, the first semiconductor region 11, the second semiconductor region 13, the third semiconductor region 15, and the isolation region are all different. Take the doping type of the substrate 10 as an example. That is, P-type epitaxial silicon is formed on the surface of a P-type silicon wafer by chemical vapor deposition or molecular beam epitaxy, and a heavily doped first semiconductor region 11 is formed above the substrate 10 by doping a high concentration of group V elements, such as non-metallic phosphorus (P) or metal arsenic (As), to form a cathode ohmic contact, and then a certain depth position on the substrate 10 can be lightly doped with group III elements, such as non-metallic boron (B) elements or metal gallium (Ga), to form a third semiconductor region 15, which is a P-type well (P-Well, referred to as PW), to form an anode ohmic contact. The doping method may be ion implantation or thermal diffusion, etc., which is not limited here. Part of the structure of the first semiconductor region 11 is exposed on the light emitting surface 103, which means that one surface of the first semiconductor region 11 is exposed on the light emitting surface 103 and is not covered by other materials.

[0059] In this embodiment, the isolation region can be formed by trench etching and filling the trench with polysilicon or metal tungsten, etc., and the isolation region is used to play the role of spacing pixels. Optionally, the isolation region can be a deep trench or a shallow trench. The isolation region is extended from the light emitting surface 103 toward the light incident surface 101, and is arranged around the first semiconductor region 11 and the third semiconductor region 15, which can effectively suppress the premature breakdown of the edge and ensure the center breakdown efficiency.

[0060] In one embodiment of the present invention, the first semiconductor region 11 includes a first doped region 111 and a second doped region 113. The surface of the first doped region 111 is exposed on the light emitting surface 103 and extends toward the light incident surface 101. The second doped region 113 is arranged around the first doped region 111, and a part of the structure of the second doped region 113 is exposed on the light emitting surface 103. The second doped region 113 extends from the light emitting surface 103 to the light incident surface 101, and the second doped region 113 is in contact with the second semiconductor region 13.

[0061] In one embodiment of the present invention, the ion concentrations doped at different positions in the first semiconductor region 11 are different. For example, a second doping region 113 (NW) is formed above the second semiconductor region 13 by doping with group V elements, such as non-metallic phosphorus (P) or metal arsenic (As), and a group V element with a higher concentration is doped on the basis of NW to form a heavily doped first doping region 111 (N+), and the first doping region 111 forms a cathode ohmic contact. The partial structure of the first doping region 111 is exposed on the light-emitting surface 103, which means that one surface of the first doping region 111 is exposed on the light-emitting surface 103, and it is not covered by other materials. The partial structure of the second doping region 113 is exposed on the light-emitting surface 103, which also means that one surface of the second doping region is exposed on the light-emitting surface 103, and it is not covered by other materials, and the second doping region 113 is arranged around the outer periphery of the first doping region 111. A first PN junction is formed on the surface where the second doped region 113 contacts the second semiconductor region 13 . In this region, the two regions have an overlapping portion in the lateral direction, thereby forming a first PN junction and enabling breakdown to occur at the junction of the two regions.

[0062] In one embodiment of the present invention, the third semiconductor region 15 includes a third doping region 151 and a fourth doping region 153, the third doping region 151 is partially exposed on the light emitting surface 103 from the third doping region 151, the third doping region 151 extends from the light emitting surface 103 to the light incident surface, the fourth doping region 153 is partially exposed on the light emitting surface 103, the fourth doping region 153 is arranged around the third doping region 151, and the fourth doping region 153 extends from the light emitting surface 103 to the direction of the light incident surface 101.

[0063] In this embodiment, a certain depth position near the edge of the substrate 10 can be lightly doped with a group III element, such as a non-metallic boron (B) element or a metal gallium (Ga), to form a third semiconductor region 15, which is a P-type well (P-Well, referred to as PW), to form an anode ohmic contact. The ion concentrations of the third doping region 151 and the fourth doping region 153 are different.

[0064] The present invention also proposes a method for preparing a single photon avalanche diode, comprising the following steps:

[0065] Depositing an insulating light-transmitting layer 21 on the light-emitting surface 103 of the device body 100;

[0066] Etching is performed on the surface of the insulating light-transmitting layer 21, so that the insulating light-transmitting layer 21 is formed into a plane 211 above the first semiconductor region 11, and the insulating light-transmitting layer 21 is formed into an inclined surface 213 above the third semiconductor region 15 and the isolation region;

[0067] A metal reflective layer 23 is deposited on the surface of the insulating light-transmitting layer 21 , and the metal reflective layer 23 and the insulating light-transmitting layer 21 form a light-focusing area in an area corresponding to the inclined surface 213 .

[0068] In one embodiment of the present invention, the device body 100 of the single-photon avalanche diode can adopt an existing structure, and optimize the reflective structure 20 on the surface of the device body 100 so that the light reflected by the reflective structure 20 is not uniformly directed to the inside of the device, but the light emitted from the edge area and the isolation area is converged to the photosensitive area located in the center, so that the photosensitive area can receive more light, effectively utilizing the light wasted in the existing solution, increasing the utilization rate of light, doubling the number of carriers generated, and improving the photon detection efficiency. Of course, the device body 100 of the single-photon avalanche diode can also adopt a new structure, and optimize the reflective structure 20 on the surface of the device body 100 adopting the new structure, so as to improve the photon detection efficiency of the single-photon avalanche diode.

[0069] The light-transmitting layer 21 is made of a transparent material, and the light-transmitting material includes one or more of silicon oxide, silicon nitride, and transparent glue. The light-transmitting material is usually made of insulating material to avoid affecting the electrode. The light-transmitting material can form a film layer of a certain thickness on the light-emitting surface 103, thereby increasing the travel of the light and providing the necessary distance for reflecting and converging the light. Among them, the thickness of each position in the light-transmitting layer 21 is not the same, and the thickness of the plane 211 is greater than the thickness of the inclined surface 213. In addition, the thickness of the inclined surface 213 changes uniformly, which can make the converged light also change uniformly, so that the light change in the photosensitive area is also relatively uniform, avoiding the appearance of bright and dark spots.

[0070] In this embodiment, the insulating light-transmitting layer 21 can be first deposited by vapor deposition to form one or more layers of light-transmitting material with uniform thickness, so as to form a flat insulating light-transmitting layer 21 on the light-emitting surface 103 of the device body 100, and then the deposited insulating transparent material is etched by etching above the position of the insulating light-transmitting layer 21 corresponding to the isolation region and the third semiconductor region 15, so that an inclined surface 213 appears on the outer edge of the transparent material. One end of the inclined surface 213 is directly connected to the light-emitting surface 103, and the other end is connected to the plane 211, so that the inclined surface 213 surrounds the outer periphery of the plane 211 structure. The angle θ formed by the inclined surface 213 and the light-emitting surface 103 is between ° and °, so that the reflection range of the focusing area can be improved to avoid the waste of light in the edge area. The material of the reflective layer 23 is a metal material, and the metal reflective layer 23 is directly deposited on the side of the light-transmitting layer 21 away from the light-emitting surface 103 by vapor deposition. It can be understood that the reflective layer 23 is opaque and can reflect light. Since the light-transmitting layer 21 is formed with a plane 211 and an inclined surface 213, the reflective surface of the reflective layer 23 is also formed with a plane 211 and an inclined surface consistent with the light-transmitting layer 21. The plane 211 can reflect the light emitted from the photosensitive area, and the inclined surface can reflect and converge the light emitted from the edge area and the isolation area, so that the reflected light converges to the photosensitive area, thereby improving the utilization rate of the light. It should be noted that the projection of the plane 211 of the light-transmitting layer 21 on the light-emitting surface 103 can extend to the outside of the photosensitive area, and is slightly larger than the width of the photosensitive area, so as to ensure that the light emitted from the photosensitive area can be evenly reflected by the plane 211 of the reflective layer 23.

[0071] The present invention also proposes a photodetector, which includes one or more single-photon avalanche diodes. The specific structure of the single-photon avalanche diode refers to the above embodiment. Since the single-photon avalanche diode adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here. Among them, multiple single-photon avalanche diodes are arranged in an array.

[0072] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A single photon avalanche diode, characterized in that: include: A device body is formed with a light incident surface and a light emitting surface which are arranged opposite to each other, a photosensitive area is also formed in the device body, the photosensitive area is extended from the light emitting surface to the light incident surface, the photosensitive area is located at the center of the device body, the photosensitive area is provided with a first semiconductor area and a second semiconductor area which are stacked downward from the light emitting surface, the device body also includes an edge area which is arranged outside the center, the edge area is provided with a third semiconductor area, and an isolation area is formed between the photosensitive area and the edge area; A reflective structure, wherein the reflective structure comprises a light-transmitting layer and a reflective layer, wherein the light-transmitting layer covers the light-emitting surface, wherein a surface of the light-transmitting layer away from the light surface is formed with a plane and an inclined surface connected to each other, wherein the plane is located above the first semiconductor region, and the inclined surface is located above the isolation region and the third semiconductor region, wherein the reflective layer covers a side of the light-transmitting layer away from the light-emitting surface, and the light-transmitting layer and the reflective layer form a light-collecting area in an area corresponding to the inclined surface; Light enters from the light incident surface and exits through the light exiting surface. The reflective structure reflects the light back to the inner side of the device body. The focusing area is used to focus the light emitted from the outer side of the photosensitive area into the photosensitive area.

2. The single photon avalanche diode according to claim 1, characterized in that: The angle formed by the inclined surface and the light emitting surface is θ, 15°≤θ≤45°.

3. The single photon avalanche diode according to claim 1, characterized in that: The projection of the plane of the light-transmitting layer on the light-emitting surface extends to the outside of the photosensitive area.

4. The single photon avalanche diode according to claim 1, characterized in that: The material of the light-transmitting layer includes one or more of silicon oxide, silicon nitride, and transparent glue; The reflective layer is made of metal.

5. The single photon avalanche diode according to any one of claims 1 to 4, characterized in that: The device body comprises: A substrate, wherein the light incident surface and the light emitting surface are respectively formed on two opposite surfaces of the substrate; A portion of the structure of the first semiconductor region is exposed on the light emitting surface and extends from the light emitting surface to the light incident surface, and the first semiconductor region is located at the center of the substrate; The second semiconductor region is arranged on a side of the first semiconductor region away from the light emitting surface, the second semiconductor region is extended from the light emitting surface to the light incident surface, a first PN junction is formed between the first semiconductor region and the second semiconductor region, and the first semiconductor region and the second semiconductor region form the photosensitive region; Part of the structure of the third semiconductor region is exposed on the light emitting surface and extends from the light emitting surface to the light incident surface. The third semiconductor region is located in the edge area of ​​the substrate.

6. The single photon avalanche diode according to claim 5, characterized in that: The first semiconductor region includes a first doped region and a second doped region. The surface of the first doped region is exposed on the light emitting surface and extends toward the light incident surface. The second doped region is arranged around the first doped region, and part of the structure of the second doped region is exposed on the light emitting surface. The second doped region extends from the light emitting surface to the light incident surface, and the second doped region is in contact with the second semiconductor region.

7. The single photon avalanche diode according to claim 6, characterized in that: The third semiconductor region includes a third doped region and a fourth doped region, wherein a portion of the structure of the third doped region is exposed on the light emitting surface, the third doped region extends from the light emitting surface toward the light incident surface, a portion of the structure of the fourth doped region is exposed on the light emitting surface, the fourth doped region is arranged around the third doped region, and the fourth doped region extends from the light emitting surface toward the light incident surface.

8. The single photon avalanche diode according to claim 6, characterized in that: The single-photon avalanche diode further includes a first electrode and a second electrode disposed on the light-emitting surface, wherein the first electrode is connected to the first semiconductor region, and the second electrode is connected to the third semiconductor region.

9. A method for preparing a single photon avalanche diode, for preparing the single photon avalanche diode as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: Depositing an insulating light-transmitting layer on the light-emitting surface of the device body; Etching the surface of the insulating light-transmitting layer so that the insulating light-transmitting layer above the first semiconductor region is formed into a flat surface, and the insulating light-transmitting layer above the third semiconductor region and the isolation region is formed into an inclined surface; A metal reflective layer is deposited on the surface of the insulating light-transmitting layer, and the metal reflective layer and the insulating light-transmitting layer form a light-focusing area in the area corresponding to the inclined surface.

10. A photoelectric detector, characterized in that: Comprising the single photon avalanche diode as claimed in any one of claims 1 to 8.

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