Single photon avalanche diodes, photodetector arrays, and image sensors

Abstract

The present disclosure relates to a single-photon avalanche diode, a photodetector array and an image sensor. The single-photon avalanche diode includes a substrate; a reflector, a semiconductor device and a microlens are sequentially stacked on the substrate; in a direction perpendicular to the substrate, the reflector includes a concave arc-shaped reflective structure; the arc range of the concave arc-shaped reflective structure is 5 degrees to 60 degrees. The technical solution provided by the present disclosure, the reflector includes a concave arc-shaped reflective structure, the arc-shaped reflective structure can reflect the light reaching the reflector back, so that the infrared light returns to the semiconductor device again and is absorbed by the semiconductor device for the second time, thereby improving the detection sensitivity. At the same time, the concave arc-shaped reflective structure can play a role in focusing light to avoid the reflected light from shining into the adjacent single-photon avalanche diode and causing optical crosstalk problems, thereby improving the detection accuracy of the single-photon avalanche diode.

Description

Technical Field

[0001] The present disclosure relates to the field of optical technology, and in particular to a single-photon avalanche diode, a photodetector array and an image sensor. Background Art

[0002] Single Photon Avalanche Diode (SPAD) is a photoelectric avalanche diode with weak light detection capability. It is widely used in Raman spectroscopy, positron emission tomography and fluorescence lifetime imaging due to its high gain, fast response and high sensitivity.

[0003] At present, microlenses are used on the surface of SPAD devices to focus light, so that the light in the non-avalanche area can be concentrated in the avalanche area to improve the fill factor. However, after adding the microlens, the incident light is not incident vertically on the SPAD device. In order to further enhance the detection capability of near-infrared light, in the related technology, a flat metal reflective film is usually added directly to the bottom of the SPAD device, so that the light reaching the metal reflective film will be reflected back, and the infrared light will return to the SPAD device again and be absorbed by the SPAD device for the second time, thereby improving the detection sensitivity of the SPAD device. However, the metal reflective film will reflect the light to the adjacent SPAD detector, thereby causing the technical problem of optical crosstalk. Summary of the invention

[0004] In order to solve the above technical problems, the present disclosure provides a single photon avalanche diode, a photodetector array and an image sensor.

[0005] The present disclosure provides a single photon avalanche diode, comprising a substrate;

[0006] A reflective device, a semiconductor device and a microlens are sequentially stacked on the substrate;

[0007] In a direction perpendicular to the substrate, the reflecting device comprises a concave arc-shaped reflecting structure; the curvature range of the concave arc-shaped reflecting structure is 5 degrees to 60 degrees.

[0008] In some embodiments, the reflective device includes multiple layers of first insulating layers; a first reflective layer is disposed inside each of the first reflective layers; and in a direction perpendicular to the substrate, the multiple layers of the first reflective layers form the concave arc-shaped reflective structure.

[0009] In some embodiments, in a direction from the substrate to the semiconductor device, the first reflective layer located at the bottom layer is arranged parallel to the substrate.

[0010] In some embodiments, in a direction from the substrate to the semiconductor device, an angle between the first reflective layer and the substrate gradually increases.

[0011] In some embodiments, the projection of the first reflective layer on the substrate can form a circle; the circular projections of the multiple layers of the first reflective layer on the substrate are multiple concentric circles.

[0012] In some embodiments, in a direction parallel to the substrate, a distance between two adjacent first reflective layers is greater than or equal to 30 nm and less than or equal to 50 nm.

[0013] In some embodiments, the reflective device includes a second reflective layer and a second insulating layer; the second reflective layer is a concave arc-shaped reflective structure; and the second reflective layer is disposed in the second insulating layer.

[0014] In some embodiments, the concave arc-shaped reflective structure comprises a reflective metalens.

[0015] The present disclosure also provides a photodetector array, comprising a plurality of single photon avalanche diodes as described above distributed in an array.

[0016] The present disclosure also provides an image sensor, comprising the photodetector array as described above.

[0017] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0018] The technical solution provided by the embodiment of the present disclosure is that a microlens is arranged above the semiconductor device, and the incident light is focused by the focusing effect of the microlens to focus the parallel incident light to the semiconductor device, and the infrared light is absorbed at the semiconductor device, and then passes through the semiconductor device to reach the reflecting device at the bottom. The reflecting device includes a concave arc-shaped reflecting structure, which can reflect the light reaching the reflecting device back, so that the infrared light returns to the semiconductor device again and is absorbed by the semiconductor device for the second time, thereby improving the detection sensitivity. At the same time, the concave arc-shaped reflecting structure can also reflect the light that is not vertically irradiated to the reflecting device into the semiconductor device, so that the light will not diverge after passing through the reflecting device, so as to avoid the optical crosstalk problem caused by the incident light passing through the planar metal reflective film and reflecting to both sides in the related art. Since there is no isolation between two adjacent single-photon avalanche diodes, in the technical solution provided by the embodiment of the present disclosure, the concave arc-shaped reflecting structure can play a role in focusing light, so as to avoid the problem of optical crosstalk caused by the reflected light shining into the adjacent single-photon avalanche diodes, thereby improving the detection accuracy of the single-photon avalanche diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0020] 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0021] Figure 1 A schematic diagram of the structure of a single photon avalanche diode provided in an embodiment of the present disclosure;

[0022] Figure 2 for Figure 1 A top view of the first reflective layer provided in;

[0023] Figure 3 A schematic diagram of the structure of another single-photon avalanche diode provided in an embodiment of the present disclosure;

[0024] Figure 4 A schematic diagram of the structure of a photodetector array provided in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0027] The present disclosure provides a single photon avalanche diode. Figure 1 A schematic diagram of the structure of a single photon avalanche diode provided in an embodiment of the present disclosure is shown in FIG. Figure 1 As shown, the single photon avalanche diode includes a substrate 1. A reflector 2, a semiconductor device 3 and a microlens 4 are sequentially stacked on the substrate 1. The reflector 2 is arranged between the substrate 1 and the semiconductor device 3. The semiconductor device 3 is arranged between the reflector 2 and the microlens 4. Figure 1 As shown, the direction perpendicular to the substrate 1 is the y direction, and the direction parallel to the substrate 1 is the x direction. In the direction y perpendicular to the substrate 1, the reflecting device 2 includes a concave arc-shaped reflecting structure. The arc range of the concave arc-shaped reflecting structure is 5 degrees to 60 degrees.

[0028] Specifically, when the incident light is irradiated to the semiconductor device 3 through the microlens 4, the semiconductor device 3 uses the avalanche multiplication effect to detect trace photons. Its working principle is: a reverse bias voltage greater than the avalanche breakdown voltage is applied to both ends of the semiconductor device 3. When photons are incident, the valence band electrons absorb the photons and transition to the conduction band, and generate photogenerated electron-hole pairs. The photogenerated electron-hole pairs are accelerated and obtain sufficient energy under the action of the external electric field, and collide with the lattice to generate new electron-hole pairs. The new electron-hole pairs are accelerated and collide with the lattice under the action of the external electric field to generate new electron-hole pairs. This is repeated, so that the number of carriers in the semiconductor device 3 increases rapidly, and the current increases sharply. This phenomenon is called the avalanche multiplication effect.

[0029] At present, single-photon avalanche diodes (SPADs) have a deep penetration depth due to the low absorption of near-infrared light in silicon. Usually, the thickness of the near-infrared semiconductor device 3 is 3-6 microns, and 70% of the near-infrared light will directly pass through the absorption part of the semiconductor device 3. In single-photon detection, when the light source is very weak, if the absorption area is too short, the probability of near-infrared light being detected will be reduced, so that the detection efficiency of the semiconductor device 3 when detecting light in the near-infrared is low. The technical solution provided by the embodiment of the present disclosure is that a microlens 4 is arranged above the semiconductor device 3, and the incident light is focused by the focusing effect of the microlens 4 to focus the parallel incident light to the semiconductor device 3, and the infrared light is absorbed at the semiconductor device 3, and then passes through the semiconductor device 3 to reach the reflecting device 2 at the bottom. The reflecting device 2 includes a concave arc-shaped reflecting structure, and the curvature range of the concave arc-shaped reflecting structure is 5 degrees to 60 degrees. In the arc range of 5 degrees to 60 degrees, the arc-shaped reflection structure can not only reflect the light reaching the reflection device 2 back, so that the infrared light returns to the semiconductor device 3 again and is absorbed by the semiconductor device 3 for the second time, thereby improving the detection sensitivity. At the same time, the concave arc-shaped reflection structure can also reflect the light that is not vertically irradiated to the reflection device 2 and focus it into the semiconductor device 3, so that the light will not diverge after passing through the reflection device 2, so as to avoid the optical crosstalk problem caused by the incident light passing through the plane metal reflection film and reflecting to both sides in the related technology. Since the two adjacent single-photon avalanche diodes are not isolated from each other, in the technical solution provided by the embodiment of the present disclosure, the arc range of the concave arc-shaped reflection structure is 5 degrees to 60 degrees, so that the concave arc-shaped reflection structure can focus the reflected light, so as to avoid the reflected light from shining into the adjacent single-photon avalanche diodes and causing optical crosstalk problems, thereby improving the detection accuracy of the single-photon avalanche diode.

[0030] In some embodiments, Figure 1As shown, the reflective device 2 includes multiple first insulating layers 22. A first reflective layer 21 is disposed in each first reflective layer 22. In the y direction perpendicular to the substrate 1, the multiple first reflective layers 21 form a concave arc-shaped reflective structure.

[0031] like Figure 1 As shown, the projections of the multi-layer first reflective layer 21 on the substrate 1 do not overlap.

[0032] The technical solution provided by the embodiment of the present disclosure can reduce the process manufacturing difficulty of the reflection device in the single-photon avalanche diode by setting multiple layers of first reflection layers to form a concave arc-shaped reflection structure, that is, the concave arc-shaped reflection structure can be prepared by a simple semiconductor manufacturing process. At the same time, it is convenient to adjust the inclination angle of each layer of the first reflection layer, that is, it is convenient to adjust the angle between the first reflection layer and the substrate, and then it is convenient to adjust the reflection light path of the incident light to meet the requirements of different single-photon avalanche diodes for focusing reflected light, and it is convenient to adjust the accuracy of the detection efficiency of the single-photon avalanche diode. In addition, by forming a concave arc-shaped reflection structure with multiple layers of first reflection layers, light that is not vertically irradiated to the reflection device can be reflected into the semiconductor device, so that the light will not diverge after passing through the reflection device, so as to avoid the optical crosstalk problem caused by the incident light passing through the plane metal reflection film and reflecting to both sides in the related art. Since two adjacent single-photon avalanche diodes are not isolated from each other, in the technical solution provided in the embodiment of the present disclosure, the concave arc-shaped reflective structure can play a role in focusing light to avoid the reflected light from entering the adjacent single-photon avalanche diodes and causing optical crosstalk problems, thereby improving the detection accuracy of the single-photon avalanche diodes.

[0033] In some embodiments, Figure 1 As shown, along the direction from substrate 1 to semiconductor device 3, the first reflective layer 21 at the bottom layer is arranged parallel to substrate 1. That is, the first reflective layer 21 arranged at the bottom layer in the reflective device 2 is arranged along the direction x parallel to substrate 1.

[0034] The technical solution provided by the embodiment of the present disclosure is that the first reflective layer at the bottom layer is arranged parallel to the substrate in the direction from the substrate to the semiconductor device. This facilitates the vertical light concentrated through the semiconductor device to be reflected back into the semiconductor device, and facilitates the semiconductor device to absorb the incident light for the second time, so as to improve the detection accuracy of the single-photon avalanche diode. At the same time, it also facilitates the overall structural design of the concave arc-shaped reflective structure in the reflective device, and the structure is simple and easy to implement.

[0035] In some embodiments, Figure 1 As shown, along the direction from the substrate 1 to the semiconductor device 3, the angle between the first reflective layer 21 and the substrate 1 gradually increases.

[0036] like Figure 1 As shown, the first reflective layer 21 located at the uppermost layer is located at the outermost area of ​​the reflective device 2, and the inward rotation angle of the first reflective layer 21 at the uppermost layer is the largest, that is, the angle between the first reflective layer 21 in the first insulating layer 22 and the substrate 1 is the largest. In the direction from the substrate 1 to the semiconductor device 3, as the height of the reflective device 2 increases, the number of layers of the first insulating layer 22 increases, and the angle between the first reflective layer 21 disposed in the first insulating layer 22 and the substrate 1 gradually increases.

[0037] In the technical solution provided by the embodiment of the present disclosure, the angle between the first reflection layer and the substrate gradually increases along the direction from the substrate to the semiconductor device. In this way, when the incident light shines into the first reflection layer through the microlens and the semiconductor device, the centripetal reflection capabilities of different first reflection layers are different. The first reflection layer located at the top layer has the largest inward rotation angle, that is, the angle between the first reflection layer located at the top layer and the substrate is the largest, so it can vertically reflect the incident light at the maximum angle back to the inside of the semiconductor device instead of reflecting it into the adjacent single-photon avalanche diode, which can effectively avoid the phenomenon of optical crosstalk. At the same time, it is also convenient to adjust the inclination angle of each layer of the first reflection layer, that is, it is convenient to adjust the angle between the first reflection layer and the substrate, and then it is convenient to adjust the reflected light path of the incident light to meet the requirements of different single-photon avalanche diodes for focusing the reflected light, and it is convenient to adjust the accuracy of the detection efficiency of the single-photon avalanche diode.

[0038] Figure 2 for Figure 1 A top view of the first reflective layer provided in FIG. 1 , in some embodiments, the projection of the multi-layer first reflective layer 21 on the substrate can be as follows: Figure 2 As shown, the projection of the first reflective layer 21 on the substrate 1 can form a circle. The circular projection of the multi-layer first reflective layer 21 on the substrate 1 is a plurality of concentric circles.

[0039] In the technical solution provided by the embodiment of the present disclosure, the projection of the first reflection layer on the substrate can form a circle, and the circular projections of the multi-layer first reflection layer on the substrate are multiple concentric circles. In this way, on any plane perpendicular to the substrate, it can be ensured that the first reflection layer can form a concave arc-shaped reflection structure to ensure that the light that is not vertically irradiated to the reflection device is reflected into the semiconductor device, so that the light will not diverge after passing through the reflection device, so as to avoid the optical crosstalk problem caused by the incident light passing through the planar metal reflection film and reflecting to both sides in the related art. Since there is no isolation between two adjacent single-photon avalanche diodes, in the technical solution provided by the embodiment of the present disclosure, the concave arc-shaped reflection structure can play a role in focusing light, so as to avoid the problem of optical crosstalk caused by the reflected light shining into the adjacent single-photon avalanche diodes, thereby improving the detection accuracy of the single-photon avalanche diode.

[0040] For example, Figure 2 As shown, the number of layers of the first insulating layer 22 is preferably 5. Along the height direction of the substrate 1, the reflecting device 2 includes a first first insulating layer, a second first insulating layer, a third first insulating layer, a fourth first insulating layer and a fifth first insulating layer stacked in sequence. Among them, the first first insulating layer includes one first reflecting layer 21. The second first insulating layer includes four first reflecting layers 21. The third first insulating layer includes eight first reflecting layers 21. The fourth first insulating layer includes twelve first reflecting layers 21. The fifth first insulating layer includes sixteen first reflecting layers 21.

[0041] In some embodiments, Figure 1 As shown, in the direction x parallel to the substrate 1 , the distance L1 between two adjacent first reflective layers 21 is greater than or equal to 30 nm and less than or equal to 50 nm.

[0042] The technical solution provided by the embodiment of the present disclosure sets the distance between two adjacent first reflective layers to be greater than or equal to 30nm and less than or equal to 50nm. This ensures that the first reflective layer can effectively reflect light that is not vertically irradiated to the reflective device into the semiconductor device, so that the light will not diverge after passing through the reflective device, so as to avoid the optical crosstalk problem caused by the incident light passing through the planar metal reflective film and reflecting to both sides in the related art. Since the two adjacent single-photon avalanche diodes are not isolated from each other, in the technical solution provided by the embodiment of the present disclosure, the concave arc-shaped reflective structure can play a role in focusing light, so as to avoid the reflected light from shining into the adjacent single-photon avalanche diodes and causing optical crosstalk problems, thereby improving the detection accuracy of the single-photon avalanche diode.

[0043] In some embodiments, Figure 1 As shown, the first reflective layer 21 is embedded in the first insulating layer 22, which is equivalent to inserting the first reflective layer 21 into the first insulating layer 22. On a plane perpendicular to the substrate 1, the thickness H1 of the first insulating layer 22 is 300-500nm, the thickness H2 of the first reflective layer 21 is 50-100nm, and the width L2 of the first reflective layer 21 is 500-1000nm.

[0044] The technical solution provided by the embodiment of the present disclosure is that, on a plane perpendicular to the substrate, the thickness of the first insulating layer is 300-500nm, the thickness of the first reflective layer is 50-100nm, and the width of the first reflective layer is 500-1000nm. This can ensure that the first reflective layer can effectively reflect the light that is not vertically irradiated to the reflective device into the semiconductor device, so that the light will not diverge after passing through the reflective device, avoiding the problem of optical crosstalk. At the same time, it can also reduce the difficulty of process preparation, improve the preparation yield of the reflective device, and make the structure of the reflective device simple and easy to implement.

[0045] Figure 3 A schematic diagram of the structure of another single photon avalanche diode provided in the embodiment of the present disclosure is shown in FIG. Figure 3 As shown, the reflective device 2 includes a second reflective layer 23 and a second insulating layer 24. The second reflective layer 23 is a concave arc-shaped reflective structure. The second reflective layer 23 is arranged in the second insulating layer 24.

[0046] For example, a groove structure is formed inside the second insulating layer 24, and the second reflective layer 23 is disposed on the inner wall of the groove structure.

[0047] like Figure 3 As shown, the direction indicated by the arrow is the optical path of the incident light passing through the microlens 4 and the semiconductor device 3 to irradiate the second reflective layer 23, and then reflected by the second reflective layer 23 back to the semiconductor device 3. Specifically, the incident light is focused by the focusing effect of the microlens 4, and the parallel incident light is focused to the semiconductor device 3, and the infrared light is absorbed at the semiconductor device 3, and then passes through the semiconductor device 3 to reach the second reflective layer 23 of the reflective device 2. The second reflective layer 23 is a concave arc-shaped reflective structure. The arc-shaped reflective structure can reflect the light reaching the second reflective layer 23 back, so that the infrared light returns to the semiconductor device 3 again and is absorbed by the semiconductor device 3 for the second time, thereby improving the detection sensitivity. At the same time, the concave arc-shaped reflective structure can also reflect the light that is not vertically irradiated to the reflective device 2 into the semiconductor device 3, so that the light will not diverge after passing through the reflective device 2, so as to avoid the optical crosstalk problem caused by the incident light passing through the planar metal reflective film and reflecting to both sides in the related art. Since two adjacent single-photon avalanche diodes are not isolated from each other, in the technical solution provided in the embodiment of the present disclosure, the concave arc-shaped reflective structure can play a role in focusing light to avoid the reflected light from entering the adjacent single-photon avalanche diodes and causing optical crosstalk problems, thereby improving the detection accuracy of the single-photon avalanche diodes.

[0048] In some embodiments, the concave curved reflective structure comprises a reflective metalens.

[0049] Metalens is a planar lens with a subwavelength structure on its surface. The focus of the metalens can be changed by adjusting the size and period of the subwavelength structure. Metalens are divided into reflective metalens and transmissive metalens according to the material used. Reflective metalens use metal materials to reflect and focus parallel light to a specified area, while transmissive metalens use dielectric materials to transmit and focus parallel light to a specified area. Compared with traditional optical lenses, metalens are lighter and thinner, and the production does not involve curved surfaces, avoiding errors such as spherical aberration and coma caused by the production process. Therefore, the technical solution provided by the embodiment of the present disclosure, the concave arc-shaped reflection structure includes a reflective metalens, which can utilize the characteristics of the reflective metalens that can reflect and focus parallel light to a specified area, and realize the reflection of light that is not vertically irradiated to the reflective device into the semiconductor device, so that the light will not diverge after passing through the reflective device, avoiding the problem of optical crosstalk.

[0050] In some embodiments, the microlens may be, for example, a transmissive metalens.

[0051] Corresponding to the single photon avalanche diode provided in the embodiment of the present disclosure, the embodiment of the present disclosure also provides a photodetector array, Figure 4 A schematic diagram of the structure of a photodetector array provided in an embodiment of the present disclosure is shown in FIG. Figure 4 As shown, the photodetector array includes a plurality of single photon avalanche diodes provided by the embodiments of the present disclosure distributed in an array. They have the same or corresponding beneficial effects, which will not be described here in order to avoid repetition.

[0052] refer to Figure 4 The structure of the photodetector array shown, when preparing the photodetector array provided by the embodiment of the present disclosure, the reflection device 2 array can be first designed using simulation software, and then a layer of the reflection device 2 array can be processed on the logic wafer 4. After the semiconductor device 3 is aligned and placed on the reflection device 2, and the semiconductor device 3 and the logic wafer 4 are bonded and fixed, the entire semiconductor device 3 and the logic wafer 4 are turned over, and then the back of the logic wafer 4 is thinned to the desired thickness. For example, the back of the logic wafer 4 can be thinned to 3-6 microns, and finally the microlens 4 array is placed on the other side of the thinned logic wafer 4 and fixed. The entire photodetector array structure is simple and easy to implement.

[0053] The embodiment of the present disclosure also provides an image sensor, including the photodetector array provided by the embodiment of the present disclosure, which has the same or corresponding beneficial effects and will not be described again to avoid repetition.

[0054] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0055] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A single photon avalanche diode, characterized in that: including a substrate; A reflective device, a semiconductor device and a microlens are sequentially stacked on the substrate; In a direction perpendicular to the substrate, the reflecting device comprises a concave arc-shaped reflecting structure; the curvature of the concave arc-shaped reflecting structure ranges from 5 degrees to 60 degrees; The reflecting device includes multiple layers of first insulating layers; a first reflecting layer is arranged in each of the first insulating layers; in a direction perpendicular to the substrate, the multiple layers of the first reflecting layers form the concave arc-shaped reflecting structure; along the direction from the substrate to the semiconductor device, the angle between the first reflecting layer and the substrate gradually increases.

2. The single photon avalanche diode according to claim 1, characterized in that: In a direction from the substrate to the semiconductor device, the first reflective layer located at the bottom layer is arranged parallel to the substrate.

3. The single photon avalanche diode according to claim 2, characterized in that: The projection of the first reflective layer on the substrate can form a circle; the circular projections of the multiple layers of the first reflective layer on the substrate are multiple concentric circles.

4. The single photon avalanche diode according to claim 2, characterized in that: In a direction parallel to the substrate, a distance between two adjacent first reflective layers is greater than or equal to 30 nm and less than or equal to 50 nm.

5. The single photon avalanche diode according to claim 1, characterized in that: The reflecting device comprises a second reflecting layer and a second insulating layer; the second reflecting layer is the concave arc-shaped reflecting structure; and the second reflecting layer is arranged in the second insulating layer.

6. The single photon avalanche diode according to claim 1, characterized in that: The concave arc-shaped reflective structure includes a reflective superlens.

7. A photodetector array, characterized in that: The invention comprises a plurality of single photon avalanche diodes as claimed in any one of claims 1 to 6 which are distributed in an array.

8. An image sensor, characterized in that: Comprising the photodetector array as claimed in claim 7.

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