A photodetector

Abstract

This application discloses a photodetector, belonging to the field of photoelectric detection technology, comprising: an optical resonant cavity, a microlens, and a first reflecting device; the optical resonant cavity includes a light incident surface and a bottom reflecting surface, and an outer wall located between the light incident surface and the bottom reflecting surface; the first reflecting device is located on the surface of the light incident surface; the first reflecting device is used to reflect external light reflected from the bottom reflecting surface to the light incident surface back to the optical resonant cavity; the microlens is located on the side surface of the first reflecting device facing away from the optical resonant cavity. This application reduces the direct reflection of light entering the optical resonant cavity back to the outside of the detector via the bottom reflecting surface of the optical resonant cavity by reflecting light entering the optical resonant cavity, thereby effectively improving the photon absorption efficiency of the photodetector compared to existing technologies.

Description

Technical Field

[0001] This application relates to the field of photoelectric detection technology, and in particular to a photodetector. Background Technology

[0002] With the development of information technology, optical signals have become the primary carrier of information transmission. Photodetectors, as components capable of photoelectric conversion, are widely used in optoelectronic systems. However, in existing technologies, when the surface reflection of a photodetector is high, light easily undergoes multiple reflections with the matched receiving lens or filter, and is then received by the photodetector, causing signal interference and resulting in low light absorption efficiency, which directly affects product performance. Therefore, there is a need to provide a photodetector to solve the problem of low light absorption efficiency in existing photodetectors. Summary of the Invention

[0003] The purpose of this application is to provide a photodetector that improves photon absorption efficiency.

[0004] To achieve the above objectives, this application provides a photodetector, comprising: an optical resonant cavity, a microlens, and a first reflecting device; The optical resonant cavity includes a light incident surface and a bottom reflecting surface, as well as an outer wall located between the light incident surface and the bottom reflecting surface; The first reflecting device is located on the surface of the light incident surface; the first reflecting device is used to reflect external light rays reflected from the bottom reflecting surface to the light incident surface back to the optical resonant cavity; The microlens is located on the side surface of the first reflecting device that faces away from the optical resonant cavity.

[0005] Optionally, the first reflecting device is a metal reflector.

[0006] Optionally, the length of the first reflecting device and the angle between the incident light and the surface normal of the microlens are matched.

[0007] Optionally, the length of the first reflecting device is matched with the curvature of the microlens.

[0008] Optionally, the photodetector further includes: a second reflective device; The second reflective device is a nanostructure layer located on the surface of the bottom reflective surface.

[0009] Optionally, the surface of the microlens includes a double-sided anti-reflective film.

[0010] Optionally, the photodetector further includes: a passivation layer; The passivation layer is located between the microlens and the optical resonant cavity.

[0011] Optionally, the photodetector further includes: a spacer layer; The spacer layer is located between the microlens and the passivation layer, and is made of the same material as the microlens.

[0012] Optionally, the length of the first reflective device is matched with the thickness of the spacer layer.

[0013] Optionally, the photodetector further includes: an anti-reflective material layer; The anti-reflective material layer is located on the surface of the microlens or between the spacer layer and the passivation layer.

[0014] This application provides a photodetector comprising: an optical resonant cavity, a microlens, and a first reflecting device; the optical resonant cavity includes a light incident surface and a bottom reflecting surface, and an outer wall located between the light incident surface and the bottom reflecting surface; the first reflecting device is located on the surface of the light incident surface; the first reflecting device is used to reflect external light reflected from the bottom reflecting surface to the light incident surface back to the optical resonant cavity; the microlens is located on the side surface of the first reflecting device facing away from the optical resonant cavity.

[0015] Obviously, this application reduces the direct reflection of light entering the optical resonant cavity back to the outside of the detector by reflecting the light directly into the optical resonant cavity through the bottom reflective surface of the optical resonant cavity. Compared with the prior art, this can effectively improve the photon absorption efficiency of the photodetector. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the longitudinal section of a photodetector provided in an embodiment of this application; Figure 2 This is a schematic diagram showing the focal position under different lens refractive indices provided in the embodiments of this application; Figure 3 This is a schematic diagram of the longitudinal section of another photodetector provided in an embodiment of this application; Figure 4 This is a schematic diagram of the longitudinal section of another photodetector provided in an embodiment of this application.

[0018] AppendixFigure 1 , 3 In section 4, the annotations are explained as follows: 101a, 101b, 101c - Beams; 102-Microlens; 103-Spacer layer; 104-Passivation layer; 105, 106 - First reflecting device; 107 - Second reflecting device; 108-Light Absorption Layer; 109 - Lateral wall; L - Length of the light-absorbing layer; L1 - The length of the first reflecting device 106; L2 - The length of the first reflecting device 105; The thickness of the S-optical resonant cavity; The angles between θ-beams 101a, 101b, and 101c and the normal to the surface of the photodetector. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In existing technologies, when the surface reflectivity of a photodetector is high, light easily undergoes multiple reflections with the matching receiving lens or filter before being received by the photodetector, causing signal interference and directly affecting product performance. Therefore, this application provides a photodetector that, by incorporating a first reflection device, reflects light entering the optical resonant cavity back into the optical resonant cavity. This reduces signal interference caused by multiple reflections of light from the lens and effectively improves the photon absorption efficiency of the photodetector.

[0021] Please refer to Figure 1 , Figure 1This is a schematic longitudinal section diagram of a photodetector provided in an embodiment of this application. The photodetector may include: an optical resonant cavity, a microlens 102, and first reflecting devices 105 and 106. The optical resonant cavity includes a light incident surface and a bottom reflecting surface, and an outer wall 109 located between the light incident surface and the bottom reflecting surface. The first reflecting devices 105 and 106 are located on the surface of the light incident surface. The first reflecting devices 105 and 106 are used to reflect external light reflected from the bottom reflecting surface to the light incident surface back to the optical resonant cavity. The microlens 102 is located on the side surface of the first reflecting devices 105 and 106 facing away from the optical resonant cavity.

[0022] It should be noted that the area surrounded by the light incident surface, the bottom reflecting surface, and the outer wall 109 forms a light absorption layer 108, which is used to detect the light signal incident on the photodetector. This embodiment does not limit the specific configuration of the light absorption layer 108, as long as it can be used to detect the light signal incident on the photodetector. For example, the light absorption layer 108 can be composed of a photodiode.

[0023] This embodiment does not limit the specific types of the first reflecting devices 105 and 106, as long as they can reflect the external light reflected from the bottom reflecting surface to the light incident surface back to the optical resonant cavity. For example, the first reflecting devices 105 and 106 can be metal reflectors. This embodiment does not limit the specific composition of the metal reflector. For example, the metal reflector can be made of aluminum, metal / oxide, or semiconductor materials.

[0024] Furthermore, in order to accommodate light beams 101a, 101b and 101c incident from different angles and positions, and to block as many non-light-incident area openings as possible without blocking the effective light beam from entering the light absorption layer 108, the lengths of the first reflecting devices 105 and 106 and the angle between the incident light and the surface normal of the microlens 102 are matched in this embodiment.

[0025] It should be noted that the different curvatures of the microlenses 102 result in different lengths of the openings in the effective light beam incident area. Furthermore, in order to block as much of the non-light-incident area opening as possible without obstructing the effective light beam from entering the light-absorbing layer 108, the lengths of the first reflecting devices 105 and 106 in this embodiment are matched with the curvature of the microlenses 102. It is understood that the photodetector is a three-dimensional structure; viewed from top to bottom, the shape of the incident area opening can be circular, rectangular, or polygonal, and the first reflecting device can be a rectangle, polygon, etc., matching the opening shape. In several embodiments of this application, the accompanying drawings only show a longitudinal cross-sectional view of the photodetector. In addition to its length, the width of the first reflecting device also needs to be set according to the width of the detector to ensure that only the opening allows external light to enter, while other parts do not receive external light. The size of the first reflecting device matches the size of the opening; those skilled in the art can easily conceive of how to set the width of the first reflecting device, which will not be elaborated here.

[0026] Furthermore, to improve the photon absorption efficiency of the photodetector, this embodiment may also include a second reflective device 107; the second reflective device 107 is a nanostructure layer located on the surface of the bottom reflective surface. This embodiment does not limit the specific shape of the nanostructure layer; for example, it may be an array of serrated waveforms of equilateral or inverted triangles, or other combinations of shapes that can form a specific reflection angle with light.

[0027] It should be noted that the microlens 102 is used to focus the incident light onto the active region of the epitaxial material inside the resonant cavity. Furthermore, to increase light transmission, the surface of the microlens 102 in this embodiment includes a double-sided anti-reflective film.

[0028] Furthermore, to provide passivation protection, this embodiment may also include a passivation layer 104; the passivation layer 104 is located between the microlens 102 and the optical resonant cavity. This embodiment does not limit the specific composition of the passivation layer 104, for example, it may be formed by one or more passivation materials. This embodiment does not limit the specific type of passivation material, for example, the passivation material may be an oxide material, a high-k dielectric material, a nitride material, or a polyimide material.

[0029] This embodiment does not limit the specific manufacturing method of the microlens 102. For example, the microlens 102 can be monolithically integrated or made of optical material mechanically attached to the passivation layer 104.

[0030] It should be noted that different thicknesses of the spacer layer 103 result in different lengths of the opening in the effective beam incident region. Furthermore, to adjust the length of the opening in the effective beam incident region, this embodiment may further include a spacer layer 103; the spacer layer 103 is located between the microlens 102 and the passivation layer 104, and is made of the same material as the microlens 102. It should be noted that the spacer layer 103 can generally be constructed using the same material as the microlens 102, in which case the spacer layer 103 can be considered as part of the microlens 102. Furthermore, in order to block as much of the non-light-incident region opening as possible without obstructing the effective beam from entering the light-absorbing layer 108, the lengths of the first reflecting devices 105 and 106 in this embodiment are matched with the thickness of the spacer layer 103.

[0031] Furthermore, in order to improve the photon absorption efficiency of the photodetector, this embodiment may also include: an anti-reflective material layer; the anti-reflective material layer is located on the surface of the microlens 102 or between the spacer layer 103 and the passivation layer.

[0032] This embodiment does not limit the specific type of anti-reflective layer; it can be any optical material, such as any one or any combination of oxides, nitrides, or metal oxides.

[0033] It should be noted that a matte surface treatment is beneficial for photon scattering and reflection. Furthermore, in order to scatter and reflect more light signals to the light absorption layer 108, enhance photon capture capability, and thus improve photon absorption efficiency, the first reflection devices 105 and 106 and the second reflection device 107 in this embodiment include matte surfaces.

[0034] This embodiment does not limit the specific structure of the outer wall. The specific structure of the outer wall can be determined according to actual needs. For example, the outer wall can be a deep trench isolation structure.

[0035] Based on the above embodiments, this application reduces the direct reflection of light entering the optical resonant cavity back to the outside of the detector via the bottom reflecting surface of the optical resonant cavity by reflecting the light. Compared with the prior art, this can effectively improve the photon absorption efficiency of the photodetector.

[0036] The following examples illustrate the photodetector described above. Please refer to them. Figure 1 , Figure 2 , Figure 3 and Figure 4 , Figure 1 This is a schematic diagram of the longitudinal section of a photodetector provided in an embodiment of this application; Figure 2 This is a schematic diagram showing the focal position under different lens refractive indices provided in the embodiments of this application; Figure 3 This is a schematic diagram of the longitudinal section of another photodetector provided in an embodiment of this application; Figure 4This is a schematic longitudinal cross-sectional view of another photodetector provided in an embodiment of this application. The photodetector specifically includes: an optical resonant cavity, a microlens 102, a passivation layer 104, a spacer layer 103, first reflecting devices 105 and 106, and a second reflecting device 107. The optical resonant cavity includes a light incident surface and a bottom reflecting surface, and an outer wall 109 located between the light incident surface and the bottom reflecting surface. The area enclosed by the light incident surface, the bottom reflecting surface, and the outer wall 109 forms a light absorption layer 108, which is used to detect the light signal incident on the photodetector. The first reflecting devices 105 and 106 are located on the surface of the light incident surface and are used to reflect external light reflected from the bottom reflecting surface back to the optical resonant cavity. The microlens 102 is located on the side surface of the first reflecting devices 105 and 106 facing away from the optical resonant cavity. The second reflecting device 107 is a nanostructure layer located on the surface of the bottom reflecting surface. The passivation layer 104 is located between the microlens 102 and the optical resonant cavity. The spacer layer 103 is located between the microlens 102 and the passivation layer 104, and is made of the same material as the microlens 102. When beams 101a, 101b, and 101c are incident perpendicularly to the surface of the photodetector, the first reflecting device can be symmetrically arranged along the optical axis of the microlens 102, that is, the length L1 of the first reflecting device 106 and the length L2 of the first reflecting device 105 are the same, i.e., they have the same blocking range. See also Figure 1 This embodiment reduces the direct reflection of light entering the optical resonant cavity back to the outside of the detector by reflecting the light into the optical resonant cavity through the bottom reflective surface of the optical resonant cavity. Compared with the prior art, this can effectively improve the photon absorption efficiency of the photodetector.

[0037] See Figure 2 (a) shows the case where the surface curvature of microlens 102 is large, resulting in a higher focal point for light convergence within the optical resonant cavity; (b) shows the case where the surface curvature of microlens 102 is small, resulting in a lower focal point for light convergence within the optical resonant cavity; (c) shows the case where the surface curvature of microlens 102 is the same as in (b), but the thickness of spacer layer 103 is larger, resulting in a higher focal point for light convergence within the optical resonant cavity. By comparison, it can be seen that when the curvature is large, the thickness S of the optical resonant cavity can be set smaller. Furthermore, when the curvature remains constant and the thickness of spacer layer 103 is large, the thickness S of the optical resonant cavity can also be set smaller.

[0038] See Figure 3 (b) is the case where the surface curvature of the microlens 102 is small. In this case, the length of the opening in the incident region is large, and the focal point where the light converges in the optical resonant cavity is low. (c) is the case where the surface curvature of the microlens 102 is large and the thickness of the spacer layer 103 is large. In this case, the length of the opening in the incident region is small, and the focal point where the light converges in the optical resonant cavity is high. Figure 1 Microlenses with small curvature.Figure 3 (a) corresponds to the microlens with a large curvature. Through comparison, it can be seen that in the case where the curvature is relatively large and the thickness of the spacer layer 103 is relatively large, the length of the opening in the incident region is relatively small, the lengths of the first reflection devices 105 and 106 need to be set relatively long; and the thickness of the optical resonant cavity is relatively small.

[0039] When the surface curvature of the microlens 102 is larger, or the curvature remains unchanged and the thickness of the spacer layer 103 is greater, the length of the opening of the effective light beam incident region is smaller, so it is necessary to set a shielding range with a larger size, that is, the length L1 of the first reflection device 106 and the length L2 of the first reflection device 105 are increased (L1 = L2 > 1 / 3L), and a thinner optical resonant cavity, that is, the thickness S of the optical resonant cavity is reduced.

[0040] See Figure 4 , when the light beams 101a, 101b and 101c form an included angle θ with the normal to the surface of the photodetector, (b) is an optical path diagram of the light entering the photodetector after passing through the microlens when θ is 15 degrees; (c) is an optical path diagram of the light entering the photodetector after passing through the microlens when θ is 10 degrees; it can be seen that when θ is 0, the length L2 of the first reflection device 105 is the same as the length L1 of the first reflection device 106, at this time L2=L1, when θ is not 0, the length L2 of the first reflection device 105 is different from the length L1 of the first reflection device 106, at this time L2>L1. And through Figure 4 (b) and Figure 4 (c) comparison, when the curvatures of the microlenses are the same, the lengths of the openings in the incident region are the same, but for the one with a larger included angle, the opening is more deviated to the left, that is, the length L1(B) of the first reflection device 106 on the left side is less than L1(C), and the length L2(C) of the first reflection device 105 on the right side is greater than L2(B). Certainly, the light may also enter from the left side, and the description here is only illustrated by taking the light entering from the right side as an example.

[0041] The photodetector array includes 10 to 10000 photodetector units. A photodetector unit facing the laser directly is equivalent to vertical light incidence; a photodetector unit facing the laser laterally is equivalent to light incidence with an included angle. As the positions of the photodetector units are different, the length L1 of the first reflection device 106 and the length L2 of the first reflection device 105 will also be different. When the light beams 101a, 101b and 101c form an included angle θ with the normal to the surface of the photodetector, the length L2 of the first reflection device 106 and the length L1 of the first reflection device 105 should be set in a matching manner as the incidence of the marginal light beam changes.

[0042] This document uses specific examples to illustrate the principles and implementation methods of this application. The various embodiments are progressive, with each embodiment focusing on its differences from others. Similar or identical parts between embodiments can be referred to interchangeably. The descriptions of the embodiments above are merely illustrative of the method and core ideas of this application. For those skilled in the art, various improvements and modifications can be made to this application without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this application.

[0043] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

Claims

1. A photodetector, characterized in that, include: Optical resonant cavity, microlens and first reflection device; The optical resonant cavity includes a light incident surface and a bottom reflecting surface, as well as an outer wall located between the light incident surface and the bottom reflecting surface; the area surrounded by the light incident surface, the bottom reflecting surface, and the outer wall forms a light absorption layer; The first reflecting device is located on the surface of the light incident surface; the first reflecting device is used to reflect external light rays reflected from the bottom reflecting surface to the light incident surface back to the optical resonant cavity; The length of the first reflecting device and the angle between the incident ray and the surface normal of the microlens are matched, including: when the angle between the incident ray and the surface normal of the microlens is 0, the lengths of the portions of the first reflecting device located on both sides of the optical axis of the microlens are the same; when the angle between the incident ray and the surface normal of the microlens is not 0, the lengths of the portions of the first reflecting device located on both sides of the optical axis of the microlens are different. The length of the first reflecting device matches the curvature of the microlens, including: different curvatures of the microlenses result in different lengths of the openings in the effective light beam incident area; the first reflecting device is used to block the openings in the non-light beam incident area without blocking the effective light beam from entering the light absorption layer. The microlens is located on the side surface of the first reflecting device that faces away from the optical resonant cavity.

2. The photodetector according to claim 1, characterized in that, The first reflecting device is a metal reflector.

3. The photodetector according to claim 1, characterized in that, Also includes: Second reflecting device; The second reflective device is a nanostructure layer located on the surface of the bottom reflective surface.

4. The photodetector according to claim 1, characterized in that, The surface of the microlens includes a double-sided anti-reflective film.

5. The photodetector according to claim 1, characterized in that, Also includes: passivation layer; The passivation layer is located between the microlens and the optical resonant cavity.

6. The photodetector according to claim 5, characterized in that, Also includes: Spacer layer; The spacer layer is located between the microlens and the passivation layer, and is made of the same material as the microlens.

7. The photodetector according to claim 6, characterized in that, The length of the first reflective device is matched with the thickness of the spacer layer.

8. The photodetector according to claim 6, characterized in that, Also includes: Anti-reflective material layer; The anti-reflective material layer is located on the surface of the microlens or between the spacer layer and the passivation layer.

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