Photodetectors, arrays and terminals

Abstract

The present invention provides a photodetector, array, and terminal including a semiconductor substrate and an optical structure formed on the semiconductor substrate, the optical structure including an optical waveguide and a light absorbing layer, the optical waveguide being suspended above the light absorbing layer, the optical waveguide including a first segment portion having a lattice structure and a second segment portion having a tapered structure, the lattice structure being used to diffract incident light and change the propagation direction of some of the light, and the light absorbing layer being disposed on the semiconductor substrate and used to absorb light transmitted through the lattice structure or absorb some of the light after diffracted by the lattice structure. The light absorption efficiency of the photodetector according to the present invention is relatively high.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to a Chinese patent application bearing application number 2022108799248 and entitled "Photodetector, Array and Terminal" filed on July 25, 2022, the contents of which are incorporated herein by reference.

[0002] The present invention relates to the field of integrated optics, and in particular to photodetectors, arrays and terminals. [Background technology]

[0003] Photodetectors are widely used in various applications, such as optical communications and optical sensing. Photodetectors are used to absorb light and convert it into photocurrent. In many optoelectronic products, such as photonic integrated circuits, photodetectors are often used for on-chip power monitoring, high-speed photoelectric demodulation, and so on. Responsivity, a measure of photoelectric conversion efficiency, is an important performance parameter of photodetectors. In some applications of integrated photonics, light needs to be coupled into the absorbing region of the photodetector from different positions. In some cases, for example, when incident perpendicularly to the surface of the photodetector, some light may be lost as it passes through the absorbing region downward into the substrate. As a result, the photodetector has a low responsivity, and maintaining a high responsivity in such cases presents a challenge.

[0004] Therefore, there is an urgent need to provide a new photodetector that can improve the light absorption efficiency of the photodetector. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a photodetector for improving photoelectric conversion efficiency. [Means for solving the problem]

[0006] According to a first aspect, the present invention provides a photodetector, array, and terminal comprising a semiconductor substrate and an optical structure formed on the semiconductor substrate, the optical structure comprising an optical waveguide and a light absorbing layer; the optical waveguide, the optical waveguide suspended above the light absorbing layer, the optical waveguide comprising a first segment portion which is a lattice structure and a second segment portion which is a tapered structure, the lattice structure being used to diffract incident light and change the propagation direction of some of the light; and the light absorbing layer, disposed on the semiconductor substrate, being used to absorb light rays transmitted through the lattice structure or absorb some of the light rays after diffracted through the lattice structure.

[0007] The beneficial effect of the photodetector according to the present invention is that the waveguide is fabricated in a tapered structure, which gradually expands the beam size and relaxes the coupling to the absorbing region. Thus, the incident light can be gradually absorbed by the light absorbing layer as it propagates along the waveguide, providing the photodetector with a relatively high photoelectric conversion efficiency. In addition to enhancing the response rate of the photodetector, the grating structure also helps improve the photodetector's resistance to large light incidence conditions, preventing saturation or damage to the detector. The grating structure can be designed as needed to allow light from any incident angle to propagate in any desired direction, thereby improving the interaction between the light and the absorbing material.

[0008] In a possible embodiment, the grating structure is a through-etched grating structure or a shallow-etched grating structure, or the grating structure is a multi-layer structure.

[0009] In another possible embodiment, the gratings of the grating structure have a curved shape that focuses on the second segment portion.

[0010] In yet another possible embodiment, the gratings of the grating structure are rectangular side corrugations.

[0011] In yet another possible embodiment, the lattices of the lattice structure are circular side risers.

[0012] In another possible embodiment, the lattices of the lattice structure are photonic crystal holes.

[0013] In yet another possible embodiment, a grating structure is provided at the interface between the lower surface of the light absorbing layer and the semiconductor substrate, and the grating structure is used to reflect light incident on the absorbing layer back into the light absorbing layer.

[0014] In yet another possible embodiment, a light reflecting layer is provided on the underside of the semiconductor substrate away from the light absorbing layer, in this way the light transmitted through the substrate can be reflected back to the absorbing region at any desired angle, thereby further improving the response rate.

[0015] In yet another possible embodiment, the realization of the light reflecting layer includes any one of a Bragg reflector, a metallic reflector, and a reflective film.

[0016] In yet another possible embodiment, the surface of the first segment part is a lattice structure.

[0017] In yet another possible embodiment, a grating structure is provided on the top surface of the light absorbing layer adjacent to the optical waveguide.

[0018] In a further possible embodiment, the photodetector further comprises a circuit layer electrically connected to the light absorbing layer for converting the optical signal absorbed by the light absorbing layer into an electrical signal.

[0019] According to a second aspect, the present invention further provides a photodetector array comprising a plurality of photodetectors distributed in an array, wherein said photodetectors comprise the photodetector according to any one of the embodiments of the first aspect.

[0020] According to a third aspect, the present invention further provides a light detection terminal including a device body and a light detector array according to the second aspect connected to the device body, wherein the device body performs photonic light detection by the light detector array. [Effects of the Invention]

[0021] The beneficial effects of the second and third aspects may be referred to the beneficial effects of the first aspect, and will not be further described. [Brief explanation of the drawings]

[0022] [Figure 1] 1A and 1B are cross-sectional and plan views of a photodetector according to the present invention; [Figure 2] FIG. 10 is a structural schematic diagram of a photodetector having another different optical waveguide structure according to the present invention. [Figure 3] FIG. 10 is a structural schematic diagram of a photodetector having another different optical waveguide structure according to the present invention. [Figure 4] 1A-1C are schematic diagrams of different gate structures according to the present invention; [Figure 5] 1 is a schematic diagram of a photodetector structure having a grating structure at the interface between the lower surface of the absorption layer and the substrate according to the present invention; [Figure 6] 1 is a schematic diagram of the structure of a photodetector having a Bragg reflector on a substrate according to the present invention; [Figure 7] 1 is a schematic diagram of a photodetector structure having a gate structure on the top surface of a light absorption layer according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0023] In order to clarify the objectives, technical solutions, and advantages of the present invention, the following clearly and completely describes the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. It is clear that the described embodiments are only a part of the embodiments of the present invention, and do not include all the embodiments. All other embodiments obtained based on the embodiments of the present invention without the need for creative efforts by those skilled in the art are within the scope of protection of the present invention. Unless otherwise defined, technical or scientific terms used herein have the ordinary meanings understood by those skilled in the art. As used in this specification, similar words such as "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects.

[0024] In response to the problems existing in the prior art, an embodiment of the present invention provides a photodetector 10, in which (a) in FIG. 1 shows a cross-sectional view of the photodetector, and (b) in FIG. 1 shows a plan view of the photodetector, and the photodetector includes a semiconductor substrate 10 and an optical structure 20 formed on the semiconductor substrate 10, wherein:

[0025] The optical structure 20 includes an optical waveguide 201 and a light absorbing layer 202. The optical waveguide 201 is suspended above the light absorbing layer 202, and includes a first segment portion having a lattice structure for diffracting incident light and changing the propagation direction of part of the light, and a second segment portion having a tapered structure. For example, (b) in FIG. 1 shows that the first segment portion of the optical waveguide 201 may have a uniform lattice structure or a non-uniform lattice structure.

[0026] In this embodiment, the optical waveguide may be made of one or more materials, including, but not limited to, silicon, silicon nitride, silicon oxynitride, silica, polymer, lithium niobate, indium phosphide, alumina, etc. The type of optical waveguide may be a channel waveguide, a ridge waveguide, a slot waveguide, a diffused waveguide, a photonic crystal waveguide, or other types. The tapered waveguide may not only exist along a straight line, but also in the form of a spiral, a ring, a folded shape, etc. Here, the contour curve of the tapered structure may be a plurality of curves, such as a linear curve, a quadratic curve, a parabolic curve, an Euler curve, a Bessel curve, etc. The optical waveguide may be single-layered or multi-layered.

[0027] The light absorbing layer 202 is disposed on the semiconductor substrate 10 and is used to absorb light after it has passed through and been diffracted by the optical waveguide 201. Optionally, the light absorbing layer 202 can be made of a variety of materials, including but not limited to germanium, silicon, metal, III-V materials, etc. The shape of the light absorbing layer 202 can be a cube, a cylinder, a cone, a pyramid, a groove, a ring, or other shapes. The absorbing layer can be a single layer or multiple layers.

[0028] In this embodiment, the photodetector can be based on many different operating principles, such as a PIN diode, a metal-semiconductor-metal photodetector, an avalanche photodiode, etc. In this embodiment, the orientation of the photodiode junction can be either horizontal or vertical. The junction can have a complex shape, such as an L-shape, a U-shape, etc.

[0029] Note that (b) in FIG. 1 shows that the first segment portion of the optical waveguide 201 is a through-etched grating, i.e., the grating structure can be fabricated by completely etching the first segment portion of the optical waveguide, and in another possible embodiment, FIG. 2 shows that the first segment portion of the optical waveguide 201 is a shallow-etched grating, i.e., the grating structure can be fabricated by partially etching the first segment portion of the optical waveguide.

[0030] In yet another possible embodiment, as shown in Fig. 3, the top surface of the first segment has a grating structure, which is the surface of the light absorption layer away from the optical waveguide. In one case, the grating structure can be formed by placing another material on the top surface of the first segment of the waveguide, and in another case, the grating structure is formed by placing the same material on the top surface of the first segment of the waveguide, thereby manufacturing a grating, as in the side view of the photodetector shown in Fig. 3. Note that the different material or the same material placed on the top surface of the first segment may cover the top surface of the first segment, and there may be a certain gap between the top surface of the first segment and the material.

[0031] In yet another possible embodiment, the lower surface of the first segment has a grating structure (not shown), which is the surface of the light absorbing layer adjacent to the optical waveguide. In one case, the grating structure can be formed by placing another material on the lower surface of the first segment of the waveguide. In another case, the grating structure is formed by placing the same material on the lower surface of the first segment of the waveguide, thereby manufacturing a grating. Note that the different material or the same material placed on the lower surface of the first segment may cover the lower surface of the first segment, and there may be a certain gap between the lower surface of the first segment and the material.

[0032] As shown in Figures 2 and 3, after passing through the lattice structure of the optical waveguide 201, a portion of the external incident light enters the optical absorption layer 202 and is absorbed, while the other portion of the light is coupled into the lattice structure. The arrows in Figure 2 illustrate the directional incidence, diffraction, penetration, and propagation. The second segment of the optical waveguide has a tapered structure, which gradually expands the beam size and couples it gently into the absorbing region, as shown in Figure 2. In this way, the light can be gradually absorbed as it propagates along the waveguide, resulting in a relatively high photoelectric conversion efficiency. As can be seen from Figure 2, depending on different application needs, the lattice design can improve the interaction between light and the absorbing material by redirecting light from any incident angle and propagating it in any desired direction. Furthermore, the lattice can be designed with different coupling coefficients, i.e., the ratio of the optical power entering the optical waveguide to the incident optical power can be adjusted as needed, for example, to 50%, 80%, or any other ratio.

[0033] Compared with conventional photodetectors, because they lack a lattice structure, all light enters the absorption region directly, and some light is wasted through the substrate, resulting in low photoelectric conversion efficiency. The photodetector structure of the present application couples some of the incident light into the optical waveguide, and as it propagates along the optical waveguide, it is gradually absorbed by the optical absorption layer, allowing the photodetector to have a relatively high photoelectric conversion efficiency. In addition to enhancing the response rate of the photodetector, the lattice structure also helps improve the photodetector's resistance to high light incidence, preventing detector saturation or damage. In conventional photodetectors without a lattice structure, strong incident light can cause the photodetector to saturate or be lost. In this embodiment, some light is guided into the waveguide and gradually absorbed by the optical absorption layer, allowing the detector to handle higher optical illumination intensities without saturating compared to conventional photodetectors.

[0034] In possible embodiments, the grating may be a focusing grating and be curved in shape, as shown in the plan view of Figure 4(a), or may have rectangular side corrugations, as shown in the plan view of Figure 4(b), or may have circular side risers, as shown in the plan view of Figure 4(c), or may have photonic crystal holes in the waveguide, as shown in the plan view of Figure 4(d).

[0035] In one possible embodiment, a grating structure is provided on the lower surface of the light-absorbing layer adjacent to the optical waveguide, as shown in FIG. 5 . Another grating structure may be provided on the interface between the lower surface of the light-absorbing layer and the semiconductor substrate. Specifically, in this embodiment, a Bragg reflection grating structure can be formed on the bottom surface of the substrate by processes such as film deposition, photoetching, and etching. In this way, light emitted toward the semiconductor substrate can be diffracted or reflected into the absorbing region at any desired angle, thereby further improving the response rate. Exemplarily, a photodetector corresponding to a grating structure provided on the lower surface of the light-absorbing layer is shown in FIG. 5(a), or a photodetector corresponding to a grating structure provided on the lower surface of the light-absorbing layer is shown in FIG. 5(b), or a photodetector corresponding to a grating structure provided on the lower surface of the light-absorbing layer is shown in FIG. 5(c). Note that a photodetector corresponding to a grating structure provided on the upper surface of the light-absorbing layer is shown in FIG. 5(d), i.e., the photodetector does not need to have an upper-layer waveguide grating.

[0036] In yet another possible embodiment, a light-reflecting layer 101 is provided on the lower surface of the semiconductor substrate away from the light-absorbing layer, so that light emitted toward the semiconductor substrate in this manner can be reflected by the absorbing region at any desired angle, thereby further improving the response rate, as shown in Figure 6. Exemplarily, a photodetector corresponding to a light-reflecting layer provided on the lower surface of the semiconductor substrate is shown in (a) of Figure 6, or a photodetector corresponding to a light-reflecting layer provided on the lower surface of the semiconductor substrate is shown in (b) of Figure 6, or a photodetector corresponding to a light-reflecting layer provided on the lower surface of the semiconductor substrate is shown in (c) of Figure 6.

[0037] In yet another possible embodiment, a grating structure is provided on the upper surface of the light absorbing layer adjacent to the optical waveguide, and light emitted toward the semiconductor substrate in this manner can be reflected by the absorbing region at any desired angle, as shown in Figure 7, thereby further improving the response rate. Exemplarily, a photodetector corresponding to a light reflective layer provided on the surface of a semiconductor substrate is shown in Figure 7(a). Alternatively, a photodetector corresponding to a light reflective layer provided on the surface of a semiconductor substrate is shown in Figure 7(b), i.e., the photodetector does not include an optical waveguide.

[0038] The operating wavelength range of the photodetector includes at least one of the visible, O, E, S, C, L, U, and mid-infrared wavebands. The waveguide grating of the photodetector can be designed to operate within one or more wavelength ranges as needed. Parameters such as bandwidth, intensity, sidelobes, and loss of the waveguide grating of the photodetector can also be designed and adjusted according to the needs of the application.

[0039] The waveguide grating of the photodetector may be uniform and periodic or non-uniform and periodic, and the dimensions of the etching depth, width, thickness, etc. of the waveguide grating of the photodetector may be uniform or non-uniform.

[0040] The size, such as shape, length, width, thickness, etc. of the absorption region of the photodetector can be designed or adjusted according to the needs of the application.

[0041] In one possible embodiment, the present application further provides a photodetector array, for example, a single photonic detector array or a silicon photomultiplier tube, which may include a plurality of photo-sensing units distributed in an array, each of which may include a photodetector as described in any one of the embodiments of the present application, wherein each unit may operate within the same or different wavelength ranges, wherein each unit may have the same or different photoresponsivity, and wherein each unit may be based on a different structure.

[0042] In one possible embodiment, the present application further provides a photonic chip that may include the photodetector or photodetector array described in any one of the above embodiments, and the photonic chip may be a ranging chip, a depth imaging chip, a time-of-flight chip, etc.

[0043] In one possible embodiment, the present application further provides a photodetector terminal that may include a device body and a photodetector array that are interconnected to perform photonic light sensing by the photodetector array described in any one of the embodiments of the present application, where the photodetector terminal may include a photosensitive distance measuring device, a mobile communication device, an image processing device, an optical sensing device, an optical interconnection device, etc.

[0044] Although the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as defined by the appended claims. Furthermore, the present invention described herein may have other embodiments and may be practiced or realized in multiple ways. [Explanation of symbols]

[0045] 10. Semiconductor substrate 101 Light reflective layer 20 optical structure, 201 Optical waveguide 202 Light absorbing layer.

Claims

1. A photodetector including a semiconductor substrate and an optical structure formed on the semiconductor substrate, the optical structure including an optical waveguide and a light absorbing layer; An optical waveguide, the optical waveguide being suspended above the light absorption layer, the optical waveguide including a first segment portion having a lattice structure for diffracting incident light and changing the propagation direction of a portion of the light, and a second segment portion having a tapered structure; a light absorbing layer disposed on the semiconductor substrate and used to absorb light rays transmitted through the grating structure or to absorb a portion of light rays after diffracted through the grating structure.

2. 2. The photodetector of claim 1, wherein the grating structure is a through-etched grating structure or a shallow-etched grating structure, or the grating structure is a multi-layer structure.

3. 3. The photodetector of claim 2, wherein the grating of the grating structure has a curved shape that focuses on the second segment portion.

4. 3. The photodetector according to claim 2, wherein the grating of the grating structure has a rectangular side corrugation.

5. 3. The photodetector of claim 2, wherein the grating of the grating structure is a circular side standpipe.

6. 3. The photodetector of claim 2, wherein the lattice of the lattice structure is a photonic crystal hole.

7. a lattice structure is provided on the interface between the lower surface of the light absorbing layer and the semiconductor substrate; 2. The photodetector of claim 1, wherein the grating structure is used to reflect light incident on the light absorbing layer back into the light absorbing layer.

8. 2. The photodetector according to claim 1, wherein a light-reflecting layer is provided on the underside of the semiconductor substrate.

9. 9. The photodetector of claim 8, wherein the implementation of the light reflecting layer includes one of a Bragg reflector, a metallic reflector, and a reflective film.

10. 9. The photodetector according to claim 1, wherein a grating structure is provided on an upper surface of the light absorption layer adjacent to the optical waveguide.

11. 9. The photodetector according to claim 1, wherein the surface of the first segment portion has a grating structure.

12. 9. The photodetector according to claim 1, further comprising a circuit layer electrically connected to the light absorbing layer for converting an optical signal absorbed by the light absorbing layer into an electrical signal.

13. A photodetector array comprising a plurality of photodetectors distributed in an array, wherein the photodetectors comprise the photodetector according to any one of claims 1 to 12.

14. 14. A photodetector terminal comprising: a device body; and a photodetector array according to claim 13 connected to said device body, wherein said device body performs photonic photodetection by said photodetector array.

Images