Photoelectric detector and preparation method thereof

Abstract

The invention discloses a photoelectric detector and a preparation method thereof. The photoelectric detector comprises a P-type junction region, an N-type junction region and an intrinsic absorption layer, wherein the P-type junction region and the N-type junction region are arranged on a substrate; the intrinsic absorption layer is arranged between the P-type junction region and the N-type junction region; and the optical metasurface structure is arranged on the intrinsic absorption layer of the light incident plane, and the optical metasurface structure is formed by an array of basic units formed by periodically arranging different sub-wavelength structures. According to the photoelectric detector, the local light field intensity on the intrinsic absorption layer can be effectively enhanced, so that the quantum efficiency of the photoelectric detector can be effectively improved, meanwhile, the thickness of the intrinsic absorption layer can be reduced, the response speed is further enhanced, and the absorption range of a communication waveband spectrum can be enhanced.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detector technology, and in particular to a photoelectric detector with high quantum efficiency, high response speed, and wide spectral range based on an optical metasurface and a preparation method thereof. Background Art

[0002] With the rapid development of the Internet, people's demand for information is increasing. The silicon-based microelectronics process, which is limited by Moore's Law, has gradually failed to meet the needs of high-bandwidth and ultra-high-speed information transmission. Silicon-based optoelectronics technology is regarded as one of the most promising technologies in the next generation of optical communications, optical sensing, and optical interconnection due to its advantages of high integration, low cost, wide-band response, high photon transmission rate, strong anti-interference, and compatibility with traditional silicon-based CMOS processes.

[0003] As one of the important active devices in silicon-based optoelectronic chips, photodetectors can be used to convert optical signals into electrical signals for output at the back end of the silicon-based optical transmission link. Types of photodetectors include surface-incident PIN (P-type junction-intrinsic layer-N-type junction) germanium photodetectors, which can realize photoelectric conversion of light absorption in free space. Its basic working principle is based on the photovoltaic effect. When a beam of photons larger than the semiconductor bandgap acts on the intrinsic germanium absorption layer (I-type layer), the electrons in the valence band absorb energy and transition to the conduction band, generating electron-hole pairs. The electron-hole pairs are separated under the action of the built-in electric field and the external reverse bias voltage. The intrinsic germanium absorption layer gradually shrinks and has a very high impedance, that is, photogenerated carriers are generated and photogenerated electron-hole pairs (EHP) are effectively collected.

[0004] Quantum efficiency and response speed are two important quality factors in photodetectors, which are related to photoelectric conversion efficiency and transmission rate. However, for surface-incident PIN photodetectors, quantum efficiency (responsivity) and response speed (bandwidth characteristics) are a pair of mutually restrictive relationships. If the quantum efficiency and responsivity are increased by increasing the thickness of the epitaxial germanium intrinsic absorption layer, the carrier transit time will increase while increasing the thickness of the germanium intrinsic absorption layer, so the response speed and bandwidth characteristics will naturally decrease. Usually, a resonant cavity reflector structure is added, that is, by placing a thin intrinsic germanium absorption layer in a micro-resonant cavity, the wavelength selectivity and resonance enhancement of the resonant cavity are used to eliminate the restrictive relationship between the quantum efficiency and response speed of the traditional PIN photodetector, thereby obtaining a high response speed and high quantum efficiency. However, the added resonant cavity structure will undoubtedly increase the complexity of the process.

[0005] Metasurface is a layered artificial electromagnetic structure composed of subwavelength basic units arranged in a special way in a plane. In essence, metasurface is a novel structural design concept. It breaks through the limitations of certain natural laws by orderly designing the structure at the key physical scale of the material, thereby obtaining extraordinary equivalent material functions. Metasurfaces can be used to flexibly and effectively control the polarization, amplitude, phase, polarization mode, propagation mode and other characteristics of electromagnetic waves or enhance the local light field intensity. The local modification of electromagnetic waves by metasurfaces was actually studied as early as 2005. For example, the new optical metasurface device based on the local phase modulation effect of SP (metal surface plasma) in the generalized Snell's law uses the characteristics of the SP propagation constant in the metal slit (metal metasurface) changing with the slit width to realize the resonance phenomenon of the metal surface plasma, and then adjust the local phase. Unlike metal metasurfaces, the resonance phenomenon of dielectric metasurfaces is not limited to the surface, and the design is more flexible, the processing is relatively simple, and there is no ohmic loss. In addition, the dielectric metasurface with subwavelength periodic structure can achieve simultaneous electrical and magnetic responses and realize collective resonance phenomena. For example, when light acts on a periodic non-magnetic polygonal dielectric metasurface material, it can also generate large magnetic dipole oscillations, thereby enhancing local electromagnetic waves. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and to provide a photoelectric detector and a method for preparing the same.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] The present invention provides a photoelectric detector, comprising:

[0009] A P-type junction region and an N-type junction region disposed on a substrate, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region;

[0010] An optical metasurface structure is arranged on the intrinsic absorption layer on the light incident surface, wherein the optical metasurface structure is formed by an array of basic units composed of periodically arranged different sub-wavelength structures.

[0011] Furthermore, the subwavelength structure includes a first subwavelength structure and a second subwavelength structure, the first subwavelength structure and the second subwavelength structure are periodically alternately arranged in the basic unit, the width of the first subwavelength structure and the length of the second subwavelength structure in a parallel direction and a vertical direction of the light incident surface of the intrinsic absorption layer are smaller than the wavelength of the communication band light, and the length of the first subwavelength structure is different from the length of the second subwavelength structure.

[0012] Furthermore, the first sub-wavelength structure and the second sub-wavelength structure are periodically and alternately arranged in the basic unit to form a discontinuous ring shape.

[0013] Furthermore, the first subwavelength structure and the second subwavelength structure are flush with each other at a first end facing the light incident surface, and the second ends of the first subwavelength structure and the second subwavelength structure relative to the first end extend into the intrinsic absorption layer and are located at different depths in the intrinsic absorption layer.

[0014] Furthermore, the first sub-wavelength structure and the second sub-wavelength structure include slots filled with a medium.

[0015] Furthermore, the medium includes graphite.

[0016] Further, the P-type junction region, the intrinsic absorption layer and the N-type junction region are arranged in sequence along the surface of the substrate, and a P-type contact region and an N-type contact region are respectively provided on the surface of the substrate outside the P-type junction region and the N-type junction region, and the first sub-wavelength structure and the second sub-wavelength structure extend from the surface of the intrinsic absorption layer toward the substrate into the intrinsic absorption layer; or, the P-type junction region, the intrinsic absorption layer and the N-type junction region are stacked in sequence along the vertical direction of the substrate surface, a P-type contact region is also provided on the surface of the substrate on the side of the P-type junction region, and an N-type contact region is also provided on the surface of the N-type junction region, and the first sub-wavelength structure and the second sub-wavelength structure extend from the surface of the N-type contact region toward the substrate through the N-type junction region into the intrinsic absorption layer.

[0017] The present invention also provides a method for preparing a photoelectric detector, comprising:

[0018] providing a substrate;

[0019] Forming a P-type junction region, an N-type junction region, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region on the substrate;

[0020] An optical metasurface structure is formed on the intrinsic absorption layer of the light incident surface, wherein the optical metasurface structure is formed by an array of basic units composed of periodically arranged different sub-wavelength structures.

[0021] Further, the forming of a P-type junction region, an N-type junction region, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region on the substrate specifically includes:

[0022] forming a phase-separated P-type junction region and an N-type junction region on the surface of the substrate;

[0023] forming a groove on the surface of the substrate between the P-type junction region and the N-type junction region, so that the sidewalls of the groove are connected to the side surfaces of the P-type junction region and the N-type junction region;

[0024] forming an intrinsic absorption layer in the groove;

[0025] The optical metasurface structure is formed on the intrinsic absorption layer of the light incident surface, wherein the optical metasurface structure is formed by an array of basic units formed by periodically arranging different sub-wavelength structures, and specifically comprises:

[0026] Forming a first slot and a second slot having different depths and having a bottom located in the intrinsic absorption layer on the surface of the intrinsic absorption layer facing the light incident surface, so that the width and depth of the first slot and the second slot are smaller than the wavelength of the communication band light, and the first slot and the second slot are periodically and alternately arranged to form a basic unit, and form an array of the basic units;

[0027] A medium is filled in the first slot and the second slot to form a first subwavelength structure and a second subwavelength structure, thereby forming an optical metasurface structure formed by an array of basic units periodically arranged by the first subwavelength structure and the second subwavelength structure on the intrinsic absorption layer of the light incident surface.

[0028] Further, the forming of a P-type junction region, an N-type junction region, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region on the substrate specifically includes:

[0029] forming a P-type junction region and a P-type contact region on the surface of the substrate;

[0030] forming a dielectric layer on the surface of the substrate to at least cover the P-type junction region;

[0031] forming a groove on the surface of the dielectric layer above the P-type junction region, stopping on the surface of the P-type junction region;

[0032] forming an intrinsic absorption layer in the groove;

[0033] forming an N-type junction region made of the same material as the intrinsic absorption layer on a surface of the intrinsic absorption layer;

[0034] forming an N-type contact region made of the same material as the substrate on the surface of the N-type junction region;

[0035] The optical metasurface structure is formed on the intrinsic absorption layer of the light incident surface, wherein the optical metasurface structure is formed by an array of basic units formed by periodically arranging different sub-wavelength structures, and specifically comprises:

[0036] A first slot and a second slot having different depths and having their bottoms located in the intrinsic absorption layer are formed on the surface of the N-type contact region facing the light incident surface, so that the width and depth of the first slot and the second slot are smaller than the wavelength of the light in the communication band, and the first slot and the second slot are periodically and alternately arranged to form a basic unit, and form an array of the basic units;

[0037] A medium is filled in the first slot and the second slot to form a first subwavelength structure and a second subwavelength structure, thereby forming an optical metasurface structure formed by an array of basic units periodically arranged by the first subwavelength structure and the second subwavelength structure on the intrinsic absorption layer of the light incident surface.

[0038] It can be seen from the above technical scheme that the present invention arranges an optical metasurface structure formed by an array of basic units composed of different subwavelength structures periodically arranged on the intrinsic absorption layer (I-type layer) of the PIN-type photodetector. When light acts on the surface of the optical metasurface structure, anti-phase electric dipole and magnetic dipole (collectively referred to as dipole) oscillation resonance modes can be generated. Since there is asymmetry between different subwavelength structures in the basic unit of the optical metasurface structure, the dipole oscillation has different dipole moments. Therefore, the incomplete destructive interference between adjacent dipoles can be used to effectively enhance the local light field intensity on the intrinsic absorption layer, thereby effectively increasing the quantum efficiency of the photodetector. At the same time, the thickness of the intrinsic absorption layer can be reduced, thereby enhancing the response speed. For light in the communication band, the absorption range of the spectrum can be enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the structure of a horizontally structured PIN-type photodetector according to a preferred embodiment of the present invention;

[0040] Figure 2-Figure 3 A top view of an optical metasurface structure according to a preferred embodiment of the present invention;

[0041] Figure 4-Figure 5 An oblique view of an optical metasurface structure according to a preferred embodiment of the present invention;

[0042] Figure 6 A schematic diagram of a vertical PIN photodetector according to a preferred embodiment of the present invention;

[0043] Figure 7-Figure 14 This is a process flow chart of a method for preparing a horizontally structured PIN-type photoelectric detector according to a preferred embodiment of the present invention;

[0044] Figure 15-Figure 21This is a process flow chart of a method for preparing a vertically structured PIN-type photodetector according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are 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. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0046] In order to solve the problems of mutual restriction between quantum efficiency and response speed, low light absorption rate and utilization rate in surface-incident PIN photodetectors, various optical structures can be used to achieve high light absorption efficiency. In this way, even in a thin intrinsic absorption layer (type I layer), good high responsiveness and photoelectric conversion efficiency can be achieved. Therefore, an optical metasurface structure can be designed on a surface-incident PIN photodetector to achieve localized absorption enhancement of light, replacing the traditional resonant cavity or reflector structure, so as to simultaneously achieve high quantum efficiency, high response speed and wide spectral absorption range, and solve the process complexity problem existing in the traditional resonant cavity structure.

[0047] A photoelectric detector of the present invention comprises:

[0048] A P-type junction region and an N-type junction region disposed on a substrate, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region;

[0049] An optical metasurface structure is arranged on the intrinsic absorption layer on the light incident surface, wherein the optical metasurface structure is formed by an array of basic units composed of periodically arranged different sub-wavelength structures.

[0050] The present invention arranges an optical metasurface structure formed by an array of basic units composed of different subwavelength structures periodically arranged on the intrinsic absorption layer (I-type layer) of a PIN-type photodetector. When light acts on the surface of the optical metasurface structure, anti-phase electric dipole and magnetic dipole (collectively referred to as dipole) oscillation resonance modes can be generated. Since different subwavelength structures in the basic units of the optical metasurface structure are asymmetric, the dipole oscillations have different dipole moments. Therefore, the incomplete destructive interference between adjacent dipoles can be used to effectively enhance the local light field intensity on the intrinsic absorption layer, thereby effectively increasing the quantum efficiency of the photodetector. At the same time, the thickness of the intrinsic absorption layer can be reduced, thereby enhancing the response speed. For light in the communication band, the absorption range of the spectrum can be enhanced.

[0051] A method for preparing a photodetector of the present invention can adopt a method compatible with CMOS process to prepare a surface-incident PIN type photodetector with an optical metasurface structure. The prepared optical metasurface structure can replace the traditional resonant cavity or reflector structure, thereby solving the process complexity problem existing in the traditional resonant cavity structure.

[0052] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0053] See also Figure 1 , Figure 1 FIG. 1 is a schematic diagram of a horizontal PIN type photodetector according to a preferred embodiment of the present invention. Figure 1 As shown, a photodetector of the present invention includes a P-type junction region 14 (P+), an N-type junction region 18 (N+), an intrinsic absorption layer 23 and an optical metasurface structure 17 arranged on a substrate 10.

[0054] The intrinsic absorption layer 23 is connected between the P-type junction region 14 and the N-type junction region 18, and the optical metasurface structure 17 is disposed on a side of the intrinsic absorption layer 23 facing the light incident surface ( Figure 1 Furthermore, the P-type junction region 14, the intrinsic absorption layer 23 and the N-type junction region 18 are sequentially arranged along the upper surface of the substrate 10 as shown in the figure, forming a PIN-type photodetector with a surface-incident horizontal structure.

[0055] The optical metasurface structure 17 is formed by an array of basic units composed of periodic arrangements of different sub-wavelength structures.

[0056] See also Figure 1 , Figure 2 and Figure 4In some embodiments, the sub-wavelength structure includes different first sub-wavelength structures 15 and second sub-wavelength structures 16. The first sub-wavelength structure 15 and the second sub-wavelength structure 16 are parallel to the light incident surface of the intrinsic absorption layer 23 ( Figure 1 The width (horizontal dimension) and vertical dimension ( Figure 1 The length (vertical direction) of the first sub-wavelength structure 15 is smaller than the wavelength of the communication band light, thereby forming a sub-wavelength structure. In addition, the length of the first sub-wavelength structure 15 is different from the length of the second sub-wavelength structure 16. For example, the first sub-wavelength structure 15 and the second sub-wavelength structure 16 can be a column, and the axial direction ( Figure 1 The first sub-wavelength structure 15 is perpendicular to the surface of the intrinsic absorption layer 23, and the length of the column of the first sub-wavelength structure 15 is greater than the length of the column of the second sub-wavelength structure 16 (or vice versa).

[0057] A plurality of first sub-wavelength structures 15 and second sub-wavelength structures 16 are arranged in an alternating periodic manner to form a basic unit 24. A plurality of basic units 24 are sequentially arranged on the surface of the intrinsic absorption layer 23 facing the light incident direction to form an array of basic units 24, and the array of basic units 24 further forms an optical metasurface structure 17 located on the surface of the intrinsic absorption layer 23 facing the light incident direction. For example, the basic unit 24 may be composed of three first sub-wavelength structures 15 and three second sub-wavelength structures 16 alternately arranged in an intermittent ring shape (i.e., the connection line of the first sub-wavelength structures 15 and the second sub-wavelength structures 16 alternately arranged at intervals forms a ring shape, the same below), such as Figure 2 , Figure 4 shown.

[0058] For another example, the basic unit 24 may be composed of two first sub-wavelength structures 15 and two second sub-wavelength structures 16 that are alternately arranged in a discontinuous ring shape, such as Figure 3 , Figure 5 It can be understood that the ring formed by connecting the multiple first sub-wavelength structures 15 and the multiple second sub-wavelength structures 16 arranged alternately at intervals can be a circular ring, an elliptical ring, a polygonal ring or a special-shaped ring, and each basic unit 24 has the same arrangement of the first sub-wavelength structure 15 and the second sub-wavelength structure 16.

[0059] In some embodiments, the first sub-wavelength structure 15 and the second sub-wavelength structure 16 of the column face the first end of the light incident surface ( Figure 1 The second ends of the first sub-wavelength structure 15 and the second sub-wavelength structure 16 ( Figure 1The first sub-wavelength structure 15 and the second sub-wavelength structure 16 are formed at different depths in the intrinsic absorption layer 23. For example, the depth of the lower end of the first sub-wavelength structure 15 in the intrinsic absorption layer 23 is greater than the depth of the lower end of the second sub-wavelength structure 16 in the intrinsic absorption layer 23, so that the length of the first sub-wavelength structure 15 is greater than the length of the second sub-wavelength structure 16.

[0060] In some embodiments, the first subwavelength structure 15 and the second subwavelength structure 16 include slots filled with a medium. In other words, the first subwavelength structure 15 is formed by a longer dielectric column filled in the first slot (deep hole), and the second subwavelength structure 16 is formed by a shorter dielectric column filled in the second slot (shallow hole). Thus, the optical metasurface structure 17 becomes a dielectric metasurface structure formed by the dielectric first subwavelength structure 15 and the dielectric second subwavelength structure 16.

[0061] In some embodiments, the substrate 10 may be made of silicon, and the intrinsic absorption layer 23 may be made of germanium.

[0062] In some embodiments, the medium filled in the slots (the first slots, the second slots) includes graphite or the like.

[0063] The present invention designs the above-mentioned novel medium metasurface structure (optical metasurface structure 17) in the form of deep and shallow holes, and forms a basic unit 24 of the metasurface by combining a deep hole structure (first subwavelength structure 15) and a shallow hole structure (second subwavelength structure 16) arranged in a subwavelength periodic manner, and further increases the light utilization rate and reduces the ohmic loss by depositing, for example, a graphite medium in the slot. When light acts on the graphite metasurface of the deep and shallow hole structure, an anti-phase electric dipole and magnetic dipole oscillation resonance mode can be generated. Due to the asymmetry of the basic unit 24 of the graphite metasurface of the deep and shallow hole structure, the above-mentioned dipole oscillations have different dipole moments, so the incomplete destructive interference between adjacent dipoles can effectively enhance the local light field intensity on the germanium intrinsic absorption layer 23, and while effectively increasing the quantum efficiency of the photodetector, can reduce the thickness of the intrinsic absorption layer 23, thereby enhancing the response speed. In addition, the subwavelength deep and shallow hole structure can enhance the spectral absorption range for light in the communication band. Moreover, for a horizontally structured PIN-type photodetector, there is a problem that the electric field distribution in the vertical direction of the germanium intrinsic absorption layer 23 is uneven, and the upper part of the germanium intrinsic absorption layer 23 cannot achieve a high saturated carrier mobility due to the small electric field. The application of the graphite metasurface in the upper part of the germanium intrinsic absorption layer 23 can solve this problem well.

[0064] In some embodiments, the substrate 10 can be formed by an SOI silicon wafer 100, which has a bottom silicon layer 101, an intermediate buried oxide layer 102 and a top silicon layer 103 from bottom to top. The top silicon layer 103 can be used as the above-mentioned substrate 10 of the present invention, and a horizontally structured PIN-type photodetector with an optical supersurface structure 17 can be established on the top silicon layer 103 of the SOI silicon wafer 100.

[0065] In some embodiments, the lower portion of the germanium intrinsic absorption layer 23 is buried in the silicon substrate 10, and the upper portion protrudes above the surface of the silicon substrate 10; the lower ends of the first subwavelength structure 15 and the second subwavelength structure 16 on the dielectric metasurface structure are located in the germanium intrinsic absorption layer 23 and are located at the upper portion of the germanium intrinsic absorption layer 23.

[0066] In some embodiments, a first dielectric layer 12 may be disposed on the surface of the silicon substrate 10 and surround the germanium intrinsic absorption layer 23 from the side.

[0067] In some embodiments, a passivation layer 13 may be provided on the surface of the first dielectric layer 12 , and covers the germanium intrinsic absorption layer 23 and the optical metasurface structure 17 .

[0068] In some embodiments, a P-type contact region 11 (P++) and an N-type contact region 22 (N++) are respectively provided on the surface of the substrate 10 outside the P-type junction region 14 and the N-type junction region 18. Furthermore, an electrode window with a bottom located on the surface of the P-type contact region 11 and the N-type contact region 22 may be provided on the surface of the passivation layer 13 above the P-type contact region 11 and the N-type contact region 22, and an electrode 21 is provided in the electrode window. The P-type contact region 11 and the N-type contact region 22 may be connected to the upper pad 19 through the electrode 21 and the electrode lead 20 (for example, a second dielectric layer may be provided on the passivation layer 13, which is omitted in the figure here; the pad 19 may be provided on the surface of the second dielectric layer, and the electrode lead 20 is located in the second dielectric layer between the pad 19 and the electrode 21).

[0069] See also Figure 6 , Figure 6 FIG. 1 is a schematic diagram of a vertical PIN photodetector according to a preferred embodiment of the present invention. Figure 6 As shown, a photodetector of the present invention includes a P-type junction region 14, an N-type junction region 18, an intrinsic absorption layer 23 and an optical metasurface structure 17 arranged on a substrate 10.

[0070] The P-type junction region 14 is disposed on the surface of the substrate 10, and the P-type junction region 14, the intrinsic absorption layer 23 and the N-type junction region 18 are stacked in sequence on the substrate 10 along the vertical direction of the surface of the substrate 10 to form a PIN-type photodetector with a surface-incident vertical structure.

[0071] In addition, a P-type contact region 11 is provided on the surface of the substrate 10 at the side of the P-type junction region 14 , and an N-type contact region 22 is provided on the surface of the N-type junction region 18 .

[0072] In this embodiment, the composition of the optical metasurface structure 17 is similar to that described above. Figure 1 The embodiment shown is the same. Figure 1 The difference between the illustrated embodiment is that, in the present embodiment, the first subwavelength structure 15 and the second subwavelength structure 16 on the optical metasurface structure 17 extend from the surface of the N-type contact region 22 downward through the N-type junction region 18 into the intrinsic absorption layer 23, and have different subwavelength depths in the intrinsic absorption layer 23.

[0073] In some embodiments, the material of the N-type junction region 18 is the same as the material of the intrinsic absorption layer 23. The material of the intrinsic absorption layer 23 may be germanium.

[0074] In some embodiments, the material of the N-type contact region 22 is the same as that of the substrate 10. The material of the substrate 10 may be silicon.

[0075] By setting an N-type contact region 22 of silicon material on the intrinsic absorption layer 23 of germanium material, and setting a graphite metasurface (optical metasurface structure 17) on the surface of the N-type contact region 22, it can not only play a role in modifying and enhancing the light field intensity, but also the N-type contact region 22 of silicon material can be used as a cap layer for the intrinsic absorption layer 23 of germanium material, which can effectively prevent the germanium oxidation problem of the intrinsic absorption layer 23.

[0076] In some embodiments, the substrate 10 can be formed by an SOI silicon wafer 100, which has a bottom silicon layer 101, an intermediate buried oxide layer 102 and a top silicon layer 103 from bottom to top. The top silicon layer 103 can be used as the above-mentioned substrate 10 of this embodiment, and a vertically structured PIN-type photodetector with an optical supersurface structure 17 is established on the top silicon layer 103 of the SOI silicon wafer 100.

[0077] In some embodiments, a first dielectric layer 12 may be disposed on the surface of the silicon substrate 10 and surround the germanium intrinsic absorption layer 23 , the N-type junction region 18 and the N-type contact region 22 from the side.

[0078] In some embodiments, a passivation layer 13 may be provided on the surface of the first dielectric layer 12 , and covers the N-type contact region 22 and the optical metasurface structure 17 .

[0079] In some embodiments, the P-type contact region 11 and the N-type contact region 22 can be respectively connected to the upper pad 19 through the electrode 21 passing through the passivation layer 13 and the electrode lead 20 connected to the electrode 21 to achieve metal interconnection (the passivation layer 13 may be provided with, for example, a second dielectric layer, which is omitted in the figure here; the pad 19 may be provided on the surface of the second dielectric layer, and the electrode lead 20 is located in the second dielectric layer between the pad 19 and the electrode 21).

[0080] A photoelectric detector preparation method of the present invention is further described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0081] See also Figure 7-Figure 14 , Figure 7-Figure 14 FIG. 1 is a process flow chart of a method for preparing a horizontal PIN type photoelectric detector according to a preferred embodiment of the present invention. Figure 7-Figure 14 As shown, a photoelectric detector preparation method of the present invention can be used to prepare, for example Figure 1 A photoelectric detector as shown may include the following steps:

[0082] Step S1: providing a substrate 10 .

[0083] like Figure 7 As shown, a SOI silicon wafer 100 may be used. The SOI silicon wafer 100 has a bottom silicon layer 101, a middle buried oxide layer 102 and a top silicon layer 103 from bottom to top. The top silicon layer 103 is used as the substrate 10 of this embodiment.

[0084] The SOI silicon wafer 100 may be cleaned first. In one example, the SOI silicon wafer 100 may be placed in an NMP (N-methylpyrrolidone) reagent and ultrasonically cleaned (e.g., for about 5 minutes); then, the SOI silicon wafer 100 may be soaked and cleaned using acetone (e.g., soaked for about 1 minute) to further remove particles, organic matter, and other contaminants on the surface of the substrate 10, and residual liquid on the surface of the substrate 10 may be blown away using, for example, N2.

[0085] Step S2 : forming a P-type junction region 14 , an N-type junction region 18 , and an intrinsic absorption layer 23 disposed between the P-type junction region 14 and the N-type junction region 18 on the substrate 10 .

[0086] like Figure 8 As shown, first, on the SOI silicon wafer 100 as the substrate 10 (the bottom silicon layer 101 is omitted in the figure, please refer to Figure 7For example, a plasma enhanced chemical vapor deposition (PECVD) process can be used to grow a stable silicon dioxide layer on the surface of the substrate 10 as the first mask layer 25 for photolithography, which can also protect the devices below.

[0087] Then, two phase-separated heavily doped regions (P++, N++) are defined on the substrate 10 by photolithography, and a P-type contact region 11 and an N-type contact region 22 are formed downward from the surface of the substrate 10 in the two heavily doped regions by ion implantation and other processes. For example, a high-energy ion implanter can be used to dope boron and phosphorus in the two defined heavily doped regions, and rapid annealing (RTP) can be used after implantation to repair the lattice damaged by ion implantation and activate electrical activity. Thus, a P-type contact region 11 is formed in a heavily doped region doped with boron, and an N-type contact region 22 is formed in another heavily doped region doped with phosphorus. The heavily doped region serves as a contact layer with the external circuit electrode 21, and a smaller ohmic contact resistance can be obtained.

[0088] like Fig. 9 As shown, two phase-separated lightly doped regions (P+, N+) are further defined on the substrate 10 by photolithography, and a P-type junction region 14 and an N-type junction region 18 are respectively formed downward on the surface of the substrate 10 of the two lightly doped regions by ion implantation and other processes, and the P-type junction region 14 is connected to the P-type contact region 11, and the N-type junction region 18 is connected to the N-type contact region 22. For example, two phase-separated lightly doped regions can be defined on the substrate 10 at the inner position of the P-type contact region 11 and the N-type contact region 22, and a large beam ion implanter is used to dope boron and phosphorus in the defined two lightly doped regions, and rapid annealing (RTP) is used after implantation to repair the lattice damaged by ion implantation and activate electrical activity. Thus, a P-type junction region 14 is formed in a lightly doped region doped with boron, and an N-type junction region 18 is formed in another lightly doped region doped with phosphorus. The lightly doped region is used to contact the intrinsic absorption layer 23 to be formed subsequently. This abrupt junction with concentration difference change can not only provide a high-speed channel, but also effectively reduce the generation of a large number of carrier recombination centers at the interface, thereby reducing dark current.

[0089] In some embodiments, the P-type junction region 14 and the P-type contact region 11, and the N-type junction region 18 and the N-type contact region 22 may also be formed in the following manner, namely: first, by photolithography, two phase-separated P-type lightly doped regions and N-type lightly doped regions that meet the required area requirements of the P-type junction region 14 and the P-type contact region 11 and the area requirements of the N-type junction region 18 and the N-type contact region 22 are defined on the substrate 10, and by ion implantation and other processes, P-type lightly doped regions and N-type lightly doped regions are formed downward from the surface of the substrate 10 in the defined region; then, by photolithography again, two phase-separated P-type heavily doped regions and N-type heavily doped regions are defined in the defined P-type lightly doped region and the N-type lightly doped region, and by ion implantation and other processes, P-type heavily doped regions and N-type heavily doped regions are formed downward from the surface of the substrate 10 in the defined region; thereafter, a unified thermal annealing is performed. Thus, a P-type contact region 11 is formed in the P-type heavily doped region, and a P-type junction region 14 is formed in the P-type lightly doped region outside the P-type contact region 11, and an N-type contact region 22 is formed in the N-type heavily doped region, and an N-type junction region 18 is formed in the N-type lightly doped region outside the N-type contact region 22. This is conducive to solving the photolithography self-alignment problem when defining the well twice, and can save a thermal annealing step.

[0090] like Fig.10 As shown, then, a groove 26 is formed on the surface of the substrate 10 between the P-type junction region 14 and the N-type junction region 18 as an epitaxial window for forming the intrinsic absorption layer 23 by using photolithography and etching processes, and the sidewalls of the groove 26 are connected to the side surfaces of the P-type junction region 14 and the N-type junction region 18. For example, a highly selective and directional inductively coupled plasma (ICP) etching technology can be used to etch the surface of the substrate 10 after photolithography (including the first mask layer 25 located on the surface of the substrate 10) to form a groove 26 with high steepness, uniform width and smoothness, as the epitaxial window of the intrinsic absorption layer 23. Using inductively coupled plasma etching can not only obtain good etching directionality, but also greatly improve the etching speed.

[0091] The material of the intrinsic absorption layer 23 can be germanium. Since there is a 4.18% lattice mismatch and thermal expansion mismatch between germanium and the silicon substrate 10, when germanium is heteroepitaxially grown on the silicon substrate 10, there are often large surface fluctuations, and a large number of defects such as threading dislocations exist at the germanium-silicon interface. Therefore, in order to grow an epitaxial germanium layer with good quality and low defect density, after etching and debonding the groove 26, an acetone and alcohol alternating immersion cleaning method can be used to remove the residual photoresist and residual particles on the substrate 10, so as to prepare for the next step of silicon-based germanium epitaxy.

[0092] like Fig.11As shown, a low-temperature and high-temperature two-step deposition method and a cyclic annealing method are then selected to epitaxially grow a single crystal germanium layer in the etched silicon-based epitaxial window (groove 26 ), thereby forming a germanium intrinsic absorption layer 23 in the groove 26 .

[0093] The epitaxial growth of germanium on silicon substrate belongs to the typical SK growth mode (first layer growth, then island growth). The germanium epitaxial layer (buffer layer) grown at low temperature (such as below 400°C) is prone to produce a large number of point defects. Therefore, stress and defects will relax and annihilate in the low-temperature buffer layer, reducing the slip movement of dislocations in the germanium epitaxial layer grown at high temperature (such as around 600°C).

[0094] Next, a chemical mechanical polishing (CMP) process can be used to remove excess germanium epitaxial layer material on the surface of the first mask layer 25 outside the groove 26 to remove uneven portions of the surface of the grown germanium epitaxial layer, thereby obtaining a germanium intrinsic absorption layer 23 with a flat surface.

[0095] Step S3: forming an optical metasurface structure 17 on the intrinsic absorption layer 23 of the light incident surface, wherein the optical metasurface structure 17 is formed by an array of basic units 24 composed of periodically arranged different sub-wavelength structures.

[0096] like Fig.12 As shown, a second mask layer 27 for photolithography can then be formed on the surface of the first mask layer 25 and the germanium intrinsic absorption layer 23. For example, a plasma enhanced chemical vapor deposition process can be used to grow a stable silicon dioxide layer on the surface of the first mask layer 25 and the germanium intrinsic absorption layer 23 as the second mask layer 27 for photolithography, which can also protect the devices below.

[0097] Next, a first slot 28 (deep hole) and a second slot 29 (shallow hole) are formed on the surface of the intrinsic absorption layer 23 (the surface facing the light incident surface) by using photolithography and etching processes, the bottom of which is located in the intrinsic absorption layer 23 and has a super surface with different depths. In fact, due to the existence of the second mask layer 27, the upper ends of the first slot 28 and the second slot 29 are located on the surface of the second mask layer 27. The width (diameter) and depth of the first slot 28 and the second slot 29 formed need to be smaller than the wavelength of the communication band light, and the first slot 28 and the second slot 29 need to be arranged periodically and alternately on the surface of the intrinsic absorption layer 23 (including the surface of the second mask layer 27) to form a basic unit 24 and form an array of the basic units 24. For example, the basic unit 24 can be composed of three first sub-wavelength structures 15 and three second sub-wavelength structures 16 that are alternately arranged in an intermittent ring shape, such as Figure 2 , Figure 4 Alternatively, the basic unit 24 may be composed of two first sub-wavelength structures 15 and two second sub-wavelength structures 16 alternately arranged in an intermittent ring shape, as shown in FIG. Figure 3 , Figure 5 shown.

[0098] Since the etching depths required for the first slot 28 and the second slot 29 are different, the above-mentioned photolithography and etching steps need to be performed twice respectively. In addition, since the diameter and depth of the first slot 28 and the second slot 29 in the metasurface are both smaller than the wavelength of the communication band light, the first slot 28 and the second slot 29 can be etched by electron beam exposure (EBL) and focused ion beam (FIB) processes.

[0099] like Fig.13 As shown, then, the first slot 28 and the second slot 29 are filled with dielectric to form the first subwavelength structure 15 and the second subwavelength structure 16. Thus, an optical metasurface (medium metasurface) structure 17 formed by an array of basic units 24 formed by periodically arranging the first subwavelength structure 15 and the second subwavelength structure 16 is formed on the germanium intrinsic absorption layer 23 on the light incident surface. For example, a hot wire chemical vapor deposition process can be used to deposit graphite in the first slot 28 and the second slot 29, and fill the first slot 28 and the second slot 29.

[0100] Afterwards, a chemical mechanical polishing process may be used to remove the over-deposited graphite material on the surface of the second mask layer 27 other than the first slot 28 and the second slot 29 until the surface of the germanium intrinsic absorption layer 23 is exposed (at this time, the second mask layer 27 will be removed). The upper ends of the final first sub-wavelength structure 15 and the second sub-wavelength structure 16 formed after graphite filling are flush with the surface of the germanium intrinsic absorption layer 23. Thus, a graphite metasurface structure (optical metasurface structure 17) having a sub-wavelength periodic structure consisting of the first sub-wavelength structure 15 and the second sub-wavelength structure 16 is formed on the surface of the germanium intrinsic absorption layer 23.

[0101] like Fig.14 As shown, since germanium single crystal is easily oxidized, the above-mentioned device can be protected by forming a passivation layer 13 on the surface of the germanium intrinsic absorption layer 23, and the dark current can also be reduced. For example, a plasma enhanced chemical vapor deposition process can be used to grow the passivation layer 13 on the surface of the first mask layer 25 and the germanium intrinsic absorption layer 23. The material of the passivation layer 13 can be an insulating material such as SiO2 or Si3N4.

[0102] Afterwards, an inductively coupled plasma etching technique may be used to open an electrode window on the surface of the passivation layer 13 above the P-type contact region 11 and the N-type contact region 22, and the bottom of the electrode window passes through the first mask layer 25 and stops on the surface of the substrate 10, exposing the surface of the P-type contact region 11 and the N-type contact region 22. Then, an electron beam evaporation (EBE) or physical vapor deposition process is used to deposit metal electrodes 21 such as Au, Ti, and Al in the electrode window, and a second dielectric layer (not shown) may be further formed on the passivation layer 13, so that the electrode 21 is connected to the pad 19 on the surface of the second dielectric layer through the electrode lead 20 formed in the second dielectric layer.

[0103] See also Figure 15-Figure 21 , Figure 15-Figure 21 FIG. 1 is a process flow chart of a method for preparing a vertical PIN type photodetector according to a preferred embodiment of the present invention. Figure 15-Figure 21 As shown, a photoelectric detector preparation method of the present invention can be used to prepare, for example Figure 6 A photoelectric detector as shown may include the following steps:

[0104] Step S1: providing a substrate 10 .

[0105] like Fig.15 As shown, a SOI silicon wafer 100 may be used, and the SOI silicon wafer 100 has a bottom silicon layer 101, a middle buried oxide layer 102 and a top silicon layer 103 from bottom to top, and the top silicon layer 103 is used as the substrate 10 of this embodiment. The SOI silicon wafer 100 may be cleaned.

[0106] Step S2 : forming a P-type junction region 14 , an N-type junction region 18 , and an intrinsic absorption layer 23 disposed between the P-type junction region 14 and the N-type junction region 18 on the substrate 10 .

[0107] like Fig.16 As shown, first, a first mask layer 25 (a part of the first dielectric layer 12 ) is formed on the surface of the top silicon layer 103 of the SOI silicon wafer 100 during photolithography.

[0108] Then, a lightly doped region (P+) for forming a P-type junction region and two phase-separated heavily doped regions (P++) located on both sides of the defined P-type junction region for forming a P-type contact region 11 are defined on the substrate 10 by photolithography, and a P-type junction region 14 is formed in the defined lightly doped region, and a P-type contact region 11 is formed in the defined heavily doped region by ion implantation. The heavily doped region may be implanted first to form a P-type contact region 11, and then a lightly doped region may be implanted between the P-type contact regions 11 to form a P-type junction region 14; or the lightly doped region may be implanted first, and then two phase-separated P-type contact regions 11 may be implanted in the lightly doped region to form a P-type contact region 11, and a P-type junction region 14 may be formed between the two P-type contact regions 11.

[0109] like Fig.17 As shown, next, a dielectric is covered on the surface of the first mask layer 25 to form a first dielectric layer 12 together with the first mask layer 25 , and the first dielectric layer 12 covers the P-type junction region 14 and the P-type contact region 11 .

[0110] Then, a groove 26 is formed on the surface of the first dielectric layer 12 above the P-type junction region 14 by photolithography and etching, and the bottom of the groove 26 stops on the surface of the P-type junction region 14 (ie, the surface of the top silicon layer 103).

[0111] like Fig.18 As shown, then, an epitaxial process is used to sequentially form a germanium intrinsic absorption layer 23 and an N-type doped germanium epitaxial layer in the groove 26 , thereby forming an N-type junction region 18 of germanium material on the germanium intrinsic absorption layer 23 .

[0112] Next, an epitaxial process is continued to be adopted to form an N-type doped silicon epitaxial layer on the surface of the N-type junction region 18 , thereby forming an N-type contact region 22 of silicon material on the N-type junction region 18 .

[0113] Afterwards, a chemical mechanical polishing process is used to remove excess silicon epitaxial layer material on the surface of the first dielectric layer 12 outside the groove 26 to obtain an N-type contact region 22 of silicon material with a flat surface.

[0114] Step S3: forming an optical metasurface structure 17 on the intrinsic absorption layer 23 of the light incident surface, wherein the optical metasurface structure 17 is formed by an array of basic units 24 composed of periodically arranged different sub-wavelength structures.

[0115] like Fig.19 As shown, a second mask layer (not shown) for photolithography may then be formed on the surfaces of the first dielectric layer 12 and the N-type contact region 22 .

[0116] Next, a first slot 28 (deep hole) and a second slot 29 (shallow hole) with a bottom located in the intrinsic absorption layer 23 and having a super surface of different depths are formed on the surface of the N-type contact region 22 by using a photolithography and etching process. The width (diameter) and depth of the first slot 28 and the second slot 29 formed need to be smaller than the wavelength of the communication band light, and the first slot 28 and the second slot 29 need to be arranged periodically and alternately on the surface of the N-type contact region 22 (including the surface of the second mask layer and the intrinsic absorption layer 23) to form a basic unit 24, and to form an array of the basic unit 24 (refer to Figure 2 , Figure 4 ,or Figure 3 , Figure 5 ).

[0117] like Fig. 20 As shown, next, by filling the first slot 28 and the second slot 29 with, for example, a graphite medium, a graphite first sub-wavelength structure 15 and a graphite second sub-wavelength structure 16 are formed.

[0118] Afterwards, a chemical mechanical polishing process may be used to remove the over-deposited graphite material on the surface of the second mask layer other than the first slot 28 and the second slot 29 until the surface of the N-type contact region 22 is exposed (at this time, the second mask layer will be removed). The upper ends of the final first sub-wavelength structure 15 and the second sub-wavelength structure 16 formed after graphite filling are flush with the surface of the N-type contact region 22. Thus, a graphite metasurface structure having a sub-wavelength periodic structure composed of the first sub-wavelength structure 15 and the second sub-wavelength structure 16 is formed on the surface of the N-type contact region 22, that is, an optical metasurface structure 17 formed by an array of basic units 24 formed by periodically arranging the first sub-wavelength structure 15 and the second sub-wavelength structure 16 is formed on the germanium intrinsic absorption layer 23 on the light incident surface.

[0119] like Fig.21 As shown, a deposition process is used to form a passivation layer 13 on the surface of the N-type contact region 22 to protect the above-mentioned device.

[0120] Afterwards, electrode windows are respectively opened on the surface of the passivation layer 13 above the P-type contact region 11 and the N-type contact region 22, so that the bottom of the electrode window stops on the surface of the substrate 10 and the surface of the N-type contact region 22, respectively, and the surface of the P-type contact region 11 and the N-type contact region 22 are exposed. Then, a metal electrode 21 is deposited in the electrode window, and a second dielectric layer (not shown) can be further formed on the passivation layer 13, so that the electrode 21 is connected to the pad 19 on the surface of the second dielectric layer through the electrode lead 20 formed in the second dielectric layer, and the P-type contact region 11 and the N-type contact region 22 are led out. Thus, a PIN-type photodetector with a vertical structure is prepared.

[0121] The above-mentioned preparation method of the present invention is compatible with CMOS process, and the prepared optical metasurface structure can replace the traditional resonant cavity or reflector structure, effectively solving the process complexity problem existing in the traditional resonant cavity structure, and at the same time achieving higher responsiveness and photoelectric conversion efficiency.

[0122] Although the embodiments of the present invention are described in detail above, it is obvious 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 described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.

Claims

1. A photoelectric detector, characterized in that: include: A P-type junction region and an N-type junction region disposed on a substrate, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region; An optical metasurface structure is arranged on the intrinsic absorption layer on the light incident surface, wherein the optical metasurface structure is formed by an array of basic units composed of periodically arranged different sub-wavelength structures.

2. The photodetector according to claim 1, characterized in that: The subwavelength structure includes a first subwavelength structure and a second subwavelength structure, the first subwavelength structure and the second subwavelength structure are periodically alternately arranged in the basic unit, the width of the first subwavelength structure and the length of the second subwavelength structure in a parallel direction and a vertical direction of the light incident surface of the intrinsic absorption layer are smaller than the wavelength of the communication band light, and the length of the first subwavelength structure is different from the length of the second subwavelength structure.

3. The photodetector according to claim 2, characterized in that: The first sub-wavelength structure and the second sub-wavelength structure are periodically and alternately arranged in a discontinuous ring shape in the basic unit.

4. The photodetector according to claim 2, characterized in that: The first subwavelength structure and the second subwavelength structure are flush with each other at first ends facing the light incident surface, and second ends of the first subwavelength structure and the second subwavelength structure relative to the first end extend into the intrinsic absorption layer and are located at different depths in the intrinsic absorption layer.

5. The photodetector according to claim 4, characterized in that: The first sub-wavelength structure and the second sub-wavelength structure include slots filled with a medium.

6. The photodetector according to claim 5, characterized in that: The medium includes graphite.

7. The photodetector according to claim 4, characterized in that: The P-type junction region, the intrinsic absorption layer and the N-type junction region are arranged in sequence along the surface of the substrate, and a P-type contact region and an N-type contact region are respectively provided on the surface of the substrate outside the P-type junction region and the N-type junction region, and the first sub-wavelength structure and the second sub-wavelength structure extend from the surface of the intrinsic absorption layer toward the substrate into the intrinsic absorption layer; or, the P-type junction region, the intrinsic absorption layer and the N-type junction region are stacked in sequence along the vertical direction of the substrate surface, a P-type contact region is also provided on the surface of the substrate on the side of the P-type junction region, and an N-type contact region is also provided on the surface of the N-type junction region, and the first sub-wavelength structure and the second sub-wavelength structure extend from the surface of the N-type contact region toward the substrate through the N-type junction region into the intrinsic absorption layer.

8. A method for preparing a photoelectric detector, characterized in that: include: providing a substrate; Forming a P-type junction region, an N-type junction region, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region on the substrate; An optical metasurface structure is formed on the intrinsic absorption layer of the light incident surface, wherein the optical metasurface structure is formed by an array of basic units composed of periodically arranged different sub-wavelength structures.

9. The method for preparing a photoelectric detector according to claim 8, characterized in that: The forming of a P-type junction region, an N-type junction region, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region on the substrate specifically includes: forming a phase-separated P-type junction region and an N-type junction region on the surface of the substrate; forming a groove on the surface of the substrate between the P-type junction region and the N-type junction region, so that the sidewalls of the groove are connected to the side surfaces of the P-type junction region and the N-type junction region; forming an intrinsic absorption layer in the groove; The optical metasurface structure is formed on the intrinsic absorption layer of the light incident surface, wherein the optical metasurface structure is formed by an array of basic units formed by periodically arranging different sub-wavelength structures, and specifically comprises: Forming a first slot and a second slot having different depths and having a bottom located in the intrinsic absorption layer on the surface of the intrinsic absorption layer facing the light incident surface, so that the width and depth of the first slot and the second slot are smaller than the wavelength of the communication band light, and the first slot and the second slot are periodically and alternately arranged to form a basic unit, and form an array of the basic units; A medium is filled in the first slot and the second slot to form a first subwavelength structure and a second subwavelength structure, thereby forming an optical metasurface structure formed by an array of basic units periodically arranged by the first subwavelength structure and the second subwavelength structure on the intrinsic absorption layer of the light incident surface.

10. The method for preparing a photoelectric detector according to claim 8, characterized in that: The forming of a P-type junction region, an N-type junction region, and an intrinsic absorption layer disposed between the P-type junction region and the N-type junction region on the substrate specifically includes: forming a P-type junction region and a P-type contact region on the surface of the substrate; forming a dielectric layer on the surface of the substrate to at least cover the P-type junction region; forming a groove on the surface of the dielectric layer above the P-type junction region, stopping on the surface of the P-type junction region; forming an intrinsic absorption layer in the groove; forming an N-type junction region made of the same material as the intrinsic absorption layer on a surface of the intrinsic absorption layer; forming an N-type contact region made of the same material as the substrate on the surface of the N-type junction region; The optical metasurface structure is formed on the intrinsic absorption layer of the light incident surface, wherein the optical metasurface structure is formed by an array of basic units formed by periodically arranging different sub-wavelength structures, and specifically comprises: A first slot and a second slot having different depths and having their bottoms located in the intrinsic absorption layer are formed on the surface of the N-type contact region facing the light incident surface, so that the width and depth of the first slot and the second slot are smaller than the wavelength of the light in the communication band, and the first slot and the second slot are periodically and alternately arranged to form a basic unit, and form an array of the basic units; A medium is filled in the first slot and the second slot to form a first subwavelength structure and a second subwavelength structure, thereby forming an optical metasurface structure formed by an array of basic units periodically arranged by the first subwavelength structure and the second subwavelength structure on the intrinsic absorption layer of the light incident surface.

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