Photoelectric detector and preparation method thereof

Abstract

The invention provides a photoelectric detector and a preparation method thereof, and the method comprises the steps: a photoelectric function region is located at one side of an input waveguide, and comprises a slow light absorption region, and a P-type doped region and an N-type doped region which are located at the two sides of the slow light absorption region respectively; the slow light absorption area is connected with an output port of the input waveguide, the slow light absorption area comprises a line defect waveguide area extending in the transmission direction of light waves and through holes distributed in the two sides of the line defect waveguide area in an array mode, and the through holes penetrate through the slow light absorption area in the thickness direction of the slow light absorption area; the output waveguide is located on one side of the photoelectric function area, and an input port of the output waveguide is connected with the slow light absorption area; the reflector is located at the output port of the output waveguide and used for reflecting the light waves which are not absorbed by the slow light absorption area to the slow light absorption area; the input waveguide, the photoelectric function area, the output waveguide and the reflector are made of silicon materials. The slow light absorption region can reduce the group velocity of the light waves, and the reflector enables the light waves to pass through the slow light absorption region for multiple times to improve the absorption efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and in particular to a photodetector and a method for fabricating the photodetector. Background Technology

[0002] With the rapid development of optical communication and optical interconnect technologies, the O-band (1260nm-1360nm) is increasingly widely used in short-distance data center interconnect scenarios. Due to its significant advantages of low dispersion and low attenuation, the O-band has become the preferred band for short-distance high-speed optical transmission. As the core device for converting optical signals to electrical signals, the performance of the photodetector directly determines the transmission quality and stability of the entire optical transmission system.

[0003] Because silicon is an indirect bandgap semiconductor near the O-band, its low single-photon absorption coefficient limits the responsivity of silicon-based photodetectors. To improve light absorption efficiency, researchers often employ schemes such as germanium-silicon heterojunctions, surface-state-assisted absorption, and evanescent wave coupling. However, these schemes require complex processes, increasing manufacturing costs and integration difficulty. Furthermore, novel silicon-based photodetectors can be developed by utilizing the strong two-photon absorption coefficient of silicon near the O-band. However, the two-photon absorption effect requires a long interaction length between light and material, necessitating a relatively long absorption region to obtain sufficient photocurrent, thus limiting the device's integration density and response speed.

[0004] Therefore, how to improve the light absorption efficiency of photodetectors while taking into account the manufacturing cost, manufacturing difficulty, and integration is one of the technical problems that urgently need to be solved.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a photodetector and a method for fabricating the photodetector, so as to solve the problems of low light absorption efficiency, high fabrication cost, high fabrication difficulty and low integration of the photodetector in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a photodetector, comprising:

[0008] Input waveguide;

[0009] An optoelectronic functional region is located on one side of the input waveguide, and the optoelectronic functional region comprises a slow-light absorption region and a P-type doped region and an N-type doped region located on two sides of the slow-light absorption region respectively; wherein the slow-light absorption region is connected with the output port of the input waveguide, and the slow-light absorption region comprises a line defect waveguide region extending along the transmission direction of the light wave and a through hole arrayed on two sides of the line defect waveguide region, and the through hole penetrates the slow-light absorption region along the thickness direction of the slow-light absorption region;

[0010] An output waveguide is located on one side of the optoelectronic functional region, and the input port of the output waveguide is connected with the slow-light absorption region;

[0011] A reflector is located at the output port of the output waveguide, and is used for reflecting the light wave not absorbed by the slow-light absorption region to the slow-light absorption region;

[0012] The materials of the input waveguide, the optoelectronic functional region, the output waveguide and the reflector comprise silicon material.

[0013] In one of the embodiments, the arrayed arrangement of the through hole comprises a hexagonal photonic crystal arrangement structure.

[0014] In one of the embodiments, the waveguide width of the line defect waveguide region is greater than or equal to 450 nanometers.

[0015] In one of the embodiments, the input waveguide comprises:

[0016] An input straight waveguide;

[0017] An input tapered waveguide, the input port of the input tapered waveguide is connected with the output port of the input straight waveguide, the output port of the input tapered waveguide is connected with the slow-light absorption region, and the waveguide width of the input tapered waveguide gradually increases along the transmission direction of the light wave.

[0018] In one of the embodiments, the output waveguide comprises:

[0019] An output tapered waveguide, the input port of the output tapered waveguide is connected with the slow-light absorption region, and the waveguide width of the output tapered waveguide gradually decreases along the transmission direction of the light wave;

[0020] An output straight waveguide, the input port of the output straight waveguide is connected with the output port of the output tapered waveguide, and the output port of the output straight waveguide is connected with the reflector.

[0021] In one of the embodiments, the through hole can comprise at least one of a circular through hole, a square through hole, a pentagonal through hole and a hexagonal through hole.

[0022] In one of the embodiments, the reflector comprises a Bragg reflector, which comprises silicon layers and silicon dioxide layers arranged alternately along the transmission direction of the light wave.

[0023] In one of the embodiments, the photodetector further comprises:

[0024] a first electrode connected to the P-type doped region;

[0025] a second electrode connected to the N-type doped region.

[0026] In a second aspect, the present application provides a method for preparing a photodetector, comprising:

[0027] providing a substrate, which comprises a substrate, an insulating layer and a silicon material layer stacked sequentially on the substrate;

[0028] etching the silicon material layer to form an input waveguide, a photoelectric functional region, an output waveguide and an initial reflection structure; wherein the photoelectric functional region is located on one side of the input waveguide, the photoelectric functional region comprises a slow-light absorption region and a P-type doped region and an N-type doped region arranged respectively on both sides of the slow-light absorption region; the slow-light absorption region is connected to the output port of the input waveguide, the slow-light absorption region comprises a linear defect waveguide region extending along the transmission direction of the light wave and a plurality of through holes arranged in an array on both sides of the linear defect waveguide region, the through holes penetrate the slow-light absorption region along the thickness direction of the slow-light absorption region; the output waveguide is located on one side of the photoelectric functional region, the input port of the output waveguide is connected to the slow-light absorption region; the initial reflection structure is located at the output port of the output waveguide, the initial reflection structure comprises a plurality of silicon layers arranged at intervals along the transmission direction of the light wave;

[0029] forming a silicon dioxide layer in at least the interval between the silicon layers to form a reflector; wherein the reflector comprises the silicon layers and the silicon dioxide layer between any two adjacent silicon layers.

[0030] In one of the embodiments, the array arrangement of the through holes comprises a hexagonal photonic crystal arrangement structure.

[0031] As described above, the photodetector and the method for preparing a photodetector of the present application have the following beneficial effects:

[0032] The photoelectric detector and the preparation method thereof, comprising: an input waveguide, a photoelectric functional area, an output waveguide and a reflector; wherein the photoelectric functional area is located on one side of the input waveguide, and the photoelectric functional area comprises a slow-light absorption area and P-type and N-type doped areas located on both sides of the slow-light absorption area; wherein the slow-light absorption area is connected with an output port of the input waveguide, and the slow-light absorption area comprises a linear defect waveguide area extending along the transmission direction of light waves and through holes arranged in an array on both sides of the linear defect waveguide area, the through holes penetrating the slow-light absorption area along the thickness direction of the slow-light absorption area; the output waveguide is located on one side of the photoelectric functional area, and an input port of the output waveguide is connected with the slow-light absorption area; the reflector is located at an output port of the output waveguide and is used for reflecting light waves not absorbed by the slow-light absorption area to the slow-light absorption area; the materials of the input waveguide, the photoelectric functional area, the output waveguide and the reflector comprise silicon materials. The present application couples light waves into the slow-light absorption area through the input waveguide, the linear defect waveguide in the slow-light absorption area is used for guiding the transmission direction of light waves, so that the unabsorbed light waves are transmitted to the reflector through the output waveguide, the through holes arranged in an array in the slow-light absorption area can enhance the dispersion of the slow-light absorption area, reduce the group velocity of the light waves in the slow-light absorption area, and equivalently increase the interaction length of the light waves and the material, thereby improving the absorption efficiency. In addition, the reflector and the slow-light absorption area cooperate with each other to make the light waves pass through the slow-light absorption area multiple times, further improving the absorption efficiency of the photoelectric detector, and the preparation process is simple and the cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. It is readily understood that the drawings are merely illustrative of some embodiments of the application.

[0034] Figure 1 A structural schematic diagram of a photoelectric detector provided in an embodiment of the present application;

[0035] Figure 2 A structural schematic diagram of a photoelectric functional area provided in an embodiment of the present application;

[0036] Figure 3 A flowchart of a preparation method of a photoelectric detector provided in an embodiment of the present application;

[0037] Figure 4 A dark current and reverse bias voltage characteristic curve of a photoelectric detector provided in an embodiment of the present application.

[0038] BRIEF DESCRIPTION OF DRAWINGS

[0039] 10, substrate; 20, insulating layer; 302, input straight waveguide; 304, input tapered waveguide; 306, P-type doped region; 308, N-type doped region; 310, line-defect waveguide region; 312, via; 314, slow-light absorption region; 316, output tapered waveguide; 318, output straight waveguide; 322, silicon layer; 324, silicon dioxide layer; 31, input waveguide; 32, optoelectronic functional region; 33, output waveguide; 34, reflector; 402, first electrode; 404, second electrode; 406, first metal pillar; 408, second metal pillar; 410, first pad; 412, second pad. DETAILED DESCRIPTION

[0040] Other advantages and benefits of the present application will become apparent to those skilled in the art upon reading and understanding the following detailed description of the application. The present application may be carried out in other specific ways than those herein set forth without departing from the essential spirit and essential characteristics of the disclosure. Embodiments of this application each have several advantageous features, and the craft skilled in the art will be able to recognize applicability of various modifications and variations of this application and equivalents thereof to carry out certain aspects of the present application.

[0041] It should also be emphasized that the terms "comprises / comprising" when used in this specification are taken to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0042] Features described and / or illustrated with respect to one implementation can be used in the same or similar manner in one or more other implementations, in combination with other features in the other implementations, or in place of other features in the other implementations.

[0043] As will be understood by those familiar with the art, the figures to be discussed below, which show device structures, are presented by way of example and not limitation. In particular, the drawings are not necessarily drawn to scale and the dimensions of the various layers and regions shown in the figures can be exaggerated relative to other layers or regions to facilitate explanation and understanding of the present application. Moreover, the same reference numerals are used consistently throughout the several drawings to refer to aspects having similar or related aspects.

[0044] For convenience of description, spatially relative terms such as "beneath", "below", "lower", "under", "above", "upper" and the like can be used herein for describing the relationship of one element or feature to other elements or features as shown in the drawings. It will be understood that these spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the drawings. For example, if a device described herein is inverted from the orientation depicted in the drawings, then the elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the examples described herein are to be understood as being inclusive of such orientations unless specified otherwise. Furthermore, descriptions of a layer "between" two layers indicate that the layer can be the only layer between the two layers or one or more intervening layers can also be present.

[0045] In the context of the present application, a structure in which the first feature is described as being "on" the second feature can include embodiments in which the first and second features are formed in direct contact, as well as embodiments in which additional features are formed between the first and second features, such that the first and second features can not be in direct contact.

[0046] It should be noted that the diagrams in the embodiments provided in the present application only schematically illustrate the basic concepts of the present application, and only show the components related to the present application in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The shapes, number and proportions of the components in actual implementation can be arbitrarily changed, and the layout pattern of the components can be more complex.

[0047] Please refer to Figure 1 The present application provides a photodetector, comprising: an input waveguide 31, a photoelectric functional area 32, an output waveguide 33 and a reflector 34; wherein the photoelectric functional area 32 is located on one side of the input waveguide 31, and the photoelectric functional area 32 comprises a slow-light absorption area 314 and a P-type doped area 306 and an N-type doped area 308 located on both sides of the slow-light absorption area respectively; wherein the slow-light absorption area 314 is connected with the output port of the input waveguide 31, and the slow-light absorption area 314 comprises a linear defect waveguide area 310 extending along the transmission direction of the light wave and a through hole 312 arranged in an array on both sides of the linear defect waveguide area 310, the through hole 312 penetrating the slow-light absorption area 314 along the thickness direction of the slow-light absorption area 314; the output waveguide 33 is located on one side of the photoelectric functional area 32, and the input port of the output waveguide 33 is connected with the slow-light absorption area 314; the reflector 34 is located at the output port of the output waveguide 33, and is used for reflecting the light wave not absorbed by the slow-light absorption area 314 to the slow-light absorption area 314; wherein the materials of the input waveguide 31, the photoelectric functional area 32, the output waveguide 33 and the reflector 34 comprise silicon material.

[0048] As an example, the shape of the input waveguide 31 can include one or a combination of rectangular waveguide, circular waveguide and ridge waveguide, and the present embodiment does not limit the shape of the input waveguide 31, which can be selected according to the needs.

[0049] As an example, the transmission direction of the light wave is the Y-axis direction.

[0050] As an example, the material of the slow-light absorption region 314 can include an intrinsic semiconductor material or a lightly doped semiconductor material, the slow-light absorption region 314 is used to absorb photons to generate photo-generated carriers, the P-type doped region 306 and the N-type doped region 308 are used to connect the voltage to form a reverse bias, and accelerate the movement of the photo-generated carriers to the P-type doped region 306 and the N-type doped region 308. Wherein, the linear defect waveguide region 310 does not form the through hole 312, which is used to guide the transmission direction of the light wave, so that the unabsorbed light wave is transmitted to the reflector 34 through the output waveguide 33, the linear defect waveguide region 310 has an array arrangement of through holes 312 on both sides, and the through holes 312 penetrate the slow-light absorption region 314 along the thickness direction of the slow-light absorption region 314. By periodically arranging the through holes 312, the dispersion of the slow-light absorption region 314 to the light wave is increased, so as to slow down the group velocity of the light wave in the slow-light absorption region 314, prolong the time of the light wave acting on the slow-light absorption region 314, and improve the absorption efficiency. As an example, the through holes 312 in the slow-light absorption region 314 are symmetrically distributed on both sides of the linear defect waveguide region 310. The through holes 312 penetrate the slow-light absorption region 314 along the thickness direction of the slow-light absorption region 314, which can include: the through holes 312 vertically penetrate the slow-light absorption region 314 along the thickness direction of the slow-light absorption region 314, or the through holes 312 obliquely penetrate the slow-light absorption region 314 along the thickness direction of the slow-light absorption region 314.

[0051] Wherein, the output waveguide 33 is used to couple the light wave that is not absorbed by the slow-light absorption region 314 into the reflector 34. As an example, the shape of the output waveguide 33 can include one or a combination of rectangular waveguides, circular waveguides, and ridge waveguides. The present embodiment does not limit the shape of the output waveguide 33, which can be selected according to the needs.

[0052] In the above embodiment, the photodetector comprises: an input waveguide, a photoelectric functional region, an output waveguide, and a reflector; the photoelectric functional region is located on one side of the input waveguide; the photoelectric functional region comprises a slow-light absorption region and a P-type doped region and an N-type doped region located on both sides of the slow-light absorption region; the slow-light absorption region is connected with an output port of the input waveguide; the slow-light absorption region comprises a line defect waveguide region extending along the transmission direction of the light wave and a plurality of through holes arranged in an array on both sides of the line defect waveguide region, the through holes penetrating the slow-light absorption region along the thickness direction of the slow-light absorption region; the output waveguide is located on one side of the photoelectric functional region; an input port of the output waveguide is connected with the slow-light absorption region; the reflector is located at an output port of the output waveguide and is used for reflecting the light wave not absorbed by the slow-light absorption region to the slow-light absorption region; and the materials of the input waveguide, the photoelectric functional region, the output waveguide, and the reflector comprise silicon material. In the present application, the slow-light absorption region is connected with the output port of the input waveguide, so that the light wave can be directly coupled into the slow-light absorption region, and the light wave will not enter the P-type doped region and the N-type doped region, thereby avoiding the generation of diffusion current; the line defect waveguide in the slow-light absorption region is used for guiding the transmission direction of the light wave, so that the unabsorbed light wave is transmitted to the reflector through the output waveguide; the plurality of through holes arranged in an array in the slow-light absorption region can enhance the dispersion of the slow-light absorption region, reduce the group velocity of the light wave in the slow-light absorption region, and equivalently increase the interaction length of the light wave and the material, thereby improving the absorption efficiency; in addition, the reflector cooperates with the slow-light absorption region, so that the light wave can pass through the slow-light absorption region multiple times, further improving the absorption efficiency of the photodetector, and the preparation process is simple; the materials of the input waveguide, the photoelectric functional region, the output waveguide, and the reflector comprise silicon material, the preparation cost is low, the silicon material ensures the compatibility with the CMOS (Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor) process, and large-scale integration and mass production are facilitated.

[0053] In some embodiments, please refer to Figure 1 , the input waveguide 31 comprises: an input straight waveguide 302 and an input tapered waveguide 304; an input port of the input tapered waveguide 304 is connected with an output port of the input straight waveguide 302; an output port of the input tapered waveguide 304 is connected with the slow-light absorption region 314; and the waveguide width of the input tapered waveguide 304 gradually increases along the transmission direction of the light wave.

[0054] As an example, the input straight waveguide 302 is used for transmitting a single-mode TE (Transverse Electric) light wave. The present application does not make specific limitations on the waveguide width of the input straight waveguide 302, as long as the requirement of single-mode transmission can be met, for example, the waveguide width of the input straight waveguide 302 is 450 nanometers.

[0055] In the above embodiment, the waveguide width of the input straight waveguide is constant, and the waveguide width of the input tapered waveguide gradually increases along the transmission direction of the optical wave, and gradually changes from the waveguide width of the input straight waveguide to the width of the slow-light absorption region, so that the optical field mode in the input waveguide is smoothly converted into a mode suitable for transmission in the slow-light absorption region, and the mode mismatch loss is reduced.

[0056] In some embodiments, please refer to Figure 1 The array arrangement of the through holes 312 includes a hexagonal lattice photonic crystal arrangement structure.

[0057] As an example, the hexagonal lattice photonic crystal arrangement structure is that each through hole 312 is located at the vertex of the hexagonal lattice. The size of the through hole 312 and the spacing (also referred to as lattice constant) between adjacent through holes 312 can be set according to the size of the slow-light absorption region 314, so that the group velocity of the optical wave in the slow-light absorption region 314 is significantly reduced. For example, in the case that the wavelength of the optical wave is 1310 nanometers, the width of the slow-light absorption region 314 is 3 micrometers, and the length of the slow-light absorption region 314 is 20 micrometers, the radius of the through hole 312 can include 104 nanometers, the spacing between adjacent through holes 312 can include 346 nanometers, the number of rows of through holes on one side of the slow-light absorption region 314 along the width direction of the slow-light absorption region 314 is 4 rows, and the arrangement period number of the through holes 312 in each row along the transmission direction of the optical wave is 30 periods.

[0058] In the above embodiment, by making the array arrangement of the through holes include a hexagonal lattice photonic crystal arrangement structure, the dispersion of the slow-light absorption region can be as large as possible, and the group velocity of the optical wave in the slow-light absorption region can be reduced.

[0059] In some embodiments, the through hole can include at least one of a circular through hole, a square through hole, a pentagonal through hole, and a hexagonal through hole.

[0060] In some embodiments, the waveguide width of the line defect waveguide region is greater than or equal to 450 nanometers.

[0061] Wherein, the waveguide width is the width of the waveguide in the X-axis direction. As an example, the waveguide width of the line defect waveguide is 450 nanometers, 455 nanometers, 460 nanometers, 465 nanometers, 470 nanometers, etc.

[0062] In some embodiments, please refer to Figure 2 The photodetector further includes a first electrode 402 and a second electrode 404; the first electrode 402 is connected with the P-type doped region 306; and the second electrode 404 is connected with the N-type doped region 308.

[0063] As an example, the photodetector further includes a first metal pillar 406, a second metal pillar 408, a first bonding pad 410 and a second bonding pad 412, the first metal pillar 406 is connected with the first electrode 402 and the first bonding pad 410 respectively, and the second metal pillar 408 is connected with the second electrode 404 and the second bonding pad 412 respectively.

[0064] In some embodiments, referring to Figure 1 continuously, the output waveguide 33 includes an output tapered waveguide 316 and an output straight waveguide 318; an input port of the output tapered waveguide 316 is connected with the slow-light absorption region 314, and a waveguide width of the output tapered waveguide 316 gradually decreases along a transmission direction of the light wave; an input port of the output straight waveguide 318 is connected with an output port of the output tapered waveguide 316, and an output port of the output straight waveguide 318 is connected with the reflector 34.

[0065] As an example, the output straight waveguide 318 is used for transmitting a single-mode light wave. The present application does not make specific limitations on the waveguide width of the output straight waveguide 318, as long as the requirement of single-mode transmission can be met, for example, the waveguide width of the output straight waveguide 318 is 450 nanometers.

[0066] In the above embodiments, the waveguide width of the output straight waveguide is constant, and the waveguide width of the output tapered waveguide gradually decreases along the transmission direction of the light wave, which gradually changes from the width of the slow-light absorption region to the waveguide width of the output straight waveguide, so that the light field mode in the slow-light absorption region is smoothly converted into a transmission mode suitable for the output waveguide, thereby reducing the mode mismatch loss.

[0067] In some embodiments, referring to Figure 1 continuously, the reflector 34 includes a Bragg reflector, and the Bragg reflector includes silicon layers 322 and silicon dioxide layers 324 which are arranged alternately along the transmission direction of the light wave.

[0068] As an example, the thicknesses of the silicon layers 322 and the silicon dioxide layers 324 along the transmission direction of the light wave and the alternating period in the Bragg reflector can be set according to the wavelength of the light wave, so that the Bragg reflector has high reflectivity to the light wave.

[0069] In some embodiments, referring to Figure 3 continuously, and referring to Figure 1 , Figure 2 The present application further provides a preparation method of a photodetector, including steps S302-S306.

[0070] Step S302: providing a substrate, the substrate includes a substrate 10, an insulating layer 20 and a silicon material layer which are sequentially stacked on the substrate 10.

[0071] As an example, the substrate 10 can adopt a semiconductor material. The substrate 10 can be a single-layer structure or a multi-layer structure. For example, the substrate can be a silicon (Si) substrate, a silicon germanium (SiGe) substrate, a silicon germanium carbon (SiGeC) substrate, a silicon carbide (SiC) substrate, a gallium arsenide (GaAs) substrate, an indium arsenide (InAs) substrate, an indium phosphide (InP) substrate, or other III / V semiconductor substrate or II / VI semiconductor substrate. Alternatively, for example, the substrate 10 can be a layered substrate including, for example, Si / SiGe, Si / SiC. Therefore, the type of the substrate 10 should not limit the protection scope of the present disclosure.

[0072] As an example, the material of the insulating layer 20 can include silicon dioxide, silicon nitride, silicon oxynitride, silicon oxycarbide, etc., and the present application does not make specific limitations on the material of the insulating layer 20. Preferably, the substrate 10 adopts a silicon substrate, and the insulating layer 20 adopts silicon dioxide, i.e., the substrate is a silicon-on-insulator (SOI) structure, which is beneficial to confine the optical field in the silicon material layer, reduce the leakage loss of the substrate 10, and ensure the compatibility with the CMOS process.

[0073] As an example, the thickness of the silicon material layer can be 180 nanometers, 200 nanometers, 220 nanometers, etc., and the present application does not make specific limitations on the thickness of the silicon material layer, which can be selected according to the wavelength of the optical wave and the requirement of single-mode transmission.

[0074] Step S304: etching the silicon material layer to form the input waveguide 31, the optoelectronic functional area 32, the output waveguide 33, and the initial reflection structure (not shown); wherein the optoelectronic functional area 32 is located on one side of the input waveguide 31, and the optoelectronic functional area 32 includes a slow-light absorption area 314 and a P-type doped area 306 and an N-type doped area 308 arranged on both sides of the slow-light absorption area 314; the slow-light absorption area 314 is connected with the output port of the input waveguide 31, and the slow-light absorption area 314 includes a linear defect waveguide area 310 extending along the transmission direction of the optical wave and a through hole 312 arranged in an array on both sides of the linear defect waveguide area 310, the through hole 312 penetrating the slow-light absorption area 314 along the thickness direction of the slow-light absorption area 314; the output waveguide 33 is located on one side of the optoelectronic functional area 32, and the input port of the output waveguide 33 is connected with the slow-light absorption area 314; the initial reflection structure is located at the output port of the output waveguide 33, and the initial reflection structure includes a plurality of silicon layers 322 arranged in an interval along the transmission direction of the optical wave.

[0075] As an example, the input waveguide 31, the optoelectronic functional area 32, the output waveguide 33, and the initial reflection structure can be formed synchronously or asynchronously.

[0076] As an example, the silicon material layer can be patterned by using photolithography and dry etching processes to simultaneously form the input waveguide 31, the optoelectronic functional region 32, the output waveguide 33, the initial reflection structure, etc. in one etching step, so as to reduce the process steps and the manufacturing cost.

[0077] As an example, the P-type doped region 306 and the N-type doped region 308 can be formed by an ion implantation process, and the dopants of the corresponding conductive type are implanted and activated by annealing. The doping concentration and the junction depth can be designed according to the electrical performance requirements of the device, so that the optoelectronic functional region 32 forms a PIN structure with good rectification characteristics. For example, in the case of a silicon substrate 10 and a silicon dioxide insulating layer 20, please refer to Figure 4 , the optoelectronic functional region 32 has good rectification characteristics and a low dark current level, which ensures the signal-to-noise ratio and dynamic range of the photodetector.

[0078] As an example, the via hole 312 can be formed by using electron beam lithography combined with inductively coupled plasma etching process to achieve the required nanoscale pattern accuracy. Forming the via hole 312 by using electron beam lithography combined with inductively coupled plasma etching process can include: spin-coating an electron beam resist on the surface of the silicon material layer, forming a mask pattern of the via hole 312 through exposure and development, and using a mixture gas of sulfur hexafluoride / octafluorocyclobutane or chlorine / hydrogen bromide (HBr) as etching gas to perform anisotropic dry etching on the silicon material layer to form the via hole 312 penetrating through the silicon material layer along the thickness direction of the slow-light absorption region 314. After etching, the residual mask pattern is removed and wet etching with hydrofluoric acid (HF) is performed to reduce the surface roughness and surface state density of the sidewall of the via hole 312, and to reduce the scattering loss. In addition, the array arrangement mode of the via hole 312 can include a hexagonal photonic crystal arrangement structure, and the ratio of the radius of the via hole 312 to the lattice constant determines the slow-light dispersion characteristics of the slow-light absorption region. The ratio of the radius of the via hole 312 to the lattice constant can be adjusted to significantly reduce the group velocity of the light wave with a wavelength in the slow-light region, thereby enhancing the two-photon absorption efficiency.

[0079] Step S306: forming a silicon dioxide layer 324 in at least the space between the silicon layers 322 to form a reflector 34; wherein the reflector 34 includes the silicon layers 322 and the silicon dioxide layer 324 located between adjacent two silicon layers 322.

[0080] As an example, a silicon dioxide layer 324 can be filled into the gaps between silicon layers 322 using chemical vapor deposition or thermal oxidation processes to form a Bragg reflector structure. The silicon layers 322 and silicon dioxide layers 324 are arranged alternately along the light wave propagation direction, and their thickness and alternation period can be designed according to the light wavelength to ensure that the reflector 34 has high reflectivity. Alternatively, as an example, a silicon dioxide layer 324 can be simultaneously formed on the substrate, covering the input waveguide 31, the photoelectric functional region 32, the output waveguide 33, and the reflector 34, serving as the upper cladding and insulating medium of the photodetector. This eliminates the need for additional dielectric deposition steps, further simplifying the fabrication process.

[0081] In some embodiments, the array arrangement of the vias includes a hexagonal lattice photonic crystal arrangement structure.

[0082] In some embodiments, the waveguide width of the line defect waveguide region is greater than or equal to 450 nanometers.

[0083] In some embodiments, the input waveguide includes: an input straight waveguide and an input tapered waveguide; the input port of the input tapered waveguide is connected to the output port of the input straight waveguide, the output port of the input tapered waveguide is connected to the slow light absorption region, and the waveguide width of the input tapered waveguide gradually increases along the propagation direction of the light wave.

[0084] In some embodiments, the output waveguide includes: an output tapered waveguide and an output straight waveguide; the input port of the output tapered waveguide is connected to the slow light absorption region, and the waveguide width of the output tapered waveguide gradually decreases along the propagation direction of the light wave; the input port of the output straight waveguide is connected to the output port of the output tapered waveguide, and the output port of the output straight waveguide is connected to the reflector.

[0085] In some embodiments, the through hole may include at least one of the following: circular through hole, square through hole, pentagonal through hole, and hexagonal through hole.

[0086] In some embodiments, before forming a silicon dioxide layer at least within the gaps between silicon layers to form a reflector, step S306 further includes forming a first electrode on a P-type doped region and a second electrode on an N-type doped region.

[0087] As an example, a metallization process can be used to deposit metal on the P-type doped region 306 and the N-type doped region 308 and then pattern it to form a first electrode 402 and a second electrode 404 that form ohmic contacts with the P-type doped region 306 and the N-type doped region 308, respectively.

[0088] In some embodiments, after forming a silicon dioxide layer at least within the gaps between silicon layers to form a reflector, step S306 further includes: etching the silicon dioxide layer located on the P-type doped region and the N-type doped region to form a connection hole, forming a first metal pillar and a second metal pillar in the connection hole, and forming a first pad and a second pad on the silicon dioxide layer; wherein the first metal pillar is connected to the first electrode and the first pad respectively, and the second metal pillar is connected to the second electrode and the second pad respectively.

[0089] In summary, the photodetector and its fabrication method of the present invention include: an input waveguide, a photoelectric functional region, an output waveguide, and a reflector; wherein, the photoelectric functional region is located on one side of the input waveguide, and the photoelectric functional region includes a slow light absorption region and P-type doped regions and N-type doped regions located on both sides of the slow light absorption region; wherein, the slow light absorption region is connected to the output port of the input waveguide, and the slow light absorption region includes a line defect waveguide region extending along the propagation direction of the light wave and through-holes arrayed on both sides of the line defect waveguide region, the through-holes penetrating the slow light absorption region along the thickness direction of the slow light absorption region; the output waveguide is located on one side of the photoelectric functional region, and the input port of the output waveguide is connected to the slow light absorption region; the reflector is located at the output port of the output waveguide and is used to reflect light waves not absorbed by the slow light absorption region back to the slow light absorption region; the materials of the input waveguide, the photoelectric functional region, the output waveguide, and the reflector include silicon. This application couples light waves into a slow-light absorption region via an input waveguide. A line-defect waveguide within the slow-light absorption region guides the propagation direction of the light wave, allowing unabsorbed light waves to be transmitted to the reflector via an output waveguide. The array of vias within the slow-light absorption region enhances dispersion and reduces the group velocity of the light wave within this region, effectively increasing the interaction length between the light wave and the material, thereby improving absorption efficiency. Furthermore, the interaction between the reflector and the slow-light absorption region allows the light wave to pass through the region multiple times, further enhancing the absorption efficiency of the photodetector. The fabrication process is simple and cost-effective. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0090] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A photodetector, comprising: The application relates to a photodetector. The photodetector comprises: an input waveguide; a photoelectric functional area located on one side of the input waveguide, the photoelectric functional area comprising a slow-light absorption area and a P-type doped area and an N-type doped area respectively located on two sides of the slow-light absorption area; wherein the slow-light absorption area is connected with an output port of the input waveguide, the slow-light absorption area comprises a linear defect waveguide area extending along a transmission direction of light waves and through-holes arranged in an array on two sides of the linear defect waveguide area, and the through-holes penetrate the slow-light absorption area along a thickness direction of the slow-light absorption area; an output waveguide located on one side of the photoelectric functional area, an input port of the output waveguide being connected with the slow-light absorption area; a reflector located at an output port of the output waveguide, used for reflecting light waves not absorbed by the slow-light absorption area to the slow-light absorption area; 2. The photodetector of claim 1, wherein, wherein the input waveguide, the photoelectric functional area, the output waveguide and the reflector are made of silicon material.

3. The photodetector of claim 1, wherein, The array arrangement mode of the through-holes comprises a hexagonal photonic crystal arrangement structure.

4. The photodetector of claim 1, wherein, The waveguide width of the linear defect waveguide area is greater than or equal to 450 nanometers. The input waveguide comprises: an input straight waveguide; 5. The photodetector of claim 1, wherein, an input tapered waveguide, an input port of the input tapered waveguide being connected with an output port of the input straight waveguide, an output port of the input tapered waveguide being connected with the slow-light absorption area, and the waveguide width of the input tapered waveguide gradually increasing along the transmission direction of the light waves. The output waveguide comprises: an output tapered waveguide, an input port of the output tapered waveguide being connected with the slow-light absorption area, and the waveguide width of the output tapered waveguide gradually decreasing along the transmission direction of the light waves; 6. The photodetector of claim 1, wherein, an output straight waveguide, an input port of the output straight waveguide being connected with an output port of the output tapered waveguide, and an output port of the output straight waveguide being connected with the reflector.

7. The photodetector of claim 1, wherein, The through-holes can comprise at least one of a circular through-hole, a square through-hole, a pentagonal through-hole and a hexagonal through-hole.

8. The photodetector of claim 1, wherein, The reflector comprises a Bragg reflector, the Bragg reflector comprising silicon layers and silicon dioxide layers arranged alternately along the transmission direction of the light waves. The photodetector further comprises: a first electrode connected with the P-type doped area; 9. A method for fabricating a photodetector, characterized in that, a second electrode connected with the N-type doped area. The application relates to a photodetector. The photodetector comprises: providing a substrate, the substrate comprising a substrate, an insulating layer and a silicon material layer sequentially stacked on the substrate; etching the silicon material layer to form an input waveguide, a photoelectric functional area, an output waveguide and an initial reflection structure; wherein the photoelectric functional area is located on one side of the input waveguide, the photoelectric functional area comprising a slow-light absorption area and a P-type doped area and an N-type doped area respectively located on two sides of the slow-light absorption area; the slow-light absorption area is connected with an output port of the input waveguide, the slow-light absorption area comprises a linear defect waveguide area extending along a transmission direction of light waves and through-holes arranged in an array on two sides of the linear defect waveguide area, the through-holes penetrate the slow-light absorption area along a thickness direction of the slow-light absorption area; the output waveguide is located on one side of the photoelectric functional area, an input port of the output waveguide being connected with the slow-light absorption area; the initial reflection structure is located at an output port of the output waveguide, and the initial reflection structure comprises a plurality of silicon layers arranged at intervals along the transmission direction of the light waves. A silicon dioxide layer is formed in at least a space between the silicon layers to form a reflector; wherein the reflector comprises the silicon layers and the silicon dioxide layer between adjacent two silicon layers.

10. The method of claim 9, wherein the method further comprises: The array arrangement of the through holes comprises a hexagonal lattice photonic crystal arrangement structure.

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