Avalanche multiplication photodetector and method of fabrication

Abstract

The application relates to the technical field of photoelectric detection, and provides an avalanche multiplication photoelectric detector and a preparation method, the detector comprising a super surface structure, a second doped layer, a first doped layer, a multiplication layer, a charge layer, an absorption layer and a dielectric super surface layer which are arranged in sequence, the super surface structure is arranged on the dielectric super surface layer or arranged on the side surface of the dielectric super surface layer and the absorption layer close to the dielectric super surface layer, and the super surface structure penetrates along the thickness direction of the dielectric super surface layer; the second doped layer is formed in the absorption layer and located on the side of the absorption layer close to the super surface structure. The avalanche multiplication photoelectric detector provided by the application realizes the regulation and control of the phase, amplitude and polarization of the incident light field by integrating the super surface structure on the incident side of the absorption layer, so that the absorption rate of the detector is improved without increasing the thickness of the absorption layer, and the gain of the detector is improved, the device bandwidth is effectively expanded, the time jitter is reduced, and the noise is suppressed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric detection, and in particular to an avalanche multiplication photoelectric detector and a preparation method thereof. BACKGROUND

[0002] The avalanche high-speed photoelectric detector has become a core device in the field of weak light and ultra-weak light detection due to its high sensitivity, fast response and controllable internal gain characteristics, and has a wide application prospect in important fields such as information transmission, intelligent sensing, life exploration and deep space communication. However, in the process of amplifying weak signals with high gain, the traditional avalanche photoelectric detector causes the device bandwidth to decrease sharply, the time jitter to increase and the noise level to rise due to the significant extension of the carrier transit time. These inherent defects seriously restrict the performance in application scenarios such as quantum communication, space optical communication, astronomical observation, laser radar, biomedical imaging and sensing, which have very high requirements on detection distance, accuracy and response speed.

[0003] The existing avalanche photoelectric detector is difficult to achieve high gain while meeting the comprehensive performance requirements of high bandwidth, low noise and low time jitter, and there is an inherent contradiction between absorption efficiency and response speed, which is difficult to meet the growing demand for high-performance photoelectric detection. SUMMARY

[0004] The present application provides an avalanche multiplication photoelectric detector and a preparation method, which solves the defect that it is difficult to achieve high bandwidth, low noise and low time jitter at high gain in the prior art. By integrating a metasurface structure on the incident side of the absorption layer, the phase, amplitude and polarization of the incident light field are regulated, thereby improving the gain of the detector while effectively expanding the device bandwidth, reducing the time jitter and suppressing the noise.

[0005] The present application provides an avalanche multiplication photoelectric detector, comprising:

[0006] A first doped layer, a multiplication layer, a charge layer, an absorption layer and a dielectric metasurface layer are arranged in sequence;

[0007] A metasurface structure is arranged on the dielectric metasurface layer, or the metasurface structure is arranged on the dielectric metasurface layer and the side surface of the absorption layer close to the dielectric metasurface layer, and the metasurface structure penetrates through the thickness direction of the dielectric metasurface layer;

[0008] A second doped layer is formed in the absorption layer and located on the side of the absorption layer close to the metasurface structure; the doping types of the first doped layer and the second doped layer are different.

[0009] According to the avalanche multiplication photoelectric detector provided by the present application, the second doped layer comprises:

[0010] a first doped region, the first doped region being in contact with a surface of the super surface structure close to the absorbing layer.

[0011] According to the present application, an avalanche multiplication photodetector is provided, the second doped layer comprises:

[0012] a first doped region, the first doped region being between the super surface structure and the charge layer, the first doped region and the super surface structure having a first preset distance therebetween;

[0013] a second doped region, the second doped region being between the super surface structure and the first doped region, the second doped region being connected to an outer edge of the first doped region, and the second doped region being outside a projection of the super surface structure.

[0014] According to the present application, an avalanche multiplication photodetector is provided, further comprising a first electrode, the first electrode being wrapped around an outside of the super surface structure, the first electrode being connected to the second doped region.

[0015] According to the present application, an avalanche multiplication photodetector is provided, the first preset distance being 40 nm ~ 90 nm.

[0016] According to the present application, an avalanche multiplication photodetector is provided, a doped thickness of the first doped region being 50 nm ~ 100 nm.

[0017] According to the present application, an avalanche multiplication photodetector is provided, a third doped layer being formed in the charge layer, a cross-sectional shape of the first doped layer, the first doped region and the third doped layer corresponding to an outer contour shape of the super surface structure.

[0018] According to the present application, an avalanche multiplication photodetector is provided, the cross-sectional shape of the first doped layer, the first doped region and the third doped layer being any one of a circular shape, a square shape, and a polygonal window shape.

[0019] According to the present application, an avalanche multiplication photodetector is provided, at least one of a distance between a side surface of the second doped layer and a side surface of the absorbing layer, and a distance between a side surface of the third doped layer and a side surface of the charge layer being greater than or equal to 40 nm.

[0020] According to the present application, an avalanche multiplication photodetector is provided, the multiplication layer being a Si multiplication layer, the absorbing layer being a Ge absorbing layer, a Ge component in the charge layer gradually increasing from a surface close to the multiplication layer to a surface close to the absorbing layer, and a Si component in the charge layer gradually decreasing from the surface close to the multiplication layer to the surface close to the absorbing layer.

[0021] The application further provides a preparation method of the avalanche multiplication photodetector.

[0022] Preparation of the first doped layer;

[0023] Sequential formation of a multiplication layer, a charge layer, an absorption layer and a dielectric metasurface layer on the first doped layer;

[0024] Preparation of a metasurface structure on the dielectric metasurface layer, or preparation of a metasurface structure on the dielectric metasurface layer and the side surface of the absorption layer close to the dielectric metasurface layer; wherein the metasurface structure penetrates through the dielectric metasurface layer along the thickness direction of the dielectric metasurface layer;

[0025] Formation of a second doped layer in the absorption layer, the second doped layer being located on the side of the absorption layer close to the metasurface structure; the doping types of the first doped layer and the second doped layer are different.

[0026] The avalanche multiplication photodetector provided by the application realizes the regulation of the phase, amplitude and polarization of the incident light field by integrating the metasurface structure on the incident side of the absorption layer, so as to improve the absorption rate of the photodetector without increasing the thickness of the absorption layer, thereby effectively expanding the bandwidth of the device, reducing the time jitter, suppressing the noise, and improving the gain of the photodetector. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Figure 1 is one of the principle schematic diagrams of the avalanche multiplication photodetector provided by the application.

[0029] Figure 2 is the second principle schematic diagram of the avalanche multiplication photodetector provided by the application.

[0030] Figure 3 is one of the structure schematic diagrams of the avalanche multiplication photodetector provided by the application.

[0031] Figure 4 is the second structure schematic diagram of the avalanche multiplication photodetector provided by the application.

[0032] Figure 5 is the third structure schematic diagram of the avalanche multiplication photodetector provided by the application.

[0033] Figure 6Figure 4 is a structural schematic diagram of the avalanche multiplication photodetector provided by the present application.

[0034] Figure 7 Figure 5 is an A-A sectional view of the avalanche multiplication photodetector provided by the present application. Figure 6

[0035] Figure 6 is a flowchart of the preparation method of the avalanche multiplication photodetector provided by the present application. Figure 8

[0036] Figure 7 is an absorption degree schematic diagram of the conventional photodetector and the avalanche multiplication photodetector provided by the present application. Figure 9 Reference signs:

[0037] 100, first doped layer; 200, multiplication layer; 300, charge layer; 310, third doped layer; 400, absorption layer; 500, dielectric metasurface layer;

[0038] 600, metasurface structure;

[0039] 700, second doped layer; 710, first doped region; 720, second doped region;

[0040] 800, buried oxygen layer; 900, top silicon layer;

[0041] 101, second electrode; 102, first electrode.

[0042] DETAILED DESCRIPTION In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0043] In the description of the embodiments of the present application, it should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0044]

[0045] ​In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0046] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0048] The following is combined Figures 1-9 The avalanche multiplication photodetector of the present invention is described.

[0049] An embodiment of the first aspect of the present invention provides an avalanche multiplication photodetector, such as... Figures 1-6 As shown, the detector includes a metasurface structure 600, a second doped layer 700, and a first doped layer 100, a multiplication layer 200, a charge layer 300, an absorption layer 400, and a dielectric metasurface layer 500 arranged in sequence.

[0050] The super surface structure 600 is arranged on the dielectric super surface layer 500, or the super surface structure 600 is arranged on the dielectric super surface layer 500 and the side surface of the absorbing layer 400 close to the dielectric super surface layer 500, and the super surface structure 600 penetrates along the thickness direction of the dielectric super surface layer 500; the second doped layer 700 is formed in the absorbing layer 400 and located on the side of the absorbing layer 400 close to the super surface structure 600; the first doped layer 100 and the second doped layer 700 have different doping types.

[0051] It can be understood that the super surface structure 600 can be arranged on the dielectric super surface layer 500, or can be arranged on the dielectric super surface layer 500 and the side surface of the absorbing layer 400 close to the dielectric super surface layer 500, and the super surface structure 600 penetrates along the thickness direction of the dielectric super surface layer 500, for regulating the phase, amplitude and polarization of the incident light field, and enhancing the effective absorption of light in the absorbing layer 400; the second doped layer 700 is formed in the absorbing layer 400 and located on the side of the absorbing layer 400 close to the super surface structure 600, and the first doped layer 100 and the second doped layer 700 have opposite doping types, so as to form a local electric field in the absorbing layer 400 that is conducive to the separation and transport of photo-generated carriers, optimize the response speed and quantum efficiency of the device, reduce the time jitter and noise, and thus improve the overall performance of the detector under high gain.

[0052] It should be noted that the super surface structure 600 is not a continuous semiconductor layer in the traditional sense, but a periodic sub-wavelength structure introduced by micro-nano processing technology in the dielectric super surface layer 500 (or the dielectric super surface layer 500 and part of the absorbing layer 400 region), and its penetration in the thickness direction can effectively regulate the propagation path of the incident light and the distribution of the local electromagnetic field. In this way, by integrating the super surface structure 600 on the incident side of the absorbing layer 400, the phase, amplitude and polarization of the incident light field are regulated, the local field effect of the light field is effectively enhanced, and the light absorption efficiency is improved. Under the premise of not increasing the thickness of the absorbing layer 400, the gain of the detector is improved, while avoiding the decrease of the bandwidth caused by the increase of the carrier transit path, and promoting the generation of photo-generated carriers mainly in the shallow layer region of the absorbing layer 400 close to the incident side, greatly shortening the carrier drift time and reducing the randomness of the transit time, thereby effectively expanding the device bandwidth and reducing the time jitter.

[0053] The second doped layer 700 is located at the area of the absorption layer 400 close to the light incident side, and forms a hetero-doped structure with the first doped layer 100 below, which helps to build a directional electric field in the absorption layer 400, accelerate the separation and drift of photo-generated carriers, effectively inhibit the diffusion process and space charge accumulation, reduce the carrier transit time, reduce the time-domain expansion and noise components caused by carrier diffusion, thereby further reduce the time jitter, reduce the gain fluctuation and excess noise, and effectively enhance the application potential of the detector in the fields of quantum communication, laser radar and deep space exploration.

[0054] The avalanche multiplication photodetector provided by the embodiment of the present application realizes the regulation of the phase, amplitude and polarization of the incident light field by integrating the super surface structure 600 on the incident side of the absorption layer 400, so as to improve the absorption rate of the detector without increasing the thickness of the absorption layer 400, thereby effectively expanding the bandwidth of the device, reducing the time jitter and suppressing the noise while improving the gain of the detector.

[0055] According to the embodiment of the present application, the super surface structure 600 penetrates along the thickness direction of the dielectric super surface layer 500 to form a periodic sub-wavelength micro-nano structure array penetrating the layer; specifically, a mask pattern with a periodic nano structure is prepared on the surface of the dielectric super surface layer 500, and an etching process is used to etch the pattern completely through the thickness of the entire dielectric super surface layer 500, so as to form a periodic sub-wavelength structure, such as a nano column or a nano hole, which penetrates the layer in depth and has a vertical sidewall; after the etching is completed, the super surface structure 600 for regulating the phase, amplitude and polarization of the incident light field is finally obtained.

[0056] In the embodiment, the super surface structure 600 includes a plurality of cylinders, and the plurality of cylinders are arranged in a periodic array, and the space between the cylinders is filled with SiO2. It should be noted that in other embodiments, the space between the cylinders can also not be filled with materials.

[0057] Optionally, the super surface structure 600 can adopt the following two setting modes:

[0058] Firstly, the super surface structure 600 is completely formed in the dielectric super surface layer 500.

[0059] It can be understood that, as shown in Figure 5 and Figure 6 , when the super surface structure 600 is completely formed in the dielectric super surface layer 500, the material constituting the super surface structure 600 is the material of the dielectric super surface layer 500 itself (such as SiO2, Si and other dielectric materials), and at this time the super surface structure 600 is a single material.

[0060] The second type of super surface structure 600 is arranged across the medium super surface layer 500 and the side surface region of the absorption layer 400 close to the medium super surface layer 500, that is, a part of the super surface structure 600 is formed on the medium super surface layer 500, and another part of the super surface structure 600 is formed on the region of the absorption layer 400 close to the medium super surface layer 500.

[0061] It can be understood that, as shown in Figure 3 and Figure 4 , the super surface structure 600 not only exists on the medium super surface layer 500, but also extends to the side surface region of the absorption layer 400 close to the medium super surface layer 500, at this time, the super surface structure 600 crosses two functional layers, and the material of the super surface structure 600 includes the material of the medium super surface layer 500 and the material of the absorption layer 400, forming a composite structure composed of two different materials.

[0062] For example, the material of the absorption layer 400 is Ge material, and the material of the medium super surface layer 500 is Si material, if the super surface structure 600 adopts the first type of arrangement, the super surface structure 600 is composed of epitaxial low refractive index Si material with a certain arrangement period, if the super surface structure 600 adopts the second type of arrangement, the super surface structure 600 is composed of epitaxial low refractive index Si material and Ge material with a certain arrangement period.

[0063] It should be noted that the material of the absorption layer 400 can also be Si semiconductor material, and the material of the medium super surface layer 500 can be SiO2.

[0064] In an embodiment of the present application, the first doped layer 100 is N-type doped, and the second doped layer 700 is P-type heavily doped, and the second doped layer 700 is reasonably designed according to the position and depth of the P-type ohmic contact.

[0065] Optionally, the second doped layer 700 includes a first doped region 710, and the first doped region 710 is in contact with the surface of the super surface structure 600 close to the absorption layer 400.

[0066] It can be understood that, as shown in Figure 4 and Figure 5 , the second doped layer 700 includes a first doped region 710 located below the super surface structure 600, the first doped region 710 is formed in the absorption layer 400 and is in contact with the surface of the super surface structure 600 close to the absorption layer 400, that is, the first doped region 710 is arranged adjacent to the super surface structure 600.

[0067] For example, the first doped region 710 can be formed by ion implantation on the surface of the absorption layer 400 close to the super surface structure 600.

[0068] In another embodiment of the present application, as shown inFigure 3 and Figure 6 As shown in FIG. 7, the second doped layer 700 includes a first doped region 710 and a second doped region 720, the first doped region 710 is located between the super surface structure 600 and the charge layer 300, and a first preset distance is provided between the first doped region 710 and the super surface structure 600; the second doped region 720 is located between the super surface structure 600 and the first doped region 710, the second doped region 720 is connected to the outer edge of the first doped region 710, and the second doped region 720 is located outside the projection of the super surface structure 600.

[0069] It can be understood that the first doped region 710 is located in the region of the super surface structure 600 and the charge layer 300, and a first preset distance is provided between the first doped region 710 and the super surface structure 600; the second doped region 720 is arranged in the super surface structure 600 and the first doped region 710, and the second doped region 720 is located outside the projection area of the super surface structure 600 in the device plane, that is, the lateral distribution range extends to the area covered by the super surface structure.

[0070] It should be noted that since the super surface structure 600 usually relies on the etching process, the surface defects and interface states introduced in the etching process will act as a recombination center of carriers, increase the surface recombination rate of carriers, cause the dark current of the device to rise, and then cause the increase of the dark count rate, thereby affecting the detection performance of the detector. Therefore, the present application sets an appropriate distance (i.e. the first preset distance) between the first doped region 710 and the super surface structure 600, which can adjust the electric field strength and direction, so as to avoid the high-density interface state area of the etching sidewall region in the high electric field area, thereby inhibiting the trapping effect of the surface recombination center on the carriers, reducing the dark current caused by the surface recombination, effectively controlling the dark count rate, and improving the detection reliability of the detector.

[0071] It should be noted that the first preset distance can be cooperatively optimized and designed according to the working wavelength of the device, the shape (such as the width and height of the nano pillar / hole) and arrangement period of the super surface structure 600, and the energy distribution characteristics of the light field in the absorption layer 400.

[0072] Optionally, the first preset distance can be 40 nm ~90nm; preferably, the first preset distance is 50 nm ~80nm.

[0073] For example, the second doped layer 700 includes a first doped region 710 and a second doped region 720, which are prepared by twice photolithography and ion implantation processes. Specifically, first photolithography is performed, after the device surface is coated with photoresist, the injection area of the first doped region 710 is defined by using a mask, which is located inside the absorption layer 400, away from the metasurface structure 600 at a certain distance below; then the required doping elements (such as P-type doping elements) are implanted into the specified depth of the absorption layer 400 by one or more times of ion implantation, to form the first doped region 710. Then the second photolithography is performed, after the first implantation is completed and the original photoresist is removed, the injection area of the second doped region 720 is defined by re-coating and aligning exposure, which is located in the near-surface region of the absorption layer 400 close to the light incident side, adjacent to the interface between the metasurface structure 600 and the absorption layer 400, and then the second ion implantation is performed to form the second doped region 720 connected to the first doped region 710 in this area.

[0074] In this embodiment, as shown in Figure 6 and Figure 7 , the first doped region 710 is circular, located inside the absorption layer 400 and at a certain distance from the metasurface structure 600, and the second doped region 720 is arranged around the outer edge of the first doped region 710, forming a concentric circular structure, and the two together constitute the second doped layer 700.

[0075] In an embodiment of the present application, the doping thickness of the first doped region 710 is 50 nm to 100 nm.

[0076] It can be understood that the first doped region 710 is located inside the absorption layer 400 and below the metasurface structure 600, and the doping thickness of the first doped region 710 is designed to be 50 nm to 100 nm, which helps to form a high electric field gradient locally, accelerate the separation and drift of photo-generated carriers, shorten the transit time, and thus reduce the temporal jitter.

[0077] In an embodiment of the present application, as shown in Figure 4 , the distance d1 between the side surface of the second doped layer 700 and the side surface of the absorption layer 400 is greater than or equal to 40 nm.

[0078] It can be understood that the second doped layer 700 side surface and the absorption layer 400 side surface have a second preset distance, and the second preset distance is greater than or equal to 40 nm, which avoids damage to the second doped layer 700 during device sidewall etching, thereby reducing the surface recombination effect caused by sidewall defects and interface states, and thus helps to maintain the stability of the local electric field and the efficiency of carrier transport, and suppresses the surface leakage current, improves the signal-to-noise ratio and detection reliability of the device.

[0079] Optionally, when the second doped layer 700 includes the first doped region 710 and the second doped region 720, the distance between the side surface of the second doped region 720 and the side surface of the absorption layer 400 is greater than 50 nm, and the distance between the side surface of the first doped region 710 and the side surface of the absorption layer 400 is less than the distance between the side surface of the second doped region 720 and the side surface of the absorption layer 400; when the second doped layer 700 only includes the first doped region 710, the distance between the side surface of the first doped region 710 and the side surface of the absorption layer 400 is greater than 50 nm.

[0080] In one embodiment of the present application, as shown in FIG. 1, the first doped layer 100 is composed of a top silicon layer 900 of an SOI (Silicon-on-Insulator) substrate, which is located above a buried oxide layer 800 (BOX) of the SOI substrate and serves as a bottom conductive layer and an electrical contact layer of the device. Figures 1-3

[0081] It should be noted that the top silicon layer 900 of the SOI substrate is used as the first doped layer 100, which forms a good lattice matching and electrical connection with the upper absorption layer 400, the multiplication layer 200, the charge layer 300 and the super surface structure 600, thereby providing a stable and reliable charge injection and carrier transport channel for the entire avalanche multiplication photodetector.

[0082] Optionally, the multiplication layer 200 is an unintentionally doped (UID) silicon epitaxial layer, which is formed by epitaxial growth of a single crystal silicon material on the top surface of the top silicon layer 900 of the SOI substrate through chemical vapor deposition or molecular beam epitaxy technology.

[0083] In one embodiment of the present application, the charge layer 300 adopts an epitaxial structure design with gradually changing components, and a gentle and controllable energy band gradient is constructed by adjusting the material components (such as the gradual change of the Si component in GeSi along the growth direction), which is beneficial to the directional transport of holes or electrons and inhibits the reverse diffusion of carriers.

[0084] For example, the multiplication layer 200 is a Si multiplication layer, the absorption layer 400 is a Ge absorption layer, the Ge component in the charge layer 300 gradually increases from the surface close to the multiplication layer 200 to the surface close to the absorption layer 400, and the Si component in the charge layer 300 gradually decreases from the surface close to the multiplication layer 200 to the surface close to the absorption layer 400.

[0085] ​It can be understood that the multiplication layer 200 adopts a silicon (Si) material, the absorption layer 400 adopts a germanium (Ge) material, and a charge layer 300 is arranged between the two, the charge layer 300 being a SiGe epitaxial layer with gradually changing components, for realizing smooth transition of energy bands and regulating internal electric field distribution. Specifically, the germanium (Ge) component in the charge layer 300 gradually and continuously increases from 0% (i.e. pure Si) near the lower surface of the multiplication layer 200 to 100% (i.e. pure Ge) near the upper surface of the absorption layer 400; correspondingly, the silicon (Si) component in the charge layer 300 gradually decreases from 100% at the lower surface to 0% at the upper surface.

[0086] It should be noted that the gradient change of the Ge component forms a gentle conduction band gradient, which is beneficial to the directional transport of holes and acts as an electron barrier to block reverse carrier injection, so as to regulate the charge density and electric field distribution of the charge layer 300, ensure that the avalanche multiplication process is concentrated in the multiplication layer 200, and improve the gain stability and reduce the noise of the device.

[0087] Optionally, as shown in Figure 3 and Figure 5 , a third doped layer 310 is formed in the charge layer 300.

[0088] In this embodiment, the third doped layer 310 is P-type doped, and the doping concentration is kept constant.

[0089] Further, the distance d2 between the side surface of the third doped layer 310 and the side surface of the charge layer 300 is greater than or equal to 40 nm.

[0090] It can be understood that the third doped layer 310 is formed in the charge layer 300, and the lateral distance between the side surface of the third doped layer 310 and the epitaxial side wall of the charge layer 300 is greater than or equal to 40 nm, so as to avoid damage to the third doped layer 310 in the device side wall etching process, thereby reducing the surface recombination effect caused by the side wall defects and interface states, and further helping to maintain the stability of the local electric field and the efficiency of the carrier transport, and suppressing the surface leakage current, thereby improving the signal-to-noise ratio and detection reliability of the device.

[0091] In this embodiment, the distance between the side surface of the third doped layer 310 and the side surface of the charge layer 300 is greater than or equal to 50 nm.

[0092] In an embodiment of the present application, the cross-sectional shape of the first doped layer 100, the first doped region 710 and the third doped layer 310 corresponds to the outer contour shape of the super surface structure 600.

[0093] It can be understood that the cross-sectional shape of the first doped layer 100, the first doped region 710 and the third doped layer 310 is consistent with the outer contour shape of the metasurface structure 600, that is, the lateral distribution area of each doped layer matches the projected contour of the metasurface structure 600, so as to realize the spatial alignment of the doped region and the light field regulation region, ensure the synchronous construction of the optimized local electric field structure under the region of the super surface enhanced light absorption and the generation of high-density photo-generated carriers, thereby effectively guiding the rapid separation and directional transport of carriers, and improving the carrier collection efficiency and response speed. It should be noted that the second doped region 720 is a hollow structure, and the inner and outer contour shapes of the second doped region 720 are adapted to the outer contour shape of the first doped region 710.

[0094] Optionally, the cross-sectional shape of the first doped layer 100, the first doped region 710 and the third doped layer 310 is any one of a circular shape, a square shape and a polygonal window.

[0095] It can be understood that the cross-sectional shape of the first doped layer 100, the first doped region 710 and the third doped layer 310 can be designed as any one of a circular shape, a square shape or a polygonal window according to the outer contour of the metasurface structure 600, so as to realize the geometric matching of the light field regulation region and the electrical function region.

[0096] For example, when the outer contour of the metasurface structure 600 is circular, the cross-sectional shape of each doped layer (the first doped layer 100, the first doped region 710 and the third doped layer 310) is also designed as circular, so that its lateral distribution range corresponds to the projected area of the circular metasurface structure 600.

[0097] Optionally, as shown in Figure 3 and Figure 5 The photodetector further includes a pair of electrodes, namely a first electrode 102 and a second electrode 101, for applying a working bias and realizing the extraction of photoelectric current. Specifically, the second electrode 101 is arranged on the first doped layer 100 and realizes Ohmic contact through a metallization process, for extracting electrons; the first electrode 102 is arranged on the second doped layer 700 and located outside the metasurface structure 600, so that it can form good electrical contact with the second doped layer 700, while avoiding shielding the incident light path, thereby fully utilizing the non-optically active region in the metasurface structure 600 to arrange the electrode, which helps to improve the responsivity and working bandwidth of the device.

[0098] For example, in the case where the second doped layer 700 includes the first doped region 710 and the second doped region 720, the first electrode 102 is arranged outside the metasurface structure 600, and the first electrode 102 is connected to the second doped region 720.

[0099] In this embodiment, the second doped region 720 has the same diameter as the third doped layer 310, and the first doped region 710 has an outer diameter slightly larger than that of the second doped region 720, ensuring that the electrical control region is aligned in the vertical direction; the first electrode 102 has a circular ring structure, is arranged outside the outer contour of the metasurface structure 600, and is concentrically distributed around the outer edge of the second doped layer 700 to achieve good electrical contact with the second doped layer 700 without blocking the incident light.

[0100] The diameter of the first doped layer 100 is larger than that of the second doped layer 700, and its outer edge extends to a more outer region, and the second electrode 101 is arranged around the outer edge of the first doped layer 100, which also has a concentric circular ring structure in this example structure.

[0101] Based on the avalanche multiplication photodetector provided by any of the above embodiments, an embodiment of the second aspect of the present application proposes a preparation method of an avalanche multiplication photodetector, as shown in the figure, which includes the following steps: Figure 8

[0102] Step 10, preparing the first doped layer 100.

[0103] Step 20, sequentially forming the multiplication layer 200, the charge layer 300, the absorption layer 400 and the dielectric metasurface layer 500 on the first doped layer 100.

[0104] Step 30, preparing the metasurface structure 600 on the dielectric metasurface layer 500, or preparing the metasurface structure 600 on the dielectric metasurface layer 500 and the side surface of the absorption layer 400 close to the dielectric metasurface layer 500; wherein the metasurface structure 600 penetrates along the thickness direction of the dielectric metasurface layer 500.

[0105] Step 40, forming the second doped layer 700 in the absorption layer 400, and the second doped layer 700 is located on the side of the absorption layer 400 close to the metasurface structure 600; the first doped layer 100 and the second doped layer 700 have different doping types.

[0106] ​It can be understood that first, the doped ions are injected into the top silicon layer 900 of the SOI substrate to form the first doped layer 100; then the multiplication layer 200, the charge layer 300, the absorption layer 400 and the dielectric metasurface layer 500 are sequentially epitaxially grown on the first doped layer 100; then the metasurface structure 600 is prepared in the dielectric metasurface layer 500, or the metasurface structure 600 is prepared in the dielectric metasurface layer 500 and the side surface of the absorption layer 400 close to the dielectric metasurface layer 500, the metasurface structure 600 is completely penetrated along the thickness direction of the dielectric metasurface layer 500 through the etching process, and a periodic subwavelength micro-nano structure array is formed, which is used for regulating the phase, amplitude and polarization of the incident light field; finally, the second doped layer 700 is formed in the absorption layer 400 close to the side region of the metasurface structure 600 by ion implantation, and the second doped layer 700 and the first doped layer 100 have opposite doping types, so that a local electric field beneficial to the rapid separation and transport of carriers is constructed in the absorption layer 400, and high-performance detection capability with high gain, high bandwidth, low noise and low time jitter is realized.

[0107] In one specific embodiment of the present application, the preparation method of the avalanche multiplication photodetector comprises the following steps:

[0108] N+ ions are injected into the top silicon layer 900 of the SOI substrate to form the first doped layer 100 doped with N type as the bottom electrical contact layer of the device.

[0109] The unintentionally doped single crystal Si film, the SiGe composition gradient film, the single crystal Ge film and the Si film are sequentially deposited on the first doped layer 100 by using the epitaxial growth technology, so as to form the multiplication layer 200, the charge layer 300, the absorption layer 400 and the dielectric metasurface layer 500 which are sequentially stacked from bottom to top on the first doped layer 100; wherein the SiGe composition gradient film is doped with P type ions during the growth process or in the subsequent process, and the doping concentration is kept constant, so as to form the third doped layer 310 doped with P type in the charge layer 300, which is used for regulating the internal electric field distribution.

[0110] According to the preset mesa pattern, the epitaxial layer (including the multiplication layer 200, the charge layer 300, the absorption layer 400 and the dielectric metasurface layer 500) and part of the top silicon layer 900 are etched to above the buried oxide layer 800 to form a device mesa structure.

[0111] A layer of SiO2 dielectric layer is deposited on the mesa sidewall and the entire surface, the deposition thickness is basically consistent with the mesa height, and the surface is planarized by chemical mechanical polishing or etching back process, so that the Si material of the dielectric metasurface layer 500 is exposed again.

[0112] The periodic sub-wavelength micro-nano structure penetrating the thickness direction is prepared on the upper region of the dielectric metasurface layer 500 and the absorption layer 400 by etching process to form the metasurface structure 600 for regulating the phase, amplitude and polarization of the incident light; meanwhile, the ohmic contact region outside the metasurface structure 600 is etched to ensure the connection channel of the subsequent metal electrode and the doped region.

[0113] According to the design of the N-type ohmic contact region, the epitaxial layer (including the multiplication layer 200, the charge layer 300, the absorption layer 400 and the dielectric metasurface layer 500) at the corresponding position is further etched to expose the top silicon layer 900.

[0114] A layer of SiO2 is deposited again as an insulating isolation layer to cover the mesa sidewall and the non-electrode region to form a sidewall isolation to inhibit the leakage and crosstalk; and the SiO2 at the metal electrode connection position is selectively removed by etching process to expose the ohmic contact region of the P-type second doped layer and the N-type first doped layer, respectively.

[0115] The first ion implantation is performed on the region near the metasurface structure 600 in the absorption layer 400 to form the first doped region 710; and then the second ion implantation is performed on the near-surface region closer to the light incident side to form the second doped region 720 between the first doped region 710 and the metasurface structure 600, and the two doped regions together constitute the P-type second doped layer 700 and the N-type first doped layer 100 to form a hetero-doped structure to construct a local electric field conducive to the rapid separation and transport of photo-generated carriers, thereby improving the response speed and quantum efficiency of the device.

[0116] The metal material is deposited on the exposed ohmic contact region, and the ohmic contact is formed by annealing to form the second electrode 101 (N-type electrode) and the first electrode 102 (P-type electrode) after photoetching patterning, thereby realizing the efficient integration of the optical and electrical paths and completing the device preparation.

[0117] It should be noted that the second electrode 101 is coated with SiO2 to form an insulating layer outside the second electrode 101, thereby ensuring the complete isolation between the adjacent detectors in terms of electricity and optics, effectively blocking the carrier diffusion and leakage current path between the adjacent detectors, inhibiting the electrical crosstalk, and limiting the lateral leakage of the optical signal by using the low refractive index characteristic to reduce the optical crosstalk.

[0118] It should be noted that the etching of the ohmic contact region and the metasurface structure 600 can be performed simultaneously.

[0119] It should be noted that in other embodiments, the absorption layer 400 can also adopt a single-crystal GeSn thin film; further, the absorption layer 400 includes a single-crystal Ge thin film epitaxially grown on the charge layer 300 and a single-crystal GeSn thin film epitaxially grown on the single-crystal Ge thin film.

[0120] As Figure 9 shown, the present application compares the absorption performance of the conventional photodetector and the avalanche multiplication photodetector integrated with the metasurface structure 600; Figure 9 In the figure, the abscissa is the wavelength of the incident light (Wavelength), in microns (μm); the ordinate is the absorption (Absorption), which represents the ratio of the absorbed light energy to the incident light energy, and its value range is between 0 and 1; Figure 9 In the figure, curve a represents the absorption characteristics of the conventional photodetector, Figure 9 In the figure, curve b represents the absorption characteristics of the avalanche multiplication photodetector integrated with the metasurface structure 600, it can be seen that in the wide spectral range of 1500~1570 nm, the absorption rate of the conventional detector is less than 10%; while the absorption rate of the present application detector is significantly improved, and the highest can reach 60%. As can be seen, compared with the conventional structure without integrated metasurface, the present application can realize efficient regulation and local enhancement of light field by introducing the metasurface structure 600, which can make the wide spectrum absorption efficiency increase by more than 4 times without increasing the thickness of the absorption layer 400, and greatly enhance the photon capture ability, thereby effectively improving the gain of the detector, and providing support for realizing high-sensitivity and high-speed photodetection. It should be noted that by optimizing the metasurface structure 600, the absorption peak can reach more than 90%.

[0121] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An avalanche multiplication photodetector, characterized in that, include: The first doped layer, multiplication layer, charge layer, absorption layer and dielectric metasurface layer are stacked in sequence. A metasurface structure is located on the incident side of the absorption layer. The metasurface structure is disposed on the dielectric metasurface layer, or the metasurface structure is disposed on the dielectric metasurface layer and the absorption layer on the side surface near the dielectric metasurface layer. The metasurface structure extends through the thickness direction of the dielectric metasurface layer. A second doped layer is formed in the absorption layer and is located on the side of the absorption layer closer to the metasurface structure; The first doped layer and the second doped layer have different doping types; The second doped layer includes: A first doped region is located between the metasurface structure and the charge layer, and a first predetermined distance exists between the first doped region and the metasurface structure. The second doped region is located between the metasurface structure and the first doped region, the second doped region is connected to the outer edge of the first doped region, and the second doped region is located outside the projection of the metasurface structure.

2. The avalanche multiplication photodetector according to claim 1, characterized in that, It also includes a first electrode, which surrounds the outside of the metasurface structure and is connected to the second doped region.

3. The avalanche multiplication photodetector according to claim 1, characterized in that, The first preset distance is 40nm ~ 90nm, and / or, The doping thickness of the first doped region is 50 nm to 100 nm.

4. The avalanche multiplication photodetector according to any one of claims 1 to 3, characterized in that, A third doped layer is formed within the charge layer, and the cross-sectional shapes of the first doped layer, the first doped region, and the third doped layer correspond to the outer contour shape of the metasurface structure.

5. The avalanche multiplication photodetector according to claim 4, characterized in that, The cross-sectional shape of the first doped layer, the first doped region, and the third doped layer is any one of a circular, square, or polygonal window.

6. The avalanche multiplication photodetector according to claim 4, characterized in that, At least one of the distance between the side of the second doped layer and the side of the absorption layer, and the distance between the side of the third doped layer and the side of the charge layer is greater than or equal to 40 nm.

7. The avalanche multiplication photodetector according to any one of claims 1 to 3, characterized in that, The multiplication layer is a Si multiplication layer, the absorption layer is a Ge absorption layer, the Ge component in the charge layer gradually increases from the surface near the multiplication layer to the surface near the absorption layer, and the Si component in the charge layer gradually decreases from the surface near the multiplication layer to the surface near the absorption layer.

8. A method for fabricating an avalanche multiplication photodetector, characterized in that, include: Prepare the first doped layer; A multiplication layer, a charge layer, an absorption layer, and a dielectric metasurface layer are sequentially formed on the first doped layer; The metasurface structure is located on the incident side of the absorption layer; A metasurface structure is prepared on the dielectric metasurface layer, or a metasurface structure is prepared on the surface of the dielectric metasurface layer and the absorber layer on the side near the dielectric metasurface layer; wherein the metasurface structure extends through the thickness direction of the dielectric metasurface layer. A second doped layer is formed in the absorption layer, and the second doped layer is located on the side of the absorption layer closer to the metasurface structure; the first doped layer and the second doped layer have different doping types; The second doped layer includes: A first doped region is located between the metasurface structure and the charge layer, and a first predetermined distance exists between the first doped region and the metasurface structure. The second doped region is located between the metasurface structure and the first doped region, the second doped region is connected to the outer edge of the first doped region, and the second doped region is located outside the projection of the metasurface structure.

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