WO2022110054A1

WO2022110054A1 - Photodetector, manufacturing method therefor, chip, and optical device

Info

Publication number: WO2022110054A1
Application number: PCT/CN2020/132411
Authority: WO
Inventors: 曹均凯; 曹高奇
Original assignee: 华为技术有限公司
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2022-06-02
Also published as: CN115943335A

Abstract

A photodetector (10), a manufacturing method therefor, a chip (100), and an optical device. The photodetector (10) comprises: a substrate (11); a first electrode contact layer (12), a photosensitive layer (13), a second electrode contact layer (14), and a passivation layer (15) which are sequentially stacked on the substrate (11); and a first electrode (161) and a second electrode (162). The photodetector (10) further comprises a through hole (V0) at least penetrating through the photosensitive layer (13) and the second electrode contact layer (14); the first electrode contact layer (12) and the second electrode contact layer (14) are doped semiconductor layers having opposite polarities; the first electrode (161) and the second electrode (162) are insulated from each other; the first electrode (161) is electrically connected to the first electrode contact layer (12) by means of a first recess (V1); the second electrode (162) is electrically connected to the second electrode contact layer (14) by means of a second recess (V2). In the photodetector (10), when light to be detected passes through the through hole (V0), the photosensitive layer (13) may capture some of photons passing through the through hole (V0) to convert an optical signal into an electric signal, thereby achieving the detection of the light to be detected, and ensuring that the light to be detected is not disturbed.

Description

Photodetector, its preparation method, chip and optical device

technical field

The present application relates to the technical field of optical communication, and in particular, to a photodetector, a preparation method thereof, a chip and an optical device.

Background technique

The working mechanism of the wavelength-selective switches (WSS) structure is that the colored light beams are incident on the free space in the WSS structure from the input fiber, and then the colored light beams are regularly transmitted through the action of various optical elements set in the free space. Dispersed into monochromatic beams of different wavelengths, and then through the action of geometric optics, the monochromatic beams of different wavelengths enter different output fibers. Therefore, the WSS structure can select different output wavelengths according to actual application needs, and can adjust the output optical power independently.

Since the light beam is transmitted in free space in the WSS structure, only the entrance and exit are provided with optical fibers. In order to realize the detection of the optical signal, it is necessary to install a fiber tap detection device on the input or output fiber of the WSS structure. Referring to Figure 1, when the light beam in the fiber 1 is transmitted to the fiber optic connection, a small amount of light beam will be emitted from the fiber optic section. Therefore, the detection of the optical signal transmitted in the optical fiber 1 can be realized without destroying the optical path of the original optical fiber 1 . Referring to FIG. 2, since the input fiber and output fiber of the WSS structure are usually fiber arrays (Fiber Array), it is necessary to install a large number of fiber tap detection devices 2 to meet the requirements of real-time detection. However, using a large number of optical fiber tap detection devices 2 requires a large installation space, which will lead to increased volume, complex structure, and increased cost of the optical fiber communication system.

SUMMARY OF THE INVENTION

The present application provides a photodetector, a preparation method thereof, a chip and an optical device, which are used to provide a new type of photodetector.

In a first aspect, a photodetector provided by the present application includes: a substrate, a first electrode contact layer, a photosensitive layer, a second electrode contact layer, and a passivation layer that are sequentially stacked on the substrate; The first electrode and the second electrode on the chemical layer; the first electrode contact layer and the second electrode contact layer are doped semiconductor layers with opposite polarities, for example, the first electrode contact layer is a P-type doped semiconductor layer, and the second electrode contact layer is a P-type doped semiconductor layer. The contact layer is an N-type doped semiconductor layer, or the first electrode contact layer is an N-type doped semiconductor layer, and the second electrode contact layer is a P-type doped semiconductor layer. The photodetector also includes a through hole penetrating at least the photosensitive layer and the second electrode contact layer; the orthographic projections of the first electrode and the second electrode on the substrate are respectively located outside the orthographic projection of the through hole on the substrate, and the first electrode and the second electrode are insulated from each other, the first electrode is electrically connected to the first electrode contact layer through a first groove penetrating the film layer between the first electrode and the first electrode contact layer, and the second electrode is electrically connected to the first electrode contact layer through the passivation layer. The second groove is electrically connected to the second electrode contact layer.

In this photodetector, the first electrode contact layer and the second electrode contact layer form a PN junction. When the photosensitive layer captures the light passing through the via hole V0, the PN junction can convert the optical signal into an electrical signal, thereby realizing Detection of optical signals. It should be pointed out that the photodetector is not limited in structure to a photodiode (Photodiode, PD), an avalanche photodiode (Avalanche Photodiode, APD) or a heterojunction phototransistor (Hetero junction Photodiode, HPT) and the like.

It should be noted that, in this application, the orthographic projections of the first electrode and the second electrode on the substrate are respectively located outside the orthographic projection of the through hole on the substrate, so that the orthographic projection of the first electrode on the substrate and the first Neither of the orthographic projections of the two electrodes on the substrate can cover the through hole, thus preventing the first electrode and the second electrode from blocking light passing through the through hole.

The photodetector of the present application can be applied to various structures based on the transmission of light in free space. Specifically, the photodetector can be arranged on the transmission path of monochromatic light in free space, and the monochromaticity and direction of the transmission of these light beams can be used. Due to the characteristics of the Gaussian distribution of light intensity and light intensity, when the monochromatic beam passes through the photodetector, a small number of photons at the edge of the beam will enter the photodetector, so that the light signal can be detected in real time without interfering with the light transmission. For example, when applied to the WSS structure, the photodetector is arranged on the transmission path of the monochromatic light in the free space of the WSS structure. Therefore, not only the monochromatic light signal can be guaranteed not to be disturbed, but also the stability of the WSS structure can be guaranteed. Volume does not increase. In addition, since the photodetector can directly obtain photons from the transmission path of monochromatic light without the help of other devices, it can be fixed on the transmission path of monochromatic light without complex mechanical fixing parts, which is different from using existing devices. Compared with the optical fiber tap detection device, the overall structure complexity and cost can be reduced.

In practical applications, the electrical contact performance between the P-type doped semiconductor layer and the metal electrode is generally not as good as the electrical contact performance between the N-type doped semiconductor layer and the metal electrode. Therefore, for the P-type doped semiconductor layer, a metal contact electrode can be formed first between the P-type doped semiconductor layer and the metal electrode. Therefore, in the present application, if the first electrode contact layer is a P-type doped semiconductor layer, a metal contact electrode may be provided between the first electrode contact layer and the first electrode. If the second electrode contact layer is a P-type doped semiconductor layer, a metal contact electrode may be provided between the second electrode contact layer and the second electrode. It is not limited here.

In specific implementation, the second electrode contact layer is generally set as a P-type doped semiconductor layer. Therefore, in this application, the second electrode contact layer is a P-type doped semiconductor layer, and the photodetector further includes a layer located on the second electrode. The metal contacts the electrode with the second electrode contact layer to improve the electrical contact performance between the second electrode and the second electrode contact layer.

The present application does not limit the shapes of the first electrode and the second electrode. However, considering the symmetry of the performance of the photodetector, the second electrode has a closed annular structure surrounding the through hole; the first electrode has an annular structure arranged around the second electrode and having an opening. The opening of the first electrode is to avoid a short circuit between the first electrode and the second electrode, and the first electrode and the second electrode are drawn out from two sides of the through hole respectively.

Further, in order to increase the contact area between the electrode and the electrode contact layer, the shape of the groove can be set to be similar to the shape of the electrode. Exemplarily, in this application, the shape of the second groove is a closed ring surrounding the through hole; The shape of a groove is an annular shape with an opening arranged around the second groove.

In the specific implementation, in order to avoid the photodetector from affecting the light passing through the area where the through hole is located, the through hole can penetrate all the film layers along the thickness direction of the substrate, that is, the through hole penetrates through the passivation layer, the second electrode contact layer, A photosensitive layer, a first electrode contact layer and a substrate. When the absorption spectrum of the substrate does not overlap the wavelength of the light to be detected, the through hole may only penetrate the second electrode contact layer, the photosensitive layer and the first electrode contact layer. Further, when the absorption spectrum of the substrate does not overlap the wavelength of the light to be detected, and the epitaxial material of the first electrode contact layer and the substrate is the same, the through hole can only penetrate the second electrode contact layer and the photosensitive layer.

The shape of the through hole is not limited in the present application, and it may be any shape, such as polymorphic shape, circular shape, oval shape, and the like. When the shape of the through hole is circular, it can be ensured that the distance from the center of the through hole to the boundary of the through hole is the same. Moreover, the circular via is easier to realize in the process.

In the present application, when the second electrode contact layer is formed, a capping layer can be formed first, and then the capping layer can be doped. If the doping area covers the area where the via hole is located, the via hole will penetrate the remaining doping area after the doping area. It is the second electrode contact layer. If the doped region does not cover the region where the through hole is located, the doped region is the second electrode contact layer. Therefore, in the present application, the photodetector further includes a cover layer provided in the same layer as the second electrode contact layer, the shape of the second electrode contact layer is annular, and the cover layer is arranged around the second electrode contact layer; The intrinsic material of the second electrode contact layer and the cover layer is the same, but the doping concentration is different. The cover layer is generally lightly doped, and the second electrode contact layer is generally heavily doped. Alternatively, the intrinsic material of the second electrode contact layer and the cover layer are the same, and the electrical doping types of the two are different, for example, the cover layer is N-type doped, the second electrode contact layer is P-type doping, or the cover layer is P-type doping type doping, and the second electrode contact layer is N-type doped.

In a second aspect, a chip provided by the present application includes a drive circuit, and at least one photodetector of any of the above-mentioned embodiments of the present application connected to the drive circuit. Among them, the photoelectric energy detector can convert the captured optical signal into an electrical signal, and the driving circuit can amplify the electrical signal and output it to realize the detection of the optical signal.

In a third aspect, the present application provides an optical device comprising a wavelength selective switch structure and at least one photodetector, wherein the photodetector is arranged on a transmission path of monochromatic light in the free space of the wavelength selective switch structure. Not only can the monochromatic optical signal be guaranteed not to be disturbed, but also the volume of the WSS structure can be guaranteed not to increase. In addition, since the photodetector can directly obtain photons from the transmission path of monochromatic light without the help of other devices, it can be fixed on the transmission path of monochromatic light without complex mechanical fixing parts, which is different from using existing devices. Compared with the optical fiber tap detection device, the overall cost and overall structural complexity can be reduced.

In a fourth aspect, the present application provides a method for preparing a photodetector, comprising: firstly forming a first electrode contact layer, a photosensitive layer and a second electrode contact layer on a substrate in sequence, and forming at least a through photosensitive layer and a through hole of the second electrode contact layer; then a first passivation layer is formed on the second electrode contact layer, and a first groove and a through passivation penetrating the first passivation layer and deep to the surface of the first electrode contact layer are formed The second groove of the passivation layer; finally, the first electrode and the second electrode are formed on the first passivation layer; wherein, the orthographic projections of the first electrode and the second electrode on the substrate are respectively located on the positive side of the through hole on the substrate. The outside of the projection; the first electrode and the second electrode are insulated from each other, the first electrode is electrically connected to the first electrode contact layer through the first groove, and the second electrode is electrically connected to the second electrode contact layer through the second groove. Wherein, the first electrode contact layer and the second electrode contact layer are doped semiconductor layers with opposite polarities, for example, the first electrode contact layer is a P-type doped semiconductor layer, and the second electrode contact layer is an N-type doped semiconductor layer, Alternatively, the first electrode contact layer is an N-type doped semiconductor layer, and the second electrode contact layer is a P-type doped semiconductor layer.

In the photodetector formed by the above-mentioned preparation method provided in this application, the first electrode contact layer and the second electrode contact layer form a PN junction. When the photosensitive layer captures the light passing through the through hole V0, the PN junction can convert the optical signal Converted into electrical signals, so as to realize the detection of optical signals. It should be pointed out that the photodetector is not limited in structure to a photodiode (Photodiode, PD), an avalanche photodiode (Avalanche Photodiode, APD) or a heterojunction phototransistor (Hetero junction Photodiode, HPT) and the like.

In a possible implementation manner, the first electrode contact layer, the photosensitive layer and the second electrode contact layer are sequentially formed on the substrate, and through holes at least penetrating through the photosensitive layer and the second electrode contact layer are formed, which may include : First, the first electrode contact layer, the photosensitive layer and the cover layer are formed on the substrate in sequence; then the second passivation layer is formed on the cover layer, and the via hole passing through the second passivation layer is formed, so that the exposed cover The layer is annular or circular; then the exposed cover layer is doped to form a second electrode contact layer; and then a through hole penetrating at least the photosensitive layer and the second electrode contact layer is formed.

Or, in another possible implementation manner, the first electrode contact layer, the photosensitive layer, and the second electrode contact layer are sequentially formed on the substrate, and a through hole penetrating at least the photosensitive layer and the second electrode contact layer is formed , which may include: firstly forming a first electrode contact layer, a photosensitive layer and a cover layer on the area of the substrate except the central area; then forming a second passivation layer on the cover layer, and forming a second passivation layer through The via hole of the chemical layer is formed, so that the exposed cover layer is annular; and then the exposed cover layer is doped to form a second electrode contact layer.

In the present application, after doping the exposed cover layer to form the second electrode contact layer, the method further includes: removing the central region of the substrate, so that in the formed photodetector, there is no film in the region where the through hole is located Floor.

In a possible implementation manner, a first passivation layer is formed on the second electrode contact layer, and a first groove that penetrates the first passivation layer and is deep to the surface of the first electrode contact layer and penetrates the passivation layer is formed The second groove may include: first forming a third groove penetrating the second passivation layer, the cover layer and the photosensitive layer; then forming the first passivation layer on the second electrode contact layer, so that the first passivation layer can be formed. The passivation layer covers the sidewall of the third groove to protect the sidewall of the third groove; then a second groove is formed through the first passivation layer, and a second groove through the third groove is formed in the area where the third groove is located. A first groove of the passivation layer, so that the first groove penetrates the first passivation layer and is deep to the surface of the first electrode contact layer.

It can be understood that since there are multiple layers between the first electrode and the contact layer of the first electrode, the depth of the third groove is relatively deep, and the first electrode needs to climb over the sidewall of the third groove and the first electrode. The contact layer is electrically connected. If the depth of the sidewall is deep, the first electrode is likely to be disconnected at the sidewall. Therefore, optionally, in this application, the first electrode contact layer, the photosensitive layer and the second electrode are sequentially formed on the substrate. After the electrode contact layer, and before forming the first passivation layer on the second electrode contact layer, the method may further include: removing the second passivation layer, the cover layer and the photosensitive layer in the preset area, so that the remaining cover layer and the photosensitive layer are removed. The sensitive layer has a ring structure. Therefore, the subsequently formed first electrode only needs to penetrate the first groove of the first passivation layer to be electrically connected to the first electrode contact layer.

As mentioned above, in the present application, among the first electrode contact layer and the second electrode contact layer, one electrode contact layer is a P-type doped semiconductor layer, and the other electrode contact layer is an N-type doped semiconductor layer. Generally, the electrical contact performance between the P-type doped semiconductor layer and the metal electrode is not as good as the electrical contact performance between the N-type doped semiconductor layer and the metal electrode. Therefore, for the P-type doped semiconductor layer, a metal contact electrode can be formed first between the P-type doped semiconductor layer and the metal electrode. Therefore, in the present application, if the first electrode contact layer is a P-type doped semiconductor layer, a metal contact electrode may be provided between the first electrode contact layer and the first electrode. If the second electrode contact layer is a P-type doped semiconductor layer, a metal contact electrode may be provided between the second electrode contact layer and the second electrode. It is not limited here.

In specific implementation, the second electrode contact layer is generally set as a P-type doped semiconductor layer. Therefore, in this application, after the first electrode contact layer, the photosensitive layer and the second electrode contact layer are sequentially formed on the substrate , before forming the first passivation layer on the second electrode contact layer, may further include: forming a ring-shaped metal contact electrode on the second electrode contact layer, and annealing the metal contact electrode, so that the second electrode to be formed The second electrode contact layer is electrically connected through the metal contact electrode.

Description of drawings

FIG. 1 is a schematic diagram of the detection performed by an optical fiber tap detection device in the related art;

Fig. 2 is the structural representation that the optical fiber tap detection device is applied in the WSS structure in the related art;

FIG. 3a is a schematic top-view structural diagram of a photodetector in an embodiment of the present application;

Fig. 3b is a schematic cross-sectional structure diagram of the photodetector shown in Fig. 3a along the AA' direction;

Fig. 3c is a schematic cross-sectional structure diagram of the photodetector shown in Fig. 3a along the BB' direction;

4 is a schematic flowchart of a method for preparing a photodetector according to an embodiment of the present application;

5 is a schematic flowchart of a method for preparing a photodetector provided by another embodiment of the present application;

6a is a top view of a structure formed after performing the steps of the preparation method in the present application;

Figure 6b is a schematic cross-sectional structure diagram of the structure shown in Figure 6a along the AA' direction;

7a is a top view of a structure formed after performing the steps of the preparation method in the present application;

Fig. 7b is a schematic cross-sectional structure diagram of the structure shown in Fig. 7a along the AA' direction;

8a is a top view of a structure formed after performing the steps of the preparation method in the present application;

Fig. 8b is a schematic cross-sectional structure diagram of the structure shown in Fig. 8a along the AA' direction;

9a is a top view of a structure formed after performing the steps of the preparation method in the present application;

Figure 9b is a schematic cross-sectional structure diagram of the structure shown in Figure 9a along the AA' direction;

10a is a top view of a structure formed after performing the steps of the preparation method in the present application;

Fig. 10b is a schematic cross-sectional structure diagram of the structure shown in Fig. 10a along the AA' direction;

11a is a top view of the structure formed after performing the steps of the preparation method in the present application;

Figure 11b is a schematic cross-sectional structure diagram of the structure shown in Figure 11a along the AA' direction;

Fig. 11c is a schematic cross-sectional structure diagram of the structure shown in Fig. 11a along the BB' direction;

Figure 12a is a top view of the structure formed after performing the steps of the preparation method in the present application;

Figure 12b is a schematic cross-sectional structure diagram of the structure shown in Figure 12a along the AA' direction;

Figure 12c is a schematic cross-sectional structure diagram of the structure shown in Figure 12a along the BB' direction;

Figure 13a is a top view of the structure formed after performing the steps of the preparation method in the present application;

Figure 13b is a schematic cross-sectional structure diagram of the structure shown in Figure 13a along the AA' direction;

Figure 13c is a schematic cross-sectional structure diagram of the structure shown in Figure 13a along the BB' direction;

FIG. 14a is a schematic top-view structural diagram of a photodetector in yet another embodiment of the present application;

Fig. 14b is a schematic cross-sectional structure diagram of the photodetector shown in Fig. 14a along the AA' direction;

Fig. 14c is a schematic cross-sectional structure diagram of the photodetector shown in Fig. 14a along the BB' direction;

FIG. 15a is a schematic top-view structural diagram of a photodetector in yet another embodiment of the present application;

Fig. 15b is a schematic cross-sectional structure diagram of the photodetector shown in Fig. 15a along the AA' direction;

Fig. 15c is a schematic cross-sectional structure diagram of the photodetector shown in Fig. 15a along the BB' direction;

16 is a schematic flowchart of a method for fabricating a photodetector provided by another embodiment of the present application;

Figure 17a is a top view of the structure formed after performing the steps of the preparation method of the present application;

Fig. 17b is a schematic cross-sectional structure diagram of the structure shown in Fig. 17a along the AA' direction;

Fig. 18a is another schematic cross-sectional structure diagram of the photodetector shown in Fig. 14a along the AA' direction;

Fig. 18b is another schematic cross-sectional structure diagram of the photodetector shown in Fig. 14a along the BB' direction;

Fig. 19a is another schematic cross-sectional structure diagram of the photodetector shown in Fig. 15a along the AA' direction;

Fig. 19b is another schematic cross-sectional structure diagram of the photodetector shown in Fig. 15a along the BB' direction;

20 is a schematic flowchart of a method for fabricating a photodetector provided by another embodiment of the present application;

Figure 21a is a top view of the structure formed after performing the steps of the preparation method in the present application;

Figure 21b is a schematic cross-sectional structure diagram of the structure shown in Figure 21a along the AA' direction;

Fig. 22a is another schematic cross-sectional structure diagram of the photodetector shown in Fig. 15a along the AA' direction;

Fig. 22b is another schematic cross-sectional structure diagram of the photodetector shown in Fig. 15a along the BB' direction;

23 is a schematic flowchart of a method for fabricating a photodetector provided by another embodiment of the present application;

Fig. 24a is another schematic cross-sectional structure diagram of the photodetector shown in Fig. 15a along the AA' direction;

Figure 24b is another schematic cross-sectional structure diagram of the photodetector shown in Figure 15a along the BB' direction;

FIG. 25 is a schematic structural diagram of a chip provided by an embodiment of the application;

26 is a schematic diagram of an arrangement of a plurality of photodetectors in a chip provided by an embodiment of the application;

FIG. 27 is a schematic diagram of an arrangement of a plurality of photodetectors in a chip according to another embodiment of the present application.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings. Example embodiments, however, can be embodied in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in this application are all described by taking the accompanying drawings as an example, but changes can also be made according to needs, and the changes are all included in the protection scope of this application. The drawings in the present application are only used to illustrate the relative positional relationship and do not represent the actual scale.

It should be noted that specific details are set forth in the following description in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar promotions without departing from the connotation of the present application. Accordingly, the present application is not limited by the specific embodiments disclosed below. Subsequent descriptions in the specification are preferred embodiments for implementing the present application. However, the descriptions are for the purpose of illustrating the general principles of the present application and are not intended to limit the scope of the present application. The scope of protection of this application should be determined by the appended claims.

In order to facilitate the understanding of the photodetector provided by the embodiment of the present application, the specific application scenario of the photodetector is first described below. The photodetectors provided in the embodiments of the present application can be widely used in various structures based on free space transmission of light. For example, when applied to the WSS structure, the photodetector is arranged on the transmission path of monochromatic light in the free space of the WSS structure. When the monochromatic beam passes through the photodetector, a small number of photons at the edge of the beam will enter the photodetector, thereby Capable of real-time tap detection of optical signals without interfering with optical transmission.

During specific implementation, the photodetector can also be applied in the aerospace field. For example, the communication between some satellite devices will use free space optical communication technology, and the photodetector can perform real-time detection on these optical communications.

In order to facilitate the understanding of the photodetector provided by the embodiments of the present application, the photodetector, its preparation method, chip and optical device provided by the present application will be described in detail below with reference to specific embodiments and accompanying drawings.

Fig. 3a exemplarily shows a schematic top view structure of a photodetector in an embodiment of the present application, Fig. 3b is a schematic cross-sectional structure diagram of the photodetector shown in Fig. 3a along the AA' direction, and Fig. 3c is a photodetector shown in Fig. 3a Schematic diagram of the cross-sectional structure of the device along the BB' direction.

3a to 3c, the photodetector 10 provided by the present application includes: a substrate 11, a first electrode contact layer 12, a photosensitive layer 13, a second electrode contact layer 14 and The passivation layer 15, and the first electrode 161 and the second electrode 162 located on the passivation layer 15; wherein, the first electrode contact layer 12 and the second electrode contact layer 14 are doped semiconductor layers with opposite polarities, such as the first electrode contact layer 12 and the second electrode contact layer 14. An electrode contact layer 12 is a P-type doped semiconductor layer, the second electrode contact layer 14 is an N-type doped semiconductor layer, or, the first electrode contact layer 12 is an N-type doped semiconductor layer, and the second electrode contact layer 14 is P-type doped semiconductor layer. The photodetector 10 further includes a through hole V0 penetrating at least the photosensitive layer 13 and the second electrode contact layer 14; The outer side of the orthographic projection of 11; the first electrode 161 and the second electrode 162 are insulated from each other, and the first electrode 161 passes through the first groove V1 and the first electrode 161 through the film layer between the first electrode 161 and the first electrode contact layer 12. An electrode contact layer 12 is electrically connected, and the second electrode 162 is electrically connected to the second electrode contact layer 14 through the second groove V2 penetrating the passivation layer 15 .

In this photodetector, the first electrode contact layer 12 and the second electrode contact layer 14 form a PN junction, which can convert the optical signal into an electrical signal when the photosensitive layer 13 captures the light passing through the via V0 , so as to realize the detection of the optical signal, and ensure that the light passing through the through hole V0 is not disturbed. It should be pointed out that the photodetector is not limited in structure to a photodiode (Photodiode, PD), an avalanche photodiode (Avalanche Photodiode, APD) or a heterojunction phototransistor (Hetero junction Photodiode, HPT) and the like.

The photodetector of the present application can be applied to various structures based on the transmission of light in free space. Specifically, the photodetector can be arranged on the transmission path of monochromatic light in free space, and the monochromaticity and direction of the transmission of these light beams can be used. After the monochromatic beam passes through the through-hole area of the photodetector, a small number of photons at the edge of the beam will enter the photodetector, so that the optical signal can be detected in real time without interfering with the optical transmission. . For example, when applied to the WSS structure, the photodetector is arranged on the transmission path of the monochromatic light in the free space of the WSS structure. Therefore, not only the monochromatic light signal can be guaranteed not to be disturbed, but also the stability of the WSS structure can be guaranteed. Volume does not increase. In addition, since the photodetector can directly obtain photons from the transmission path of monochromatic light without the help of other devices, it can be fixed on the transmission path of monochromatic light without complex mechanical fixing parts, which is different from using existing devices. Compared with the optical fiber tap detection device, the overall structure complexity and cost can be reduced.

FIG. 4 exemplarily shows a schematic flowchart of a method for fabricating a photodetector provided by an embodiment of the present application. As shown in Figure 4, the method mainly includes the following steps:

S401, forming a first electrode contact layer, a photosensitive layer and a second electrode contact layer on the substrate in sequence, and forming through holes at least penetrating the photosensitive layer and the second electrode contact layer; the first electrode contact layer and the second electrode contact layer The contact layer is a doped semiconductor layer of opposite polarity.

S402 , forming a first passivation layer on the second electrode contact layer, and forming a first groove penetrating the first passivation layer and deep to the surface of the first electrode contact layer and a second groove penetrating the passivation layer.

S403, forming a first electrode and a second electrode on the first passivation layer; wherein the orthographic projections of the first electrode and the second electrode on the substrate are respectively located outside the orthographic projection of the through hole on the substrate; the first electrode The second electrode is insulated from each other, the first electrode is electrically connected to the first electrode contact layer through the first groove, and the second electrode is electrically connected to the second electrode contact layer through the second groove.

In a possible implementation manner, step S401 sequentially forms the first electrode contact layer, the photosensitive layer and the second electrode contact layer on the substrate, and forms at least through holes penetrating the photosensitive layer and the second electrode contact layer, It may include: firstly forming a first electrode contact layer, a photosensitive layer and a cover layer on the substrate in sequence; then forming a second passivation layer on the cover layer, and forming a via hole penetrating the second passivation layer, so as to expose the The cover layer is annular or circular; then the exposed cover layer is doped to form a second electrode contact layer; and then a through hole penetrating at least the photosensitive layer and the second electrode contact layer is formed.

In yet another possible implementation manner, step S401 sequentially forms a first electrode contact layer, a photosensitive layer and a second electrode contact layer on the substrate, and forms at least through holes penetrating the photosensitive layer and the second electrode contact layer , may include: firstly forming the first electrode contact layer, the photosensitive layer and the cover layer on the substrate except the central area, so that while the first electrode contact layer, the light sensitive layer and the cover layer are formed, A through hole is formed in the central area through the first electrode contact layer, the photosensitive layer and the cover layer; then a second passivation layer is formed on the cover layer, and a via hole through the second passivation layer is formed, so that the exposed cover The layer is annular; the exposed cap layer is then doped to form a second electrode contact layer. The central area is the area where the through hole is located, which may be a circular area. Further, after doping the exposed capping layer to form the second electrode contact layer, the method further includes: removing the central region of the substrate, so that the through hole still penetrates the substrate.

In a possible implementation manner, step S402 forms a first passivation layer on the second electrode contact layer, and forms a first groove and a through passivation penetrating the first passivation layer and deep to the surface of the first electrode contact layer The second groove of the passivation layer may include: firstly forming a third groove penetrating the second passivation layer, the cover layer and the photosensitive layer; then forming the first passivation layer on the second electrode contact layer, so that the first passivation layer can be formed. A passivation layer covers the sidewall of the third groove to protect the sidewall of the third groove; then a second groove is formed through the first passivation layer, and is formed in the area where the third groove is located The first groove penetrates through the first passivation layer, so that the first groove penetrates through the first passivation layer and is deep to the surface of the first electrode contact layer.

In the specific implementation, the second electrode contact layer is generally set as a P-type doped semiconductor layer. Therefore, in this application, the second electrode contact layer is a P-type doped semiconductor layer, and the first electrodes are sequentially formed on the substrate. After the contact layer, the photosensitive layer and the second electrode contact layer, and before the first passivation layer is formed on the second electrode contact layer, the method may further include: forming a ring-shaped metal contact electrode on the second electrode contact layer, and contacting the metal The contact electrode is annealed so that the second electrode to be formed is electrically connected to the second electrode contact layer through the metal contact electrode.

In the following, taking the first electrode contact layer as an N-type doped semiconductor layer, the second electrode contact layer as a P-type doped semiconductor layer, and a metal contact electrode disposed between the second electrode contact layer and the second electrode as an example, the combination The specific embodiments describe the present application in detail. It should be noted that this embodiment is for better explanation of the present invention, but does not limit the present application.

Embodiment 1.

FIG. 5 exemplarily shows a schematic flowchart of a method for fabricating a photodetector provided by another embodiment of the present application. As shown in Figure 5, the method mainly includes the following steps:

S501 , forming a first electrode contact layer, a photosensitive layer and a cover layer on the substrate in sequence.

6a and 6b, FIG. 6a is a top view of the structure formed after performing the steps of the preparation method in the present application, and FIG. 6b is a schematic cross-sectional structure diagram of the structure shown in FIG. 6a along the AA' direction. First, the first electrode contact layer 12 may be epitaxially grown on the substrate 11 , then the photosensitive layer 13 may be epitaxially grown on the first electrode contact layer 12 , and then the cover layer 17 may be epitaxially grown on the photosensitive layer 13 . In specific implementation, the materials of the first electrode contact layer 12 , the photosensitive layer 13 and the capping layer 17 may be InP/InGaAs, Ge/Si, GaN, GaAs and other material systems, but are not limited thereto.

S502 , forming a second passivation layer on the cover layer, and forming a via hole penetrating the second passivation layer, so that the exposed cover layer is annular or circular.

7a and 7b, FIG. 7a is a top view of the structure formed after performing the steps of the preparation method in the present application, and FIG. 7b is a schematic cross-sectional structure diagram of the structure shown in FIG. 7a along the AA' direction. In order to facilitate the subsequent doping of the capping layer 17 , a second passivation layer 152 may be formed on the capping layer 17 first, and the second passivation layer 152 may be patterned to form via holes penetrating the second passivation layer 152 , so that the exposed cover layer 17 is annular or circular or regular polygon as shown in FIG. 7 a , which is not limited herein.

S503 , doping the exposed cover layer to form a second electrode contact layer.

Referring to Figures 8a and 8b, Figure 8a is a top view of a structure formed after performing the steps of the preparation method in the present application, and Figure 8b is a schematic cross-sectional structure diagram of the structure shown in Figure 8a along the AA' direction. The second electrode contact layer 14 may be formed by doping the exposed capping layer 17 through a diffusion or ion implantation process. That is, the epitaxial materials of the second electrode contact layer 14 and the cover layer 17 are the same, the intrinsic materials of the two are the same, but the doping concentration is different, the cover layer 17 is generally lightly doped, and the second electrode contact layer 14 is generally heavily doped . Alternatively, the intrinsic material of the second electrode contact layer 14 and the cover layer 17 are the same, and the electrical doping types of the two are different, for example, the cover layer 17 is N-type doped, and the second electrode contact layer 14 is P-type doped, or, The capping layer 17 is P-type doped, and the second electrode contact layer 14 is N-type doped.

In this application, the boundary shape of the second electrode contact layer and the shape of the subsequently formed through hole can be designed to be the same, and the center of the second electrode contact layer and the center of the subsequently formed through hole can be designed to overlap, so as to ensure photoelectric detection. The performance of the device in the same plane perpendicular to the light passing direction is as centrosymmetric as possible.

S504 , forming an annular metal contact electrode on the second electrode contact layer, and annealing the metal contact electrode, so that the second electrode to be formed is electrically connected to the second electrode contact layer through the metal contact electrode.

Referring to Figures 9a and 9b, Figure 9a is a top view of a structure formed after performing the steps of the preparation method in the present application, and Figure 9b is a schematic cross-sectional structure diagram of the structure shown in Figure 9a along the AA' direction. A ring-shaped metal contact electrode 18 is formed on the second electrode contact layer 14, and the metal contact electrode 18 is annealed. The center of the metal contact electrode 18 may coincide with the center of the through hole to be formed.

S505 , forming a through hole penetrating at least the photosensitive layer and the second electrode contact layer.

10a and 10b, FIG. 10a is a top view of a structure formed after performing the steps of the preparation method in the present application, and FIG. 10b is a schematic cross-sectional structure diagram of the structure shown in FIG. 10a along the AA' direction. The through hole V0 may penetrate through the second electrode contact layer 14 , the photosensitive layer 13 , the first electrode contact layer 12 and the substrate 11 . When the absorption spectrum of the substrate does not overlap with the wavelength of the light to be detected, the through hole V0 may only penetrate the second electrode contact layer 14 , the photosensitive layer 13 and the first electrode contact layer 12 . Further, when the absorption spectrum of the substrate does not overlap with the wavelength of the light to be detected, and the epitaxial material of the first electrode contact layer and the substrate is the same, the through hole V0 may only penetrate the second electrode contact layer 14 and the photosensitive layer 13 .

The shape of the through hole is not limited in the present application, and it may be any shape, such as polymorphic shape, circular shape, oval shape, and the like. When the shape of the through hole V0 is a circle, it can be ensured that the distance from the center of the through hole V0 to the boundary of the through hole V0 is the same. Moreover, the circular via is easier to realize in the process.

10a and 10b, after forming the through hole V0, the cover layer 17 is arranged around the second electrode contact layer 14, and the through hole V0 penetrates through the second electrode contact layer 14 to ensure that the functional area of the photodetector (ie the first electrode contacts Layer 12 , photosensitive layer 13 and second electrode contact layer 14 are facing the edge of the via hole V0 ), so that the photons passing through the via hole V0 are easily captured, thereby improving the sensitivity.

S506 , forming a third groove penetrating the second passivation layer, the photosensitive layer and the capping layer.

11a to 11c, FIG. 11a is a top view of a structure formed after performing the steps of the preparation method in the present application, FIG. 11b is a schematic cross-sectional structure diagram of the structure shown in FIG. 11a along the AA' direction, and FIG. 11c is the structure shown in FIG. 11a. Schematic diagram of the cross-sectional structure along the BB' direction. A third groove V3 is formed through the second passivation layer 152 , the photosensitive layer 13 and the capping layer 17 .

S507, forming a first passivation layer on the metal contact electrode.

12a to 12c, FIG. 12a is a top view of a structure formed after performing the steps of the preparation method in the present application, FIG. 12b is a schematic cross-sectional structure diagram of the structure shown in FIG. 12a along the direction AA', and FIG. 12c is the structure shown in FIG. 12a Schematic diagram of the cross-sectional structure along the BB' direction. The first passivation layer 151 formed on the metal contact electrode 18 may cover the sidewalls of the via hole V0 and the sidewalls of the third groove V3, so as to protect the epitaxial material at the via hole V0 and the third groove V3 to protection.

S508 , forming a second groove penetrating the first passivation layer, and forming a first groove penetrating the first passivation layer in the region where the third groove is located, so that the first groove penetrates the first passivation layer and deep to the surface of the first electrode contact layer.

13a to 13c, FIG. 13a is a top view of a structure formed after performing the steps of the preparation method in the present application, FIG. 13b is a schematic cross-sectional structure diagram of the structure shown in FIG. 13a along the AA' direction, and FIG. 13c is the structure shown in FIG. 13a. Schematic diagram of the cross-sectional structure along the BB' direction. A photolithography process can be used to form the second groove V2 penetrating the first passivation layer 151, and a photolithography process can be used to form the first groove V1 penetrating the first passivation layer 151 in the region where the third groove V3 is located, so as to The first groove V1 penetrates through the first passivation layer 151 and is deep to the surface of the first electrode contact layer 12 .

In a specific implementation, the second groove V2 and the first groove V1 penetrating through the first passivation layer 151 may be formed simultaneously by one photolithography process.

S509 , forming a first electrode and a second electrode on the first passivation layer.

14a to 14c, FIG. 14a is a top view of a structure formed after performing the steps of the preparation method in the present application, FIG. 14b is a schematic cross-sectional structure diagram of the structure shown in FIG. 14a along the direction AA', and FIG. 14c is the structure shown in FIG. 14a Schematic diagram of the cross-sectional structure along the BB' direction. The orthographic projection of the first electrode 161 and the second electrode 162 located on the first passivation layer 151 on the substrate 11 is located outside the orthographic projection of the through hole V0 on the substrate 11, and the first electrode 161 and the second electrode 162 are mutually Insulation, the first electrode 161 is electrically connected to the first electrode contact layer 12 through the first groove V1, and the second electrode 162 is electrically connected to the metal contact electrode 18 through the second groove V2.

During specific implementation, the shapes of the first electrode and the second electrode are not limited. However, considering the symmetry of the performance of the photodetector, as shown in FIG. 14a, the second electrode 162 has a closed annular structure surrounding the through hole V0; the first electrode 161 has an annular structure arranged around the second electrode 162 and having an opening, The opening of the first electrode 161 is to prevent the first electrode 161 and the second electrode 162 from being short-circuited, and the first electrode 161 and the second electrode 162 are drawn out from two sides of the through hole, respectively.

Further, in order to increase the contact area between the electrode and the electrode contact layer, the shape of the groove can be set to be similar to the shape of the electrode. Referring to FIG. 13a, the shape of the second groove V2 is a closed ring surrounding the through hole V0; the first groove The shape of V1 is an annular shape provided around the second groove V2 and having an opening.

After the above steps S501 to S509, the photodetector in the present application is formed. In the photodetector, the passivation layer is formed by two passivation layers, a first passivation layer and a second passivation layer. Figures 14a to 14c can be seen for the case where the through hole V0 penetrates all the film layers. For the case where the through hole V0 does not penetrate all the film layers, please refer to FIG. 15a to FIG. 15c.

Embodiment two,

FIG. 16 exemplarily shows a schematic flowchart of a method for fabricating a photodetector provided by another embodiment of the present application. As shown in Figure 16, the method mainly includes the following steps:

S1601 , forming a first electrode contact layer, a photosensitive layer and a cover layer on the substrate in sequence.

S1602 , forming a second passivation layer on the capping layer, and forming a via hole penetrating the second passivation layer, so that the exposed capping layer is annular or circular.

S1603 , doping the exposed cover layer to form a second electrode contact layer.

S1604 , forming a ring-shaped metal contact electrode on the second electrode contact layer, and annealing the metal contact electrode, so that the second electrode to be formed is electrically connected to the second electrode contact layer through the metal contact electrode.

S1605 , forming a through hole penetrating at least the photosensitive layer and the second electrode contact layer.

S1606 , removing the second passivation layer, the cover layer and the photosensitive layer in the preset area, so that the remaining cover layer and the photosensitive layer have a ring structure.

17a and 17b, FIG. 17a is a top view of the structure formed after performing the steps of the preparation method in the present application, and FIG. 17b is a schematic cross-sectional structure diagram of the structure shown in FIG. 17a along the AA' direction. The second passivation layer 152 , the cover layer 17 and the photosensitive layer 13 in the preset area S1 are removed, so that the remaining cover layer 17 and the photosensitive layer 13 have a ring structure.

S1607, forming a first passivation layer on the metal contact electrode.

S1608 , forming a second groove penetrating the first passivation layer, and forming a first groove penetrating the first passivation layer in the region where the third groove is located, so that the first groove penetrates the first passivation layer and deep to the surface of the first electrode contact layer.

S1609, forming a first electrode and a second electrode on the first passivation layer.

Compared with the first example, only step S1506 is different from step S506 in the first example, and other steps can be referred to in the first embodiment, which will not be repeated here.

After the above steps S1601 to S1609, the photodetector in the present application is formed. In the photodetector, the passivation layer is formed by two passivation layers, a first passivation layer and a second passivation layer. 14a and 18a and 18b. FIG. 18a is a schematic cross-sectional structure diagram of the structure shown in FIG. 14a along the AA' direction, and FIG. 18b is the structure shown in FIG. 14a along the BB' direction. Schematic diagram of the cross-sectional structure. 15a and 19a and 19b, FIG. 19a is a schematic cross-sectional structure diagram of the structure shown in FIG. 15a along the direction AA', and FIG. 19b is the structure shown in FIG. 15a along BB Schematic diagram of the cross-sectional structure in the 'direction'.

Example three,

FIG. 20 exemplarily shows a schematic flowchart of a method for fabricating a photodetector provided by another embodiment of the present application. As shown in Figure 20, the method mainly includes the following steps:

S2001 , forming a first electrode contact layer, a photosensitive layer and a cover layer in sequence on the regions except the central region on the substrate.

21a and 21b, FIG. 21a is a top view of the structure formed after performing the steps of the preparation method in the present application, and FIG. 21b is a schematic cross-sectional structure diagram of the structure shown in FIG. 21a along the AA' direction. A first electrode contact layer 12 , a photosensitive layer 13 and a capping layer 17 are epitaxially grown on the substrate 11 on regions other than the central region in sequence. Thus, while forming the first electrode contact layer 12 , the photosensitive layer 13 and the capping layer 17 , a through hole V0 penetrating the first electrode contact layer 12 , the photosensitive layer 13 and the capping layer 17 is formed in the central region. The central area is the area where the through hole is located, which may be a circular area.

S2002 , forming a second passivation layer on the cover layer, and forming a via hole penetrating the second passivation layer, so that the exposed cover layer is annular.

S2003 , doping the exposed cover layer to form a second electrode contact layer.

S2004 , forming an annular metal contact electrode on the second electrode contact layer, and annealing the metal contact electrode, so that the second electrode to be formed is electrically connected to the second electrode contact layer through the metal contact electrode.

S2005 , forming a third groove penetrating the second passivation layer, the photosensitive layer and the cover layer.

S2006, forming a first passivation layer on the metal contact electrode.

S2007, forming a second groove penetrating the first passivation layer, and forming a first groove penetrating the first passivation layer in the region where the third groove is located, so that the first groove penetrates the first passivation layer and deep to the surface of the first electrode contact layer.

S2008, forming a first electrode and a second electrode on the first passivation layer.

Compared with the first embodiment, this example is only different from step S2001 and step S501 in the first embodiment. In addition, this example has been formed in step S2001, and the through hole only penetrates the first electrode contact layer 12, the photosensitive layer 13 and the The second electrode contacts 17. Therefore, compared with Example 1, step S505 is omitted, and other steps can be referred to in Example 1, which will not be repeated here.

After the above steps S2001 to S2008, the formed photodetector can be seen in FIGS. 15a, 22a and 22b. FIG. 22a is a schematic cross-sectional structure diagram of the structure shown in FIG. 15a along the direction AA', and FIG. 22b is the structure shown in FIG. 15a along BB Schematic diagram of the cross-sectional structure in the 'direction'.

Further, in this example, after step 2004, before step S2005, it may further include removing the central region of the substrate. Therefore, in the photodetector finally formed, the through hole penetrates through all the film layers, as shown in FIG. 14a to FIG. 14c for details.

Example 4.

FIG. 23 exemplarily shows a schematic flowchart of a method for fabricating a photodetector provided by another embodiment of the present application. As shown in Figure 23, the method mainly includes the following steps:

S2301 , forming a first electrode contact layer, a photosensitive layer and a cover layer in sequence on the regions except the central region on the substrate.

S2302 , forming a second passivation layer on the cover layer, and forming a via hole penetrating the second passivation layer, so that the exposed cover layer is in a ring shape.

S2303 , doping the exposed cover layer to form a second electrode contact layer.

S2304 , forming an annular metal contact electrode on the second electrode contact layer, and annealing the metal contact electrode, so that the second electrode to be formed is electrically connected to the second electrode contact layer through the metal contact electrode.

S2305 , removing the second passivation layer, the cover layer and the photosensitive layer in the preset area, so that the remaining cover layer and the photosensitive layer have a ring structure.

S2306, forming a first passivation layer on the metal contact electrode.

S2307 , forming a second groove penetrating the first passivation layer, and forming a first groove penetrating the first passivation layer in the region where the third groove is located, so that the first groove penetrates the first passivation layer and deep to the surface of the first electrode contact layer.

S2308, forming a first electrode and a second electrode on the first passivation layer.

Compared with the third example, only step S2305 is different from the step S2005 in the third example. For other steps, refer to the third embodiment, which will not be repeated here.

After the above steps S2301 to S2308, the photodetector formed can be seen in FIGS. 15a, 24a and 24b. FIG. 24a is a schematic cross-sectional structure diagram of the structure shown in FIG. 15a along the direction AA', and FIG. 24b is the structure shown in FIG. 15a along BB Schematic diagram of the cross-sectional structure in the 'direction'.

Further, in this example, after step S2304, before step S2005, it may further include removing the central region of the substrate. Therefore, in the photodetector finally formed, the through holes penetrate through all the film layers, as shown in FIG. 14a to FIG. 14c for details.

In the photodetector provided by the present application, the first electrode contact layer, the photosensitive layer and the second electrode contact layer are stacked and arranged around the through hole, and when the photosensitive layer captures the light passing through the through hole, it can The optical signal is converted into an electrical signal, thereby realizing the detection of the optical signal.

Referring to FIG. 25 , the present application also provides a chip 100 , the chip 100 includes a driving circuit 101 and at least one photodetector 10 provided in any of the above-mentioned embodiments connected to the driving circuit 101 (in FIG. 25 , a photoelectric detector 10 The detector 10 is shown as an example). The photoelectric energy detector 10 can convert the captured optical signal into an electrical signal, and the driving circuit 101 can amplify the electrical signal and output it to realize the detection of the optical signal.

During specific implementation, the number and arrangement of the photodetectors 10 can be designed according to the actual application, which is not limited herein. For example, in one embodiment, as shown in FIG. 26 , a plurality of the photodetectors 10 are arranged along the first direction. In another embodiment, as shown in FIG. 27 , a plurality of the photodetectors 10 are arranged along the first direction. arranged in a matrix.

The present application also provides an optical device, comprising a wavelength selective switch structure and at least one photodetector, wherein the photodetector is arranged on a transmission path of monochromatic light in the free space of the wavelength selective switch structure. Not only can the monochromatic optical signal be guaranteed not to be disturbed, but also the volume of the WSS structure can be guaranteed not to increase. In addition, since the photodetector can directly obtain photons from the transmission path of monochromatic light without the help of other devices, it can be fixed on the transmission path of monochromatic light without complex mechanical fixing parts, which is different from using existing devices. Compared with the optical fiber tap detection device, the overall cost and overall structural complexity can be reduced.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the protection scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

A photodetector is characterized by comprising: a substrate, a first electrode contact layer, a photosensitive layer, a second electrode contact layer, a passivation layer, a first electrode and a first electrode contact layer, a photosensitive layer, a second electrode contact layer, a passivation layer, and a first electrode and a two electrodes;

The photodetector further includes a through hole penetrating at least the photosensitive layer and the second electrode contact layer;

The first electrode contact layer and the second electrode contact layer are doped semiconductor layers with opposite polarities;

Orthographic projections of the first electrode and the second electrode on the substrate are respectively located outside the orthographic projection of the through hole on the substrate;

The first electrode and the second electrode are insulated from each other, and the first electrode is connected to the first electrode through a first groove penetrating the film layer between the first electrode and the first electrode contact layer. The electrode contact layer is electrically connected, and the second electrode is electrically connected to the second electrode contact layer through a second groove penetrating the passivation layer.
The photodetector according to claim 1, wherein the second electrode is in a closed annular structure surrounding the through hole;

The first electrode has an annular structure arranged around the second electrode and having an opening.
The photodetector according to claim 2, wherein the shape of the second groove is a closed ring surrounding the through hole;

The shape of the first groove is an annular shape arranged around the second groove and having an opening.
The photodetector according to any one of claims 1 to 3, wherein the through hole further penetrates the first electrode contact layer.
The photodetector according to claim 4, wherein the through hole further penetrates through the substrate and the passivation layer.
The photodetector according to any one of claims 1 to 3, wherein the shape of the through hole is a circle.
The photodetector according to any one of claims 1 to 3, wherein the shape of the second electrode contact layer is annular;

The photodetector further includes a cover layer arranged in the same layer as the second electrode contact layer, and the cover layer is arranged around the second electrode contact layer;

The second electrode contact layer and the cover layer have the same intrinsic material, different doping concentrations or different electrical doping types.
The photodetector according to any one of claims 1 to 3, wherein the first electrode contact layer is an N-type doped semiconductor layer, and the second electrode contact layer is a P-type doped semiconductor layer; The photodetector also includes a metal contact electrode between the second electrode and the second electrode contact layer.
A chip, characterized by comprising a driving circuit, and at least one photodetector according to any one of claims 1 to 8 connected to the driving circuit.
An optical device, characterized by comprising a wavelength selective switch structure and at least one photodetector according to any one of claims 1 to 8;

The photodetector is arranged on the transmission path of monochromatic light in the free space of the wavelength selective switch structure.
A method for preparing a photodetector, comprising:

A first electrode contact layer, a photosensitive layer and a second electrode contact layer are sequentially formed on the substrate, and a through hole is formed at least through the photosensitive layer and the second electrode contact layer; wherein, the first electrode The contact layer and the second electrode contact layer are doped semiconductor layers with opposite polarities;

A first passivation layer is formed on the second electrode contact layer, and a first groove penetrating the first passivation layer and deep to the surface of the first electrode contact layer and a groove penetrating the passivation layer are formed the second groove;

A first electrode and a second electrode are formed on the first passivation layer; wherein, the orthographic projections of the first electrode and the second electrode on the substrate are respectively located on the substrate of the through hole. The outer side of the orthographic projection of the bottom; the first electrode and the second electrode are insulated from each other, the first electrode is electrically connected to the first electrode contact layer through the first groove, and the second electrode is The second groove is electrically connected to the second electrode contact layer.
The preparation method according to claim 11, wherein a first electrode contact layer, a photosensitive layer and a second electrode contact layer are sequentially formed on the substrate, and at least through the photosensitive layer and the second electrode contact layer are formed. Through holes for electrode contact layers, including:

forming a first electrode contact layer, a photosensitive layer and a cover layer in sequence on the substrate;

forming a second passivation layer on the cover layer, and forming a via hole passing through the second passivation layer, so that the exposed cover layer is annular or circular;

Doping the exposed cover layer to form a second electrode contact layer;

A through hole is formed through at least the photosensitive layer and the second electrode contact layer.
The preparation method according to claim 11, wherein a first electrode contact layer, a photosensitive layer and a second electrode contact layer are sequentially formed on the substrate, and at least through the photosensitive layer and the second electrode contact layer are formed. Through holes for electrode contact layers, including:

forming a first electrode contact layer, a photosensitive layer and a cover layer in sequence on the region except the central region on the substrate;

forming a second passivation layer on the cover layer, and forming a via hole passing through the second passivation layer, so that the exposed cover layer is annular;

Doping the exposed capping layer to form a second electrode contact layer.
The preparation method according to claim 13, wherein after doping the exposed cover layer to form the second electrode contact layer, further comprising:

The central region of the substrate is removed.
The preparation method according to any one of claims 12 to 14, wherein a first passivation layer is formed on the second electrode contact layer, and is formed through the first passivation layer and deep to the The first groove on the surface of the first electrode contact layer and the second groove through the passivation layer, including:

forming a third groove through the second passivation layer, the capping layer and the photosensitive layer;

forming a first passivation layer on the second electrode contact layer;

forming a second groove penetrating the first passivation layer, and forming a first groove penetrating the first passivation layer in the region where the third groove is located, so that the first groove penetrates The first passivation layer is deep to the surface of the first electrode contact layer.
The preparation method according to any one of claims 12 to 14, wherein after the first electrode contact layer, the photosensitive layer and the second electrode contact layer are sequentially formed on the substrate, the second electrode contact layer is formed on the substrate. Before forming the first passivation layer thereon, it also includes:

The second passivation layer, the cover layer and the photosensitive layer in the preset area are removed, so that the remaining cover layer and the photosensitive layer have a ring structure.
The preparation method according to any one of claims 12 to 14, wherein the first electrode contact layer is an N-type doped semiconductor layer, and the second electrode contact layer is a P-type doped semiconductor layer; After the first electrode contact layer, the photosensitive layer and the second electrode contact layer are sequentially formed on the substrate, and before the first passivation layer is formed on the second electrode contact layer, the method further includes:

An annular metal contact electrode is formed on the second electrode contact layer, and the metal contact electrode is annealed, so that the second electrode to be formed is electrically connected to the second electrode contact layer through the metal contact electrode.