WO2024027359A1

WO2024027359A1 - Photodetector and manufacturing method therefor and optical receiver

Info

Publication number: WO2024027359A1
Application number: PCT/CN2023/101759
Authority: WO
Inventors: 周德; 桂成程; 李洋
Original assignee: 华为技术有限公司
Priority date: 2022-08-05
Filing date: 2023-06-21
Publication date: 2024-02-08
Also published as: CN117558779A

Abstract

The present application discloses a photodetector and a manufacturing method therefor and an optical receiver. The photodetector comprises at least one PIN junction; each PIN junction comprises a semiconductor substrate; and an N-type region, an intrinsic region, a first P-type region, a second P-type region, and a third P-type region that are arranged adjacently in sequence; the semiconductor substrate is provided with a groove in a region corresponding to the second P-type region; and an absorption layer is provided in the groove, and the material of the absorption layer comprises a P-type doped material. When light is absorbed by the absorption layer and photogenerated charge carriers are generated, only electrons can enter a depletion region of the PIN junction under the action of P-type doping of the absorption layer, thereby mitigating the space charge effect and achieving high power. Moreover, the absorption layer and the intrinsic region are spaced apart from each other by the first P-type region, and the doping concentration of the first P-type region can be adjusted according to the doping concentration of the absorption layer, such that the difference between internal electric fields in the intrinsic region and the absorption layer can be adjusted, thereby improving responsivity and bandwidth.

Description

A photoelectric detector, its preparation method and optical receiver

Cross-references to related applications

This application requires the priority of the Chinese patent application submitted to the China Patent Office on August 5, 2022, with the application number 202210938393.5 and the application title "A photoelectric detector, its preparation method and an optical receiver", and its entire content has been approved This reference is incorporated into this application.

Technical field

The present application relates to the field of optoelectronic technology, and in particular to a photoelectric detector, its preparation method and an optical receiver.

Background technique

Photodetectors are responsible for converting optical signals into electrical signals. They are one of the core components in optical communication systems and are also key components that affect the performance of optical communication systems. With the continuous development of communication technology, indicators such as responsivity, dark current, and saturation power of photodetectors have gradually attracted attention. However, there are many contradictions in these performance indicators in device design, and it is difficult to take into account both at the same time. Therefore, how to optimize photodetectors in a targeted manner so that they are suitable for different application scenarios is a very important issue.

The evaluation indicators of optical communication systems mainly include noise index, gain, spurious-free dynamic range (Spurious-Free Dynamic Range, SFDR), etc. Large-bandwidth, high-power photodetectors can improve the noise index and spurious-free dynamic range of optical communication systems. However, contradictions in the design of photodetectors make the improvement of a single indicator lead to the degradation of other indicators. Therefore, in the context of optical communication applications, how to simultaneously take into account the large bandwidth and high power of photodetectors is an urgent technical problem that those skilled in the art need to solve.

Contents of the invention

This application provides a photoelectric detector, its preparation method and an optical receiver, which are used to provide a large-bandwidth, high-power photoelectric detector.

In a first aspect, embodiments of the present application provide a photodetector, in which at least one PIN junction is provided. Each PIN junction may include: a semiconductor substrate, an absorption layer located in the semiconductor substrate, and An N-type region, an intrinsic region, a first P-type region, a second P-type region and a third P-type region arranged adjacently in sequence, a first electrode electrically connected to the N-type region and a first electrode electrically connected to the third P-type region the second electrode. Wherein, the semiconductor substrate has a groove in a region corresponding to the second P-type region, the absorption layer is disposed in the groove, and the material of the absorption layer includes P-type doping material. In this way, when light is absorbed by the absorbing layer and photogenerated carriers (including electrons and holes) are generated, under the action of P-type doping of the absorbing layer, only electrons can enter the depletion region of the PIN junction, thereby alleviating the space Charge effect, achieving high power. And the absorption layer is arranged between the second P-type region and the third P-type region, that is, there is a first P-type region between the absorption layer and the intrinsic region. The doping concentration of the absorption layer can be used to adjust the first P-type region. The doping concentration can adjust the internal electric field difference between the intrinsic region and the absorption layer, thereby improving the responsivity and broadband.

For example, in this application, the material of the semiconductor substrate may include silicon, and the material of the absorption layer may include P-type germanium. Of course, the semiconductor substrate and the absorption layer can also be formed of Group III and V materials, which are not limited here. When the material of the semiconductor substrate is silicon and the material of the absorption layer is P-type germanium, the natural energy band difference of the silicon germanium material can be used to form a quasi-single row carrier structure, thereby improving the space charge effect. At the same time, compared with Group III and V materials, silicon materials have high thermal conductivity, and the preparation process can be achieved through existing silicon photonics processes.

In specific implementation, the doping concentration of the intrinsic region is very low, almost an intrinsic semiconductor, while the P-type region can be formed by doping the semiconductor substrate with P-type ions, and the N-type region can be formed by doping the semiconductor substrate. The bottom is formed by N-type ion doping.

For example, the P-type ions doped in the P-type region can be trivalent elements such as boron (B) or aluminum (Al), and the N-type ions doped in the N-type region can be phosphorus (P) or arsenic (As). ) and other 5-valent elements.

In this application, the N-type region, the intrinsic region, the first P-type region, the second P-type region and the third P-type region are arranged adjacently in sequence, which means that the N-type region, the intrinsic region, the third P-type region are sequentially arranged along a certain direction. There is no other area between any adjacent P-type area, the second P-type area and the third P-type area.

For example, in this application, both the first electrode and the second electrode can be disposed on the side of the semiconductor substrate where the groove is provided, that is, the first electrode, the second electrode and the absorption layer are relative to the second P-type region, are located on the same side of the second P-type area.

During specific implementation, this application does not limit the materials of the first electrode and the second electrode, and they can be any conductive material. For example, the first electrode and the second electrode are made of metal material.

In this application, the doping concentration of the first P-type region, the second P-type region and the third P-type region can be the same, so that the first P-type region, the second P-type region and the third P-type region can be formed simultaneously through one ion implantation process. The third P-type zone.

For example, the doping concentration of the first P-type region can be set to be greater than the doping concentration of the second P-type region, thereby blocking holes from entering the intrinsic region and effectively mitigating the space charge effect.

For example, the doping concentration of the third P-type region can be set to be greater than the doping concentration of the second P-type region, thereby reducing the series resistance of the photodetector and increasing the bandwidth of the device.

For example, in this application, the doping concentration of the first P-type region may be similar to the doping concentration of the third P-type region, but the doping concentration is not limited to the same.

In order to reduce the contact resistance between the first electrode and the N-type region, an N-type contact region between the N-type region and the first electrode can also be provided in the semiconductor substrate, and the doping concentration of the N-type contact region is generally greater than that of the N-type contact region. doping concentration of the region. Similarly, in order to reduce the contact resistance between the second electrode and the third P-type region, a P-type contact region between the third P-type region and the second electrode can also be provided in the semiconductor substrate, and the P-type contact region The doping concentration is generally greater than that of the third P-type region.

In specific implementation, the thickness of the absorption layer in this application may be equal to the depth of the groove. Of course, the thickness of the absorption layer may also be greater than the depth of the groove, which is not limited here.

This application does not limit the width, length and thickness of the absorption layer. Optionally, in order to further achieve large bandwidth and high power, in this application, the width of the absorption layer can be set to less than or equal to 1 μm, such as 0.01 μm, 0.05 μm, 0.1μm, 0.5μm, 0.7μm, 1μm, etc. The thickness of the absorption layer can be set to be less than or equal to 500nm, such as 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc. The length of the absorbing layer can be set to be greater than or equal to 20 μm, such as 20 μm, 30 μm, 50 μm, 100 μm, etc.

In specific implementation, the width of the intrinsic region is generally relatively small. For example, the width of the intrinsic region in this application can be set to be less than or equal to 500nm, such as 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc., which is not limited here.

The photodetector provided by the embodiment of the present application can implement a surface incidence detector and a waveguide coupling type detector. Among them, there are two ways of light incidence in surface-incidence detectors: 1) vertical incidence mode, light is injected into the absorption layer from the side of the absorption layer away from the second P-type region; 2) back-side incidence mode, light is incident from the second P-type region The side of the mold area away from the absorption layer is injected into the absorption layer. There are also two ways of light incident in waveguide coupling detectors: 1) evanescent wave coupling method, which requires setting the second P-type region in the PIN junction as the optical waveguide layer, and the light enters the absorption layer from the optical waveguide layer; 2) butt coupling In this way, an optical waveguide layer is set on the top of the absorption layer, and the light enters the absorption layer from the optical waveguide layer.

In this application, the optical waveguide layer is arranged at the top of the absorption layer, which means that the optical waveguide layer is arranged at the top of the absorption layer along its length direction, that is, the optical waveguide layer and the absorption layer are arranged adjacent to each other along the length direction of the absorption layer, so that the light passes from the After exiting from the waveguide layer, it enters the absorption layer from the top of the absorption layer.

This application does not limit the number of PIN junctions in the photodetector, and the design can be based on actual products. When the photodetector includes multiple PIN junctions, the semiconductor substrates of different PIN junctions may be of an integrated structure, that is, all PIN junctions are arranged on the same semiconductor substrate. Of course, the semiconductor substrates with different PIN junctions can also be arranged independently in physical locations, which is not limited here.

Optionally, the photodetector may include two PIN junctions, and the two PIN junctions are connected in parallel. In this way, when two PIN junctions are connected in parallel, since the total capacitance value increases, but the total resistance value decreases, non-uniform light absorption can be improved, the electric field in the junction area can be increased, and the saturated output power can be increased. Moreover, since RC can remain unchanged, it can be ensured that the saturation output power is increased without reducing the bandwidth, thereby realizing a large-width, high-power photodetector.

For example, in order to simplify the device structure, the two PIN junctions may share the third P-type region and the second electrode. Alternatively, the two PIN junctions may share the N-type region and the first electrode.

In specific implementation, when the photodetector includes two PIN junctions, and the light incident mode is an evanescent wave coupling mode. In order to further increase the saturated output power, N photodetector arrays can be arranged. The signal light is divided into two beams of light after passing through the first beam splitter. The two beams of light are divided into N beams of light through the second beam splitter. The N beams of light are Each beam of light is delayed by the optical waveguide delay line and then enters the two waveguide layers of a corresponding photodetector through a third optical splitter. Both ends of the optical waveguide layer of each photodetector correspond to a third optical splitter. , that is, light enters the absorption layer from both ends of the optical waveguide layer. Then the electrical signals output by the N photodetectors are summed up through traveling wave electrodes, thereby achieving high-power photoelectric conversion of the photodetector array.

In a second aspect, embodiments of the present application also provide a method for preparing a photodetector, which method includes forming at least one PIN junction; wherein forming each PIN junction may include the following steps: forming sequential phases in a semiconductor substrate. The N-type region, the intrinsic region, the first P-type region, the second P-type region and the third P-type region are arranged adjacently; then a groove is formed in the region corresponding to the second P-type region; and a groove is formed in the groove The absorption layer includes a P-type doped material; then a first electrode electrically connected to the N-type region is formed, and a second electrode electrically connected to the third P-type region is formed.

Optionally, the material of the semiconductor substrate includes silicon; forming the absorption layer in the groove includes: forming P-type germanium in the groove.

For example, there are two ways to form P-type germanium in the groove: the first is to epitaxially grow a germanium layer in the groove, and then dope the germanium layer with P-type ions; the second is to grow the germanium layer epitaxially in the groove. A mixed material of germanium and P-type ions is deposited in the tank.

Optionally, after forming the N-type region and before forming the first electrode electrically connected to the N-type region, an N-type contact region may be formed on the side of the N-type region close to the first electrode, and the doping of the N-type contact region The impurity concentration is generally greater than that of the N-type region, which can reduce the first Contact resistance between electrode and N-type region.

Correspondingly, after forming the third P-type region and before forming the second electrode electrically connected to the third P-type region, a P-type contact region may be formed on the side of the third P-type region close to the second electrode, and P The doping concentration of the P-type contact region is generally greater than the doping concentration of the third P-type region, thereby reducing the contact resistance between the second electrode and the third P-type region.

In a third aspect, embodiments of the present application also provide an optical receiver, including a transimpedance amplifier and a photodetector as in the first aspect or various embodiments of the first aspect. Among them, the transimpedance amplifier is used to perform transimpedance gain on the current signal output by the photodetector to obtain a voltage signal. Since the problem-solving principle of this optical receiver is similar to that of the aforementioned photodetector, the implementation of this optical receiver can be referred to the implementation of the aforementioned photodetector, and repeated details will not be repeated.

The technical effects that can be achieved by the above third aspect can be described with reference to the technical effects that can be achieved by any possible design in the above first aspect, and will not be repeated here.

Description of the drawings

Figure 1 is a schematic structural diagram of a large-bandwidth, high-power silicon-based germanium UTC PD proposed in related technologies;

Figure 2 is a schematic structural diagram of a photodetector provided by an embodiment of the present application;

Figure 3 is a schematic cross-sectional structural diagram of the photodetector shown in Figure 2 along the direction AA';

Figure 4 is a schematic diagram of a light incident mode of the photodetector provided by the embodiment of the present application;

Figure 5 is a schematic diagram of another light incident mode of the photodetector provided by the embodiment of the present application;

Figure 6 is a schematic diagram of another light incident mode of the photodetector provided by the embodiment of the present application;

Figure 7 is a schematic diagram of another light incident mode of the photodetector provided by the embodiment of the present application;

Figure 8 is a schematic structural diagram of a photodetector provided by another embodiment of the present application;

Figure 9 is a schematic circuit diagram corresponding to the photodetector provided by an embodiment of the present application;

Figure 10 is a schematic structural diagram of a photodetector provided by yet another embodiment of the present application;

Figure 11 is a schematic cross-sectional structural diagram of the photodetector shown in Figure 10 along the BB’ direction;

Figure 12 is a schematic structural diagram of a photodetector provided by another embodiment of the present application;

Figure 13 is a schematic cross-sectional structural diagram of the photodetector shown in Figure 12 along the CC' direction;

Figure 14 is a schematic structural diagram of a photodetector provided by another embodiment of the present application;

Figure 15 is a simulation result diagram of the responsivity of the photodetector shown in Figure 14;

Figure 16 is a simulation result diagram of the electric field intensity of the photodetector shown in Figure 14;

Figure 17 is a schematic structural diagram of a photodetector array provided by an embodiment of the present application;

Figure 18 is a schematic flow chart of a method for preparing a photodetector provided by an embodiment of the present application;

Figure 19 is a schematic structural diagram of an optical receiver provided by an embodiment of the present application;

Figure 20 is a schematic structural diagram of a coherent optical receiver provided by an embodiment of the present application.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be described in further detail below in conjunction with the accompanying drawings.

The terminology used in the following examples is for the purpose of describing specific embodiments only and is not intended to limit the application. As used in the specification and appended claims of this application, the singular expressions "a", "an", "said", "above", "the" and "the" are intended to also Expressions such as "one or more" are included unless the context clearly indicates otherwise.

Reference in this specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Therefore, the phrases "in one embodiment", "in some embodiments", "in other embodiments", "in other embodiments", etc. appearing in different places in this specification are not necessarily References are made to the same embodiment, but rather to "one or more but not all embodiments" unless specifically stated otherwise. The terms “including,” “includes,” “having,” and variations thereof all mean “including but not limited to,” unless otherwise specifically emphasized.

In order to facilitate understanding of the embodiments of the present application, some terms involved in the embodiments of the present application are first introduced below.

Space charge effect: In the light absorption region, photo-generated carriers quickly separate and form drift motion under the action of external electric field. However, the mobilities of electrons and holes in semiconductors are different, which leads to natural differences in carrier movement speeds in the intrinsic region, which in turn causes a charge imbalance within the intrinsic region, thus affecting the division of the external electric field. The unbalanced charges in the above are called space charges, and this effect that affects the external electric field is called the space charge effect. Generally speaking, in order to enable photogenerated carriers to move at saturation drift speed, external The average field strength formed by the boundary voltage should be greater than 10kV/cm. When more and more photogenerated carriers are generated, the space charge effect will become more and more significant. Under the premise that the external field strength remains unchanged, the internal field strength decreases, the drift speed of photogenerated carriers decreases, and even diffusion motion dominates. From a macro perspective, the generation of space charge effect will cause a serious decrease in device response speed. Therefore, when designing high-power photodetectors, attention must be paid to mitigating space charge effects.

Dark current: The dark current of a photodetector is defined as the current output by the photodetector in the absence of light. Under DC, dark current directly determines the minimum photocurrent that a photodetector can detect. At the same time, the size of this indicator also reflects the noise characteristics of the photodetector to a certain extent.

Bandwidth: For photodetectors, frequency response bandwidth (hereinafter referred to as "bandwidth") is a key indicator. It characterizes the high-speed response capability of the photodetector and is one of the core indicators restricting the optical communication system. The bandwidth of the photodetector is defined as the corresponding frequency point after the response of the photodetector drops by 3dB from low frequency. According to the basic principles of photodetectors, the influencing factors of bandwidth can be summarized into two categories: (1) carrier transit time; (2) RC cut-off effect.

Saturation power: The DC saturation power or power handling capability of the photodetector is defined as the input optical power that causes the photodetector to output the maximum photocurrent for the first time. After that, if the input optical power continues to increase, the photocurrent will not continue to increase. This indicator directly reflects the maximum optical power that the photodetector can withstand. Once the input optical power exceeds this value, the photodetector will no longer work. The RF saturation power of the photodetector can be characterized by the 1dB suppression point of the output power. The 1dB suppression point is defined as the corresponding output RF power and output photocurrent when the photodetector output power is 1dB smaller than the output power under ideal linear conditions. This indicator reflects the maximum power that the photodetector can output while ensuring linearity. In microwave photonic links and wireless communication links, this indicator restricts the spurious-free dynamic range (SFDR) of the microwave system. In high-fidelity communications, the system requirement for photodetectors is to increase their 1dB suppression point.

Photodetectors are responsible for converting optical signals into electrical signals. They are one of the core components in optical communication systems and are also key components that affect the performance of optical communication systems. With the continuous development of optical communication technology, other indicators such as the responsivity, dark current, and saturation power of photodetectors have gradually attracted attention. Since large-bandwidth, high-power photodetectors can significantly improve the noise index and SFDR of optical communication systems, there is an urgent need for large-bandwidth, high-power photodetectors in optical communication systems. For example, in the receiver of a coherent optical communication system, due to the existence of local oscillation light, the photodetector is required to be able to withstand high optical input power (>10mW) while maintaining high bandwidth. In optical wireless communications, photodetectors need to have large bandwidth and high power characteristics so that wireless microwave signals can be transmitted to front-end circuits and amplifiers without distortion. In a lidar system based on frequency modulated continuous wave detection, due to the existence of local oscillation light, the photodetector needs to be able to withstand higher optical input power while maintaining a high bandwidth.

In the existing technology, a variety of large-bandwidth, high-power photodetectors have been proposed and verified on the III-V integrated platform, such as Uni-traveling-carrier Photodetector (UTC PD) and Modified Uni-traveling-carrier Photodetector (MUTC PD). However, the thermal conductivity of III-V materials is very low, and under high injected light power, the device will still be damaged due to thermal failure effects. On the other hand, large-bandwidth and high-power photodetectors based on silicon-based integrated platforms have also attracted the attention of many researchers. This is due to the unique advantages of silicon-based integrated platforms such as low loss, high thermal conductivity, and compatibility with CMOS processes. . On the silicon-based integrated platform, the natural energy band difference of silicon germanium materials is used to form a quasi-single row carrier structure, thereby improving the space charge effect. At the same time, compared with Group III and V materials, silicon materials have high thermal conductivity. Based on the above two advantages, the related technology proposes a large-bandwidth, high-power silicon-based germanium UTC PD as shown in Figure 1, which mainly includes an N-type silicon substrate 01, an epitaxial silicon intrinsic layer 02, and a P-type germanium layer 03 , silicon nitride layer 04 and metal electrode 05, but this solution requires an additional silicon epitaxial process and is incompatible with the existing silicon photonics process.

Based on this, embodiments of the present application provide a photoelectric detector, a preparation method thereof, and an optical receiver. The present application will be described in further detail below with reference to the accompanying drawings.

Referring to Figures 2 and 3, Figure 2 is a schematic structural diagram of a photodetector provided by an embodiment of the present application; Figure 3 is a schematic cross-sectional structural diagram of the photodetector shown in Figure 2 along the direction AA'. The photodetector 10 is provided with at least one PIN junction. In FIGS. 2 and 3 , a PIN junction is taken as an example for schematic explanation. For example, each PIN junction may include: a semiconductor substrate 100, an absorption layer 106, an N-type region 101, an intrinsic region 102, a first P-type region 103, a second region located adjacently in the semiconductor substrate 100. The P-type region 104 and the third P-type region 105, the first electrode 107 (ie, the cathode) electrically connected to the N-type region 101, and the second electrode 108 (ie, the anode) electrically connected to the third P-type region 105. The material of the absorption layer 106 includes P-type doped material; the semiconductor substrate 100 has a groove V in a region corresponding to the second P-type region 104 , and the absorption layer 106 is disposed in the groove V, that is, the absorption layer 106 They are adjacent to the first P-type region 103 and the third P-type region 105 respectively, and the absorption layer 106 and the second P-type region 104 are stacked along the thickness direction of the semiconductor substrate 100 . In this way, when light is absorbed by the absorption layer 106 and photogenerated carriers (including electrons and holes) are generated, only electrons can enter the depletion region of the PIN junction due to the P-type doping of the absorption layer 106, so that Alleviating space charge effects and achieving high power. And the absorption layer 106 is disposed between the second P-type region 104 and the third P-type region 105, that is, the first P-type region 103 is spaced between the absorption layer 106 and the intrinsic region 102, and the doping of the absorption layer 106 can be utilized. The concentration adjusts the doping concentration of the first P-type region 103, so that the intrinsic region 102 and the absorption layer 106 can be adjusted internal electric field difference, thereby improving the responsivity and bandwidth.

For example, in this application, the material of the semiconductor substrate 100 may include silicon, and the material of the absorption layer 106 may include P-type germanium. Of course, the semiconductor substrate 100 and the absorption layer 106 can also be formed of Group III and V materials, which is not limited here.

When the material of the semiconductor substrate 100 is silicon and the material of the absorption layer 106 is P-type germanium, the natural energy band difference of the silicon germanium material can be used to form a quasi-single row carrier structure, thereby improving the space charge effect. At the same time, compared with Group III and V materials, silicon materials have high thermal conductivity, and the preparation process can be achieved through existing silicon photonics processes.

During specific implementation, the doping concentration of the intrinsic region 102 is very low, close to an intrinsic semiconductor, while the P-type region can be formed by doping the semiconductor substrate 100 with P-type ions, and the N-type region 101 can be formed by doping the semiconductor substrate 100. The bottom 100 is formed by N-type ion doping.

For example, the P-type ions doped in the P-type region may be trivalent elements such as boron (B) or aluminum (Al), and the N-type ions doped in the N-type region 101 may be phosphorus (P) or arsenic ( As) and other 5-valent elements.

The horizontal direction in this application refers to the direction perpendicular to the thickness of the semiconductor substrate 100 . The N-type region 101, the intrinsic region 102, the first P-type region 103, the second P-type region 104 and the third P-type region 105 are arranged adjacently in sequence, which means that the N-type region 101, the intrinsic region 102, the first P-type region 103, the second P-type region 104 and the third P-type region 105 are sequentially arranged in the direction perpendicular to the thickness of the semiconductor substrate. Type region 101, intrinsic region 102, first P-type region 103, second P-type region 104 and third P-type region 105, there is no other region between any adjacent two, for example, from left to right in Figure 3 They are N-type region 101, intrinsic region 102, first P-type region 103, second P-type region 104 and third P-type region 105.

For example, as shown in FIG. 3 , both the first electrode 107 and the second electrode 108 can be disposed on the side of the semiconductor substrate 100 where the groove V is provided, that is, the first electrode 107 , the second electrode 108 and the absorption layer. 106 are located on the same side of the second P-type region 104 relative to the second P-type region 104 .

During specific implementation, this application does not limit the materials of the first electrode 107 and the second electrode 108, and they can be any conductive material. For example, the first electrode 107 and the second electrode 108 are made of metal material.

In this application, the doping concentration of the first P-type region 103, the second P-type region 104 and the third P-type region 105 can be the same, so that the first P-type region 103, the second P-type region 103 and the second P-type region 105 can be formed simultaneously through one ion implantation process. P-type region 104 and third P-type region 105 .

For example, the doping concentration of the first P-type region 103 can be set to be greater than the doping concentration of the second P-type region 104 , thereby blocking holes from entering the intrinsic region 102 and effectively mitigating the space charge effect.

For example, the doping concentration of the third P-type region 105 can be set to be greater than the doping concentration of the second P-type region 104, thereby reducing the series resistance of the photodetector and increasing the bandwidth of the device.

For example, in this application, the doping concentration of the first P-type region 103 may be similar to the doping concentration of the third P-type region 105, but is not limited to the same doping concentration.

Referring to Figures 2 and 3, in order to reduce the contact resistance between the first electrode 107 and the N-type region 101, an N-type contact region 109 between the N-type region 101 and the first electrode 107 can also be provided in the semiconductor substrate 100. And the doping concentration of the N-type contact region 109 is generally greater than the doping concentration of the N-type region 101 . Similarly, in order to reduce the contact resistance between the second electrode 108 and the third P-type region 105, a P-type contact region 110 between the third P-type region 105 and the second electrode 108 can also be provided in the semiconductor substrate 100. And the doping concentration of the P-type contact region 110 is generally greater than the doping concentration of the third P-type region 105 .

In specific implementation, the N-type contact region 109 can be formed by continuing to perform N-type ion doping on the area where the N-type region 101 contacts the first electrode 107 . Correspondingly, the P-type contact region 110 can be formed by continuing to perform P-type ion doping on the region where the third P-type region 105 contacts the second electrode 108 .

It should be noted that in this application, the thickness of the absorption layer 106 can be equal to the depth of the groove V. Of course, the thickness of the absorption layer 106 can also be greater than the depth of the groove V. The specific design is based on the actual product and is not limited here.

The width, length and thickness of the absorption layer 106 are not limited in this application. Optionally, in order to further achieve large bandwidth and high power, in this application, the width m1 of the absorption layer 106 can be set to less than or equal to 1 μm, for example, 0.01 μm. , 0.05μm, 0.1μm, 0.5μm, 0.7μm, 1μm, etc. The thickness h1 of the absorption layer 106 may be set to be less than or equal to 500 nm, for example, 10 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, etc. The length l1 of the absorption layer 106 may be set to be greater than or equal to 20 μm, for example, 20 μm, 30 μm, 50 μm, 100 μm, etc.

In specific implementation, the width m2 of the intrinsic region 102 is generally relatively small. Illustratively, the width m2 of the intrinsic region 102 in this application can be set to be less than or equal to 500nm, for example, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc.

The photodetector 10 provided in the embodiment of the present application can implement a surface incidence detector and a waveguide coupling type detector. Among them, there are two modes of light incidence in the surface-incidence detector: 1) vertical incidence mode, as shown in Figure 4, light is incident into the absorption layer 106 from the side of the absorption layer 106 away from the second P-type region 104; 2) back-side incidence mode In the incident mode, as shown in FIG. 5 , light is incident from the side of the second P-type region 104 away from the absorbing layer 106 Absorbent layer 106. There are also two light incident modes for waveguide coupling detectors: 1) Evanescent wave coupling mode, as shown in Figure 6, the second P-type region 104 in the PIN junction needs to be set as the optical waveguide layer 111, and the light passes from the optical waveguide layer 111 enters the absorption layer 106; 2) Butt coupling mode, as shown in Figure 7, an optical waveguide layer 111 is set on the top of the absorption layer 106, and the light enters the absorption layer 106 from the optical waveguide layer 111. Among them, the direction of arrows in Figures 4 to 7 represents the incident direction of light.

It should be noted that the optical waveguide layer 111 is arranged at the top of the absorption layer 106 means that the optical waveguide layer 111 is arranged at the top of the absorption layer 106 along its length direction, that is, the optical waveguide layer 111 and the absorption layer 106 are along the length of the absorption layer 106 As shown in FIG. 2 , the length direction of the absorbing layer 106 is the same as the length direction of the groove V. In this way, the light emerges from the optical waveguide layer 111 and then enters the absorption layer 106 from the top of the absorption layer 106 .

This application does not limit the number of PIN junctions in the photodetector 10, and the design can be based on actual products. When the photodetector 10 includes multiple PIN junctions, the semiconductor substrate 100 of different PIN junctions may be an integrated structure, that is, all PIN junctions are disposed on the same semiconductor substrate 100 . Of course, the semiconductor substrates 100 of different PIN junctions can also be arranged independently in physical locations, which is not limited here.

Optionally, see FIG. 8 , which is a schematic structural diagram of a photodetector provided by another embodiment of the present application. The photodetector 10 may include two PIN junctions, and the two PIN junctions are connected in parallel. The corresponding The schematic diagram of the circuit is shown in Figure 9. The N-type region 101, the intrinsic region 102 and the first P-type region 103 in the PIN junction can be equivalent to the parallel first resistor R1 and capacitor C1, and the remaining regions can be equivalent to the second resistor. R2, when two PIN junctions are connected in parallel, since the total capacitance value increases, but the total resistance value decreases, it can improve non-uniform light absorption, increase the electric field in the junction area, and increase the saturated output power. Moreover, since the total capacitance value increases and the total resistance value decreases, RC can remain unchanged, thereby ensuring that the saturated output power is increased without reducing the bandwidth, thereby realizing a large-width, high-power photodetector 10.

Illustratively, in order to simplify the device structure, as shown in Figures 10 and 11, Figure 10 is a schematic structural diagram of a photodetector provided by another embodiment of the present application; Figure 11 is a BB along the photodetector shown in Figure 10 '' direction cross-sectional structural diagram, the two PIN junctions can share the third P-type region 105 and the second electrode 108. Or as shown in Figures 12 and 13, Figure 12 is a schematic structural diagram of a photodetector provided by another embodiment of the present application; Figure 13 is a schematic cross-sectional structural diagram of the photodetector shown in Figure 12 along the CC' direction. Two PIN junctions may share the N-type region 101 and the first electrode 107 .

It should be noted that when the photodetector 10 includes two PIN junctions or more PIN junctions, the implementation of each PIN junction may refer to the embodiments shown in FIGS. 2 to 7 , which will not be described again here.

As an example, the photodetector 10 includes two PIN junctions, and the light incident mode is an evanescent wave coupling mode. As shown in Figure 14, after the signal light enters the optical waveguide through the grating coupler 12, it is divided into two parts through the optical splitter 13, and is respectively input to the optical input ports 1 and 2 of the two PIN junctions (i.e., the light in the two PINs the top of the waveguide layer 111). The signal light enters the absorption layer 106 through the optical waveguide layer 111 and is absorbed by the absorption layer 106. Among the generated photogenerated carriers, only electrons can enter the depletion region for drift movement. In order to further optimize the large bandwidth and high power performance of the photodetector 10, in one embodiment, the width of the absorption layer 106 is set to less than 1 um, the thickness is set to less than 500 nm, and the length is set to greater than 20 um; the intrinsic region 102 The width is set to around 500nm. Through testing, it can be concluded that the photodetector 10 can achieve a responsivity of 1A/W, a bandwidth >30GHz, and a saturated output power >0dBm. Figure 15 shows the specific responsivity simulation results. The solid line represents the change curve of responsivity with bias voltage when the input light is 1550nm, and the dotted line represents the change curve of responsivity with bias voltage when the input light is 1310nm. The results It was also shown that responsivity >1A/W can be achieved at both operating wavelengths. Figure 16 shows the specific electric field simulation results. It can be seen from it that the internal field strength division of the photodetector 10 is mainly concentrated in the depletion region, which can make the photogenerated carriers move at a saturated drift speed and achieve high-speed detection.

In specific implementation, when the photodetector 10 includes two PIN junctions, and the light incident mode is an evanescent wave coupling mode. In order to further increase the saturated output power, as shown in Figure 17, N photodetectors 10_1~10_N can be arranged in an array. The signal light is divided into two beams of light after passing through the first beam splitter 14, and the two beams of light pass through the second beam splitter respectively. The detector 15 is divided into N beams of light. Each beam of light in the N beams is delayed by the optical waveguide delay line 16_n and then passes through the third beam splitter 17_n and enters the two waveguide layers of a corresponding photodetector 10_n. Each photodetector The two ends of the optical waveguide layer 111 of 1010_n respectively correspond to a third optical splitter 17_n, that is, the light enters the absorption layer 106 from both ends of the optical waveguide layer 111. Then, the electrical signals output by the N photodetectors 10_1 to 10_N are combined through traveling wave electrodes (not shown in the figure), thereby realizing high-power photoelectric conversion of the photodetector array.

Correspondingly, embodiments of the present application also provide a method for preparing a photodetector, including: forming at least one PIN junction; as shown in Figure 18, forming each PIN junction may include the following steps:

Step S101: Form an N-type region 101, an intrinsic region 102, a first P-type region 103, a second P-type region 104 and a third P-type region 105 arranged adjacently in sequence in the semiconductor substrate 100.

Exemplarily, the material of the semiconductor substrate 100 may include silicon, so that the preparation process of step S101 can be accomplished through existing silicon photonics. Process realization. And silicon material has high thermal conductivity.

During specific implementation, the doping concentration of the intrinsic region 102 is very low, almost an intrinsic semiconductor, while the P-type region can be formed by P-type ion doping of the semiconductor substrate 100, and the N-type region 101 can be formed by The semiconductor substrate 100 is formed by N-type ion doping. Among them, P-type ions can be 3-valent elements such as boron (B) or aluminum (Al), and N-type ions can be 5-valent elements such as phosphorus (P) or arsenic (As).

For example, the doping concentration of the first P-type region 103 may be set to be greater than the doping concentration of the second P-type region 104 , and the doping concentration of the third P-type region 105 may be set to be greater than the second P-type region 104 The doping concentration of the first P-type region 103 is similar to the doping concentration of the third P-type region 105, but is not limited to the same doping concentration.

Step S102: Form a groove V in a region corresponding to the second P-type region 104.

In specific implementation, the groove V may be formed through an etching process.

Step S103: Form an absorption layer 106 in the groove V, where the material of the absorption layer 106 includes a P-type doped material.

During specific implementation, the thickness of the absorption layer 106 in this application may be equal to the depth of the groove V. Of course, the thickness of the absorption layer 106 may also be greater than the depth of the groove V. The specific design is based on the actual product and is not limited here.

For example, the material of the absorption layer 106 may include P-type germanium, which can utilize the natural energy band difference of the silicon germanium material to form a quasi-single row carrier structure, thereby improving the space charge effect.

For example, there are two ways to form P-type germanium in the groove V: the first is to epitaxially grow a germanium layer in the groove V, and then dope the germanium layer with P-type ions; the second is to A mixed material of germanium and P-type ions is deposited in groove V.

Step S104: Form the first electrode 107 electrically connected to the N-type region 101.

Step S105: Form a second electrode 108 electrically connected to the third P-type region 105.

This application does not limit the order of steps S104 and step S105. They may be executed at the same time, or step S104 may be executed first and then step S105, or step S105 may be executed first and then step S104.

For example, in order to reduce process steps, step S104 and step S105 are performed at the same time, that is, the first electrode 107 and the second electrode 108 are formed at the same time.

Optionally, after forming the N-type region 101 and before forming the first electrode 107 electrically connected to the N-type region 101, an N-type contact region 109 can also be formed on the side of the N-type region 101 close to the first electrode 107, and The doping concentration of the N-type contact region 109 is generally greater than the doping concentration of the N-type region 101 , thereby reducing the contact resistance between the first electrode 107 and the N-type region 101 .

Correspondingly, after forming the third P-type region 105 and before forming the second electrode 108 electrically connected to the third P-type region 105, a P-type electrode may be formed on the side of the third P-type region 105 close to the second electrode 108. The contact region 110 , and the doping concentration of the P-type contact region 110 is generally greater than the doping concentration of the third P-type region 105 , thereby reducing the contact resistance between the second electrode 108 and the third P-type region 105 .

Correspondingly, refer to FIG. 19 , which is a schematic structural diagram of an optical receiver provided by an embodiment of the present application. The optical receiver 1 mainly includes a transimpedance amplifier 20 and any photodetector 10 provided in the embodiment of the present application; wherein, the transimpedance amplifier 20 is used to perform transimpedance gain on the current signal output by the photodetector 10, to obtain voltage signal. Since the problem-solving principle of the optical receiver 1 is similar to that of the aforementioned photodetector 10, the implementation of the optical receiver 1 can be referred to the implementation of the aforementioned photodetector 10, and repeated details will not be repeated.

For example, the optical receiver provided by the embodiment of the present application can be used in optical communication systems and optical sensing systems, such as optical communication modules, radar modules, etc.

For example, in the coherent optical receiver of the coherent optical communication system, as shown in Figure 20, the local oscillation light and the signal light enter multiple photodetectors 10 after passing through the 90° mixer 21. Due to the existence of the local oscillation light, photoelectric detection is required. The detector 10 can withstand high optical input power (>10mW) while maintaining high bandwidth. In optical wireless communication, the photodetector 10 needs to have large bandwidth and high power characteristics so that the wireless microwave signal can be transmitted to the front-end circuit and amplifier without distortion. In a lidar system based on frequency modulated continuous wave detection, due to the existence of local oscillation light, the photodetector 10 needs to be able to withstand higher optical input power while maintaining a high bandwidth.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. In this way, if these modifications and variations of the present application fall within the scope of the claims of the present application and equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

A photodetector, characterized in that it includes at least one PIN junction, and each of the at least one PIN junction includes:

semiconductor substrate;

The N-type region, the intrinsic region, the first P-type region, the second P-type region and the third P-type region are located in the semiconductor substrate and are arranged adjacently in sequence, and the semiconductor substrate is in contact with the second P-type region. The area corresponding to the P-type area has grooves;

An absorption layer located in the groove, the material of the absorption layer includes P-type doped material;

a first electrode electrically connected to the N-type region;

a second electrode electrically connected to the third P-type region.
The photodetector of claim 1, wherein the doping concentration of the first P-type region is greater than the doping concentration of the second P-type region.
The photodetector of claim 1, wherein the doping concentration of the third P-type region is greater than the doping concentration of the second P-type region.
The photodetector of claim 1, wherein the doping concentration of the first P-type region is equal to the doping concentration of the third P-type region.
The photodetector according to any one of claims 1 to 4, wherein the material of the semiconductor substrate includes silicon, and the P-type doping material includes P-type germanium.
The photodetector of claim 5, wherein the width of the absorption layer is less than or equal to 1 μm;

And/or, the thickness of the absorption layer is less than or equal to 500nm;

And/or, the length of the absorption layer is greater than or equal to 20 μm.
The photodetector according to claim 5 or 6, characterized in that the width of the intrinsic region is less than or equal to 500 nm.
The photodetector according to any one of claims 1 to 7, wherein the second P-type region in the PIN junction is an optical waveguide layer.
The photodetector according to any one of claims 1 to 7, further comprising an optical waveguide layer provided for the PIN junction, the optical waveguide layer being in contact with the absorbing layer along the length direction of the absorbing layer. The absorbing layers are arranged adjacent to each other.
The photodetector according to any one of claims 1 to 9, characterized in that the PIN junction further includes:

an N-type contact region located within the semiconductor substrate and between the N-type region and the first electrode;

A P-type contact region located within the semiconductor substrate and between the third P-type region and the second electrode.
The photodetector according to any one of claims 1 to 10, characterized in that it includes two PIN junctions, and the two PIN junctions are connected in parallel.
The photodetector of claim 11, wherein two of the PIN junctions share the third P-type region and the second electrode; or, the two PIN junctions share the third P-type region. type region and the second electrode.
A method for preparing a photodetector, characterized in that it includes: forming at least one PIN junction; wherein forming each of the PIN junctions includes:

Forming an N-type region, an intrinsic region, a first P-type region, a second P-type region and a third P-type region arranged adjacently in sequence in the semiconductor substrate;

Forming a groove in a region corresponding to the second P-type region;

An absorption layer is formed in the groove, and the material of the absorption layer includes a P-type doped material;

Forming a first electrode electrically connected to the N-type region;

A second electrode electrically connected to the third P-type region is formed.
The preparation method according to claim 13, wherein the material of the semiconductor substrate includes silicon;

The forming the absorption layer in the groove includes: forming P-type germanium in the groove.
The preparation method of claim 14, wherein forming P-type germanium in the groove includes:

epitaxially growing a germanium layer in the groove, and doping P-type ions in the germanium layer;

Alternatively, a mixed material of germanium and P-type ions is deposited in the groove.
The preparation method according to any one of claims 13 to 15, characterized in that, after forming the N-type region and before forming the first electrode electrically connected to the N-type region, it further includes: An N-type contact region is formed on the side of the N-type region close to the first electrode;

After forming the third P-type region, and before forming a second electrode electrically connected to the third P-type region, the method further includes: forming a P on a side of the third P-type region close to the second electrode. contact area.
An optical receiver, characterized in that it includes a transimpedance amplifier and a photodetector according to any one of claims 1 to 12; the transimpedance amplifier is used to transpose a current signal output by the photodetector across resistor gain and get the voltage signal.