Avalanche photodiode, photoelectric detection chip, and optical communication device

Abstract

Embodiments of the present application relate to the technical field of photoelectric conversion components, and provide an avalanche photodiode, a photoelectric detection chip, and an optical communication device, which are used for alleviating the problems of large noise and dark current in a waveguide avalanche photodiode. The avalanche photodiode comprises a first semiconductor layer and a second semiconductor layer. The first semiconductor layer comprises a waveguide portion and a component portion that are arranged in a first direction. In a second direction perpendicular to the first direction, the component portion comprises a first ohmic contact region, a first charge region, a first multiplication region, a second charge region, and a second ohmic contact region arranged in sequence. The first charge region, the second charge region, and the first ohmic contact region are P-type doped regions, the second ohmic contact region is an N-type doped region, and the first multiplication region is an intrinsic region. The second semiconductor layer is disposed on a side of the first semiconductor layer and is in contact with the first charge region and is used to absorb incident light to generate photo-generated carriers. The described avalanche photodiode can be applied to optical communication.

Description

An avalanche photodiode, a photodetector chip, and an optical communication device

[0001] This application claims priority to Chinese Patent Application No. 202411578064.X, filed on November 5, 2024, entitled “An Avalanche Photodiode, a Photodetector Chip and an Optical Communication Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of optoelectronic conversion device technology, and in particular to an avalanche photodiode, a photodetector chip, and an optical communication device. Background Technology

[0003] An avalanche photodiode (APD) is a photoelectric conversion device based on the photoelectric effect and the avalanche multiplication effect. Because it amplifies the photoelectric signal using the avalanche multiplication effect of charge carriers while simultaneously achieving photoelectric conversion, it has higher sensitivity than ordinary photodetector chips, making it advantageous for detecting weak light signals. APDs also have the advantage of fast response speed; they are currently widely used in optical communication, laser ranging, and single-photon counting.

[0004] Depending on their structure, avalanche photodiodes can be classified into planar, mesa, and waveguide types. In planar and mesa-type avalanche photodiodes, the light absorption direction is the same as the carrier motion direction, leading to a trade-off between responsivity and bandwidth, meaning that high responsivity and high bandwidth cannot be achieved simultaneously. In waveguide-type avalanche photodiodes, the light absorption direction is orthogonal to the carrier motion direction, thus decoupling responsivity and bandwidth, allowing for the simultaneous achievement of high responsivity and high bandwidth; notably, germanium-silicon waveguide APDs are compatible with CMOS (Complementary Metal Oxide Semiconductor) processes. However, waveguide-type avalanche photodiodes still suffer from problems such as high noise and dark current. Summary of the Invention

[0005] This application provides an avalanche photodiode, a photodetector chip, and an optical communication device to improve the problems of high noise and dark current in waveguide-type avalanche photodiodes.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] In a first aspect, an avalanche photodiode is provided, which includes a first semiconductor layer, a second semiconductor layer, a first electrode, and a second electrode.

[0008] The first semiconductor layer includes a waveguide portion and a device portion arranged in a first direction; the waveguide portion guides incident light to the device portion. In a second direction perpendicular to the first direction, the device portion includes a first ohmic contact region, a first charge region, a first multiplication region, a second charge region, and a second ohmic contact region arranged sequentially; the first charge region, the second charge region, and the first ohmic contact region are all P-type doped regions, the second ohmic contact region is an N-type doped region, and the first multiplication region is an intrinsic region. A first electrode is in contact with the first ohmic contact region, and a second electrode is in contact with the second ohmic contact region.

[0009] The second semiconductor layer is used to absorb incident light and generate photogenerated carriers; the second semiconductor layer and the first semiconductor layer are stacked in a third direction and cover a portion of the first charge region; wherein the first direction, the second direction, and the third direction are mutually perpendicular. In the second direction, the portion of the first charge region is closer to the second ohmic contact region relative to the second semiconductor layer.

[0010] The avalanche photodiode provided in this application is a waveguide-type avalanche photodiode, and it employs a separate absorption charge and multiplication (SACM) design. In this case, the incident light is incident on the avalanche photodiode in a direction parallel to a first direction, and the carrier motion direction in the avalanche photodiode is parallel to a second direction, with the first and second directions perpendicular to each other. That is, the light absorption direction is orthogonal to the carrier motion direction, thereby decoupling the responsivity and bandwidth issues, which is beneficial for simultaneously achieving high responsivity and high bandwidth.

[0011] In the avalanche photodiode provided in this application, a first charge region, a first multiplication region, and a second charge region are included between the first ohmic contact region and the second ohmic contact region. The second charge region is a P-type doped region, and the second ohmic contact region is an N-type doped region. The direct contact between the second charge region and the second ohmic contact region forms a PN junction. Under the action of an applied electric field, this PN junction forms a depletion region at the contact location between the second charge region and the second ohmic contact region. The number of electrons and holes in this depletion region is equal, and it can be considered equivalent to an intrinsic region; therefore, this depletion region can be used as a multiplication region. In other words, the avalanche photodiode provided in this application has a combination of two pairs of charge regions and multiplication regions.

[0012] This design offers several advantages. First, the combination of two pairs of charge regions and multiplication regions allows for precise control of the electric field, enabling a more sloping electric field distribution. This concentrates the avalanche multiplication region near the second ohmic contact region, thus reducing excess noise in the avalanche photodiode. Second, using the depletion region in the PN junction as the multiplication region simplifies the structure and reduces the overall device size compared to using a separate multiplication region. With the same overall device size, it allows for a larger second charge region in the second direction, reducing the fabrication difficulty of the avalanche photodiode and improving its performance.

[0013] Furthermore, since the first charge region is designed to extend beyond the second semiconductor layer, the distance between the light absorption region (second semiconductor layer) and the high-field avalanche multiplication region (e.g., the first multiplication region) during photoelectric conversion can be increased. In this case, it is beneficial to reduce the electric field strength in the light absorption region (second semiconductor layer), thereby reducing the dark current of the avalanche photodiode. Moreover, compared to a combination of a single pair of charge regions and multiplication regions, a combination of two pairs of charge regions and multiplication regions, due to the implementation of a tilted electric field distribution, can further increase the distance between the light absorption region (second semiconductor layer) and the high-field avalanche multiplication region (e.g., the PN junction depletion region used as the multiplication region), thereby further reducing the dark current of the avalanche photodiode.

[0014] It can be seen that the avalanche photodiode 1 provided in this application embodiment can reduce noise level and dark current while achieving high responsivity and high bandwidth, thereby further improving the performance of the device.

[0015] In some possible implementations, the device portion further includes a second multiplication region located between the second charge region and the second ohmic contact region, the second multiplication region being an intrinsic region. By providing a separate second multiplication region, it is beneficial to improve the multiplication performance of the avalanche photodiode and to enhance the stability of device operation.

[0016] In some possible implementations, the doping concentrations of the first charge region and the second charge region are the same. This design allows the first and second charge regions to be formed in a single doping process during the fabrication of the avalanche photodiode, thereby simplifying the fabrication process and reducing manufacturing difficulty and cost.

[0017] In some possible implementations, between the first multiplication region and the second charge region, the device portion further includes at least one pair of third charge regions and third multiplication regions; the third charge region is a P-type doped region, and the third multiplication region is an intrinsic region.

[0018] In the second direction, the third charge region and the third multiplication region are in contact, and the first charge region is closer to the first ohmic contact region relative to the third multiplication region.

[0019] This design allows for more precise control of the electric field by setting up more combinations of charge regions and multiplication regions, which is beneficial for further improving the performance of avalanche photodiodes.

[0020] In some possible implementations, the doping concentrations of the third charge region, the first charge region, and the second charge region are equal. This design allows the first, second, and third charge regions to be formed in a single doping process during the fabrication of the avalanche photodiode, thereby simplifying the fabrication process and reducing manufacturing difficulty and cost.

[0021] In some possible implementations, the first semiconductor layer is a ridge waveguide structure extending along a first direction, and the second semiconductor layer is disposed on top of the ridge protrusion in the ridge waveguide structure. This design can limit the propagation area of ​​incident light in the first semiconductor layer, concentrating the propagation area near the ridge protrusion, thereby facilitating the efficient guidance of incident light to the second semiconductor layer located on one side of the device portion, and improving the absorption efficiency of the avalanche photodiode for incident light.

[0022] In some possible implementations, the device portion further includes an intermediate intrinsic region located between the first charge region and the first ohmic contact region, with the second semiconductor layer in contact with the intermediate intrinsic region.

[0023] In the avalanche photodiode provided in this application, the intermediate intrinsic region is the spacing region between the doped regions in the first semiconductor layer. By setting an intermediate intrinsic region, the positional accuracy requirements of the doped regions can be relaxed, thereby reducing the fabrication difficulty of the avalanche photodiode. Furthermore, by setting an intermediate intrinsic region, the proportion of doped regions in the first semiconductor layer can be reduced, which helps to mitigate the problem of impurity elements in the first semiconductor layer affecting the avalanche photodiode's absorption efficiency of incident light.

[0024] In some possible implementations, the first semiconductor layer is made of silicon, and the second semiconductor layer is made of germanium. Germanium has good photodetector properties, while silicon has a low k-value; avalanche photodiodes made of silicon and germanium can achieve better performance.

[0025] In some possible implementations, the semiconductor material in the first semiconductor layer includes at least one of indium phosphide, indium aluminum arsenide, and gallium arsenide; the material of the first multiplication region includes at least one of indium phosphide, indium gallium arsenide, indium aluminum arsenide, and indium gallium arsenide phosphide; and the semiconductor material of the second semiconductor layer includes at least one of indium gallium arsenide, indium aluminum arsenide, and gallium arsenide. The avalanche photodiode provided in this application can also be fabricated using a III-V group material system, offering good adaptability and meeting the needs of different scenarios.

[0026] In some possible implementations, the first ohmic contact region includes a first sub-contact region and a second sub-contact region in contact with each other; the doping concentration of the first sub-contact region is higher than that of the second sub-contact region, and the doping concentration of the second sub-contact region is higher than that of the first charge region and the second charge region; the first electrode is in contact with the first sub-contact region.

[0027] And / or, the second ohmic contact region includes a third sub-contact region and a fourth sub-contact region in contact; the doping concentration of the third sub-contact region is higher than that of the fourth sub-contact region, and the doping concentration of the fourth sub-contact region is higher than that of the first charge region and the second charge region; the second electrode is in contact with the third sub-contact region.

[0028] This design allows the first and second ohmic contact regions to utilize heavily doped regions to improve contact performance with external metal electrodes (such as the first and second electrodes), reducing contact resistance and achieving high-quality ohmic contact. On the other hand, the "high-low" doping concentration design reduces the proportion of heavily doped regions, which helps to improve the problem of impurity elements in the first semiconductor layer affecting the avalanche photodiode's absorption efficiency of incident light.

[0029] In a second aspect, a photoelectric detection chip is provided, which includes an avalanche photodiode as described in any one of the first aspects and a packaging structure. The packaging structure is used to encapsulate the avalanche photodiode and has an optical port and a pad. The optical port is used to expose the light-gathering end face of the waveguide portion in the avalanche photodiode. The pad is used to bring out the first electrode and the second electrode in the avalanche photodiode.

[0030] Thirdly, an optical communication device is provided, which includes a photodetector chip as described in the second aspect and a signal processing circuit, wherein the signal processing circuit is electrically connected to the pads in the photodetector chip.

[0031] The technical effects achievable by the photoelectric detection chip and optical communication equipment provided in this application are the same as those achievable by the avalanche photodiode provided in the first aspect, and will not be repeated here. Attached Figure Description

[0032] Figure 1 is a perspective view of an avalanche photodiode provided in an embodiment of this application;

[0033] Figure 2 is a cross-sectional view of an avalanche photodiode provided in an embodiment of this application along line A' in Figure 1;

[0034] Figure 3 is a cross-sectional view of another avalanche photodiode provided in an embodiment of this application, along line A' in Figure 1.

[0035] Figure 4 is a cross-sectional view of another avalanche photodiode provided in the embodiment of this application along A-A' in Figure 1;

[0036] Figure 5 is a cross-sectional view of another avalanche photodiode provided in the embodiment of this application along line A' in Figure 1;

[0037] Figure 6 is a cross-sectional view of an avalanche photodiode provided in the comparative embodiment along line A' in Figure 1;

[0038] Figure 7 shows the comparison parameters and comparison results in the comparative experiment provided in the embodiments of this application;

[0039] Figure 8 is an electric field distribution diagram of the comparative embodiment in the comparative test provided in this application;

[0040] Figure 9 is an electric field distribution diagram of the first embodiment in the comparative test provided in this application;

[0041] Figure 10 is an electric field distribution diagram of the second embodiment in the comparative test provided in this application;

[0042] Figure 11 is a comparison chart of equivalent k values ​​in comparative experiments provided in the embodiments of this application;

[0043] Figure 12 is a perspective view of another avalanche photodiode provided in an embodiment of this application;

[0044] Figure 13 is a cross-sectional view of an avalanche photodiode provided in an embodiment of this application, along line B' in Figure 12.

[0045] Figure 14 is a cross-sectional view of another avalanche photodiode provided in an embodiment of this application, along B-B' in Figure 12.

[0046] Figure 15 is a schematic diagram of the structure of a photoelectric detection chip provided in an embodiment of this application;

[0047] Figure 16 is a schematic diagram of the structure of an optical communication device provided in an embodiment of this application;

[0048] Figure 17 is an architecture diagram of a PON network provided in an embodiment of this application. Detailed Implementation

[0049] The technical solutions of the embodiments of this application will now be described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them.

[0050] In the following embodiments of this application, the terms "first," "second," etc., are used for descriptive convenience only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0051] In the embodiments of this application, "upper", "lower", "left" and "right" are not limited to the orientation of the components in the accompanying drawings. It should be understood that these directional terms can be relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0052] In the embodiments of this application, unless the context otherwise requires, the term "comprising" is interpreted as open and encompassing throughout the specification and claims, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "exemplarily," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this application. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0053] As used herein, “about,” “approximately,” or “approximately” includes the stated value and the average value within an acceptable range of deviation from the given value, wherein the acceptable range of deviation is determined by a person skilled in the art taking into account the measurement under discussion and the error associated with the measurement of the given quantity (i.e., the limitations of the measurement system).

[0054] As used herein, “parallel,” “perpendicular,” and “equal” include the described situation and situations that are similar to the described situation, within an acceptable range of deviation, which is determined by those skilled in the art taking into account the measurement under discussion and the error associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, “parallel” includes absolute parallelism and approximate parallelism, where an acceptable range of deviation for approximate parallelism may be, for example, within 5°; “perpendicular” includes absolute perpendicularity and approximate perpendicularity, where an acceptable range of deviation for approximate perpendicularity may also be, for example, within 5°; “equal” includes absolute equality and approximate equality, where an acceptable range of deviation for approximate equality may be, for example, a difference between the two equals being less than or equal to 5% of either one.

[0055] It should be understood that when a layer or element is referred to as being on another layer or substrate, it can mean that the layer or element is directly on the other layer or substrate, or that there is an intermediate layer between the layer or element and the other layer or substrate.

[0056] Exemplary embodiments are described in this application with reference to cross-sectional views and / or plan views and / or equivalent circuit diagrams, which are idealized exemplary drawings. In the drawings, the thickness of layers and regions is enlarged for clarity. Therefore, variations in shape relative to the drawings are contemplated due to, for example, manufacturing techniques and / or tolerances. Thus, exemplary embodiments should not be construed as being limited to the shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing processes. For example, etched regions shown as rectangular would typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shapes of the regions of the device, nor are they intended to limit the scope of the exemplary embodiments.

[0057] This application provides an avalanche photodiode, which is a waveguide-type avalanche photodiode and employs a Separate Absorption Charge Multiplication (SACM) design. As shown in Figures 1 and 2, the avalanche photodiode 1 includes a first semiconductor layer 2, and the semiconductor material in the first semiconductor layer 2 includes silicon (Si). The first semiconductor layer 2 can be a silicon layer in a substrate, a silicon epitaxial layer on a substrate, or a silicon epitaxial layer after removing the substrate. In this embodiment, the first semiconductor layer 2 is a silicon layer in silicon-on-insulator (SOI).

[0058] The first semiconductor layer 2 is divided into a waveguide portion 210 and a device portion 220 in the first direction X. The waveguide portion 210 is used to guide external incident light to the device portion 220, that is, the first direction X is the propagation direction of the incident light in the first semiconductor layer 2. The device portion 220 is used to form a structure for photoelectric conversion in the avalanche photodiode 1. This photoelectric conversion structure is used to perform photoelectric conversion on the incident light propagating through the waveguide portion 210 to the device portion 220.

[0059] In device section 220, the first semiconductor layer 2 includes doped regions containing impurity elements. These impurity elements are formed by doping the first semiconductor layer 2 through a doping process. The doping process can be ion implantation or thermal diffusion, among others. Depending on the impurity element used, doping can be classified into two types: N-type doping and P-type doping. N-type doping uses Group V elements such as phosphorus (P), arsenic (As), antimony (Sb), or bismuth (Bi). These impurity elements provide additional electrons, making electrons the majority carriers in the semiconductor material. Semiconductor materials doped with N-type doping are called N-type semiconductor materials or electron-type semiconductor materials. P-type doping uses Group III elements such as boron (B), gallium (Ga), or indium (In). These impurity elements provide additional holes, making holes the majority carriers in the semiconductor material. Semiconductor materials doped with P-type doping are called P-type semiconductor materials or hole-type semiconductor materials.

[0060] In the first semiconductor layer 2, the N-type doped region is called the N-type doped region, and the P-type doped region is called the P-type doped region.

[0061] As shown in Figure 2, in the second direction Y, perpendicular to the first direction X, the device portion 220 includes a first ohmic contact region 4, an intermediate intrinsic region 5, a first charge region 6, a first multiplication region 7, a second charge region 8, a second multiplication region 9, and a second ohmic contact region 10 arranged in sequence. The first ohmic contact region 4, the first charge region 6, the second charge region 8, and the second ohmic contact region 10 are all doped regions containing impurity elements, and the first charge region 6, the second charge region 8, and the first ohmic contact region 4 are all P-type doped regions, while the second ohmic contact region 10 is an N-type doped region. The intermediate intrinsic region 5, the first multiplication region 7, and the second multiplication region 9 are all intrinsic regions without impurity elements, and the number of electrons and holes in these intrinsic regions is equal.

[0062] In the avalanche photodiode 1 provided in this embodiment, the first multiplication region 7 and the second multiplication region 9 are the regions where charge carriers achieve avalanche multiplication, that is, under the action of an electric field, charge carriers can collide and ionize with the lattice in the first multiplication region 7 and the second multiplication region 9, generating more new electron-hole pairs. The first charge region 6 and the second charge region 8 are used to control the electric field distribution in the first multiplication region 7 and the second multiplication region 9; by adjusting the size and doping concentration of the first charge region 6 and the second charge region 8 in the first direction X, the electric field in the first multiplication region 7 and the second multiplication region 9 can be finely controlled; thereby helping to reduce the dark current and excess noise of the avalanche photodiode 1 (for details, please refer to the analysis and comparative simulation experiments below).

[0063] The doping concentrations of the first charge region 6 and the second charge region 8 can be the same or different. In this embodiment, the first charge region 6 and the second charge region 8 are designed with the same doping concentration. This allows the first charge region 6 and the second charge region 8 to be formed in a single doping process during the fabrication of the avalanche photodiode 1, thereby simplifying the fabrication process of the avalanche photodiode 1 and reducing the fabrication difficulty and cost.

[0064] In the avalanche photodiode 1 provided in this embodiment, the first ohmic contact region 4 and the second ohmic contact region 10 are heavily doped regions with a higher doping concentration than other doped regions, used to achieve high-quality ohmic contact with external metal electrodes (the first electrode 11 and the second electrode 12 as described below). In this embodiment, as shown in FIG2, both the first ohmic contact region 4 and the second ohmic contact region 10 include two sub-contact regions with different doping concentrations. Specifically, the first ohmic contact region 4 includes a first sub-contact region 41 and a second sub-contact region 42 arranged along the second direction Y, and the first sub-contact region 41 and the second sub-contact region 42 are in contact with each other; the first sub-contact region 41 is located on the outside, and the second sub-contact region 42 is closer to the intermediate intrinsic region 5 relative to the first sub-contact region 41 and is in contact with the intermediate intrinsic region 5. The doping concentration of the first sub-contact region 41 is higher than that of the second sub-contact region 42, and the doping concentration of the second sub-contact region 42 is higher than that of the first charge region 6 and the second charge region 8. In the first sub-contact area 41 and the second sub-contact area 42, the first sub-contact area 41 is used for contact electrical connection with an external metal electrode (such as the first electrode 11).

[0065] Referring to Figure 2, the second ohmic contact region 10 includes a third sub-contact region 102 and a fourth sub-contact region 101 arranged along the second direction Y. The third sub-contact region 102 and the fourth sub-contact region 101 are in contact with each other. The third sub-contact region 102 is located on the outer side, and the fourth sub-contact region 101 is closer to the second multiplication region 9 relative to the third sub-contact region 102 and is in contact with the second multiplication region 9. The doping concentration of the third sub-contact region 102 is higher than that of the fourth sub-contact region 101, and the doping concentration of the fourth sub-contact region 101 is higher than that of the first charge region 6 and the second charge region 8. In the third sub-contact region 102 and the fourth sub-contact region 101, the third sub-contact region 102 is used for contact electrical connection with an external metal electrode (such as the second electrode 12).

[0066] The first ohmic contact region 4 and the second ohmic contact region 10 adopt the above design, which on the one hand enables high-quality ohmic contact with the external metal electrode, reduces contact resistance, and improves electrical connection performance. On the other hand, by reducing the proportion of heavily doped regions, the overall doping concentration is reduced, which helps to improve the problem of impurity elements doped in the first semiconductor layer 2 affecting the avalanche photodiode 1's absorption efficiency of incident light.

[0067] In some embodiments, as shown in FIG3, the two sub-contact regions with different doping concentrations in the first ohmic contact region 4 and the second ohmic contact region 10 can be arranged along a third direction Z, wherein the first direction X, the second direction Y, and the third direction Z are mutually perpendicular, and the third direction Z is the thickness direction of the first semiconductor layer 2. For example, the first ohmic contact region 4 includes a first sub-contact region 41 and a second sub-contact region 42; compared to the first sub-contact region 41, the second sub-contact region 42 has a larger area and a deeper doping depth, but a lower doping concentration. The second sub-contact region 42 is in contact with the intermediate intrinsic region 5, and the first sub-contact region 41 is located at the top center of the second sub-contact region 42. An external metal electrode (such as the first electrode 11) is in contact with the first sub-contact region 41.

[0068] The second ohmic contact region 10 includes a third sub-contact region 102 and a fourth sub-contact region 101. Compared to the third sub-contact region 102, the fourth sub-contact region 101 has a larger area and a deeper doping depth, but a lower doping concentration. The fourth sub-contact region 101 is in contact with the second multiplication region 9, and the third sub-contact region 102 is located at the top center of the fourth sub-contact region 101. An external metal electrode (such as the second electrode 12) is in contact with the third sub-contact region 102.

[0069] The first ohmic contact area 4 and the second ohmic contact area 10 can achieve the same technical effect as the above embodiment by adopting the above design.

[0070] In some embodiments, as shown in FIG4, the first ohmic contact region 4 and the second ohmic contact region 10 may not employ a partitioned design, and the entire region may be a heavily doped region with a high doping concentration. In this case, the first ohmic contact region 4 or the second ohmic contact region 10 can be formed in a single doping process during the fabrication of the avalanche photodiode 1, thereby simplifying the fabrication process of the avalanche photodiode 1 and reducing the fabrication difficulty and cost.

[0071] In the avalanche photodiode 1 provided in this embodiment, the intermediate intrinsic region 5 is a spacing region between the doped regions in the first semiconductor layer 2. By setting the intermediate intrinsic region 5, the positional accuracy requirements of the doped regions can be relaxed, thereby reducing the fabrication difficulty of the avalanche photodiode 1. In addition, by setting the intermediate intrinsic region 5, the proportion of doped regions in the first semiconductor layer 2 can be reduced, which helps to improve the problem of impurity elements doped in the first semiconductor layer 2 affecting the absorption efficiency of the avalanche photodiode 1 for incident light.

[0072] In some embodiments, the intermediate intrinsic region 5 can be omitted. In this case, the end of the first charge region 6 near the first ohmic contact region 4 along the second direction Y can directly contact the first ohmic contact region 4.

[0073] Please continue referring to Figures 1 and 2. The avalanche photodiode 1 also includes a second semiconductor layer 3, which is used to absorb incident light to generate photogenerated carriers (hereinafter referred to as carriers), and is therefore often referred to as an absorption layer. The semiconductor material in the second semiconductor layer 3 includes germanium (Ge).

[0074] The first semiconductor layer 2 and the second semiconductor layer 3 are stacked in the third direction Z; that is, the second semiconductor layer 3 is disposed on one side of the first semiconductor layer 2 along the third direction Z, for example, on the top side of the first semiconductor layer 2 shown in Figures 1 and 2. The first semiconductor layer 2 and the second semiconductor layer 3 can be in direct contact or connected through an intermediate layer (e.g., a buffer layer, a gradient layer). The second semiconductor layer 3 can cover a portion of the first charge region 6 in the first semiconductor layer 2, and a portion or all of the intermediate intrinsic region 5. Here, "covering" can be understood as the orthographic projection relationship of the second semiconductor layer 3, the intermediate intrinsic region 5, and the first charge region 6 in a reference plane perpendicular to the third direction Z; where M covers N means that in the orthographic projection of the reference plane, the orthographic projection of M covers the orthographic projection of N; in this case, M and N do not necessarily need to be in contact.

[0075] Referring again to Figure 2, in this embodiment, in the second direction Y, the end of the second semiconductor layer 3 near the first ohmic contact region 4 is flush with the end of the intermediate intrinsic region 5 near the first ohmic contact region 4; a portion of the first charge region 6 is near the second ohmic contact region 10 relative to the second semiconductor layer 3, that is, on the side near the second ohmic contact region 10, a portion of the first charge region 6 extends beyond the coverage area of ​​the second semiconductor layer 3. This portion is referred to herein as the first extended portion, which can control the distance between the light absorption region (second semiconductor layer 3) and the avalanche multiplication region (e.g., the first multiplication region 7) during photoelectric conversion.

[0076] In embodiments without the intermediate intrinsic region 5, in the second direction Y, the end of the first charge region 6 near the first ohmic contact region 4 may be flush with the end of the second semiconductor layer 3 near the first ohmic contact region 4; or it may be closer to the first ohmic contact region 4 than the end of the second semiconductor layer 3 near the first ohmic contact region 4.

[0077] Please continue referring to Figures 1 to 4. The first semiconductor layer 2 has ridge waveguide grooves 22 on both sides of the second semiconductor layer 3 along the second direction Y. The two ridge waveguide grooves 22 cause the first semiconductor layer 2 to form a ridge-shaped waveguide structure extending along the first direction X. The second semiconductor layer 3 is disposed on top of the ridge protrusion 21 in this ridge-shaped waveguide structure. This design can limit the propagation area of ​​incident light in the first semiconductor layer 2, concentrating the propagation area near the ridge protrusion 21. This facilitates the efficient guidance of incident light to the second semiconductor layer 3 located on one side of the device portion 220, improving the absorption efficiency of the avalanche photodiode 1 for incident light.

[0078] The avalanche photodiode 1 also includes a first electrode 11 and a second electrode 12. The first electrode 11 is in contact with a first ohmic contact region 4, and the second electrode 12 is in contact with a second ohmic contact region 10. The first electrode 11 and the second electrode 12 enable the application of a bias voltage to the avalanche photodiode 1 and the extraction of the electrical signal generated during the photoelectric conversion process. The first electrode 11 and the second electrode 12 can be made of metal materials such as copper (Cu), aluminum (Al), and tungsten (W).

[0079] The working principle of the avalanche photodiode 1 provided in this application embodiment is explained exemplarily as follows:

[0080] During operation, a bias voltage is applied through the first electrode 11 and the second electrode 12, and the first charge region 6 and the second charge region 8 are used to control the electric field distribution in the second semiconductor layer 3, the first multiplication region 7 and the second multiplication region 9.

[0081] Incident light shines onto the first semiconductor layer 2, and the waveguide portion 210 in the first semiconductor layer 2 guides the incident light to propagate along the first direction X to the location of the device portion 220. The second semiconductor layer 3 (absorption layer) located on top of the device portion 220 absorbs the incident light and generates photogenerated carriers (which can be simply referred to as carriers). Under the action of an electric field, the carriers are transported through the first charge region 6 to the first multiplication region 7, where the first avalanche multiplication occurs, i.e., the number of carriers increases. The increased number of carriers in the first multiplication region 7 are transported through the second charge region 8 to the second multiplication region 9 under the action of an electric field, where the second avalanche multiplication occurs, i.e., the number of carriers increases again. The carriers after the two avalanche multiplications are transported to the second ohmic contact region 10. The aforementioned movement of charge carriers can generate an electrical signal between the first ohmic contact region 4 and the second ohmic contact region 10. This electrical signal can be read out through the first electrode 11 and the second electrode 12, thereby converting the incident light into a corresponding electrical signal and achieving the purpose of photoelectric conversion.

[0082] In the aforementioned operation of the avalanche photodiode 1, the charge carriers generated by the second semiconductor layer 3 (absorption layer) include electrons and holes. However, the multiplication gain of the multiplication material (such as the material in the first multiplication region 7 and the second multiplication region 9) differs for different charge carriers (electrons or holes), resulting in random fluctuations in the current after avalanche multiplication. This random fluctuation introduces additional noise, known as multiplication noise or excess noise. Excess noise affects the signal-to-noise ratio (SNR), thus affecting the sensitivity of the avalanche photodiode 1. Therefore, materials with a relatively small electron-to-hole ionization ratio are typically chosen as the multiplication material. The electron-to-hole ionization ratio refers to the ratio of the smaller of the electron ionization rate and the larger of the hole ionization rate, usually represented by the k-value. When a material with a small k-value is used as the multiplication material, avalanche multiplication primarily targets one type of charge carrier (electron or hole), thereby reducing excess noise in the device.

[0083] In this embodiment, the material of the first multiplication region 7 and the second multiplication region 9 is silicon, and the k value of silicon can be as low as 0.02.

[0084] In addition, the equivalent k-value is usually used to characterize the overall multiplication characteristics of the avalanche photodiode 1, where the equivalent k-value is the ratio of electron-hole ionization rate obtained by theoretical calculation of the device gain process.

[0085] As can be seen from the above description, the avalanche photodiode 1 provided in this application embodiment is a waveguide avalanche photodiode 1, and adopts a laterally separated absorption charge multiplication (SACM) design. In this case, the direction of incident light on the avalanche photodiode 1 is parallel to the first direction X, and the direction of carrier movement in the avalanche photodiode 1 is parallel to the second direction Y. The first direction X and the second direction Y are perpendicular. That is to say, the light absorption direction is orthogonal to the carrier movement direction, thereby decoupling the responsivity and bandwidth issues, which is beneficial to achieving high responsivity and high bandwidth at the same time.

[0086] In the avalanche photodiode 1 provided in this embodiment, a combination of two pairs of charge regions and multiplication regions is included between the first ohmic contact region 4 and the second ohmic contact region 10; specifically, a first charge region 6, a first multiplication region 7, a second charge region 8, and a second multiplication region 9. This design, on the one hand, utilizes the combination of the two pairs of charge regions and multiplication regions to improve the performance of the avalanche photodiode 1; on the other hand, it utilizes the first charge region 6 and the second charge region 8 to achieve precise control of the electric field in the avalanche photodiode 1, thereby facilitating the generation of a relatively more tilted electric field distribution, concentrating the avalanche multiplication region closer to the second ohmic contact region 10, thus helping to reduce the excess noise of the avalanche photodiode 1.

[0087] Furthermore, the first charge region 6 is designed to extend beyond the second semiconductor layer 3, which increases the distance between the light absorption region (second semiconductor layer 3) and the high-electric-field avalanche multiplication region (e.g., the first multiplication region 7) during photoelectric conversion. In this case, it is beneficial to reduce the electric field strength in the light absorption region (second semiconductor layer 3), thereby reducing the dark current of the avalanche photodiode 1. Moreover, compared to a single pair of charge regions and multiplication regions, the combination of two pairs of charge regions and multiplication regions, due to the implementation of a tilted electric field distribution, can further increase the distance between the light absorption region (second semiconductor layer) and the high-electric-field avalanche multiplication region (e.g., the second multiplication region), thereby further reducing the dark current of the avalanche photodiode.

[0088] It can be seen that the avalanche photodiode 1 provided in this application embodiment can reduce noise level and dark current while achieving high responsivity and high bandwidth, thereby further improving the performance of the device (e.g., receiving sensitivity).

[0089] Please continue referring to Figure 2. For ease of description, the length of the first extended portion of the first charge region 6 in the second direction Y is referred to as the first length, denoted as Wp1 in Figure 2. The length of the first multiplication region 7 in the second direction Y is referred to as the second length, denoted as Wm1 in Figure 2. The length of the second charge region 8 in the second direction Y is referred to as the third length, denoted as Wp2 in Figure 2. The length of the second multiplication region 9 in the second direction Y is referred to as the fourth length, denoted as Wm2 in Figure 2.

[0090] In some embodiments, the first length Wp1 is from 40 nanometers (nm) to 160 nanometers (nm), such as 50 nm, 100 nm, or 150 nm. Using a first length Wp1 within the above range can avoid the problem of excessively high electric field in the second semiconductor layer 3, which is beneficial for reducing dark current.

[0091] In some embodiments, the third length Wp2 is 40 nm to 160 nm, such as 50 nm, 100 nm, or 150 nm. When a third length Wp2 within the above range is used, a relatively more sloping electric field distribution can be formed in conjunction with the first charge region 6 throughout the multiplication region, thereby helping to reduce the excess noise of the avalanche photodiode 1.

[0092] In some embodiments, the second length Wm1 is 50 nm to 300 nm; the fourth length Wm2 is 50 nm to 300 nm; and the sum of the second length Wm1 and the fourth length Wm2 is less than or equal to 500 nm. For example, the second length Wm1 is 50 nm and the fourth length is 150 nm; the second length Wm1 is 100 nm and the fourth length is 100 nm; the second length Wm1 is 150 nm and the fourth length is 150 nm; the second length Wm1 is 100 nm and the fourth length is 200 nm; the second length Wm1 is 200 nm and the fourth length is 200 nm, etc.

[0093] In avalanche photodiode 1, the longer the total length of the multiplication region in the second direction Y, the larger the multiplication factor and the higher the responsivity; however, this leads to a decrease in bandwidth. When the second length Wm1 and the fourth length Wm2 are selected from the above range, a higher bandwidth can be achieved while meeting the responsivity requirements.

[0094] This application also provides another avalanche photodiode 1, as shown in Figure 5. The difference between this avalanche photodiode 1 and those shown in Figures 2 to 4 is that it does not have a second multiplication region 9. As described above, the second charge region 8 is a P-type doped region, and the second ohmic contact region 10 is an N-type doped region. The direct contact between the second charge region 8 and the second ohmic contact region 10 forms a PN junction. Under the action of an applied electric field, this PN junction forms a narrow depletion region at the contact position between the second charge region 8 and the second ohmic contact region 10. The number of electrons and holes in this depletion region is equal, which can be considered equivalent to the intrinsic region. Therefore, this depletion region can be used as a multiplication region, equivalent to the second multiplication region 9 in the above embodiment. Using the above design, compared to setting a separate multiplication region, the structure can be simplified and the overall size of the device reduced. With the same overall device size, it is beneficial to increase the size of the first charge region, the first multiplication region, and the second charge region in the second direction, thereby reducing the fabrication difficulty of the avalanche photodiode and improving device performance.

[0095] The other parts of the avalanche photodiode 1 can be referred to in the description of the avalanche photodiode 1 in Figure 2 above, and will not be repeated here.

[0096] Please continue referring to Figure 5. In some embodiments, the first length Wp1 is 40nm to 160nm, for example, 50nm, 100nm, or 150nm. Using a first length Wp1 within the above range can avoid the problem of excessively high electric field in the second semiconductor layer 3, which is beneficial for reducing dark current.

[0097] In some embodiments, the third length Wp2 is 40 nm to 160 nm, such as 50 nm, 100 nm, or 150 nm. When a third length Wp2 within the above range is used, a relatively more inclined electric field distribution can be formed over a larger area in conjunction with the first charge region 6, which is beneficial for reducing the excess noise of the avalanche photodiode 1.

[0098] In some embodiments, the second length Wm1 is 50nm to 300nm, such as 100nm, 150nm, 200nm, 250nm, or 300nm. Using a second length Wm1 within the above range allows for higher bandwidth while meeting responsiveness requirements.

[0099] To verify the aforementioned advantages of the avalanche photodiode 1 provided in this application embodiment, simulation comparison experiments were conducted between the two avalanche photodiodes 1 with different structures in the above embodiments and the comparative embodiments. For ease of description, the avalanche photodiode 1 shown in Figures 1 and 2 is referred to as the avalanche photodiode 1 in the first embodiment; and the avalanche photodiode 1 shown in Figures 1 and 5 is referred to as the avalanche photodiode 1 in the second embodiment.

[0100] As shown in Figure 6, compared with the avalanche photodiode 1 provided in the first and second embodiments, the difference of the avalanche photodiode 1 provided in the comparative embodiment is that the device portion 220 includes a first ohmic contact region 4, an intermediate intrinsic region 5, a charge region 13, a multiplication region 14, and a second ohmic contact region 10 arranged sequentially along the second direction Y; that is, a design using a single pair of charge regions 13 and multiplication regions 14. The second semiconductor layer 3 covers the intermediate intrinsic region 5 and part of the charge region 13. The charge region 13 has a portion in the second direction Y that is close to the second ohmic contact region 10 relative to the second semiconductor layer 3; this portion is called the second extended portion. The length of this second extended portion in the second direction Y is the fifth length, denoted as Wp3 in Figure 6. The distance of the multiplication region 14 in the second direction Y is the sixth length, denoted as Wm3 in Figure 6.

[0101] In order to unify the parameter conditions of the avalanche photodiode 1 in the first embodiment, the second embodiment and the comparative embodiment, the first semiconductor layer 2 and the second semiconductor layer 3 in different avalanche photodiodes 1 are kept consistent in shape, size and material properties, and the first ohmic contact region 4, the second ohmic contact region 10 and the intermediate intrinsic region 5 are kept consistent in shape, size and material properties.

[0102] Furthermore, the first charge region 6 in the first embodiment and the second embodiment and the charge region 13 in the comparative embodiment are kept consistent in shape, size and material properties, such as having the same doping concentration; for example, as shown in FIG7, the first length Wp1 of the first charge region 6 in the first embodiment and the second embodiment and the fifth length Wp3 of the charge region 13 in the comparative embodiment are both 50nm.

[0103] For the different designs of the avalanche photodiode 1 in the first embodiment, the second embodiment and the comparative embodiment, it is necessary to control the distance from the second semiconductor layer 3 to the second ohmic contact region 10 along the second direction Y to be basically close, and to control the total length of the multiplication region in the second direction Y to be basically close.

[0104] Specifically, as shown in Figure 5, the fourth length Wm3 in the comparative embodiment is 200 nm. In the first embodiment, the second length Wm1 and the fourth length Wm2 are equal, both being 100 nm; the first length Wp2 and the third length Wp2 are both 50 nm. In this case, the total distance of the multiplication regions (including the first multiplication region 7 and the second multiplication region 9) in the second direction Y is approximately 200 nm; and in the second direction Y, the distance from the second semiconductor layer 3 to the second ohmic contact region 10 is close to that in the comparative embodiment.

[0105] In the second embodiment, the first length Wp2 is 50 nm, the second length Wm1 is 150 nm, and the third length Wp2 is 100 nm. In this case, the length of the multiplication region (including the first multiplication region and the depletion region formed by the second charge region 8 and the second ohmic contact region 10) in the second direction Y is basically close to that of the comparative embodiment. Furthermore, in the second direction Y, the distance from the second semiconductor layer 3 to the second ohmic contact region 10 is the same as that in the first embodiment and the comparative embodiment.

[0106] For the different avalanche photodiodes 1 described above, the dark current values ​​under different responsivity were simulated and tested, and the simulation results are shown in Figure 7. As can be seen from Figure 7, compared with the comparative embodiment, both the first embodiment and the second embodiment can obtain lower dark current values ​​under the same responsivity.

[0107] For the comparative embodiment, the first embodiment, and the second embodiment, the electric field intensity at different locations along the second direction Y from the first charge region 6 to the second ohmic contact region 10 in the avalanche photodiode 1 is extracted to form electric field intensity curves; the electric field intensity curves of the comparative embodiment, the first embodiment, and the second embodiment are shown in Figures 8 to 10, respectively. As can be seen from Figures 8 to 10, compared with the comparative embodiment, both the first embodiment and the second embodiment can achieve a relatively more tilted electric field distribution by controlling the electric field, which is beneficial to reducing the excess noise of the avalanche photodiode 1.

[0108] By combining the electric field intensity curve with the material ionization rate and other parameters, and using a classic dead-zone model for simulation, the relationship between the excess noise factor and the multiplication factor can be obtained. This allows for the deduction of the equivalent k-values ​​of the avalanche photodiode 1 in the comparative embodiment, the first embodiment, and the second embodiment. As shown in Figure 11, the noise is highest in the comparative embodiment, corresponding to an equivalent k-value of approximately 0.1; the equivalent k-value of the first embodiment is approximately 0.07, and the equivalent k-value of the second embodiment is approximately 0.06, representing a reduction of approximately 30% to 40% compared to the comparative embodiment, indicating a significant decrease in noise level.

[0109] This application also provides another avalanche photodiode 1, as shown in Figures 12 and 13. The difference between this avalanche photodiode 1 and the one shown in Figures 1 and 2 is that the first semiconductor layer 2 does not have ridge waveguide grooves 22 on both sides of the second semiconductor layer 3. In other words, the first semiconductor layer 2 is a layered structure with uniform thickness, forming a band waveguide; this differs from the ridge waveguide structure in the avalanche photodiode 1 shown in Figures 1 and 2. This design achieves high responsivity, high bandwidth, and low noise level and dark current; it also reduces the requirements for the fabrication process and equipment of the avalanche photodiode 1.

[0110] This application also provides another avalanche photodiode 1, as shown in Figures 12 and 14. The difference between this avalanche photodiode 1 and those shown in Figures 1 and 5 is that the first semiconductor layer 2 does not have ridge waveguide grooves 22 on both sides of the second semiconductor layer 3. In other words, the first semiconductor layer 2 is a layered structure with uniform thickness, and the waveguide formed is a band waveguide. This differs from the ridge waveguide structure in the avalanche photodiode 1 shown in Figures 1 and 5. This design achieves high responsivity, high bandwidth, and low noise level and dark current; it also reduces the requirements for the fabrication process and equipment of the avalanche photodiode 1.

[0111] This application also provides another avalanche photodiode 1, which differs from the avalanche photodiode 1 in that the device portion 220 further includes at least one pair of third charge regions and third multiplication regions disposed between the first multiplication region 7 and the second charge region 8; the third charge region is a P-type doped region, and the third multiplication region is an intrinsic region. In the first direction X, the third charge region and the third multiplication region are in contact, with the third charge region closer to the first ohmic contact region 4 relative to the third multiplication region. This design allows for more precise control of the electric field by setting more combinations of charge regions and multiplication regions, which is beneficial for further improving the performance of the avalanche photodiode 1.

[0112] The doping concentrations of the third charge region, the first charge region 6, and the second charge region 8 can be equal or unequal. In this embodiment, the third charge region, the first charge region 6, and the second charge region 8 are designed with equal doping concentrations. This allows the first charge region 6, the second charge region 8, and the third charge region to be formed in a single doping process during the fabrication of the avalanche photodiode 1, thereby simplifying the fabrication process of the avalanche photodiode 1 and reducing its fabrication difficulty and cost.

[0113] In the above embodiments, the material of the first semiconductor layer 2 is silicon, and the material of the second semiconductor layer 3 is germanium; however, the avalanche photodiode 1 provided in this application is not limited to this. The avalanche photodiode 1 provided in this application can also be fabricated using a III-V group material system. For example, in some embodiments, the semiconductor material in the first semiconductor layer 2 may include at least one of indium phosphide (InP), indium aluminum arsenide (InAlAs), or gallium arsenide (GaAs); the material of the multiplication region (e.g., the first multiplication region 7 and the second multiplication region 9) may include at least one of indium phosphide (InP), indium gallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), and indium gallium arsenide phosphide (InGaAsP); and the semiconductor material of the second semiconductor layer 3 may include at least one of indium gallium arsenide (InGaAs), indium aluminum arsenide (InAlAs), and gallium arsenide (GaAs).

[0114] This application also provides a photoelectric detection chip, as shown in FIG15. The photoelectric detection chip 100 includes a package structure 110 and the avalanche photodiode 1 described in the above embodiment. The package structure 110 is used to encapsulate the avalanche photodiode 1 and has an optical port 120 and a pad 130. The optical port 120 is directly opposite to the light-incoming end face of the waveguide portion 210 in the avalanche photodiode 1, allowing external light to enter the avalanche photodiode 1 through the optical port 120. The pad 130 is used to bring out the first electrode 11 and the second electrode 12 in the avalanche photodiode 1.

[0115] This application also provides an optical communication device, as shown in FIG16. The optical communication device 200 includes the photodetector chip 100 and the signal processing circuit 201 described in the above embodiments. The signal processing circuit 201 is electrically connected to the pads 130 in the photodetector chip 100 and is used to process the electrical signals generated by the photodetector chip 100. The optical communication device 200 can be a receiver optical subassembly (ROSA), a bidirectional optical subassembly, an optical module, or an active optical module, etc., capable of detecting optical signals and forming electrical signals in an optical communication scenario.

[0116] The optical communication device 200 provided in this application embodiment can be applied in Passive Optical Network (PON). PON network is a network architecture that adopts a point-to-multipoint topology and is a commonly used technology for fixed network access. It is widely used in FTTH (Fiber To The Home) and FTTR (Fiber To The Room) scenarios.

[0117] For example, as shown in Figure 17, the PON network 1000 includes an optical line terminal (OLT) 1100, an optical distribution network (ODN) 1300, and multiple optical network units (ONUs) 1200. The OLT 1100 is a network-side device used to connect the upper-layer network and the user-side devices (multiple ONUs 1200). It is responsible for broadcasting downlink data to each ONU 1200, receiving uplink data from the ONUs 1200, and performing functions such as uplink bandwidth allocation and multiple access control.

[0118] The optical network unit 1200 is a user-side device located close to the user, and the user's communication equipment can be connected to the optical network unit 1200. The optical network unit 1200 is responsible for receiving and processing downlink data sent by the optical line terminal 1100, and sending uplink data to the optical line terminal 1100; it provides network services to the user. For example, the optical network unit 1200 can be an optical modem (optical modem).

[0119] The PON network 1000 includes multiple optical network units 1200, which are distributed in different locations to provide network services to users in different locations. For example, the multiple optical network units 1200 can be distributed in various rooms of a user's home. As another example, the multiple optical network units 1200 can be distributed in various factory buildings within a business park.

[0120] 1300 is used to connect optical line terminal 1100 and multiple optical network units 1200, providing an optical channel for the optical line terminal 1100 and the multiple optical network units 1200. 1300 includes a passive optical splitter 1310, a trunk optical fiber 1320, and multiple branch optical fibers 1330. One end of the trunk optical fiber 1320 is connected to the passive optical splitter 1310, and the other end is connected to the optical line terminal 1100. The multiple branch optical fibers 1330 correspond one-to-one with the multiple optical network units 1200. One end of each branch optical fiber 1330 is connected to the passive optical splitter 1310, and the other end is connected to the corresponding optical network unit 1200.

[0121] For the aforementioned PON network 1000, the downlink data transmission method is as follows: downlink data sent by the optical line terminal 1100 is broadcast and transmitted to the optical network unit 1200 via the backbone fiber 1320, passive optical splitter 1310, and branch fiber 1330 in 1300. The uplink data transmission method is as follows: the optical network unit 1200 sends uplink data to 1300, and this uplink data is transmitted to the optical line terminal 1100 via the branch fiber 1330, passive optical splitter 1310, and backbone fiber 1320 in 1300; furthermore, the uplink data sent by each optical network unit 1200 will only reach the optical line terminal 1100 and will not reach other optical network units 1200.

[0122] The PON network 1000 is a single-fiber bidirectional system. To avoid data conflicts between uplink and downlink data and improve network transmission efficiency, different wavelengths are used for uplink and downlink, and wavelength division multiplexing (WDM) technology is employed for transmission within the same optical fiber. For example, the uplink and downlink wavelengths can be 1310nm and 1490nm, respectively; or 1270nm and 1550nm, respectively; or 1286nm and 1342nm, respectively.

[0123] The optical communication device 200 provided in this application embodiment can be the optical line terminal 1100 and optical network unit 1200 in the PON network 1000 described above, or it can be applied to the optical line terminal 1100 and optical network unit 1200.

[0124] The technical effects achievable by the photoelectric detection chip 100 and optical communication device 200 provided in this application embodiment are the same as those achievable by the avalanche photodiode 1 in any of the above embodiments, and will not be repeated here.

[0125] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An avalanche photodiode, characterized in that, The avalanche photodiode includes: A first semiconductor layer includes a waveguide portion and a device portion arranged in a first direction; the waveguide portion is used to guide incident light to the device portion; in a second direction perpendicular to the first direction, the device portion includes a first ohmic contact region, a first charge region, a first multiplication region, a second charge region, and a second ohmic contact region arranged sequentially; the first charge region, the second charge region, and the first ohmic contact region are all P-type doped regions, the second ohmic contact region is an N-type doped region, and the first multiplication region is an intrinsic region; A second semiconductor layer is used to absorb incident light and generate photogenerated carriers; the second semiconductor layer and the first semiconductor layer are stacked in a third direction and cover a portion of the first charge region; wherein the first direction, the second direction, and the third direction are mutually perpendicular; in the second direction, a portion of the first charge region is closer to the second ohmic contact region relative to the second semiconductor layer; and A first electrode and a second electrode, wherein the first electrode is in contact with the first ohmic contact area and the second electrode is in contact with the second ohmic contact area.

2. The avalanche photodiode according to claim 1, characterized in that, The device portion also includes a second multiplication region located between the second charge region and the second ohmic contact region, the second multiplication region being an intrinsic region.

3. The avalanche photodiode according to claim 1 or 2, characterized in that, The first charge region and the second charge region have the same doping concentration.

4. The avalanche photodiode according to any one of claims 1 to 3, characterized in that, Between the first multiplication region and the second charge region, the device portion further includes at least one pair of third charge regions and third multiplication regions; the third charge region is a P-type doped region, and the third multiplication region is an intrinsic region; In the second direction, the third charge region and the third multiplication region are in contact, and the first charge region is closer to the first ohmic contact region relative to the third multiplication region.

5. The avalanche photodiode according to claim 4, characterized in that, The doping concentrations of the third charge region, the first charge region, and the second charge region are equal.

6. The avalanche photodiode according to any one of claims 1 to 5, characterized in that, The first semiconductor layer is a ridge waveguide structure extending along the first direction, and the second semiconductor layer is disposed on top of the ridge protrusion in the ridge waveguide structure.

7. The avalanche photodiode according to any one of claims 1 to 6, characterized in that, The device portion also includes an intermediate intrinsic region located between the first charge region and the first ohmic contact region, and the second semiconductor layer is in contact with the intermediate intrinsic region.

8. The avalanche photodiode according to any one of claims 1 to 7, characterized in that, The semiconductor material in the first semiconductor layer includes silicon, and the semiconductor material in the second semiconductor layer includes germanium.

9. The avalanche photodiode according to any one of claims 1 to 7, characterized in that, The semiconductor material in the first semiconductor layer includes at least one of indium phosphide, indium aluminum arsenide, and gallium arsenide; The material of the first multiplication region includes at least one of indium phosphide, indium gallium arsenide, indium aluminum arsenide, and indium gallium arsenide phosphide; The semiconductor material of the second semiconductor layer includes at least one of indium gallium arsenide, indium aluminum arsenide, and gallium arsenide.

10. The avalanche photodiode according to any one of claims 1 to 9, characterized in that, In the second direction, the portion of the first charge region that is closer to the second ohmic contact region relative to the second semiconductor layer is a first extended portion, and the length of the first extended portion in the second direction is a first length. The length of the second charge region in the second direction is the second length; Wherein, the first length is 40 nanometers to 160 nanometers; and / or, the second length is 40 nanometers to 160 nanometers.

11. The avalanche photodiode according to any one of claims 1 to 10, characterized in that, The length of the first multiplication region in the second direction is 50 nanometers to 300 nanometers.

12. The avalanche photodiode according to claim 2, characterized in that, The length of the first multiplication region in the second direction is 50 nanometers to 300 nanometers, and the length of the second multiplication region in the second direction is 50 nanometers to 300 nanometers; The total length of the first and second multiplication regions in the second direction is less than or equal to 500 nanometers.

13. The avalanche photodiode according to any one of claims 1 to 12, characterized in that, The first ohmic contact region includes a first sub-contact region and a second sub-contact region that are in contact with each other; the doping concentration of the first sub-contact region is higher than the doping concentration of the second sub-contact region, and the doping concentration of the second sub-contact region is higher than the doping concentration of the first charge region and the second charge region; the first electrode is in contact with the first sub-contact region. And / or, the first ohmic contact region includes a third sub-contact region and a fourth sub-contact region in contact with each other; the doping concentration of the third sub-contact region is higher than that of the fourth sub-contact region, and the doping concentration of the fourth sub-contact region is higher than that of the first charge region and the second charge region; the second electrode is in contact with the third sub-contact region.

14. A photoelectric detection chip, characterized in that, The photoelectric detection chip includes: Avalanche photodiode as claimed in any one of claims 1 to 13; and The packaging structure is used to encapsulate the avalanche photodiode and has an optical port and a pad; the optical port is used to expose the light-incoming end face of the waveguide portion in the avalanche photodiode, and the pad is used to lead out the first electrode and the second electrode in the avalanche photodiode.

15. An optical communication device, characterized in that, The optical communication equipment includes: The photoelectric detection chip as described in claim 14; and A signal processing circuit is electrically connected to the pads in the photoelectric detection chip.

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