Waveguide integrated avalanche detector

Abstract

The invention discloses a waveguide integrated avalanche detector, belongs to the technical field of optical interconnection, and mainly aims to improve optical coupling efficiency and response speed. According to the main technical scheme, the waveguide integrated avalanche detector comprises an active layer, a first waveguide structure and a second waveguide structure; p-type impurities and N-type impurities which are distributed in a gradient manner are injected into the active layer so as to form an APD structure with an avalanche multiplication effect; the first waveguide structure and the second waveguide structure are located above the active layer, and the first waveguide structure and the second waveguide structure are coupled in an evanescent mode; wherein the first waveguide structure is used for receiving an optical signal and coupling optical energy to the second waveguide structure through an evanescent field; the second waveguide structure and the APD structure form a vertical overlapping region, and the second waveguide structure and the APD structure are evanescently coupled to transmit light energy to the APD structure to excite the APD structure to generate a photoelectric effect.

Description

Technical Field

[0001] This application belongs to the field of optical interconnect technology, specifically relating to a waveguide integrated avalanche detector. Background Technology

[0002] In cloud computing, data centers, and high-speed interconnect systems, the requirements for transmission capacity, power consumption, and integration density in short-distance data communication are becoming increasingly stringent. Optical interconnect technology, with its advantages of large transmission bandwidth, low power consumption, low latency, strong anti-interference capability, and high-speed, crosstalk-free parallel transmission, is gradually becoming a core solution to replace electrical interconnect. However, achieving efficient optical signal detection and integration remains a key challenge restricting the further development of optical interconnect technology.

[0003] Currently, photodetectors used for optical interconnects face numerous technical bottlenecks in practical applications. On one hand, traditional photodetectors often use a vertical incidence method to receive optical signals. This method is not only difficult to integrate with planar waveguide systems, requiring additional optical components such as lenses and gratings for optical coupling, leading to complex system structures, increased size, and higher power consumption, but also its optical coupling efficiency is highly dependent on optical alignment accuracy, making it difficult to meet the demands of large-scale integration. On the other hand, even with waveguide integration, existing waveguide-detector coupling structures suffer from low optical energy transfer efficiency. For example, direct coupling between the waveguide and detector results in significant differences in their mode field distributions and a limited overlap between the optical field and the detector's active layer, causing substantial optical energy loss during transmission. This fails to effectively excite the detector to generate the photoelectric effect, leading to insufficient detector responsivity and low detection sensitivity. Furthermore, traditional waveguide-integrated detector structures also suffer from slow response speeds, failing to meet the requirements of high-speed data communication for rapid signal processing. Summary of the Invention

[0004] In view of this, this application provides a waveguide-integrated avalanche detector, the main purpose of which is to improve optical coupling efficiency and response speed.

[0005] To achieve the above objectives, this application mainly provides the following technical solutions:

[0006] This application provides a waveguide-integrated avalanche detector, comprising:

[0007] An active layer is implanted with gradient-distributed P-type and N-type impurities to form an APD structure with an avalanche multiplication effect.

[0008] A first waveguide structure and a second waveguide structure are located above the active layer, and the first waveguide structure and the second waveguide structure are evanescently coupled; wherein:

[0009] The first waveguide structure is used to receive optical signals and couple optical energy to the second waveguide structure through an evanescent field;

[0010] The second waveguide structure forms a vertically overlapping region with the APD structure, and the second waveguide structure is evanescently coupled to the APD structure to transfer the light energy to the APD structure and excite the APD structure to generate a photoelectric effect.

[0011] Optionally, the first waveguide structure and the second waveguide structure are configured to support only single-mode transmission at a wavelength of 850 nm, and the single mode is a transverse electric mode.

[0012] Optionally, the cross-sectional dimensions of the first waveguide structure are 600 nm wide and 220 nm thick; the cross-sectional dimensions of the second waveguide structure are also 600 nm wide and 220 nm thick.

[0013] Optionally, the first waveguide structure is a strip waveguide, and the second waveguide structure is a ring waveguide, wherein the inner radius of the ring waveguide is 90 to 110 μm.

[0014] Optionally, the lateral coupling distance between the first waveguide structure and the second waveguide structure is 100 to 200 nm, and the coupling length is 2 to 10 μm.

[0015] Optionally, the longitudinal coupling distance between the second waveguide structure and the APD structure is 50 to 200 nm, and the coupling length is 3 to 6 μm.

[0016] Optionally, the cross-sectional shape of the APD structure is rectangular or ridge-shaped.

[0017] Optionally, the waveguide-integrated avalanche detector further includes:

[0018] Substrate; the substrate is located below the active layer and is used to support the overall structure of the waveguide integrated avalanche detector;

[0019] An insulating layer is located between the substrate and the active layer, and the insulating layer is used to isolate the substrate from the active layer.

[0020] Optionally, the insulating layer is made of one or more of the following materials: silicon dioxide, silicon nitride, aluminum oxide, hafnium oxide, and tantalum oxide.

[0021] Optionally, the substrate is made of one or more of the following materials: silicon, germanium, gallium nitride, silicon carbide, mercuric iodide, gallium arsenide, titanium bromide, cadmium telluride, zinc cadmium telluride, cadmium selenide, gallium phosphide, mercuric sulfide, lead iodide, and aluminum antimonide.

[0022] By employing the above technical solution, this application has at least the following beneficial effects:

[0023] The waveguide-integrated avalanche detector provided in the embodiments of this application adopts a planar integration method for the first waveguide structure and the second waveguide structure, which eliminates the need for additional optical components such as lenses, avoids the complexity of optical alignment in the traditional vertical incidence method, reduces system size and power consumption, and is more suitable for large-scale integration, especially for scenarios with high integration density requirements such as cloud computing and data centers.

[0024] The waveguide-integrated avalanche detector provided in the embodiments of this application features a first waveguide structure coupled to a second waveguide structure via evanescent field coupling. The second waveguide structure is also evanescently coupled to an APD structure. Compared to the energy loss caused by mode field distribution differences in traditional direct coupling, evanescent coupling more precisely confines optical energy to the overlapping region of the waveguide structure and the active layer, reducing optical energy loss during transmission and allowing more optical energy to be absorbed by the APD structure. Simultaneously, by directly transferring optical energy through evanescent coupling, the delay caused by the conversion of optical signals through external optical elements in traditional structures is avoided. The transmission path of optical energy in the waveguide structure and active layer is shorter and more direct, which helps to accelerate the conversion speed from optical signals to electrical signals.

[0025] The waveguide-integrated avalanche detector provided in the embodiments of this application has a second waveguide structure that forms a vertically overlapping region with the APD structure. Through evanescent coupling, light energy is directly transferred to the active layer of the APD structure, which expands the overlapping area between the light field and the active layer, so that the light energy can more efficiently excite the APD to generate the photoelectric effect, thereby improving the detector's responsivity and detection sensitivity.

[0026] The waveguide-integrated avalanche detector provided in the embodiments of this application has an APD structure formed by gradient-distributed P-type and N-type impurities in the active layer. The avalanche multiplication effect can be used to amplify the electrical signal of photogenerated carriers. Combined with efficient optical energy transfer, the detector can generate a strong electrical signal output when receiving weak optical signals, thereby further improving sensitivity. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a waveguide-integrated avalanche detector according to an optional embodiment of this application;

[0028] Figure 2 This is a cross-sectional view of a waveguide-integrated avalanche detector according to an alternative embodiment of this application.

[0029] The reference numerals in the attached figures are as follows:

[0030] 1. Active layer; 2. First waveguide structure; 3. Second waveguide structure; 4. APD structure. Detailed Implementation

[0031] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0033] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0034] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0035] See Figure 1 and Figure 2 As shown, according to an embodiment of this application, a waveguide integrated avalanche detector is provided, including an active layer 1, a first waveguide structure 2, and a second waveguide structure 3; the active layer 1 is injected with gradient-distributed P-type and N-type impurities to form an APD structure 4 with an avalanche multiplication effect; the first waveguide structure 2 and the second waveguide structure 3 are located above the active layer 1, and the first waveguide structure 2 and the second waveguide structure 3 are evanescently coupled; wherein: the first waveguide structure 2 is used to receive optical signals and couple optical energy to the second waveguide structure 3 through an evanescent field; the second waveguide structure 3 and the APD structure 4 form a vertically overlapping region, and the second waveguide structure 3 and the APD structure 4 are evanescently coupled to transfer optical energy to the APD structure 4 and excite the APD structure 4 to generate a photoelectric effect.

[0036] The waveguide-integrated avalanche detector provided in this embodiment adopts a planar integration method for the first waveguide structure 2 and the second waveguide structure 3, which eliminates the need for additional optical components such as lenses. This avoids the complexity of optical alignment in the traditional vertical incidence method, reduces system size and power consumption, and is more suitable for large-scale integration. It is especially suitable for scenarios with high integration density requirements, such as cloud computing and data centers, such as lidar detection, medical diagnosis, large scientific facilities, and aerospace. This application does not limit this application.

[0037] The waveguide-integrated avalanche detector provided in this embodiment uses evanescent coupling between the first waveguide structure 2 and the second waveguide structure 3. The second waveguide structure 3 is also evanescently coupled to the APD structure 4. Compared to the energy loss caused by mode field distribution differences in traditional direct coupling, evanescent coupling can more accurately confine optical energy to the overlapping area of ​​the waveguide structure and the active layer 1, reducing optical energy loss during transmission and allowing more optical energy to be absorbed by the APD structure 4. At the same time, by directly transmitting optical energy through evanescent coupling, the delay caused by the conversion of optical signals through external optical elements in traditional structures is avoided. The transmission path of optical energy in the waveguide structure and the active layer 1 is shorter and more direct, which helps to accelerate the conversion speed of optical signals to electrical signals.

[0038] The waveguide-integrated avalanche detector provided in this embodiment forms a vertically overlapping region between the second waveguide structure 3 and the APD structure 4. Through evanescent coupling, the light energy is directly transferred to the active layer 1 of the APD structure 4, which expands the overlapping area between the light field and the active layer 1, so that the light energy can more efficiently excite the APD to generate the photoelectric effect, thereby improving the detector's responsivity and detection sensitivity.

[0039] The waveguide-integrated avalanche detector provided in this embodiment has an APD structure 4 formed by gradient-distributed P-type and N-type impurities in the active layer 1. The avalanche multiplication effect can be used to amplify the electrical signal of photogenerated carriers. Combined with efficient optical energy transfer, the detector can generate a strong electrical signal output when receiving weak optical signals, thereby further improving sensitivity.

[0040] Among them, APD structure 4 is an avalanche photodiode structure.

[0041] In this structure, the active layer 1 is formed by gradient injection of P-type impurities (such as boron) and N-type impurities (such as phosphorus) to create a gradient-doped structure along the horizontal direction (parallel to the waveguide propagation direction). Specifically, it includes a heavily doped N-type region, a lightly doped N-type region, an intrinsic region, a lightly doped P-type region, and a heavily doped P-type region. This gradient doping creates a continuous electric field gradient, driving the directional transport of photogenerated carriers. Simultaneously, the electric field distribution is modulated by the gradual change in impurity concentration, satisfying the high electric field conditions required for the avalanche multiplication effect.

[0042] In this design, both the first waveguide structure 2 and the second waveguide structure 3 are located above the active layer 1 and are arranged in a planar integration manner. In practical applications, after receiving an optical signal, the first waveguide structure 2 couples the energy to the second waveguide structure 3 through an evanescent field, rather than through traditional direct mode field overlap, thus reducing energy loss caused by mode field mismatch. The second waveguide structure 3 forms a vertical overlap region with the APD structure 4 of the active layer 1, and similarly transfers optical energy to the intrinsic region of the active layer 1 through an evanescent field, ensuring high overlap efficiency between the optical field and the active layer 1.

[0043] Understandably, the first waveguide, acting as the input channel, confines the optical signal within the first waveguide structure 2 for transmission. It is coupled to the second waveguide structure 3 via an evanescent field, ensuring that the optical field is primarily distributed in the evanescent region near the waveguide structure surface during energy transfer. This avoids energy leakage caused by differences in mode field distribution during direct coupling. The vertical overlap design of the second waveguide structure 3 with the active layer 1 allows the evanescent region of the optical field to directly cover the intrinsic region, maximizing optical absorption efficiency. After absorbing light energy, the intrinsic region excites electron-hole pairs. The gradient electric field drives electrons to move towards the heavily doped N-type region, and holes to move towards the heavily doped P-type region. In high-electric-field regions (such as the boundary between the lightly doped N-type region and the intrinsic region), photogenerated carriers are accelerated, colliding with the lattice to generate new carriers, forming an avalanche effect that amplifies the electrical signal. For example, one photogenerated carrier may generate tens to hundreds of carriers through a multiplication effect, significantly improving the detector's sensitivity.

[0044] In some possible embodiments disclosed in this application, the first waveguide structure 2 and the second waveguide structure 3 are configured to support only single-mode transmission at a wavelength of 850nm, and the single mode is a transverse electric mode.

[0045] In this embodiment, single-mode transmission eliminates the mode dispersion problem, ensuring consistent transmission delay of the optical signal within the waveguide structure. This results in a more stable and precise response of the detector to the optical signal. Simultaneously, single-mode transmission makes the optical field distribution of the detector more consistent across different locations and operating conditions, avoiding performance fluctuations caused by mode competition in multi-mode transmission. This is beneficial for improving the integration consistency and reliability of the detector array.

[0046] Single-mode transmission means that the optical field propagates in only one mode in the waveguide structure, which can avoid interference loss between different modes in multimode transmission.

[0047] Since the first waveguide structure 2 and the second waveguide structure 3, and the second waveguide structure 3 and the active layer 1 are all coupled through evanescent field, single-mode transmission can make the optical field distribution more uniform and stable, and the mode field matching degree with the adjacent waveguide structure or the active layer 1 is higher, thereby reducing leakage in the energy transfer process and improving coupling efficiency.

[0048] In this mode, the electric field direction is perpendicular to the waveguide transmission plane (lateral), and its optical field is mainly concentrated in the evanescent region near the waveguide core layer. This allows the optical field to more accurately confine the energy to the overlapping region when coupled with the second waveguide structure 3 or the active layer 1, thereby further reducing transmission loss.

[0049] The 850nm wavelength is commonly used in short-distance optical communication (such as high-speed interconnection in data centers), VCSEL (vertical-cavity surface-emitting laser) light source systems, and lidar. The single-mode transmission design at this wavelength allows the detector to be directly compatible with existing 850nm light sources and fiber optic systems without the need for additional mode conversion components, simplifying system integration and reducing costs.

[0050] In the above embodiments, the cross-sectional dimensions of the first waveguide structure 2 are 600 nm wide and 220 nm thick; the cross-sectional dimensions of the second waveguide structure 3 are also 600 nm wide and 220 nm thick.

[0051] In this design, the cross-section of the first waveguide structure 2 is perpendicular to the plane of the first waveguide structure 2, and the cross-section of the second waveguide structure 3 is perpendicular to the plane of the second waveguide structure 3. Here, when the cross-sectional dimensions of the first waveguide structure 2 are 600 nm wide and 220 nm thick, and the cross-sectional dimensions of the second waveguide structure 3 are both 600 nm wide and 220 nm thick, the single-mode transmission condition is met, and this is the optimal parameter combination for achieving efficient optical signal transmission, coupling, and detection.

[0052] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 1 As shown, the first waveguide structure 2 is a strip waveguide, and the second waveguide structure 3 is a ring waveguide with an inner radius of 90 to 110 μm.

[0053] In this embodiment, the second waveguide structure 3 is a ring waveguide, which allows light to propagate cyclically within a closed path, extending the interaction time between the light and the APD structure 4 and improving the absorption efficiency of weak light signals. Simultaneously, the ring waveguide can form a resonant cavity, enhancing the light intensity within the cavity and amplifying the photoelectric conversion efficiency.

[0054] The strip waveguide has a rectangular cross-section and consists of a core layer (high refractive index material) and a cladding layer (low refractive index material). The optical signal is confined to the core layer and transmitted through the refractive index difference between the core layer and the cladding layer.

[0055] The ring waveguide is a closed loop, and a resonant cavity structure is formed by using a curved waveguide. Light is transmitted in a loop through the ring via total internal reflection.

[0056] Understandably, the bending radius (inner radius) of a ring waveguide directly affects the bending loss during optical transmission. An inner diameter that is too small (e.g., less than 90 μm) will cause energy attenuation at the bend due to increased radiation loss; an inner diameter that is too large (e.g., greater than 110 μm) will increase the chip area, which is detrimental to integration. In this embodiment, the inner radius of the ring waveguide is preferably 100 μm, which can control the bending loss at a low level and optimize the coupling efficiency.

[0057] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 1 and Figure 2 As shown, the lateral coupling distance between the first waveguide structure 2 and the second waveguide structure 3 is 100 to 200 nm, and the coupling length is 2 to 10 μm.

[0058] In this context, the lateral coupling distance between the first waveguide structure 2 and the second waveguide structure 3 refers to the horizontal spacing between them. A lateral coupling distance of 100 to 200 nm allows the evanescent field of the first waveguide structure 2 to fully overlap with that of the second waveguide structure 3, ensuring efficient energy transfer through the evanescent field and reducing coupling efficiency loss due to excessive distance, thus avoiding energy transmission losses. It is understood that if the coupling distance is too small (e.g., less than 100 nm), crosstalk between the waveguide structures may increase, and the requirements for process precision may be too high, increasing manufacturing difficulty; if the coupling distance is too large (e.g., greater than 200 nm), the evanescent field coupling efficiency will be significantly reduced. In this embodiment, the lateral coupling distance between the first waveguide structure 2 and the second waveguide structure 3 is preferably 150 nm, balancing process feasibility and structural compactness, facilitating large-scale integration.

[0059] The coupling length between the first waveguide structure 2 and the second waveguide structure 3 refers to the overlap length between them in the optical transmission direction, i.e., the effective range of energy transfer between them through the evanescent field. Here, the lateral coupling length between the first waveguide structure 2 and the second waveguide structure 3 is preferably 6 μm. This reduces the transmission path of the optical signal in the coupling region, lowers transmission delay, and allows the optical signal to be transmitted from the first waveguide structure 2 to the second waveguide structure 3 more quickly, thus improving the detector's response speed and timing accuracy.

[0060] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 1 and Figure 2 As shown, the longitudinal coupling distance between the second waveguide structure 3 and the APD structure 4 is 50 to 200 nm, and the coupling length is 3 to 6 μm.

[0061] The longitudinal coupling distance between the second waveguide structure 3 and the APD structure 4 refers to the vertical spacing between them. A longitudinal coupling distance of 50 to 200 nm allows the evanescent field of the second waveguide structure 3 to fully overlap with the active layer 1 of the APD structure 4, ensuring efficient transmission of optical energy to the active layer 1 via the evanescent field. This reduces the decrease in coupling efficiency caused by excessive distance and prevents excessive energy loss during transmission. Understandably, if the coupling distance is too small (e.g., less than 50 nm), it may lead to process compatibility issues between the waveguide structure and the active layer 1, increasing manufacturing difficulty; if the coupling distance is too large (e.g., greater than 200 nm), it will significantly reduce the evanescent field coupling efficiency, affecting the transmission of optical energy to the APD structure 4.

[0062] The coupling length between the second waveguide structure 3 and the APD structure 4 refers to the overlap length between them in the optical transmission direction, i.e., the effective range of energy transfer between them via the evanescent field. Here, a coupling length of 3 to 6 μm ensures sufficient overlap between the optical field and the active layer 1 while reducing the optical signal's transmission path in the coupling region, lowering transmission delay, and enabling the optical energy to more quickly and directly excite the APD structure 4 to generate the photoelectric effect. This helps improve the detector's response speed and timing accuracy to the optical signal. It is understandable that if the coupling length is too short (e.g., less than 3 μm), the overlap area between the optical field and the active layer 1 is insufficient, leading to inadequate optical energy absorption; if the coupling length is too long (e.g., greater than 6 μm), it increases the transmission distance of the optical signal in the waveguide, introducing additional transmission loss, and may also increase the chip area, which is detrimental to integration.

[0063] It should be noted that, in this embodiment, the longitudinal coupling distance between the second waveguide structure 3 and the APD structure 4 is preferably 125 nm, and the coupling length is preferably 5 μm. This maximizes the overlap efficiency between the optical field and the active layer 1 of the APD, allowing more optical energy to be absorbed by the active layer 1, thereby exciting more photogenerated carriers. Combined with the avalanche multiplication effect of the APD structure 4, the detector's response to weak optical signals can be significantly improved, enhancing detection sensitivity and responsivity.

[0064] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 2 As shown, the cross-sectional shape of APD structure 4 is rectangular or ridge-shaped.

[0065] Among them, the APD structure 4 with a rectangular cross-section has a simple structure, is easy to fabricate using conventional semiconductor processes (such as photolithography and etching), has strong process compatibility, and is suitable for large-scale mass production. At the same time, its symmetrical cross-section design makes the electric field distribution in the active layer 1 relatively uniform, which is beneficial for photogenerated carriers to maintain stable transport characteristics during avalanche multiplication. It is suitable for scenarios with high requirements for device consistency, such as detector array integration.

[0066] Among them, the APD structure 4 corresponding to the ridge-shaped cross section, compared with the rectangular cross section, can further reduce the longitudinal coupling distance between the second waveguide structure 3 and the APD structure 4, so that the effective working area of ​​the APD structure 4 is closer to the upper second waveguide structure 3, and the optical field energy can penetrate into the intrinsic region more directly, thereby improving the coupling efficiency.

[0067] It should be noted that when the cross-sectional shape of the APD structure 4 is ridge-shaped, its intrinsic region forms a ridge-like protrusion structure with a height difference of 50 to 70 nm relative to other regions. At a wavelength of 850 nm, this height difference enhances the evanescent field intensity by about 20% in the ridge apex region, effectively confining the light energy within the intrinsic layer and improving the photoelectric conversion efficiency.

[0068] In some possible implementations disclosed in this application, see [link to relevant documentation]. Figure 1 and Figure 2 As shown, the waveguide integrated avalanche detector also includes a substrate and an insulating layer; the substrate is located below the active layer 1 and is used to support the overall structure of the waveguide integrated avalanche detector; the insulating layer is located between the substrate and the active layer 1 and is used to isolate the substrate from the active layer 1.

[0069] In the above embodiments, the insulating layer is made of one or more of the following materials: silicon dioxide, silicon nitride, aluminum oxide, hafnium oxide, and tantalum oxide.

[0070] In the above embodiments, the substrate is made of one or more of the following materials: silicon, germanium, gallium nitride, silicon carbide, mercuric iodide, gallium arsenide, titanium bromide, cadmium telluride, zinc cadmium telluride, cadmium selenide, gallium phosphide, mercuric sulfide, lead iodide, and aluminum antimonide.

[0071] Furthermore, in this embodiment, the waveguide-integrated avalanche detector is constructed based on a silicon nitride-on-silicon-insulator (SiN-on-SOI) photonic platform, with the following standard layer structure parameters: the active layer 1 has a thickness of 220 nm, is made of silicon, and forms an APD structure 4 through gradient implantation of P-type and N-type impurities. The insulating layer has a thickness of 2.2 μm, is made of silicon dioxide, and achieves electrical isolation between the top silicon layer and the substrate. The substrate has a thickness of 300 to 500 μm, is made of highly doped silicon, and provides mechanical support and a heat dissipation path.

[0072] Furthermore, in this embodiment, the first waveguide structure 2 and the second waveguide structure 3 are made of silicon nitride. It is understood that waveguide materials also include, but are not limited to, germanium, silicon, and combinations thereof; any material that can potentially realize the waveguide structure of this application is within the scope of protection of this application.

[0073] Furthermore, the waveguide integrated avalanche detector provided in this embodiment can have a shape that is a regular geometric shape such as a circle, square, or polygon, or an irregular shape such as a non-closed shape; the above-mentioned single graphic structure and any arrangement and combination of graphics (including array, matrix and other layout methods) are all within the protection scope of this application.

[0074] Furthermore, the waveguide structure, active layer 1, and related functional regions of the aforementioned waveguide-integrated avalanche detector can be fabricated using any etching process, such as wet etching, dry etching (e.g., reactive ion etching (RIE), inductively coupled plasma etching (ICP), Bosch etching (deep reactive ion etching (DRIE)), or laser etching. Regardless of whether a single process or a combination of multiple processes is used, all process implementation schemes based on the structural design of this application fall within the protection scope of this application.

Claims

1. A waveguide-integrated avalanche detector, characterized in that, include: An active layer is implanted with gradient-distributed P-type and N-type impurities to form an APD structure with an avalanche multiplication effect. A first waveguide structure and a second waveguide structure are located above the active layer, and the first waveguide structure and the second waveguide structure are evanescently coupled; wherein: The first waveguide structure is used to receive optical signals and couple optical energy to the second waveguide structure through an evanescent field; The second waveguide structure forms a vertically overlapping region with the APD structure, and the second waveguide structure is evanescently coupled to the APD structure to transfer the light energy to the APD structure and excite the APD structure to generate a photoelectric effect.

2. The waveguide-integrated avalanche detector according to claim 1, characterized in that, The first waveguide structure and the second waveguide structure are configured to support only single-mode transmission at a wavelength of 850nm, and the single-mode is a transverse electric mode.

3. The waveguide-integrated avalanche detector according to claim 2, characterized in that, The first waveguide structure has a cross-sectional dimension of 600 nm in width and 220 nm in thickness; the second waveguide structure also has a cross-sectional dimension of 600 nm in width and 220 nm in thickness.

4. The waveguide-integrated avalanche detector according to claim 1, characterized in that, The first waveguide structure is a strip waveguide, and the second waveguide structure is a ring waveguide with an inner radius of 90 to 110 μm.

5. The waveguide-integrated avalanche detector according to claim 1, characterized in that, The lateral coupling distance between the first waveguide structure and the second waveguide structure is 100 to 200 nm, and the coupling length is 2 to 10 μm.

6. The waveguide-integrated avalanche detector according to claim 1, characterized in that, The longitudinal coupling distance between the second waveguide structure and the APD structure is 50 to 200 nm, and the coupling length is 3 to 6 μm.

7. The waveguide-integrated avalanche detector according to claim 1, characterized in that, The cross-sectional shape of the APD structure is rectangular or ridge-shaped.

8. The waveguide-integrated avalanche detector according to claim 1, characterized in that, Also includes: Substrate; the substrate is located below the active layer and is used to support the overall structure of the waveguide integrated avalanche detector; An insulating layer is located between the substrate and the active layer, and the insulating layer is used to isolate the substrate from the active layer.

9. The waveguide integrated avalanche detector according to claim 8, characterized in that, The insulating layer is made of one or more of the following materials: silicon dioxide, silicon nitride, aluminum oxide, hafnium oxide, and tantalum oxide.

10. The waveguide-integrated avalanche detector according to claim 8, characterized in that, The substrate is made of one or more of the following materials: silicon, germanium, gallium nitride, silicon carbide, mercuric iodide, gallium arsenide, titanium bromide, cadmium telluride, zinc cadmium telluride, cadmium selenide, gallium phosphide, mercuric sulfide, lead iodide, and aluminum antimonide.

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