Uniform-absorption silicon-based germanium photoelectric detector and method for forming same
By optimizing the lateral distance and doped region design of the incident light waveguide and germanium waveguide in a silicon-based germanium photodetector, the performance degradation caused by the space charge shielding effect was solved, and the electrical bandwidth and photocurrent output were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-05
- Publication Date
- 2026-03-13
AI Technical Summary
In transverse junction waveguide silicon-based germanium photodetectors, the small size of germanium leads to an excessively high concentration of photogenerated carriers, which easily forms a space charge shielding effect, weakens the effect of the applied voltage on the detector, and reduces the drift velocity and electrical bandwidth of photogenerated carriers.
A silicon-based germanium photodetector with uniform absorption is designed by forming an incident light waveguide and a germanium waveguide on a silicon layer. The lateral distance between the germanium waveguide and the incident light waveguide decreases as the incident light propagation distance increases. The absorption distribution of light energy is optimized by combining doped regions and groove structures.
It effectively mitigates the space charge shielding effect, improves the electrical bandwidth and photocurrent output of the device, and enhances the performance of the detector.
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Figure CN121665761A_ABST
Abstract
Description
Technical Field
[0001] This application generally relates to photodetector devices, and more specifically to silicon-based photonic integrated devices. Background Technology
[0002] Due to its advantages such as high integration, strong light field confinement capability, and compatibility with traditional complementary metal-oxide-semiconductor (CMOS) process platforms, silicon-based photonic integration platforms are considered to be one of the most promising platforms for future integrated optics.
[0003] Waveguide-type silicon-based germanium photodetectors are key components in silicon-based photonics integration platforms for converting optical signals into electrical signals. In operation, the waveguide-type silicon-based germanium photodetector propagates light waves in the communication band through a silicon waveguide, which are then absorbed by germanium and converted into photocurrent, thus achieving photoelectric detection.
[0004] Waveguide-type silicon-based germanium photodetectors can generally be divided into two structures: longitudinal junction and transverse junction. Longitudinal junction waveguide-type silicon-based germanium photodetectors require doping on the germanium waveguide and making corresponding metal contacts, which leads to the following defects in the detector: (1) It is easy to introduce complex surface states on the surface of germanium, which leads to an increase in the dark current of the device; (2) Making metal contacts on the surface of germanium will cause some optical signals to be absorbed by the metal, which will lead to a decrease in the responsivity of the device.
[0005] In contrast, lateral junction waveguide silicon-based germanium photodetectors do not require metal contacts on germanium, thus avoiding the defects of longitudinal junction waveguide silicon-based germanium photodetectors. Furthermore, lateral junction waveguide silicon-based germanium photodetectors have smaller junction capacitance, making them easier to fabricate into high-speed devices.
[0006] However, due to the small volume of germanium in lateral junction waveguide-type silicon-based germanium photodetectors, the concentration of photogenerated carriers is easily excessively high. Consequently, when the input optical power to the silicon-based germanium photodetector is high, a strong space charge electric field is easily formed, leading to a space charge shielding effect in germanium. This space charge shielding effect weakens the effect of the applied voltage on the detector, thereby reducing the drift velocity of photogenerated carriers and decreasing the electrical bandwidth of the detector. Furthermore, the electric field strength of germanium in lateral junction waveguide-type silicon-based germanium photodetectors is relatively weak, making it more susceptible to the effects of the space charge shielding effect. Therefore, mitigating the impact of the space charge shielding effect on lateral junction waveguide-type silicon-based germanium photodetectors is of great significance for further improving device performance.
[0007] Figure 1This is a three-dimensional structural schematic diagram of a conventional waveguide-type silicon-based germanium photodetector 100. The silicon-based germanium photodetector 100 may include a silicon substrate 110, a buried oxide layer 120 above the silicon substrate, and a silicon layer 130 above the buried oxide layer 120. A silicon waveguide 135 may be formed in the silicon layer 130. The silicon-based germanium photodetector 100 may also include a germanium waveguide 140 formed above the silicon waveguide 135. In this lateral junction waveguide-type silicon-based germanium photodetector 100, the silicon waveguide 135 faces the germanium waveguide 140, thereby coupling incident light to the germanium waveguide 140. Consequently, the energy of the incident light decreases exponentially with increasing absorption length, meaning that most of the light energy is absorbed at the front end of the silicon-based germanium photodetector 100. When the input optical power of the silicon-based germanium photodetector 100 is high, the photogenerated carriers at its front end become overly concentrated, resulting in a strong space charge shielding effect and causing saturation of the output photocurrent.
[0008] There is a need in the field for waveguide-type silicon-based germanium photodetectors that can improve the space charge shielding effect. Summary of the Invention
[0009] This invention is provided to provide a waveguide-type silicon-based photodetector that can improve the space charge shielding effect.
[0010] One aspect of the present invention provides a silicon-based germanium photodetector with uniform absorption, comprising: a silicon-on-insulator substrate, the silicon-on-insulator substrate comprising: a silicon substrate; a buried oxide layer above the silicon substrate; and a silicon layer above the buried oxide layer, wherein the silicon layer comprises: an incident light waveguide for receiving and propagating incident light therein, the cross-section of the incident light waveguide being designed to allow the incident light to propagate therein in a single-mode manner; and a germanium waveguide above the silicon layer, the germanium waveguide being disposed on one side of the incident light waveguide for optical coupling with the incident light waveguide, and the lateral distance between the germanium waveguide and the incident light waveguide decreasing as the propagation distance of the incident light in the incident light waveguide increases.
[0011] In the silicon-based germanium photodetector described above, the incident waveguide includes a strip waveguide, a converter, and a ridge waveguide connected to each other, and wherein the width of the converter gradually widens along the direction from the strip waveguide to the ridge waveguide.
[0012] In a silicon-based germanium photodetector as described in any of the preceding claims, the incident light waveguide is formed by etching the silicon layer.
[0013] The silicon-based germanium photodetector as described in any of the above embodiments, wherein the silicon layer further includes a silicon ridge waveguide, the germanium waveguide is above the silicon ridge waveguide, and the width of the silicon ridge waveguide is greater than the width of the germanium waveguide.
[0014] The silicon-based germanium photodetector as described in any of the above embodiments, wherein the silicon layer further includes doped regions of different doping types located on both sides of the germanium waveguide, and / or wherein the silicon layer includes doped regions of different lateral doping concentrations on each side of the germanium waveguide.
[0015] The silicon-based germanium photodetector as described in any of the preceding claims, wherein the silicon layer includes a groove on top, and the germanium waveguide is formed in the groove.
[0016] In the silicon-based germanium photodetector described in any of the above embodiments, the lateral distance between the germanium waveguide and the incident light waveguide is determined through simulation calculation and iterative optimization.
[0017] Another aspect of the present invention provides a method for forming a silicon-based germanium photodetector with uniform absorption, comprising: providing a silicon-on-insulator substrate, the silicon-on-insulator substrate including a silicon substrate, a buried oxide layer above the silicon substrate, and a silicon layer above the buried oxide layer; forming an incident light waveguide on the silicon layer, the incident light waveguide being used to receive incident light and to propagate the incident light therein, the cross section of the incident light waveguide being designed to allow the incident light to propagate therein in a single-mode manner; and forming a germanium waveguide above the silicon layer and on one side of the incident light waveguide, the germanium waveguide being coupled to the incident light waveguide, and the lateral distance between the germanium waveguide and the incident light waveguide decreasing as the propagation distance of the incident light in the incident light waveguide increases.
[0018] In the method described above, the incident waveguide includes a strip waveguide, a converter, and a ridge waveguide connected to each other, and the width of the converter gradually widens along the direction from the strip waveguide to the ridge waveguide.
[0019] The method described in any of the above methods, wherein forming the incident light waveguide includes etching the silicon layer.
[0020] The method of any of the above further includes: forming a silicon ridge waveguide on the silicon layer, and forming a germanium waveguide includes: forming the germanium waveguide above the silicon ridge waveguide, wherein the width of the silicon ridge waveguide is greater than the width of the germanium waveguide.
[0021] The method described in any of the above methods further includes: forming doped regions of different doping types on the silicon layer on both sides of the germanium waveguide to be formed; and / or forming doped regions of different doping concentrations laterally on each side of the germanium waveguide to be formed on the silicon layer.
[0022] The method described in any of the above methods further includes: forming a groove on top of the silicon layer, and forming a germanium waveguide includes: forming the germanium waveguide in the groove.
[0023] The method described in any of the above embodiments, wherein the lateral distance between the germanium waveguide and the incident optical waveguide is determined by simulation calculation and iterative optimization.
[0024] The silicon-based photodetector and the method for forming it according to embodiments of the present invention can improve the space charge shielding effect, thereby improving the electrical bandwidth of the device. Attached Figure Description
[0025] Various embodiments of this application are described in conjunction with the accompanying drawings. Wherein:
[0026] Figure 1 This is a schematic diagram of the three-dimensional structure of a traditional waveguide-type silicon-based germanium photodetector.
[0027] Figure 2 These are three-dimensional structural schematic diagrams, top view schematic diagrams, and cross-sectional schematic diagrams of waveguide-type silicon-based germanium photodetectors according to some embodiments of the present invention.
[0028] Figure 3 This is a simulation diagram of the electric field distribution of light waves in the xz plane at the center of germanium in a conventional waveguide-type silicon-based germanium photodetector and a waveguide-type silicon-based germanium photodetector according to some embodiments of the present invention.
[0029] Figure 4 This is a simulation calculation graph showing the change of light absorptivity as incident light travels over a conventional waveguide-type silicon-based germanium photodetector and a waveguide-type silicon-based germanium photodetector according to some embodiments of the present invention.
[0030] Figure 5 This is a flowchart illustrating a method for forming a silicon-based germanium photodetector according to some embodiments of the present invention. Detailed Implementation
[0031] In this application, the expression "A is above B" can mean that A is in contact with B and is directly on B, or it can mean that A is above B and there are one or more intermediate objects between A and B.
[0032] According to one aspect of the present invention, a silicon-based germanium photodetector with uniform absorption is provided.
[0033] Figure 2 These are three-dimensional structural schematic diagrams, top view schematic diagrams, and cross-sectional schematic diagrams of the yz plane of a waveguide-type silicon-based germanium photodetector 200 according to some embodiments of the present invention.
[0034] The silicon-based germanium photodetector 200 may include a silicon-on-insulator (SOI) substrate. The SOI substrate may include a silicon substrate 210, a buried oxide layer 220 above the silicon substrate 210, and a top silicon layer 230 above the buried oxide layer.
[0035] In some embodiments, the buried oxide layer 220 may be silicon dioxide, which serves to separate the substrate 210 from the top silicon layer 230. The silicon dioxide of the buried oxide layer 220 has a low refractive index, resulting in a high-low-high refractive index distribution from bottom to top in the SOI substrate, thereby creating a refractive index difference within the SOI substrate. This confines incident light within an optical waveguide formed in the top silicon layer 230, thus preventing energy leakage.
[0036] The silicon layer 230 may include an incident light waveguide 240. This incident light waveguide 240 can be used to receive and propagate incident light therein. The cross-section of the incident light waveguide 240 is designed to allow the incident light to propagate in a single-mode configuration. In some embodiments, the thickness of the incident light waveguide 240 can be defined. For example, the thickness of the silicon layer on top of a typical SOI substrate can be 220 nm. Accordingly, the design of the cross-section of the incident light waveguide 240 can actually depend on the width of the incident light waveguide 240.
[0037] The silicon-based germanium photodetector 200 may further include a germanium waveguide 250. The germanium waveguide 250 may be formed, for example, on the silicon layer 230 by deposition. The germanium waveguide 250 may be disposed on one side of the incident light waveguide 240 for optical coupling with the incident light waveguide 240, thereby absorbing the incident light received and propagated by the incident light waveguide 240 (e.g., by evanescent wave coupling). The lateral distance d(x) between the germanium waveguide 250 and the incident light waveguide 240 decreases as the propagation distance x of the incident light in the incident light waveguide 240 increases.
[0038] By placing the incident light waveguide 240 on one side of the germanium waveguide 250 and setting the lateral distance between them to decrease as the propagation distance of the incident light increases, the intensity of the incident light received by the germanium waveguide 250 along the propagation distance of the incident light can be made more uniform. This reduces the absorbed incident light energy at the front end and increases the absorbed incident light energy at the rear end, thereby effectively mitigating the space charge shielding effect and improving device performance (e.g., electrical bandwidth).
[0039] In some embodiments, the incident waveguide 240 may be formed by etching (e.g., shallow etching) the silicon layer 230.
[0040] In some embodiments, the incident waveguide 240 may include a strip waveguide 241, a converter 242, and a ridge waveguide 243. The converter 242 may be connected to the strip waveguide 241 and the ridge waveguide 243 at both ends, and the width of the converter 242 gradually widens along the direction from the strip waveguide 241 to the ridge waveguide 243. By using the gradually widening converter 242, more incident light received by the strip waveguide 241 can be coupled to the ridge waveguide 243, thereby increasing the efficiency of the incident waveguide 240 in receiving and propagating incident light. In embodiments using this configuration of the incident waveguide 240, at least a portion of the incident waveguide 240 may correspond to the ridge waveguide 243. The lateral distance d(x) between the incident waveguide 240 and the germanium waveguide 250 can be defined by the lateral distance between the ridge waveguide 243 and the germanium waveguide 250.
[0041] In some embodiments, the silicon layer 230 may include a silicon ridge waveguide, and a germanium waveguide 250 may be formed on the silicon ridge waveguide, wherein the width of the silicon ridge waveguide may be greater than the width of the germanium waveguide 250. In this embodiment, the germanium waveguide 250 may form an optical waveguide together with the underlying silicon ridge waveguide, so that the energy of the received light is better confined within the germanium waveguide.
[0042] In some embodiments, the silicon layer 230 may include doped regions of different doping types on both sides of the germanium waveguide 250. As an example, in Figure 2 In the cross-sectional view shown in the lower right corner, the silicon layer 230 may include an N-type doped region on the left side of the germanium waveguide 250, and a P-type doped region on the right side. It should be noted that the doping types on both sides of the germanium waveguide 250 can be interchanged.
[0043] In some embodiments, the silicon layer 230 may include doped regions with different lateral doping concentrations on each side of the germanium waveguide 250. As an example, in Figure 2 In the cross-sectional view shown in the lower right corner, the silicon layer 230 may include N-type silicon on the left side of the germanium waveguide 250. ++ Doped regions 231 and N + Doped region 232. In other embodiments, the doping concentrations of these two doped regions can be interchanged. The silicon layer 230 may include P-type silicon on the right side of the germanium waveguide 250. + Doped regions 233 and P ++ Doped region 234. In other embodiments, the doping concentrations of these two doped regions can be interchanged. High doping concentration N ++ Doped region 231 can be used as the metal cathode of an ohmic contact detector, and the high doping concentration of P ++ Doped region 234 can be used as the metal anode of an ohmic contact detector.
[0044] In some embodiments, the silicon layer 230 may include a groove 255 on top, and a germanium waveguide 250 may be formed in the groove 255. By forming the germanium waveguide 250 in a groove of a certain depth, the electric field strength in the germanium waveguide 250 can be enhanced.
[0045] In some embodiments, the lateral distance between the germanium waveguide 250 and the incident optical waveguide 240 can be determined through simulation calculations and iterative optimization. The following section combines... Figure 4 An example of simulation optimization is shown and described. It should be noted that, although in Figure 2 In the embodiment shown, the germanium waveguide 250 extends along the length direction of the silicon layer 230 while the incident light waveguide 240 is tilted relative to the length direction of the silicon layer 230. However, in an alternative embodiment, the incident light waveguide 250 may also extend along the length direction of the silicon layer 230 while the germanium waveguide 250 is tilted relative to the length direction of the silicon layer 230. In the latter case, N ++ Doped regions 231, N + Doped regions 232, P + Doped regions 233 and P ++ The extension direction of the doped region 234 can be parallel to the extension direction of the germanium waveguide 250.
[0046] Figure 3 This is a simulation diagram of the electric field distribution of light waves in the xz plane at the center of germanium in a conventional waveguide-type silicon-based germanium photodetector and a waveguide-type silicon-based germanium photodetector according to some embodiments of the present invention.
[0047] Specifically, Figure 3 The simulation results for a conventional waveguide-type silicon-based germanium photodetector are shown above (e.g., for...). Figure 1 Simulation results for the silicon-based germanium photodetector 100 shown are presented below, and simulation results for waveguide-type silicon-based germanium photodetectors according to some embodiments of the present invention are shown below (e.g., for...). Figure 2 Simulation results of the silicon-based germanium photodetector 200 shown.
[0048] The simulation results above show that the electric field energy at the front end of the device (i.e., at a smaller distance along the x-axis) is significantly greater than that at the rear end. In contrast, the simulation results below show that the electric field intensity of the device becomes more uniform as the propagation distance along the incident light propagation direction (i.e., the x-axis direction) increases.
[0049] Figure 4 This is a simulation calculation graph showing the change of light absorptivity as incident light travels over a conventional waveguide-type silicon-based germanium photodetector and a waveguide-type silicon-based germanium photodetector according to some embodiments of the present invention.
[0050] The simulation results show that the light absorption rate of the waveguide-type silicon-based germanium photodetector according to some embodiments of the present invention increases uniformly with the increase of the incident light propagation distance, thereby indicating that the germanium waveguide can absorb incident light with more uniform energy along the propagation distance of the incident light.
[0051] According to another aspect of the present invention, a method for a silicon-based germanium photodetector is provided.
[0052] Figure 5 This is a flowchart illustrating a method 500 for forming a silicon-based germanium photodetector with uniform absorption according to some embodiments of the present invention. Method 500 can be used to form the aforementioned... Figure 2 The silicon-based germanium photodetector 200 is described, but the scope of the invention is not limited thereto.
[0053] Method 500 may include: providing an SOI substrate at block 510. As an example, the SOI substrate may be a combination of the above. Figure 2 The SOI substrate of the silicon-based germanium photodetector 200 is described.
[0054] In some embodiments, the buried oxide layer may be silicon dioxide, which is used to separate the substrate from the top silicon layer. The silicon dioxide of the buried oxide layer has a low refractive index, thereby creating a refractive index difference between the silicon substrate and the silicon layer. This confines incident light within the top silicon layer to form an optical waveguide, thus preventing energy leakage.
[0055] Method 500 may include: forming an incident optical waveguide on a silicon layer at block 531. The incident optical waveguide is used to receive and propagate incident light therein, and the cross-section of the incident optical waveguide is designed to allow the incident light to propagate in a single-mode configuration therein. As an example, the incident optical waveguide may be a combination of the above. Figure 2 The described silicon-based germanium photodetector 200 has an incident light waveguide 240. In some embodiments, the thickness of the incident light waveguide can be defined. For example, the thickness of the silicon layer on top of a common SOI substrate can be 220 nm. Accordingly, the design of the cross-section of the incident light waveguide can actually depend on the width of the incident light waveguide.
[0056] In some embodiments, the incident light waveguide can be formed by etching (e.g., shallow etching) a silicon layer.
[0057] In some embodiments, the incident waveguide may include a strip waveguide, a converter, and a ridge waveguide. The converter may be connected to the strip waveguide and the ridge waveguide at both ends, respectively, and the width of the converter gradually increases from the strip waveguide to the ridge waveguide. By using a gradually widening converter, more incident light received by the strip waveguide can be coupled to the ridge waveguide, thereby increasing the efficiency of the incident waveguide in receiving and propagating incident light. As an example, the strip waveguide, converter, and ridge waveguide may be a combination of the above-described components. Figure 2The silicon-based germanium photodetector 200 is described as having a strip waveguide 241, a converter 242, and a ridge waveguide 243.
[0058] Optionally, in some embodiments, method 500 may include: forming a silicon ridge waveguide on a silicon layer at block 532. As an example, the silicon ridge waveguide may be a combination of the above descriptions. Figure 2 The silicon ridge waveguide of the silicon-based germanium photodetector 200 is described.
[0059] Optionally, in some embodiments, method 500 may include: forming, at block 533, doped regions of different doping types on the silicon layer, on both sides of the germanium waveguide to be formed. As an example, the doped regions of different doping types may be those described above... Figure 2 The silicon-based germanium photodetector 200 is described, featuring N-type and P-type doped regions. The doped regions with different doping types on either side of the germanium waveguide are interchangeable.
[0060] Optionally, in some embodiments, method 500 may include: at block 534, forming doped regions with different doping concentrations laterally on each side of the germanium waveguide to be formed on the silicon layer. As an example, the doped regions with different doping concentrations may be those described above. Figure 2 The silicon-based germanium photodetector 200 described in N ++ Doped regions 231, N + Doped regions 232, P + Doped regions 233 and P ++ Doped region 234. The doped regions with different doping concentrations formed laterally on each side of the germanium waveguide are interchangeable.
[0061] Optionally, in some embodiments, method 500 may include forming a groove on top of the silicon layer at block 535. The germanium waveguide may be as described above. Figure 2 The groove 255 of the silicon-based germanium photodetector 200 is described.
[0062] Method 500 may include: forming a germanium waveguide at block 550, above a silicon layer and on one side of the incident optical waveguide. This germanium waveguide may be coupled to the incident optical waveguide, and the lateral distance between the germanium waveguide and the incident optical waveguide decreases as the propagation distance of the incident light in the incident optical waveguide increases. As an example, the germanium waveguide may be a combination of the above... Figure 2 The germanium waveguide 250 of the silicon-based germanium photodetector 200 is described.
[0063] In an embodiment including the step at block 532, the step at block 550 may include forming a germanium waveguide above the silicon ridge waveguide, and the width of the silicon ridge waveguide may be greater than the width of the germanium waveguide. In this embodiment, the germanium waveguide may form an optical waveguide together with the underlying silicon ridge waveguide to better confine the energy of light within the germanium waveguide.
[0064] In an embodiment that includes the step at block 535, the step at block 550 may include forming a germanium waveguide in a groove. By forming the germanium waveguide in a groove of a certain depth, the electric field strength in the germanium waveguide can be enhanced.
[0065] The silicon-based germanium photodetector formed according to method 500, by placing the incident light waveguide on one side of the germanium waveguide and setting the lateral distance between them to decrease as the propagation distance of the incident light increases, can make the intensity of the incident light received by the germanium waveguide along the propagation distance of the incident light more uniform, reduce the absorbed incident light energy at the front end and increase the absorbed incident light energy at the rear end, thereby effectively alleviating the valence charge shielding effect and improving device performance (e.g., electrical bandwidth).
[0066] Various embodiments of the invention have been described with reference to the accompanying drawings. These embodiments are illustrative and not restrictive.
Claims
1. A silicon-based germanium photodetector, comprising: Silicon-on-insulator substrate, the silicon-on-insulator substrate comprising: Silicon substrate; A buried oxide layer is placed over the silicon substrate; and A silicon layer, above the buried oxide layer, wherein the silicon layer comprises: An incident light waveguide for receiving and propagating incident light therein, the cross-section of which is designed to allow the incident light to propagate in a single-mode manner; and A germanium waveguide is disposed on one side of the incident light waveguide above the silicon layer to optically couple with the incident light waveguide, and the lateral distance between the germanium waveguide and the incident light waveguide decreases as the propagation distance of the incident light in the incident light waveguide increases.
2. The silicon-based germanium photodetector as described in claim 1, in, The incident waveguide includes a strip waveguide, a converter, and a ridge waveguide connected to each other, and The width of the converter gradually increases from the strip waveguide to the ridge waveguide.
3. The silicon-based germanium photodetector as described in claim 1, in, The incident light waveguide is formed by etching the silicon layer.
4. The silicon-based germanium photodetector as described in claim 1, in, The silicon layer further includes a silicon ridge waveguide, the germanium waveguide is above the silicon ridge waveguide, and the width of the silicon ridge waveguide is greater than the width of the germanium waveguide.
5. The silicon-based germanium photodetector as described in claim 1, in, The silicon layer also includes doped regions of different doping types located on both sides of the germanium waveguide, and / or The silicon layer comprises doped regions with different lateral doping concentrations on each side of the germanium waveguide.
6. The silicon-based germanium photodetector as described in claim 1, in, The silicon layer includes a groove on top, and the germanium waveguide is formed in the groove.
7. The silicon-based germanium photodetector as described in claim 1, in, The lateral distance between the germanium waveguide and the incident optical waveguide was determined through simulation calculations and iterative optimization.
8. A method for forming a silicon-based germanium photodetector, comprising: A silicon-on-insulator substrate is provided, the silicon-on-insulator substrate comprising a silicon substrate, a buried oxide layer above the silicon substrate, and a silicon layer above the buried oxide layer; An incident light waveguide is formed on the silicon layer. The incident light waveguide receives and propagates incident light therein. The cross-section of the incident light waveguide is designed to allow the incident light to propagate in a single-mode configuration. A germanium waveguide is formed above the silicon layer and on one side of the incident light waveguide. The germanium waveguide is coupled to the incident light waveguide, and the lateral distance between the germanium waveguide and the incident light waveguide decreases as the propagation distance of the incident light in the incident light waveguide increases.
9. The method as described in claim 8, in, The incident waveguide includes a strip waveguide, a converter, and a ridge waveguide connected to each other, and The width of the converter gradually increases from the strip waveguide to the ridge waveguide.
10. The method of claim 8, wherein, Forming an incident light waveguide includes etching the silicon layer.
11. The method of claim 8, further comprising: A silicon ridge waveguide is formed on the silicon layer, and Forming a germanium waveguide includes: forming the germanium waveguide above the silicon ridge waveguide, wherein the width of the silicon ridge waveguide is greater than the width of the germanium waveguide.
12. The method of claim 9, further comprising: Different doping regions of different doping types are formed on the silicon layer on both sides of the germanium waveguide to be formed; and / or On the silicon layer, doped regions with different doping concentrations are formed laterally on each side of the germanium waveguide to be formed.
13. The method of claim 9, further comprising: A groove is formed on the top of the silicon layer, and Forming a germanium waveguide includes: forming the germanium waveguide in the groove.
14. The method as described in claim 9, in, The lateral distance between the germanium waveguide and the incident optical waveguide was determined through simulation calculations and iterative optimization.