Waveguide type germanium-silicon avalanche photodiode and preparation method thereof

Abstract

The invention discloses a waveguide type germanium-silicon avalanche photodiode and a preparation method thereof, the waveguide type germanium-silicon avalanche photodiode comprises a substrate, a light transmission area and a resonance detection area, and the light transmission area and the resonance detection area are both located on a top silicon Si layer of the substrate; the light transmission area comprises an incident waveguide structure, an incident interlayer conversion structure, a resonant silicon Si waveguide structure, an emergent interlayer conversion structure and an emergent bent waveguide structure; the resonance detection region comprises a P-type metal contact region, a germanium Ge annular resonance waveguide structure, a charge control region, an intrinsic avalanche region and an N-type metal contact region. The preparation method is used for preparing the waveguide type germanium-silicon avalanche photodiode. According to the waveguide type germanium-silicon avalanche photodiode, separation coupling and oscillation absorption of specific wave band optical signals are achieved, and high light absorption efficiency is obtained; and the light signal which is not completely absorbed is recoupled into the light incident waveguide through the bent waveguide, so that multiple coupling absorption of the light signal is realized, and high responsivity is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoelectric detectors, in particular to a waveguide type germanium-silicon avalanche photodiode. BACKGROUND

[0002] In recent years, with the rapid increase of market demand in the field of optical fiber communication, optical interconnection and other fields, photoelectric detectors with high detection rate and high photoelectric bandwidth have become the focus of research. Among them, the waveguide type avalanche photodiode can effectively detect weak light due to its internal avalanche multiplication effect, and has high bandwidth and high sensitivity, etc. It has become one of the indispensable important components in the optical fiber communication market.

[0003] At present, the silicon-based waveguide type avalanche photodiode usually uses germanium Ge material with high absorption efficiency in the near-infrared waveband and its advantage of being easy to grow on silicon-based material as an absorption layer, and uses silicon Si material with a low electron-hole collision ionization factor ratio (k≈0.02) as an avalanche multiplication layer to obtain low excess noise and high avalanche gain. In addition, compared with InP-based avalanche photodiode (indium phosphide-based avalanche photodiode), the silicon-based waveguide type avalanche photodiode chip preparation process is similar to other silicon-based devices, and is highly compatible with the complementary metal oxide semiconductor (CMOS) process, and is easy to realize large-scale integrated preparation at low production cost. However, due to the characteristics of germanium Ge and silicon Si materials, the bandwidth, responsivity and other device performance of the silicon-based waveguide type avalanche photodiode chip still have a large gap compared with the InP-based avalanche photodiode. Therefore, for the waveguide type avalanche photodiode, enhancing the light absorption efficiency, improving the responsivity and bandwidth and other performance parameters are still the key to the subsequent development of such chips. SUMMARY

[0004] The first object of the present application is to provide a waveguide type germanium-silicon avalanche photodiode, which adopts the following technical scheme: A waveguide type germanium-silicon avalanche photodiode, comprising a substrate, a light transmission zone and a resonance detection zone, the light transmission zone and the resonance detection zone are located on the top silicon Si layer of the substrate; the light transmission zone is used for light signal transmission, realizing light signal incidence and recycling transmission of the light signal in the annular resonant waveguide structure which is not completely coupled to the resonance detection zone; the resonance detection zone is used for coupling and transmitting the light signal of the light transmission zone into the annular resonant waveguide, realizing light signal resonance and detection. The light transmission zone comprises an incident waveguide structure, an incident interlayer conversion structure, a resonant silicon (Si) waveguide structure, an exit interlayer conversion structure and an exit curved waveguide structure, the resonant silicon (Si) waveguide structure is located outside the resonant detection zone, and the two ends of the resonant silicon (Si) waveguide structure are connected to the incident waveguide structure and the exit curved waveguide structure through the incident interlayer conversion structure and the exit interlayer conversion structure respectively; The resonant detection zone comprises a P-type metal contact zone, a germanium (Ge) ring resonant waveguide structure, a charge control zone, an intrinsic avalanche zone and an N-type metal contact zone. The germanium (Ge) ring resonant waveguide structure is close to the resonant silicon (Si) waveguide structure, the germanium (Ge) ring resonant waveguide structure is located inside the top silicon (Si) layer of the substrate and has a ring shape as a whole, the P-type metal contact zone and the charge control zone are located on the two sides of the germanium (Ge) ring resonant waveguide structure in parallel, the P-type metal contact zone is located outside the germanium (Ge) ring resonant waveguide structure, and the charge control zone is located inside the germanium (Ge) ring resonant waveguide structure; the N-type metal contact zone is located inside the charge control zone, and the intrinsic avalanche zone is located between the N-type metal contact zone and the charge control zone; a P-type electrode and an N-type electrode are respectively prepared above the P-type metal contact zone and the N-type metal contact zone, and a heating electrode is prepared above the germanium (Ge) ring resonant waveguide structure, and the heating electrode is close to the resonant silicon (Si) waveguide structure.

[0005] Further preferably, the incident waveguide structure is an incident silicon nitride (Si3N4) waveguide structure, a silicon nitride (Si3N4) strip waveguide structure is adopted, and the strip width is 0.1um-0.4um; the exit curved waveguide structure is an exit silicon nitride (Si3N4) curved waveguide structure, a silicon nitride (Si3N4) strip waveguide structure is adopted, and the strip width is 0.1um-0.4um; the incident waveguide structure and the exit curved waveguide structure adopt a silicon nitride (Si3N4) waveguide structure, so as to reduce the insertion loss generated when the optical signal is coupled into the waveguide, realize efficient coupling of the optical signal and reduce the transmission loss generated when the optical signal is transmitted.

[0006] Further preferably, the width of one side of the end of the exit silicon nitride (Si3N4) curved waveguide structure gradually narrows, and a shape such as a right trapezoid is formed at the end of the exit silicon nitride (Si3N4) curved waveguide structure, so as to circularly transmit the optical signal back to the incident silicon nitride (Si3N4) waveguide structure, so as to realize repeated and efficient coupling and absorption of the optical signal.

[0007] Further preferably, the incident interlayer conversion structure and the exit interlayer conversion structure each comprise a silicon nitride (Si3N4) strip waveguide to strip Si waveguide structure and a strip Si waveguide to ridge Si waveguide structure, so as to convert the silicon nitride (Si3N4) strip transmission waveguide into a ridge Si waveguide, so as to facilitate coupling of the optical signal into the germanium (Ge) ring resonant waveguide structure.

[0008] Further optimization reveals that the cross-section of the germanium (Ge) ring resonant waveguide structure is rectangular, with a width of 0.04 μm-0.3 μm and a height of 0.15 μm-0.32 μm, in order to achieve optical signal coupling and absorption, and reduce device capacitance and carrier transport time.

[0009] Further optimization reveals that the resonant silicon (Si) waveguide structure is a ridge waveguide with a ridge mesa depth of 0.15µm-0.32µm.

[0010] Further optimization involves forming the P-type metal contact region, charge control region, and N-type metal contact region on the top silicon Si layer using ion implantation, with the doping concentration of the P-type and N-type metal contact regions being ≥1×10⁻⁶. 20 cm -3 The doping concentration range of the charge control region is 5 × 10⁻⁶. 17 cm -3 -3×10 18 cm -3 .

[0011] Further optimization involves selecting an intrinsic avalanche region with a width of 0.05 μm–0.45 μm. This region constitutes the intrinsic layer, and the carrier concentration must be ≤1 × 10⁻⁶. 17 cm -3 This is used to generate avalanche gain, increase the weak light detection capability of waveguide-type germanium-silicon avalanche photodiodes, and improve responsivity.

[0012] The second objective of this invention is to provide a method for fabricating a waveguide-type germanium-silicon avalanche photodiode, comprising the following steps: S1. An SOI substrate is selected for chip fabrication. Ion implantation is performed on the top silicon Si layer at the N-type metal contact area to form an N-type heavily doped region. After ion implantation, rapid thermal annealing is performed. S2. On the top silicon Si layer, a resonant silicon Si waveguide structure is etched out using silicon dioxide as a hard mask layer. At the same time, the ridge-shaped Si waveguide structure and the strip-shaped Si waveguide structure in the incident interlayer conversion structure and the output interlayer conversion structure are etched out. The required annular silicon window is opened for the epitaxial fabrication of the germanium Ge annular resonant waveguide structure. S3. In the prepared annular silicon window, an annular silicon dioxide window is opened for epitaxial growth of the germanium Ge absorber layer; S4. Remove the germanium-Ge absorption layer material outside the region of the germanium-Ge ring resonant waveguide structure; S5. Using an in-situ doped epitaxial growth method, a P-type heavily doped region is epitaxially grown on the surface of the top silicon Si layer; the epitaxial silicon Si layer on the surface of the top silicon Si layer, except for the required P-type heavily doped region, is removed, and a P-type metal contact region is formed on the remaining P-type heavily doped region. S6. Using an in-situ doped epitaxial growth method, a P-type doped region is epitaxially grown on the surface of the top silicon Si layer; the epitaxial silicon Si layer on the surface of the top silicon Si layer, except for the required P-type doped region, is removed, and a charge control region is formed on the remaining P-type doped region; some areas between the N-type metal contact region and the charge control region are not doped, forming an intrinsic avalanche region. S7. Deposit and grow a silicon dioxide SiO2 dielectric layer on the surface of the top silicon Si layer, remove the silicon dioxide SiO2 dielectric layer and the top silicon Si layer in the specified area, and then deposit and grow a silicon nitride Si3N4 layer. Prepare the incident silicon nitride Si3N4 waveguide structure and the outgoing silicon nitride Si3N4 bent waveguide structure in the specified area. At the same time, etch out the silicon nitride Si3N4 strip waveguide structure required in the incident interlayer conversion structure and the outgoing interlayer conversion structure. S8. A silicon dioxide (SiO2) dielectric layer is deposited and grown on the epitaxial wafer to prepare a P-type electrode, an N-type electrode, and a heating electrode.

[0013] The third objective of this invention is to provide a method for fabricating a waveguide-type germanium-silicon avalanche photodiode, comprising the following steps: S1. The chip is fabricated using an SOI substrate. Ion implantation is performed on the top silicon Si layer in the N-type metal contact region, P-type metal contact region, and charge control region to form N-type heavily doped region, P-type heavily doped region, and P-type doped region, respectively. After ion implantation, rapid thermal annealing is performed. S2. On the top silicon Si layer, the resonant silicon Si waveguide structure is etched out using silicon dioxide as a hard mask layer. At the same time, the ridge Si waveguide structure and the strip Si waveguide structure in the incident interlayer conversion structure and the outgoing interlayer conversion structure are etched out. The annular silicon window required for the epitaxial fabrication of the germanium Ge annular resonant waveguide structure is also etched out. S3. In the prepared annular silicon window, an annular silicon dioxide window is opened for epitaxial growth of the germanium Ge absorber layer; S4. Remove the germanium-Ge absorption layer material outside the region of the germanium-Ge ring resonant waveguide structure. The germanium-Ge absorption layer in the region of the germanium-Ge ring resonant waveguide structure is flush with the surface of the top silicon-Si layer. S5. Deposit and grow a silicon dioxide SiO2 dielectric layer on the surface of the top silicon Si layer, remove the silicon dioxide SiO2 dielectric layer and the top silicon Si layer in the specified area, and then deposit and grow a silicon nitride Si3N4 layer. Prepare the incident silicon nitride Si3N4 waveguide structure and the outgoing silicon nitride Si3N4 bent waveguide structure in the specified area, and simultaneously etch out the silicon nitride Si3N4 strip waveguide structure required in the incident interlayer conversion structure and the outgoing interlayer conversion structure. S6. A silicon dioxide (SiO2) dielectric layer is deposited and grown on the epitaxial wafer to prepare a P-type electrode, an N-type electrode, and a heating electrode.

[0014] The advantages of this invention compared to the prior art are as follows: 1. The waveguide-type germanium-silicon avalanche photodiode of the present invention, wherein the avalanche photodiode is based on a ring resonant cavity structure to achieve separation coupling and oscillation absorption of optical signals in a specific band to obtain high light absorption efficiency, and the device recouples the optical signal that is not completely absorbed into the incident waveguide through a bent waveguide to achieve multiple coupling absorption of the optical signal, thereby obtaining high responsivity.

[0015] 2. The waveguide-type germanium-silicon avalanche photodiode of the present invention recouples the optical signal that is not completely absorbed into the incident silicon nitride (Si3N4) waveguide through a bent silicon nitride (Si3N4) waveguide. The use of the silicon nitride (Si3N4) waveguide structure can effectively reduce the loss of light during transmission, and the cyclic transmission of the optical signal can achieve multiple coupling absorptions, thereby obtaining high responsivity.

[0016] 3. The waveguide-type germanium-silicon avalanche photodiode of the present invention has a small width of germanium (Ge) absorption layer, which greatly reduces the RC capacitance and carrier transport time of the device, thereby achieving high bandwidth.

[0017] 4. The waveguide-type germanium-silicon avalanche photodiode of the present invention adds a heating electrode structure above the germanium (Ge) absorption layer to convert electrical energy into heat energy, thereby achieving adjustment of the operating wavelength of the waveguide-type germanium-silicon avalanche photodiode and obtaining high responsivity and high bandwidth at the required specific wavelength.

[0018] 5. The fabrication method of the waveguide-type germanium-silicon avalanche photodiode of the present invention is simple, has good compatibility with CMOS technology, is easy to achieve large-scale on-chip integration, and effectively controls production costs. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the waveguide-type germanium-silicon avalanche photodiode according to an embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of the detection region of the waveguide-type germanium-silicon avalanche photodiode according to an embodiment of the present invention; Among them, 1-incident silicon nitride Si3N4 waveguide structure, 2-incident interlayer transition structure, 3-resonant silicon Si waveguide structure, 4-outgoing interlayer transition structure, 5-outgoing silicon nitride Si3N4 bent waveguide structure, 6-germanium Ge ring resonant waveguide structure, 7-P-type metal contact region, 8-P-type electrode, 9-charge control region, 10-intrinsic avalanche region, 11-N-type metal contact region, 12-N-type electrode, 13-heating electrode, 15-substrate silicon Si layer. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figures 1-2The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] like Figure 1 and 2 As shown, this embodiment is a waveguide-type germanium-silicon avalanche photodiode, including a substrate, a light transmission region, and a resonant detection region.

[0022] The substrate comprises a substrate silicon Si layer 15, a silicon dioxide SiO2 layer 14, and a top silicon Si layer. Both the light transmission region and the resonant detection region are fabricated on the top silicon Si layer.

[0023] The optical transmission region includes an incident silicon nitride (Si3N4) waveguide structure 1, an incident interlayer transition structure 2, a resonant silicon (Si) waveguide structure 3, an outgoing interlayer transition structure 4, and an outgoing silicon nitride (Si3N4) bent waveguide structure 5. This region is mainly used for low-loss cyclic transmission of optical signals to improve the quantum efficiency and chip responsivity in waveguide-type germanium-silicon avalanche photodiodes.

[0024] The resonant detection region includes a P-type metal contact region 7, a germanium-Ge ring resonant waveguide structure 6, a charge control region 9, an intrinsic avalanche region 10, and an N-type metal contact region 11. The metal electrodes, corresponding to different types of metal contact regions, are divided into P-type electrodes 8 and N-type electrodes 12. The P-type electrode 8 is located above the P-type metal contact region 7; the N-type electrode 12 is located above the N-type metal contact region 11; and the heating electrode 13 is located above the germanium-Ge ring resonant waveguide structure 6. The resonant detection region is used to couple and transmit the optical signal from the optical transmission region into the ring resonant waveguide, realizing optical signal resonance and detection.

[0025] The germanium-Ge ring resonant waveguide structure 6, serving as the main light absorption region of the waveguide-type germanium-silicon avalanche photodiode, is located close to the resonant silicon-Si waveguide structure 3 to achieve efficient coupling and absorption of specific wavelength light fields, thereby increasing the chip's responsivity. The P-type metal contact region 7 and the charge control region 9 are located parallel to each other on both sides of the germanium-Ge ring resonant waveguide structure 6. The P-type metal contact region 7 is located on the outer side of the germanium-Ge ring resonant waveguide structure 6, while the charge control region 9 is located on the inner side. These regions are used to adjust the internal electric field distribution of the germanium-Ge ring resonant waveguide structure 6, ensuring a uniform electric field distribution. Under the influence of this uniform electric field, photogenerated carriers drift towards the intrinsic avalanche region 10. Simultaneously, the internal electric field strength of the germanium-Ge ring resonant waveguide structure 6 is adjusted, ensuring that photogenerated carriers within the germanium-Ge absorption region of the germanium-Ge ring resonant waveguide structure 6 move at saturation drift velocities, thus improving the bandwidth of the waveguide-type germanium-silicon avalanche photodiode chip.

[0026] In this embodiment, the substrate is an SOI substrate, and the thickness of the top silicon Si layer is 220 nm or 340 nm.

[0027] Furthermore, in this embodiment, the incident silicon nitride (Si3N4) waveguide structure 1 adopts a silicon nitride (Si3N4) strip waveguide structure with a strip width of 0.1µm-0.4µm, which is used to reduce the insertion loss generated when the optical signal is coupled into the waveguide, thereby achieving efficient coupling of the optical signal and reducing the transmission loss generated during optical signal transmission.

[0028] Furthermore, in this embodiment, both the incident interlayer conversion structure 2 and the outgoing interlayer conversion structure 4 include two conversion structures: one for silicon nitride Si3N4 strip waveguide to strip Si waveguide and the other for strip Si waveguide to ridge Si waveguide. This converts the silicon nitride Si3N4 strip transmission waveguide into a ridge Si waveguide, which facilitates the coupling of optical signals into the germanium Ge ring resonant waveguide structure 6.

[0029] Furthermore, in this embodiment, the outgoing silicon nitride (Si3N4) bent waveguide structure 5 adopts a silicon nitride (Si3N4) strip waveguide structure with a strip width of 0.1µm-0.4µm. The end of the outgoing silicon nitride (Si3N4) bent waveguide structure 5 adopts a structure with a gradually narrowing width on one side, such as a right-angled trapezoid, to cyclically transmit the optical signal back to the incident silicon nitride (Si3N4) waveguide structure 1, so as to achieve repetitive and efficient coupling absorption of the optical signal.

[0030] In this embodiment, the germanium-Ge ring resonant waveguide structure 6 is located close to the resonant silicon-Si waveguide structure 3. The germanium-Ge ring resonant waveguide structure 6 is situated inside the top silicon-Si layer, and its cross-section is rectangular to achieve optical signal coupling and absorption, thereby reducing device capacitance and carrier transport time. The width of the germanium-Ge ring resonant waveguide structure 6 is 0.04µm-0.3µm, and its height is 0.15µm-0.32µm.

[0031] In this embodiment, the P-type metal contact region 7 is located outside the germanium-Ge ring resonant waveguide structure 6, using boron (B) as the element ion, and the final doping concentration obtained in the P-type metal contact region 7 is ≥1×10⁻⁶. 20 cm -3 The P-type electrode 8 is located above the P-type metal contact area 7 and can be made of high-conductivity metal materials such as Al, Cu, and Au to reduce contact resistance and form a good ohmic contact.

[0032] In this embodiment, the N-type metal contact region 11 is located inside the germanium-Ge ring resonant waveguide structure 6, using arsenic (As) or phosphorus (P) ions as elemental ions. The final doping concentration obtained in the N-type metal contact region 11 is ≥1×10⁻⁶. 20 cm-3 The N-type electrode 12 is located above the N-type metal contact area 11 and can be made of high-conductivity metal materials such as Al, Cu, and Au to reduce contact resistance and form a good ohmic contact.

[0033] In this embodiment, the charge control region 9 is located inside the germanium-Ge ring resonant waveguide structure 6, using boron (B) as the element ion. The final doping concentration range obtained within the charge control region 9 is 5 × 10⁻⁶. 17 cm -3 -3×10 18 cm -3 It is used to control the electric field intensity in the germanium-Ge ring resonant waveguide structure 6, so that the carriers in the germanium-Ge absorption layer reach the saturation drift velocity, and prevent the carrier avalanche gain effect in the germanium-Ge absorption layer, thereby increasing the avalanche breakdown voltage and reducing excess noise.

[0034] Furthermore, in this embodiment, the intrinsic avalanche region 10 is located inside the germanium-Ge ring resonant waveguide structure 6, and between the N-type metal contact region 11 and the charge control region 9; this region is the intrinsic layer, and the carrier concentration must be ≤1×10⁻⁶. 17 cm -3 It is used to generate avalanche gain, increase the weak light detection capability of waveguide-type germanium-silicon avalanche photodiode, and improve responsivity; the width of the intrinsic avalanche region 10 is 0.05um-0.45um.

[0035] In this embodiment, the heating electrode 13 can be made of TiN material. The heating electrode 13 is located above the germanium-Ge ring resonant waveguide structure 6. The heating electrode 13 converts electrical energy into heat energy to adjust the operating wavelength of the waveguide-type germanium-silicon avalanche photodiode.

[0036] This embodiment provides a method for fabricating a waveguide-type germanium-silicon avalanche photodiode, comprising the following steps: S1. An SOI substrate was selected for chip fabrication. First, a 5nm-10nm thick silicon dioxide (SiO2) layer was deposited on the surface of the top silicon (Si) layer. Photoresist was then applied, and a photoresist window was created using photolithography. Afterward, arsenic (As) or phosphorus (P) elements were implanted into the N-type metal contact region 11 on the surface of the top silicon (Si) layer using ion implantation to form a heavily doped N-type region. The SiO2 layer was used as a dielectric layer to reduce damage to the surface of the top silicon (Si) layer during ion implantation and minimize surface defects. After the ion implantation process, a rapid thermal annealing process was used to implant arsenic (As) or phosphorus (P) ions into the interior of the top silicon (Si) layer, achieving good uniformity and a doping concentration ≥1×10⁻⁶. 20 cm -3 The N-type heavily doped region is used to reduce the metal contact resistance and form a good ohmic contact with the N-type electrode 12.

[0037] Rapid thermal annealing is a known process in the art and is known to those skilled in the art.

[0038] S2, using photolithography, dry etching and wet etching processes, silicon dioxide is used as a hard mask layer to etch a resonant silicon-Si waveguide structure 3 on the top silicon-Si layer. The resonant silicon-Si waveguide structure 3 is mainly a ridge waveguide. The incident light waveguide width in the incident silicon nitride Si3N4 waveguide structure 1 is 0.04um ~ 1um. At the same time, the ridge-shaped Si and strip-shaped Si waveguide structures in the incident interlayer conversion structure 2 and the outgoing interlayer conversion structure 4 are obtained, and the required annular silicon window is opened for the epitaxial fabrication of the germanium-Ge annular resonant waveguide structure (6). The silicon dioxide window is prepared by combining dry etching and wet etching processes, which can accurately control the window size and morphology and reduce damage to the surface of the top silicon-Si layer.

[0039] S3, epitaxial growth of a germanium-Ge absorber layer is performed in the annular silica window on the surface of the top silicon (Si) layer. The height of the annular silica window in the germanium-Ge annular resonant waveguide structure 6 is 0.15µm-0.32µm. Due to the growth characteristics of the germanium-Ge material itself and the influence of process errors, the cross-section of the prepared germanium-Ge absorber layer is trapezoidal with a base angle of 30°, and the width of the upper base is smaller than the width of the lower base. Therefore, the annular silica window in the germanium-Ge annular resonant waveguide structure 6 is larger than the germanium-Ge annular resonant waveguide structure 6. The width of the annular silica window is the sum of the widths of the P-type metal contact region 7, the germanium-Ge annular resonant waveguide structure 6, and the charge control region 9, and the thickness of the grown germanium-Ge absorber layer is relatively thick.

[0040] S4 uses photolithography, dry etching, and wet etching processes to etch away the germanium-Ge absorption layer material outside region 6 of the germanium-Ge ring resonant waveguide structure, leaving only the germanium-Ge absorption layer material within region 6 of the germanium-Ge ring resonant waveguide structure.

[0041] S5 employs an in-situ doped epitaxial growth method to epitaxially grow a layer with a doping concentration ≥1×10⁻⁶ on the surface of the top silicon Si layer. 20 cm -3 The P-type heavily doped region is formed by impurity element boron (B). Then, chemical mechanical polishing (CMP) is used to remove the excess thickness of the epitaxial silicon Si layer on the surface of the top silicon Si layer. Photolithography, dry etching and wet etching processes are then used to retain only the required P-type heavily doped region to form the P-type metal contact region 7.

[0042] S6 employs an in-situ doped epitaxial growth method to epitaxially grow a silicon Si layer with a doping concentration of 5×10⁻⁶ on the surface of the top silicon Si layer. 17 cm -3 -3×10 18cm -3 The P-type doped region is impurity element boron (B). Then, chemical mechanical polishing (CMP) is used to remove the excess thickness of the epitaxial silicon Si layer on the top silicon Si layer surface outside the desired P-type doped region. Photolithography, dry etching and wet etching processes are then used to retain only the desired P-type doped region to form charge control region 9. Some areas between the N-type metal contact region 11 and the charge control region 9 are not doped, forming intrinsic avalanche region 10.

[0043] S7. A silicon dioxide SiO2 dielectric layer is deposited and grown on the surface of the top silicon Si layer. Photolithography, dry etching, and wet etching processes are used to remove the silicon dioxide SiO2 dielectric layer and the top silicon Si layer in a specified area. Then, a silicon nitride Si3N4 layer is deposited and grown. Using photolithography, dry etching, and wet etching processes, the incident silicon nitride Si3N4 waveguide structure 1 and the outgoing silicon nitride Si3N4 bent waveguide structure 5 are fabricated. At the same time, the required silicon nitride Si3N4 strip waveguide structures in the incident interlayer conversion structure 2 and the outgoing interlayer conversion structure 4 are obtained.

[0044] S8. A silicon dioxide (SiO2) dielectric layer is deposited and grown on the epitaxial wafer. Windows are opened at designated positions above the corresponding P-type metal contact region 7 and N-type metal contact region 11 to prepare N-type electrode 12 and P-type electrode 8, respectively. The electrode materials can be high-conductivity metal materials such as Al, Cu and Au to reduce contact resistance and form good ohmic contact. A silicon dioxide (SiO2) window is opened in a designated area of ​​the germanium (Ge) ring resonant waveguide structure 6 to prepare heating electrode 13. The electrode material can be made of TiN material.

[0045] This preparation method employs an in-situ doping process, which ensures a uniform distribution of dopant elements in the doped region, facilitating a uniform electric field distribution within the germanium (Ge) absorption region. Furthermore, the doping distribution within the doped region prepared by the in-situ doping process is unaffected by factors such as long process times or elevated temperatures during preparation, effectively suppressing the diffusion of dopant elements into the germanium (Ge) absorption region. This ensures that all charge carriers within the absorption region remain at their saturated drift velocity, preventing a decrease in chip bandwidth.

[0046] In addition, this embodiment provides another method for fabricating a waveguide-type germanium-silicon avalanche photodiode, including the following steps: S1. An SOI substrate was selected for chip fabrication. First, a 5nm-10nm thick silicon dioxide (SiO2) layer was deposited on the surface of the top silicon (Si) layer. Photoresist was then applied, and photoresist windows were created using photolithography. Arsenic (As) or phosphorus (P) ions were implanted into the N-type metal contact region 11 on the surface of the top silicon (Si) layer using ion implantation to form heavily doped N-type regions. The SiO2 layer was used as a dielectric layer to reduce damage to the surface of the top silicon (Si) layer during ion implantation and minimize surface defects. After ion implantation, a rapid thermal annealing process was used to implant arsenic (As) or phosphorus (P) ions into the silicon (Si) layer, achieving good uniformity and a doping concentration ≥1×10⁻⁶. 20 cm -3 The N-type heavily doped region is used to reduce the metal contact resistance and form a good ohmic contact with the N-type electrode 12. Similarly, ion implantation and rapid thermal annealing are used to form a doping concentration ≥1×10⁻⁶ in the P-type metal contact region 7. 20 cm -3 The P-type heavily doped region contains boron (B) as the impurity element; a doping concentration of 5 × 10⁻⁶ is formed in charge control region 9. 17 cm -3 -3×10 18 cm -3 The P-type doped region contains boron (B) as the impurity element.

[0047] S2 employs photolithography, dry etching, and wet etching processes, using silicon dioxide as a hard mask layer, to etch a resonant silicon-Si waveguide structure 3 on the top silicon-Si layer. The resonant silicon-Si waveguide structure 3 is primarily composed of ridge-shaped waveguides with a ridge mesa depth of 0.15µm-0.32µm. The incident waveguide width within the incident silicon nitride (Si3N4) waveguide structure 1 is 0.04µm-1µm. Simultaneously, the ridge-shaped Si and strip-shaped Si waveguide structures in the incident interlayer conversion structure 2 and the exit interlayer conversion structure 4 are obtained, and the required annular silicon window is created for the epitaxial fabrication of the germanium-Ge annular resonant waveguide structure 6. The combination of dry etching and wet etching to prepare the silicon dioxide window allows for precise control of the window size and morphology, and reduces damage to the surface of the top silicon-Si layer. The annular silicon dioxide window height in the germanium-Ge annular resonant waveguide structure 6 is 0.15µm-0.32µm.

[0048] S3, epitaxial growth of a germanium-Ge absorber layer is performed in the annular silicon dioxide window on the surface of the top silicon (Si) layer. Due to the growth characteristics of germanium-Ge material itself and the influence of process errors, the cross-section of the prepared germanium-Ge absorber layer 7 is trapezoidal with a base angle of 30°, and the width of the upper base is smaller than that of the lower base. In order to ensure that a vertical and uniform germanium-Ge absorber layer is grown in the germanium-Ge annular resonant waveguide structure 6, the thickness of the germanium-Ge absorber layer needs to be relatively thick, ranging from 2µm to 10µm.

[0049] S4. Using chemical mechanical polishing (CMP) process, the germanium-Ge absorption layer material outside the region of germanium-Ge ring resonant waveguide structure 6 is etched away, leaving only the germanium-Ge absorption layer material inside germanium-Ge ring resonant waveguide structure 6. The germanium-Ge absorption layer of germanium-Ge ring resonant waveguide structure 6 is flush with the surface of the top silicon Si layer.

[0050] S5, a silicon dioxide SiO2 dielectric layer is deposited and grown on the surface of the top silicon Si layer. Photolithography, dry etching and wet etching processes are used to remove the silicon dioxide SiO2 dielectric layer and the top silicon Si layer in the specified area. Then, a silicon nitride Si3N4 layer is deposited and grown. Using photolithography, dry etching and wet etching processes, the incident silicon nitride Si3N4 waveguide structure 1 and the outgoing silicon nitride Si3N4 bent waveguide structure 5 are fabricated. At the same time, the required silicon nitride Si3N4 layer waveguide strip waveguide structures in the incident interlayer conversion structure 2 and the outgoing interlayer conversion structure 4 are obtained.

[0051] S6. A silicon dioxide (SiO2) dielectric layer is deposited and grown on the epitaxial wafer. Windows are opened at designated positions above the corresponding P-type metal contact region 7 and N-type metal contact region 11 to prepare N-type electrode 12 and P-type electrode 8, respectively. The electrode materials can be high-conductivity metal materials such as Al, Cu and Au to reduce contact resistance and form good ohmic contact. A silicon dioxide (SiO2) window is opened in a designated area of ​​the germanium (Ge) ring resonant waveguide structure 6 to prepare heating electrode 13. The electrode material can be made of TiN material.

[0052] This fabrication method fully complies with the CMOS fabrication process for silicon-based devices. Its process is simple and can greatly shorten the fabrication time of waveguide-type germanium-silicon avalanche photodiode chips and reduce their fabrication costs.

[0053] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waveguide-type germanium-silicon avalanche photodiode, characterized in that, It includes a substrate, an optical transmission region, and a resonant detection region. Both the optical transmission region and the resonant detection region are located on the top silicon Si layer of the substrate. The optical transmission region is used for optical signal transmission, enabling optical signal incident and recirculating optical signals in the ring resonant waveguide structure that are not fully coupled to the resonant detection region. The resonant detection region is used to couple and transmit the optical signal from the optical transmission region into the ring resonant waveguide, thereby realizing optical signal resonance and detection. The optical transmission region includes an incident waveguide structure, an incident interlayer conversion structure (2), a resonant silicon-Si waveguide structure (3), an outgoing interlayer conversion structure (4), and an outgoing curved waveguide structure. The resonant silicon-Si waveguide structure (3) is located outside the resonant detection region. The two ends of the resonant silicon-Si waveguide structure (3) are connected to the incident waveguide structure and the outgoing curved waveguide structure through the incident interlayer conversion structure (2) and the outgoing interlayer conversion structure (4), respectively. The resonant detection region includes a P-type metal contact region (7), a germanium-Ge ring resonant waveguide structure (6), a charge control region (9), an intrinsic avalanche region (10), and an N-type metal contact region (11). The germanium-Ge ring resonant waveguide structure (6) is close to the resonant silicon-Si waveguide structure (3). The germanium-Ge ring resonant waveguide structure (6) is located inside the top silicon-Si layer of the substrate and is ring-shaped. The P-type metal contact region (7) and the charge control region (9) are located parallel to each other on both sides of the germanium-Ge ring resonant waveguide structure (6). The P-type metal contact region (7) is located outside the germanium-Ge ring resonant waveguide structure (6), and the charge control region (9) is located inside the germanium-Ge ring resonant waveguide structure (6). The N-type metal contact region (11) is located inside the charge control region (9), and the intrinsic avalanche region (10) is located between the N-type metal contact region (11) and the charge control region (9). The P-type electrode (8) and the N-type electrode (12) are respectively prepared above the P-type metal contact region (7) and the N-type metal contact region (11). The heating electrode (13) is prepared on the germanium-Ge ring resonant waveguide structure (6) and is close to the resonant silicon-Si waveguide structure (3).

2. The waveguide-type germanium-silicon avalanche photodiode according to claim 1, characterized in that, The incident waveguide structure is an incident silicon nitride (Si3N4) waveguide structure (1), which adopts a silicon nitride (Si3N4) strip waveguide structure with a strip width of 0.1um-0.4um; The outgoing curved waveguide structure is an outgoing silicon nitride (Si3N4) curved waveguide structure (5), which adopts a silicon nitride (Si3N4) strip waveguide structure with a strip width of 0.1um-0.4um.

3. The waveguide-type germanium-silicon avalanche photodiode according to claim 2, characterized in that, The width of the end side of the outgoing silicon nitride Si3N4 bent waveguide structure (5) gradually narrows.

4. The waveguide-type germanium-silicon avalanche photodiode according to claim 2, characterized in that, Both the incident interlayer conversion structure (2) and the outgoing interlayer conversion structure (4) include a silicon nitride Si3N4 strip waveguide to strip Si waveguide structure and a strip Si waveguide to ridge Si waveguide structure.

5. The waveguide-type germanium-silicon avalanche photodiode according to claim 1, characterized in that, The cross-section of the germanium (Ge) ring resonant waveguide structure (6) is rectangular, with a width of 0.04um-0.3um and a height of 0.15um-0.32um.

6. The waveguide-type germanium-silicon avalanche photodiode according to claim 1, characterized in that, The resonant silicon Si waveguide structure (3) is a ridge waveguide with a ridge depth of 0.15um-0.32um.

7. The waveguide-type germanium-silicon avalanche photodiode according to claim 1, characterized in that, The P-type metal contact region (7), charge control region (9), and N-type metal contact region (11) are all formed on the top silicon Si layer by ion implantation. The doping concentration of the P-type metal contact region (7) and the N-type metal contact region (11) is ≥1×10⁻⁶. 20 cm -3 The doping concentration range of the charge control region (9) is 5 × 10⁻⁶. 17 cm -3 -3×10 18 cm -3 .

8. The waveguide-type germanium-silicon avalanche photodiode according to claim 1, characterized in that, The width of the intrinsic avalanche zone (10) is 0.05um-0.45um.

9. The method for fabricating a waveguide-type germanium-silicon avalanche photodiode according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Select an SOI substrate for chip fabrication. Ion implantation is performed on the top silicon Si layer at the N-type metal contact area (11) to form an N-type heavily doped region. After ion implantation, rapid thermal annealing is performed. S2. On the top silicon Si layer, a resonant silicon Si waveguide structure (3) is etched out using silicon dioxide as a hard mask layer. At the same time, the ridge-shaped Si waveguide structure and the strip-shaped Si waveguide structure in the incident interlayer conversion structure (2) and the outgoing interlayer conversion structure (4) are etched out. The required annular silicon window is opened for the epitaxial fabrication of the germanium Ge annular resonant waveguide structure (6). S3. In the prepared annular silicon window, an annular silicon dioxide window is opened for epitaxial growth of the germanium Ge absorber layer; S4. Remove the germanium-Ge absorption layer material outside the region of the germanium-Ge ring resonant waveguide structure (6); S5. Using in-situ doped epitaxial growth, a P-type heavily doped region is epitaxially grown on the surface of the top silicon Si layer; the epitaxial silicon Si layer on the surface of the top silicon Si layer other than the required P-type heavily doped region is removed, and a P-type metal contact region is formed on the remaining P-type heavily doped region (7). S6. Using in-situ doped epitaxial growth, a P-type doped region is epitaxially grown on the surface of the top silicon Si layer; the epitaxial silicon Si layer on the surface of the top silicon Si layer other than the required P-type doped region is removed, and a charge control region (9) is formed on the remaining P-type doped region; some areas between the N-type metal contact region (11) and the charge control region (9) are not doped, forming an intrinsic avalanche region (10). S7. Deposit and grow a silicon dioxide SiO2 dielectric layer on the surface of the top silicon Si layer, remove the silicon dioxide SiO2 dielectric layer and the top silicon Si layer in the specified area, and then deposit and grow a silicon nitride Si3N4 layer. Prepare the incident silicon nitride Si3N4 waveguide structure (1) and the outgoing silicon nitride Si3N4 bent waveguide structure (5) in the specified area. At the same time, etch out the required silicon nitride Si3N4 strip waveguide structure in the incident interlayer conversion structure (2) and the outgoing interlayer conversion structure (4). S8. A silicon dioxide (SiO2) dielectric layer is deposited and grown on the epitaxial wafer to prepare a P-type electrode (8), an N-type electrode (12), and a heating electrode (13).

10. The method for fabricating a waveguide-type germanium-silicon avalanche photodiode according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Select an SOI substrate for chip fabrication. On the top silicon Si layer, ion implantation is performed in the N-type metal contact region (11), P-type metal contact region (7) and charge control region (9) to form an N-type heavily doped region, a P-type heavily doped region and a P-type doped region, respectively. After ion implantation, rapid thermal annealing is performed. S2. On the top silicon Si layer, a resonant silicon Si waveguide structure (3) is etched out using silicon dioxide as a hard mask layer. At the same time, the ridge Si waveguide structure and the strip Si waveguide structure in the incident interlayer conversion structure (2) and the outgoing interlayer conversion structure (4) are etched out. The annular silicon window required for the epitaxial fabrication of the germanium Ge annular resonant waveguide structure (6) is also etched out. S3. In the prepared annular silicon window, an annular silicon dioxide window is opened for epitaxial growth of the germanium Ge absorber layer; S4. Remove the germanium-Ge absorption layer material outside the region of the germanium-Ge ring resonant waveguide structure (6). The germanium-Ge absorption layer in the region of the germanium-Ge ring resonant waveguide structure (6) is flush with the surface of the top silicon-Si layer. S5. A silicon dioxide SiO2 dielectric layer is deposited and grown on the surface of the top silicon Si layer. The silicon dioxide SiO2 dielectric layer and the top silicon Si layer in the specified area are removed. Then, a silicon nitride Si3N4 layer is deposited and grown. An incident silicon nitride Si3N4 waveguide structure (1) and an outgoing silicon nitride Si3N4 bent waveguide structure (5) are prepared in the specified area. At the same time, the required silicon nitride Si3N4 strip waveguide structure in the incident interlayer conversion structure (2) and the outgoing interlayer conversion structure (4) are etched. S6. A silicon dioxide (SiO2) dielectric layer is deposited and grown on the epitaxial wafer to prepare a P-type electrode (8), an N-type electrode (12), and a heating electrode (13).

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