Waveguide avalanche photodetector with low dark current
Patent Information
- Application Number
- CN202611028957.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-10
- Publication Date
- 2026-10-27
AI Technical Summary
[0028]1、本发明的低暗电流的波导式雪崩光电探测器，在传统侧向结SACM APD结构基础上，增加多次掺杂形成的电场控制区,有效降低了APD侧向泄露电流，可以同时实现低暗电流和高响应度的波导式APD。
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Figure CN122995290A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of high-speed optical communication and optical chip technology, specifically to a waveguide avalanche photodetector with low dark current. Background Technology
[0002] On-chip photodetectors are one of the core components of integrated optoelectronic chips, serving as the receiver in optical transmission systems to convert high-speed optical signals into electrical signals. Currently, integrated photonic chips primarily employ conventional PIN-type photodetectors. In applications with long optical links, avalanche photodetectors (APDs) can utilize the avalanche collision ionization effect to amplify the photocurrent, significantly improving the detection capability of optical signals and compensating for attenuation caused by long-distance transmission. Furthermore, waveguide-type APDs can be integrated on-chip with other photonic devices, making them an important component of future high-performance photonic chips.
[0003] Currently, waveguide-type APD chips are mainly divided into two architectures: vertical junction waveguide APDs and side junction waveguide APDs. Vertical junction waveguide APDs can achieve low dark current, but they have the disadvantage of complex manufacturing processes. Side junction waveguide APDs have relatively simple manufacturing processes, are easy to integrate with other devices, and have high light absorption efficiency, but they suffer from excessively high dark current, which cannot support the normal operation of photonic chips at high temperatures.
[0004] The main reason for the excessive dark current in lateral junction waveguide APDs is that the region where the electric field is concentrated is very close to the edge of the light absorption region, which leads to severe lateral leakage current.
[0005] The cross-sectional structure of a traditional lateral junction waveguide APD is shown in Figure 1(a). A SACM structure, i.e., a structure with separated absorption and multiplication layers, is formed by doping the top silicon layer of an SOI wafer. Through ion implantation, a P-electrode contact region 201, an intrinsic silicon region 202, an electric field control region I 203, a multiplication region 204, and an N-electrode contact region 205 are formed on the top silicon layer. The absorption region 301 is located above the silicon layer, which includes the P-electrode contact region 201, the intrinsic silicon region 202, the electric field control region I 203, the multiplication region 204, and the N-electrode contact region 205.
[0006] In a traditional lateral junction waveguide APD, the electric field control region I 203 is achieved through a single ion implantation, and its doped ion distribution is shown in Figure 1(c). The ion concentration on the substrate silicon surface is very low, which causes the area with a strong electric field to spread to the edge of the absorption region, as shown in Figure 1(e). When the electric field at the edge of the absorption region 301 is too strong, this approach can cause a large dark current. Summary of the Invention
[0007] To address the aforementioned challenge, the present invention aims to propose a waveguide avalanche photodetector with low dark current. Based on the traditional side-junction SACM APD structure, an electric field control region formed by multiple doping is added, which effectively reduces the lateral leakage current of the APD and can simultaneously achieve low dark current and high responsivity.
[0008] The technical solution adopted is as follows:
[0009] A waveguide avalanche photodetector with low dark current includes a lateral junction waveguide APD with a SACM structure, and multiple doping to form one or two electric field control regions.
[0010] Further preferred options include waveguide-type avalanche photodetectors with low dark current, including
[0011] The substrate layer has a P-electrode contact region, an intrinsic region, an electric field control region, a multiplication region, and an N-electrode contact region arranged sequentially on top of it. The electric field control region I is a lightly doped P-type region. The electric field control region I undergoes multiple ion doping processes, and the ion implantation energy decreases sequentially. The electric field control region I forms a uniform ion concentration distribution in the vertical direction.
[0012] The absorption region is located above the intrinsic region;
[0013] The passivation layer, located above the silicon layer and encapsulating the absorption region, provides support for the metal electrode.
[0014] The electrode region is located above the passivation layer.
[0015] Further preferred options include waveguide-type avalanche photodetectors with low dark current, including
[0016] A substrate layer is formed, and above the substrate layer, a P-electrode contact region, an intrinsic region, an electric field control region I, a multiplication region, an electric field control region II, and an N-electrode contact region are sequentially arranged. Among them, the electric field control region I is a lightly doped P-type region, which undergoes multiple ion doping processes with the ion implantation energy decreasing sequentially. The electric field control region I forms a uniform ion concentration distribution from top to bottom in the vertical direction. The electric field control region II undergoes ion doping, and the N-type doped ion concentration in the electric field control region II first increases and then decreases from top to bottom in the vertical direction.
[0017] The absorption region is located above the intrinsic region;
[0018] The passivation layer, located above the silicon layer and encapsulating the absorption region, provides support for the metal electrode.
[0019] The electrode region is located above the passivation layer.
[0020] Further optimization involves multiple P-type ion implantations in the electric field control region I as follows: using the same type of ion implantation or different types of ion implantation, performing three or more ion implantations, with the ion implantation energy decreasing sequentially.
[0021] Further preferred, the lateral dimension of the adjacent ion implantation step is increased by 20-50 nm compared to the previous ion implantation step.
[0022] Further optimization involves multiple ion implantations in the electric field control region I, with an additional ion implantation near the edge of the absorption region to form an isolation zone.
[0023] Further optimization involves using the following ion implantation method in the electric field control region II: a single medium-energy implantation using an N-type ion.
[0024] Further optimization is made to use the following ion implantation method in the electric field control region II: a single ion implantation method in which N-type ions and P-type ions compensate for each other, with the implantation energy of N-type ions being higher than that of P-type ions.
[0025] Further preferred, the electric field control region II is located between the multiplication region and the N electrode contact region, and is connected to or partially overlaps with the N electrode contact region; the ion implantation width of the electric field control region II is 50~200nm.
[0026] Further optimization is that the width of the doped region in the electric field control region I is 50~150nm.
[0027] The advantages of this invention compared to the prior art are as follows:
[0028] 1. The low dark current waveguide avalanche photodetector of the present invention, based on the traditional side junction SACM APD structure, adds an electric field control region formed by multiple doping, which effectively reduces the side leakage current of the APD and can simultaneously achieve a waveguide APD with low dark current and high responsivity.
[0029] 2. The waveguide avalanche photodetector with low dark current of the present invention has an electric field control layer that is doped multiple times or has a guard ring design, which effectively reduces the electric field at the edge of the absorption region and suppresses dark current.
[0030] 3. The low dark current waveguide avalanche photodetector of the present invention includes first and second electric field control region structures, and proposes multiple ion implantation methods to mainly confine the electric field of the multiplication region to the central region of the longitudinal waveguide, which greatly suppresses the dark current. Attached Figure Description
[0031] Figure 1(a) is a schematic diagram of a traditional lateral junction waveguide APD;
[0032] Figure 1(b) is a schematic diagram of the lateral junction waveguide APD of the present invention;
[0033] Figure 1(c) is a schematic diagram of the doped ion distribution in the electric field control region of a conventional side junction waveguide APD.
[0034] Figure 1(d) is a schematic diagram of the doped ion distribution in the electric field control region of the lateral junction waveguide APD of the present invention;
[0035] Figure 1(e) is a schematic diagram of the electric field distribution of a traditional lateral junction waveguide APD;
[0036] Figure 1(f) is a schematic diagram of the electric field distribution of the lateral junction waveguide APD of the present invention;
[0037] Figure 2 This is a schematic diagram of the low dark current lateral junction waveguide APD of the first ion implantation scheme in Example 1.
[0038] Figure 3 This is a schematic diagram of the ion implantation doping distribution in the electric field control region I of the first scheme in Example 1;
[0039] Figure 4 This is a schematic diagram of the low dark current lateral junction waveguide APD of the second ion implantation scheme in Example 1.
[0040] Figure 5 This is a schematic diagram of the low dark current lateral junction waveguide APD of the third ion implantation scheme in Example 1.
[0041] Figure 6 This is a schematic diagram of the low dark current lateral junction waveguide APD of the first ion implantation scheme in Example 2.
[0042] Figure 7 This is a schematic diagram of the ion implantation doping distribution in the electric field control region II of the first scheme in Example 2;
[0043] Figure 8 This is a schematic diagram of the low dark current lateral junction waveguide APD structure of the second ion implantation scheme in Example 2;
[0044] Figure 9 This is a schematic diagram of the ion implantation doping distribution in the electric field control region II of the second scheme in Example 2;
[0045] Among them, 101 is the substrate layer; 201 is the P-electrode contact region; 202 is the intrinsic region; 203 is the electric field control region I; 203-1 is the isolation zone; 204 is the multiplication region; 205 is the N-electrode contact region; and 206 is the electric field control region II. Detailed Implementation
[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with Figure 1- Figure 9 The 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.
[0047] This embodiment proposes a low dark current waveguide avalanche photodetector, which is a side-junction waveguide APD. Specifically, it is based on a traditional side-junction waveguide APD with a SACM structure, as shown in Figure 1(b). By changing the injection method of the electric field control layer or adding a second electric field control layer (electric field control layer II), the advantage is that the electric field is concentrated entirely in the multiplication region. The electric field is very weak at the edge of the absorption region and the part where the multiplication region contacts, as shown in Figure 1(f). Because of the lattice mismatch at the contact between the absorption region and the multiplication region, this region is very sensitive to the electric field. The stronger the electric field, the higher the dark current. Conversely, this scheme concentrates the electric field mainly in the multiplication region, thereby achieving the purpose of reducing dark current, as shown in Figure 1(d).
[0048] Example 1
[0049] This embodiment proposes a low dark current side-junction waveguide APD, such as... Figure 2 As shown, it includes:
[0050] Substrate 101, the material of substrate 101 is SOI material or bulk silicon material;
[0051] Above the substrate layer 101, a P-electrode contact region 201, an intrinsic region 202, an electric field control region I 203, a multiplication region 204, and an N-electrode contact region 205 are sequentially disposed. The P-electrode contact region 201 is formed by ion implantation to form a P-type doped region, providing a positive electrode for the APD. The intrinsic region 202 may not be ion implanted or may be lightly doped with P-type implantation. The electric field control region I 203 is lightly doped with P-type, and the width of the doped region is not limited, generally 50-150nm. The multiplication region 204 is undoped and is the region where avalanche breakdown occurs. The N-electrode contact region 205 is formed by ion implantation to form an N-type doped region, providing a negative electrode for the APD.
[0052] Absorption layer 301, intrinsic absorption region, can be made of Ge (germanium) or InGaAs (indium gallium arsenide), located above intrinsic region 202, and its thickness is not limited;
[0053] Passivation layer 401 provides support for the metal electrode;
[0054] Electrode region 402, the metal electrode provides electrical connection for the APD.
[0055] In this embodiment, the purpose of the electric field control region I 203 is to form a uniform ion concentration distribution from top to bottom in the vertical direction; therefore, the electric field control region I 203 needs to be injected multiple times.
[0056] In this embodiment, the electric field control region I 203 is p-type doped using ion implantation to reduce the electric field intensity at the edge of the absorption region; the specific scheme is as follows:
[0057] In the first approach, the electric field control region I 203 is a lightly doped P-type region. Multiple ion implantations are performed within I 203, with the energy of each implantation decreasing sequentially. For example... Figure 3 As shown, the ion concentration in the longitudinal direction of a single ion implantation exhibits a Gaussian distribution, which is non-uniform. Since the ion implantation depth can be adjusted by the implantation energy, the higher the implantation energy, the deeper the ion implantation depth. Through multiple ion implantations with energies decreasing from high to low, the ion concentration will be superimposed at different positions in the longitudinal direction. The final result is that after multiple doping, the electric field control region I 203 forms a uniform concentration distribution in the longitudinal direction. That is, the ion concentration in the electric field control region I 203 is the same from top to bottom in the longitudinal direction (while the electric field control layer of the traditional lateral junction waveguide APD is achieved by a single ion implantation, and the ion concentration first increases and then decreases from top to bottom). The effect is that the electric field is also uniformly distributed in the longitudinal direction, and the electric field is relatively weakened at the edge of the absorption layer 301, resulting in a decrease in dark current.
[0058] In this specific case, multiple ion implantations are performed in the electric field control region I 203, and the combination of multiple ion implantations includes the following two forms:
[0059] Format 1: Using the same ion implantation, such as Boron ions, perform three or more Boron ion implantations:
[0060] For the first injection, the dose (injection volume) = 4e12 and the energy = 40keV;
[0061] The second injection had a dose of 3e12 and an energy of 30keV.
[0062] The third injection had a dose of 1e12 and an energy of 10keV.
[0063] Format 2: Using two types of ion implantation, such as Boron (boron ions) and BF2 (boron difluoride ions). It is known that at the same implantation energy, Boron is more likely to be implanted deeper vertically, while BF2 is shallower. Therefore, secondary or more ion implantations can be performed.
[0064] The first injection of Boron had a dose of 4e12 and an energy of 40keV.
[0065] The second injection of BF2 had a dose of 3e12 and an energy of 20keV.
[0066] The second approach involves multiple ion implantations within the electric field-controlled region I 203. The energy of each implantation decreases, and the lateral region of each implantation gradually increases, with adjacent implantation steps having a lateral dimension 20-50 nm larger than the previous one. For example... Figure 4 As shown, the electric field control region I 203 forms a concentration distribution from high to low in the longitudinal direction, which has the effect of further reducing the electric field near the absorption region.
[0067] Specifically, multiple ion implantations are performed in the electric field control region 203, and the combination of multiple ion implantations includes the following two forms:
[0068] Using the same type of ion implantation or multiple types of ion implantation, performing two or more implantation processes:
[0069] For the first implantation, the first mask is used to define the lateral dimension of the first ion implantation, with a lateral width of 100 nm. The ion implantation can be Boron or BF2, with a dose of 4e12 and an energy of 40 keV, forming an ion distribution with a smaller lateral dimension.
[0070] For the second implantation, a second mask is used to define the lateral dimension of the second ion implantation. The lateral width is 150 nm. The ion implanter can be Boron or BF2. The lateral implantation width is larger than that of the first mask. The dose is 4e12 and the energy is 20 keV, forming an ion distribution with a larger lateral dimension.
[0071] The third approach involves multiple ion implantations in the electric field control region I 203, and simultaneously, an additional ion implantation near the edge of the absorption region 301, creating an effect similar to the guard ring 203-1. Figure 5 As shown, the electric field at the edge of the absorption region is effectively reduced; the newly added GR structure (isolation zone) has a smaller lateral dimension than the electric field control region.
[0072] Specifically, in this scheme, the electric field control region I 203 undergoes multiple ion implantations in the same way as in the first scheme; in addition, new ion implantations are performed near the edge of the absorption region 31, with a dose of 1e12 and an energy of 10keV, to form a GR structure.
[0073] Example 2
[0074] This embodiment proposes a low dark current side junction waveguide APD. Unlike Embodiment 1, Embodiment 2 includes electric field control region I 203 and electric field control region II 206.
[0075] In this embodiment, the ion implantation scheme for the electric field control region I 203 is the same as that in Embodiment 1. The electric field control region II 206 is located between the multiplication region 204 and the N electrode contact region 205, and is connected to or partially overlaps with the N electrode contact region 205.
[0076] The objective of electric field control region II 206 is to achieve an ion concentration distribution that first increases and then decreases from top to bottom in the vertical direction; therefore, electric field control region II 206 only requires one injection.
[0077] The ion implantation scheme for the electric field control region II 206 involves increasing and then decreasing the concentration of N-type doped ions vertically from top to bottom. The beneficial effect is that the electric field is concentrated only in the central vertical region of the intrinsic silicon, with the electric field further decreasing near the edge of the absorption region, significantly reducing dark current. The implantation width of the electric field control region II 206 is unrestricted, typically ranging from 50 to 200 nm.
[0078] Specifically,
[0079] like Figure 6 As shown, the first ion implantation method in the electric field control region II 206 uses a single ion implantation, selecting arsenic or phosphorus, with medium-energy implantation, for example, dose = 1e14, energy = 35keV. The ion implantation distribution of this scheme is as follows. Figure 7 As shown, the ion concentration is concentrated in the longitudinal middle region of the waveguide, which effectively reduces the electric field intensity on the waveguide surface and weakens the electric field at the edge of the absorption region.
[0080] The second ion implantation method in electric field control region II 206 uses a mutual compensation method between N-type and P-type ions. The N-type ions can be arsenic or phosphorus, and the P-type ions can be boron or BF2. Figure 8 As shown.
[0081] In actual implantation, the implantation energy of N-type ions is high, while that of P-type ions is low.
[0082] For example, N-type ion dose = 1e14, energy = 40keV; P-type ion dose = 1e12~1e13, energy = 12keV.
[0083] The ion implantation concentration distribution of this scheme is as follows: Figure 9 As shown, the ion implantation concentration near the longitudinal upper surface of the waveguide is almost zero, which greatly reduces the electric field at the edge of the absorption region.
[0084] 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 low dark current waveguide avalanche photodetector, comprising a lateral junction waveguide APD with a SACM structure, characterized in that, Multiple doping processes can be used to create one or two electric field control regions.
2. The low dark current waveguide avalanche photodetector according to claim 1, characterized in that, include A substrate layer (101) is provided above the substrate layer (101) in sequence, including a P-electrode contact region (201), an intrinsic region (202), an electric field control region (203), a multiplication region (204), and an N-electrode contact region (205). The electric field control region I (203) is a lightly doped P-type region. The electric field control region I (203) is subjected to multiple ion doping processes, and the ion implantation energy decreases sequentially. The electric field control region I (203) forms a uniform ion concentration distribution in the vertical direction. The absorption region (301) is located above the intrinsic region (202); The passivation layer (401), located above the silicon layer and enclosing the absorption region (301), provides support for the metal electrode; The electrode region (402) is located above the passivation layer (401).
3. The waveguide avalanche photodetector with low dark current according to claim 1, characterized in that, include A substrate layer (101) is provided above the substrate layer (101) in sequence, including a P-electrode contact region (201), an intrinsic region (202), an electric field control region I (203), a multiplication region (204), an electric field control region II (206), and an N-electrode contact region (205). Among them, the electric field control region I (203) is a lightly doped P-type region. The electric field control region I (203) is subjected to multiple ion doping, and the ion implantation energy decreases sequentially. The electric field control region I (203) forms a uniform ion concentration distribution from top to bottom in the vertical direction. The electric field control region II (206) is subjected to ion doping. In the electric field control region II (206), the N-type doped ion concentration first increases and then decreases from top to bottom in the vertical direction. The absorption region (301) is located above the intrinsic region (202); The passivation layer (401), located above the silicon layer and enclosing the absorption region (301), provides support for the metal electrode; The electrode region (402) is located above the passivation layer (401).
4. The low dark current waveguide avalanche photodetector according to claim 2 or 3, characterized in that, The method for multiple P-type ion implantations in the electric field control region I (203) is as follows: using the same ion implantation or different ion implantations, perform three or more ion implantations, with the ion implantation energy decreasing sequentially.
5. The low dark current waveguide avalanche photodetector according to claim 4, characterized in that, The lateral dimension of an adjacent ion implantation step is 20-50 nm larger than that of the previous ion implantation step.
6. The low dark current waveguide avalanche photodetector according to claim 4, characterized in that, Multiple ion implantations are formed in the electric field control region I (203). An additional ion implantation is performed near the edge of the absorption region (301) to form an isolation zone.
7. The low dark current waveguide avalanche photodetector according to claim 3, characterized in that, The ion implantation method for electric field control region II (206) is as follows: a medium-energy implantation is performed using an N-type ion.
8. The low dark current waveguide avalanche photodetector according to claim 3, characterized in that, The ion implantation method in the electric field control region II (206) is as follows: a single ion implantation method in which N-type ions and P-type ions compensate each other, and the implantation energy of N-type ions is higher than that of P-type ions.
9. The low dark current waveguide avalanche photodetector according to claim 7 or 8, characterized in that, The electric field control region II (206) is located between the multiplication region (204) and the N electrode contact region (205), and is connected to or partially overlaps with the N electrode contact region (205); the ion implantation width of the electric field control region II (206) is 50~200nm.
10. The low dark current waveguide avalanche photodetector according to claim 2, characterized in that, The width of the doped region in the electric field control region I (203) is 50~150nm.