Avalanche photodiode and method of manufacturing the same
By using InAlAs/GaAsSb superlattice as the multiplication layer material for InP-based APDs, the problems of high noise factor and high preparation cost in existing technologies have been solved, achieving low-cost and high-efficiency APD preparation and improving signal-to-noise ratio and production capacity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUZHOU JINGGE SEMICON CO LTD
- Filing Date
- 2026-03-23
- Publication Date
- 2026-07-24
AI Technical Summary
Existing InP-based avalanche photodiode (APD) multiplication layer materials suffer from high noise factors and high fabrication costs. In particular, InAlAsSb materials are difficult to grow in MOCVD, resulting in high fabrication costs and low yields.
An InAlAs/GaAsSb superlattice was used as the multiplication layer material and prepared using MOCVD. By growing the Sb-containing and Al-containing materials separately, the problems of gas phase reaction and high impurity background were avoided, and an undoped InAlAs/GaAsSb superlattice was formed as the charge layer.
The APD with low noise factor was achieved, which reduced manufacturing costs, increased production capacity and yield, and improved the signal-to-noise ratio.
Smart Images
Figure CN121888705B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of optoelectronics and semiconductor technology, specifically, it relates to an avalanche photodiode and its fabrication method. Background Technology
[0002] InP-based avalanche photodiodes (APDs) are now widely used in commercial, military, and scientific research fields, driving the development of technologies such as optical communication, imaging, and single-photon detection.
[0003] The core of an APD (Active Detector) is the multiplication layer, which determines the detector's noise and signal-to-noise ratio. For InP-based APDs, existing technologies use multiplication layers made of materials such as InP, InAlAs, and InAlAsSb. While InP and InAlAs materials have relatively high noise factors, they can be prepared using the industry-standard metal-organic chemical vapor deposition (MOCVD), resulting in relatively low manufacturing costs and a cost-effectiveness advantage. Antimony compound InAlAsSb, however, has extremely low noise factors, but growing materials containing Al and Sb using MOCVD results in a high impurity background, and the gas-phase reaction makes Sb incorporation difficult. Therefore, APDs containing InAlAsSb multiplication layers can currently only be prepared using molecular beam epitaxy (MBE), leading to higher costs and lower yields.
[0004] Therefore, a new multiplication layer material is needed that has both a low noise factor and can be prepared using low-cost MOCVD. Summary of the Invention
[0005] To address the aforementioned technical problems in the existing technology, embodiments of the present invention provide an avalanche photodiode with a novel multiplication layer material and a method for fabricating the same, which has both a low noise factor and can be fabricated using low-cost MOCVD.
[0006] According to one aspect of the embodiments of the present invention, the substrate of the avalanche photodiode is an InP substrate, wherein the multiplication layer of the avalanche photodiode is an undoped InAlAs / GaAsSb superlattice, and the charge layer of the avalanche photodiode is a P-type InAlAs / GaAsSb superlattice.
[0007] In one example of the avalanche photodiode provided above, the avalanche photodiode further includes an N-type contact layer, a transition layer, an absorption layer, a blocking layer, a P-type contact layer, a first electrode, and a second electrode; wherein the N-type contact layer, the multiplication layer, the charge layer, the transition layer, the absorption layer, and the blocking layer are sequentially stacked on the substrate with respect to the P-type contact layer in a direction away from the substrate, the first electrode is in contact with the N-type contact layer, and the second electrode is disposed on the P-type contact layer.
[0008] In one example of the avalanche photodiode provided above, portions of the P-type contact layer, the blocking layer, the absorption layer, the transition layer, the charge layer, and the multiplication layer are etched away to form a mesa structure exposing the N-type contact layer, and the first electrode is disposed on the exposed N-type contact layer.
[0009] In one example of the avalanche photodiode provided above, the N-type contact layer is made of N-type InGaAs material, the transition layer is made of undoped InAlGaAs material, the absorption layer is made of undoped InGaAs material, the blocking layer is made of P-type InAlAs material, and the P-type contact layer is made of P-type InGaAs material.
[0010] In one example of the avalanche photodiode provided above, the InAlAs / GaAsSb superlattice is composed of alternating layers of InAlAs and GaAsSb thin layers, wherein both the InAlAs and GaAsSb thin layers are lattice-matched with the substrate, or both the InAlAs and GaAsSb thin layers are lattice-mismatched with the substrate, and the InAlAs / GaAsSb superlattice is stress-balanced.
[0011] A method for fabricating an avalanche photodiode according to another aspect of an embodiment of the present invention includes: forming a multiplication layer of the avalanche photodiode on a substrate using an undoped InAlAs / GaAsSb superlattice, and forming a charge layer of the avalanche photodiode on the substrate using a P-type InAlAs / GaAsSb superlattice; wherein the substrate of the avalanche photodiode is an InP substrate.
[0012] In one example of the avalanche photodiode fabrication method provided in the other aspect above, before forming the multiplication layer, the fabrication method further includes: forming an N-type contact layer stacked on a substrate; the method of forming the multiplication layer specifically includes: forming a multiplication layer stacked on the N-type contact layer using an undoped InAlAs / GaAsSb superlattice; the method of forming the charge layer specifically includes: forming a charge layer stacked on the multiplication layer using a P-type InAlAs / GaAsSb superlattice; after forming the charge layer, the fabrication method further includes: forming a transition layer, an absorption layer, a barrier layer, and a P-type contact layer sequentially stacked on the charge layer; forming a first electrode in contact with the N-type contact layer, and forming a second electrode on the P-type contact layer.
[0013] In one example of the avalanche photodiode fabrication method provided in the other aspect above, the method for forming the first electrode and the second electrode specifically includes: partially etching the P-type contact layer, the barrier layer, the absorption layer, the transition layer, the charge layer, and the multiplication layer to form a mesa structure exposing the N-type contact layer; depositing the first electrode on the exposed N-type contact layer, and depositing the second electrode on the P-type contact layer.
[0014] In one example of the avalanche photodiode fabrication method provided in the other aspect above, the N-type contact layer is an N-type InGaAs material, the transition layer is an undoped InAlGaAs material, the absorption layer is an undoped InGaAs material, the blocking layer is a P-type InAlAs material, and the P-type contact layer is a P-type InGaAs material.
[0015] In one example of the method for fabricating an avalanche photodiode provided in the other aspect above, the InAlAs / GaAsSb superlattice is composed of alternating layers of InAlAs thin layers and GaAsSb thin layers, wherein both the InAlAs thin layers and the GaAsSb thin layers are lattice-matched with the substrate, or both the InAlAs thin layers and the GaAsSb thin layers are lattice-mismatched with the substrate, and the InAlAs / GaAsSb superlattice is stress-balanced.
[0016] Beneficial effects: The avalanche photodiode and its fabrication method according to embodiments of the present invention have at least one of the following effects: (1) According to the embodiments of the present invention, InAlAs / GaAsSb superlattice is used as the multiplication layer material of InP-based APD, and the low noise factor characteristics of Sb-containing materials and superlattice materials are utilized, so the signal-to-noise ratio of InP-based APD can be greatly improved. (2) The InAlAs / GaAsSb superlattice material according to the embodiments of the present invention grows Sb-containing materials and Al-containing materials separately, avoiding problems such as gas phase reaction, difficulty in Sb incorporation, and high impurity background that occur when Sb-containing and Al-containing materials (such as InAlAsSb) are directly grown in MOCVD. In other words, high-quality InAlAs / GaAsSb superlattice materials and InP-based APDs can be obtained by MOCVD, reducing manufacturing costs and improving production capacity and yield. Attached Figure Description
[0017] The above and other aspects, features, and advantages of embodiments of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 This is a schematic diagram of the structure of an avalanche photodiode according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the excess noise factor and gain curve of an InP-based APD with an InAlAs / GaAsSb superlattice multiplication layer according to an embodiment of the present invention. Figure 3a This is a schematic diagram of a substrate provided in a method for fabricating an avalanche photodiode according to an embodiment of the present invention; Figure 3b This is a schematic diagram of the growth of an N-type contact layer, a multiplication layer, a charge layer, a transition layer, an absorption layer, a blocking layer, and a P-type contact layer in the fabrication method of an avalanche photodiode according to an embodiment of the present invention. Figure 3c This is a schematic diagram of the formation of a mesa structure in the fabrication method of an avalanche photodiode according to an embodiment of the present invention; Figure 3d This is a schematic diagram of the formation of the first electrode and the second electrode in the fabrication method of an avalanche photodiode according to an embodiment of the present invention. Detailed Implementation
[0018] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention can be implemented in many different forms, and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the various embodiments of the invention and various modifications suitable for particular intended applications.
[0019] As used herein, the term "comprising" and its variations are open terms meaning "including but not limited to". The terms "based on", "according to", etc., mean "at least partially based on" or "at least partially based on". The terms "embodiment", "an example", "one embodiment", and "an embodiment" mean "at least one embodiment". The terms "another embodiment", "another embodiment", "another example", "yet another example" mean "at least one other embodiment". The terms "first", "second", etc., may refer to different or the same objects. Other definitions, whether explicit or implicit, may be included below. Unless explicitly indicated by the context, the definition of a term remains consistent throughout the specification.
[0020] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related are omitted.
[0021] As described in the background section, materials such as InAlAsSb with low noise factors must be prepared using molecular beam epitaxy (MBE) because direct growth using metal-organic chemical vapor deposition (MOCVD) leads to gas-phase reactions between Al and Sb, making Sb incorporation difficult. Furthermore, materials containing Al and Sb have extremely high C and O impurity backgrounds, hindering the development of high-quality devices. This invention addresses this problem by proposing the use of InAlAs / GaAsSb superlattice materials as the multiplication layer material for InP-based APDs. First, both the superlattice material and the Sb-containing material can reduce the noise factor, thus enabling the development of APDs with extremely low noise factors. Second, this material can be grown using MOCVD. While MOCVD can grow high-quality InAlAs and GaAsSb materials in the prior art, this invention proposes an InAlAs / GaAsSb superlattice, intentionally growing Sb-containing and Al-containing materials separately. This avoids the problems of gas-phase reactions, difficulty in Sb incorporation, and high impurity background that occur during the direct growth of Sb-containing and Al-containing materials (such as InAlAsSb). Therefore, the InP-based APD using InAlAs / GaAsSb superlattice material as the multiplication layer possesses both extremely high performance and can be prepared using low-cost MOCVD, resulting in a significantly improved cost-effectiveness compared to existing technologies. The following provides a detailed description of specific embodiments of the InP-based APD of this invention.
[0022] Figure 1 This is a schematic diagram of the structure of an avalanche photodiode according to an embodiment of the present invention.
[0023] like Figure 1As shown, an avalanche photodiode according to an embodiment of the present invention includes: a substrate 10; an N-type contact layer 11, a multiplication layer 12, a charge layer 13, a transition layer 14, an absorption layer 15, a blocking layer 16, and a P-type contact layer 17 sequentially stacked on the substrate 10; a first electrode 20; and a second electrode 21. The first electrode 20 is in contact with the N-type contact layer 11, and the second electrode 21 is disposed on the P-type contact layer 17.
[0024] In one example, the substrate 10 is a semi-insulating InP substrate with a thickness of 350µm.
[0025] In one example, the N-type contact layer 11 is an N-type InGaAs material with a thickness of 200 nm to 500 nm, and the doping source is Si or Te with a doping concentration of 5 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
[0026] In one example, the multiplication layer 12 is an undoped InAlAs / GaAsSb superlattice with a thickness of 500 nm to 1500 nm. The InAlAs / GaAsSb superlattice is composed of alternating thin layers of InAlAs and GaAsSb, each layer having a thickness of 1 to 5 nm. The InAlAs and GaAsSb layers can be lattice-matched or stress-balanced with the substrate 10.
[0027] In one example, the charge layer 13 is a p-type InAlAs / GaAsSb superlattice with a thickness of 50 nm to 150 nm, and the doping source is Zn or C with a doping concentration of 1 × 10⁻⁶. 17 cm -3 ~1×10 18 cm -3 The P-type InAlAs / GaAsSb superlattice is composed of alternating InAlAs and GaAsSb thin layers, each with a thickness of 1-5 nm. The InAlAs and GaAsSb can be lattice-matched with the substrate 10, or the InAlAs and GaAsSb can be lattice-mismatched with the substrate 10, while the InAlAs / GaAsSb superlattice is stress-balanced.
[0028] In one example, the transition layer 14 is an undoped InAlGaAs material with a thickness of 30nm~100nm.
[0029] In one example, the absorber layer 15 is an undoped InGaAs material with a thickness of 500nm~1000nm.
[0030] In one example, the barrier layer 16 is a p-type InAlAs material with a thickness of 100 nm to 300 nm. The doping source can be Zn or C, and the doping concentration is 1 × 10⁻⁶. 18 cm -3 ~1×10 19 cm -3 .
[0031] In one example, the P-type contact layer 17 is a P-type InGaAs material with a thickness of 30nm~100nm. The doping source can be Zn or C, and the doping concentration is 5×10⁻⁶. 18 cm -3 ~3×10 19 cm -3 .
[0032] Figure 2 This is a schematic diagram of the excess noise factor and gain curve of an InP-based APD with an InAlAs / GaAsSb superlattice multiplication layer according to an embodiment of the present invention. (Refer to...) Figure 2 As can be seen, the fitted collisional ionization coefficient ratio k is only 0.01, which is comparable to the InP-based APD with InAlAsSb multiplication layers in the prior art. However, the InP-based APD according to the embodiments of the present invention is prepared by MOCVD, which reduces the cost of epitaxial wafers by at least half compared to the MBE preparation of the prior art.
[0033] The manufacturing process of the avalanche photodiode according to an embodiment of the present invention will be described in detail below. Figures 3a to 3d This is a process diagram illustrating a method for fabricating an avalanche photodiode according to an embodiment of the present invention; wherein, Figure 3a This is a schematic diagram of a substrate provided in a method for fabricating an avalanche photodiode according to an embodiment of the present invention; Figure 3b This is a schematic diagram of the growth of an N-type contact layer, a multiplication layer, a charge layer, a transition layer, an absorption layer, a blocking layer, and a P-type contact layer in the fabrication method of an avalanche photodiode according to an embodiment of the present invention. Figure 3c This is a schematic diagram of the formation of a mesa structure in the fabrication method of an avalanche photodiode according to an embodiment of the present invention; Figure 3d This is a schematic diagram of the formation of the first electrode and the second electrode in the fabrication method of an avalanche photodiode according to an embodiment of the present invention.
[0034] Reference Figure 3a A substrate 10 is provided. In one example, the substrate 10 is a semi-insulating InP substrate with a thickness of 350 µm.
[0035] Reference Figure 3bAn N-type contact layer 11, a multiplication layer 12, a charge layer 13, a transition layer 14, an absorption layer 15, a barrier layer 16, and a P-type contact layer 17 are sequentially grown from bottom to top on the substrate 10.
[0036] In one example, an N-type contact layer 11, a multiplication layer 12, a charge layer 13, a transition layer 14, an absorber layer 15, a barrier layer 16, and a P-type contact layer 17 are sequentially grown on the substrate 10 from bottom to top using a metal-organic chemical vapor deposition (MOCVD) process. Specifically, MOCVD is used as the growth process, with growth sources including TMIn, TMAl, TMGa, TMSb, and AsH3, an n-type dopant source of SiH4, and a p-type dopant source of DEZn. The growth temperature is set to approximately 600°C, and the reaction chamber pressure is set to 200 Torr. After removing impurities from the surface of the substrate 10 through high-temperature treatment, the following layers are sequentially grown on the substrate 10 from bottom to top: (1) N-type contact layer 11. In one example, the N-type contact layer 11 is an N-type InGaAs material with a thickness of 300 nm, doped with Si, and the doping concentration is 8 × 10⁻⁶. 18 cm -3 .
[0037] (2) Multiplication layer 12. In one example, the multiplication layer 12 is an undoped InAlAs / GaAsSb superlattice with a thickness of 1000 nm, wherein InAlAs is 2 nm and GaAsSb is 3 nm, and the InAlAs and GaAsSb are lattice-matched with the substrate 10. In another example, the multiplication layer 12 is an undoped InAlAs / GaAsSb superlattice with a thickness of 1200 nm, wherein InAlAs is 1 nm and GaAsSb is 1 nm, InAlAs is subjected to 0.5% tensile stress and GaAsSb is subjected to 0.5% compressive stress, maintaining overall stress balance.
[0038] (3) Charge layer 13. In one example, charge layer 13 is a p-type InAlAs / GaAsSb superlattice with a thickness of 100 nm, doped with Zn at a concentration of 2 × 10⁻⁶. 17 cm -3 In this structure, InAlAs is 2 nm thick and GaAsSb is 3 nm thick, with InAlAs and GaAsSb lattice-matched to the substrate 10. In another example, the charge layer 13 is a p-type InAlAs / GaAsSb superlattice with a thickness of 120 nm, doped with Zn at a concentration of 5 × 10⁻⁶. 17 cm -3 In AlAs is 1 nm and GaAsSb is 1 nm. In AlAs is subjected to 0.5% tensile stress and GaAsSb is subjected to 0.5% compressive stress, and the whole remains in stress balance.
[0039] (4) Transition layer 14. In one example, the transition layer 14 is an undoped InAlGaAs material with a thickness of 50 nm.
[0040] (5) Absorbing layer 15. In one example, the absorbing layer 15 is an undoped InGaAs material with a thickness of 800 nm.
[0041] (6) Barrier layer 16. In one example, barrier layer 16 is a p-type InAlAs material with a thickness of 200 nm, doped with Zn at a concentration of 5 × 10⁻⁶. 18 cm -3 .
[0042] (7) P-type contact layer 17. In one example, the P-type contact layer 17 is a P-type InGaAs material with a thickness of 50 nm, doped with Zn, and the doping concentration is 1×10⁻⁶. 19 cm -3 .
[0043] Reference Figure 3c The P-type contact layer 17, the barrier layer 16, the absorption layer 15, the transition layer 14, the charge layer 13 and the multiplication layer 12 are partially etched to form a mesa structure A that exposes the N-type contact layer 11.
[0044] In one example, inductively coupled plasma etching (ICP) is used to locally etch the P-type contact layer 17, the barrier layer 16, the absorber layer 15, the transition layer 14, the charge layer 13, and the multiplication layer 12 to expose the N-type contact layer 11, thereby forming a mesa structure A.
[0045] Reference Figure 3d A first electrode 20 is deposited on the exposed N-type contact layer 11, and a second electrode 21 is deposited on the P-type contact layer 17.
[0046] In one example, an electron beam evaporation process is used to deposit a first electrode 20 on the exposed N-type contact layer 11 and a second electrode 21 on the P-type contact layer 17. Both the first electrode 20 and the second electrode 21 are Ti(500Å) / Pt(500Å) / Au(2000Å) combinations.
[0047] In summary, according to the embodiments of the present invention, an InP-based APD with antimony-containing material and a superlattice multiplication layer was prepared using the MOCVD process. The prepared InP-based APD has an extremely low noise factor and a low manufacturing cost, which greatly improves the cost-effectiveness compared with the prior art.
[0048] The foregoing description of this specification is provided to enable any person skilled in the art to implement or use the content of this specification. Various modifications to the content of this specification will be apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the scope of protection of this specification. Therefore, this specification is not limited to the examples and designs described herein, but is consistent with the widest scope of the principles and novel features disclosed herein.
Claims
1. An avalanche photodiode, the avalanche photodiode comprising a substrate (10), the substrate (10) being an InP substrate, characterized in that, The avalanche photodiode further includes: an N-type contact layer (11), a multiplication layer (12), a charge layer (13), a transition layer (14), an absorption layer (15), a barrier layer (16), a P-type contact layer (17), a first electrode (20), and a second electrode (21). The N-type contact layer (11), the multiplication layer (12), the charge layer (13), the transition layer (14), the absorption layer (15), and the barrier layer (16) are sequentially stacked on the substrate (10) with the P-type contact layer (17) in a direction away from the substrate (10). The first electrode (20) is in contact with the N-type contact layer (11), and the second electrode (21) is disposed on the P-type contact layer (17). The multiplication layer (12) is an undoped InAlAs / GaAsSb superlattice, and the charge layer (13) is a P-type InAlAs / GaAsSb superlattice. The N-type contact layer (11) is an N-type InGaAs material, the transition layer (14) is an undoped InAlGaAs material, the absorption layer (15) is an undoped InGaAs material, the barrier layer (16) is a P-type InAlAs material, and the P-type contact layer (17) is a P-type InGaAs material.
2. The avalanche photodiode according to claim 1, characterized in that, The P-type contact layer (17), the barrier layer (16), the absorption layer (15), the transition layer (14), the charge layer (13), and the multiplication layer (12) are partially etched away to form a mesa structure (A) exposing the N-type contact layer (11), and the first electrode (20) is disposed on the exposed N-type contact layer (11).
3. The avalanche photodiode according to claim 1 or 2, characterized in that, The InAlAs / GaAsSb superlattice is composed of alternating layers of InAlAs and GaAsSb thin layers, wherein both the InAlAs and GaAsSb thin layers are lattice-matched with the substrate (10), or both the InAlAs and GaAsSb thin layers are lattice-mismatched with the substrate (10), and the InAlAs / GaAsSb superlattice is stress-balanced.
4. A method for fabricating an avalanche photodiode, characterized in that, The manufacturing method includes: A substrate (10) is provided, wherein the substrate (10) is an InP substrate; An N-type contact layer (11) is formed on the substrate (10); A multiplication layer (12) is formed on an N-type contact layer (11) using an undoped InAlAs / GaAsSb superlattice. A charge layer (13) is formed on the multiplication layer (12) using a P-type InAlAs / GaAsSb superlattice. A transition layer (14), an absorption layer (15), a barrier layer (16), and a P-type contact layer (17) are sequentially stacked on the charge layer (13). A first electrode (20) is formed in contact with the N-type contact layer (11), and a second electrode (21) is formed on the P-type contact layer (17). The N-type contact layer (11) is an N-type InGaAs material, the transition layer (14) is an undoped InAlGaAs material, the absorption layer (15) is an undoped InGaAs material, the barrier layer (16) is a P-type InAlAs material, and the P-type contact layer (17) is a P-type InGaAs material.
5. The method for manufacturing an avalanche photodiode according to claim 4, characterized in that, The methods for forming the first electrode (20) and the second electrode (21) specifically include: The P-type contact layer (17), the barrier layer (16), the absorption layer (15), the transition layer (14), the charge layer (13) and the multiplication layer (12) are partially etched to form a mesa structure (A) that exposes the N-type contact layer (11). A first electrode (20) is deposited on the exposed N-type contact layer (11), and a second electrode (21) is deposited on the P-type contact layer (17).
6. The method for manufacturing an avalanche photodiode according to claim 4 or 5, characterized in that, The InAlAs / GaAsSb superlattice is composed of alternating layers of InAlAs and GaAsSb thin layers, wherein both the InAlAs and GaAsSb thin layers are lattice-matched with the substrate (10), or both the InAlAs and GaAsSb thin layers are lattice-mismatched with the substrate (10), and the InAlAs / GaAsSb superlattice is stress-balanced.