Single-photon avalanche diode and single-photon detector

Abstract

The invention provides a single-photon avalanche diode and a single-photon detector, and relates to the technical field of semiconductor photoelectric detection, and the single-photon avalanche diode comprises a plurality of avalanche diode units. The avalanche diode units are sequentially stacked in the propagation direction of incident light to be detected. Each avalanche diode unit is provided with an electric field control module which is used for independently adjusting the bias electric field of each avalanche diode unit. In the propagation direction of the incident light, the avalanche diode unit of the next stage is used for absorbing the remaining photons which are not absorbed by the avalanche diode unit of the previous stage and generating carriers, so that avalanche current is formed. The light absorption wavelength ranges of adjacent avalanche diode units are at least partially overlapped. The single-photon avalanche diode solves the problem that the existing single-photon avalanche diode cannot balance high detection efficiency and low dark current, and achieves the purpose of improving the detection efficiency of a single-photon detector on the premise of not increasing the dark current.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor photoelectric detection technology, in particular to a single-photon avalanche diode and a single-photon detector. Background Art

[0002] A single-photon detector primarily consists of a single-photon avalanche diode (SPAD) and a readout circuit. A SPAD is a special type of avalanche diode that operates in Geiger mode. In Geiger mode, when the negative bias voltage is higher than the breakdown voltage, electron-hole pairs (carriers) are generated when the absorption layer absorbs a single photon. These carriers are accelerated to the multiplication layer by the electric field and collide with the multiplication layer lattice to produce new electron-hole pairs. These new carriers continue to collide and repeat under the action of the electric field, forming an avalanche current. Semiconductor single-photon avalanche diodes primarily include lnGaAs / lnP, lnGaAs / lnAlAs, and Ge-on-Si SPADs. Among them, lnGaAs / lnP SPADs are primarily used for 1550nm wavelength light detection, offer the best overall performance, and are currently the most widely used devices. Currently, the detection efficiency of single-photon detectors is usually improved by increasing the thickness of the absorption layer to increase the probability of photon capture; however, thick absorption layers require a higher bias voltage to maintain the electric field strength, which will lead to an increase in dark current. Summary of the Invention

[0003] In view of the above problems, the present invention is proposed to provide a single-photon avalanche diode and a single-photon detector that overcome the above problems or at least partially solve the above problems. It can solve the problem that the existing single-photon avalanche diode cannot balance high detection efficiency and low dark current, and achieve the purpose of improving the detection efficiency of the single-photon detector without increasing the dark current.

[0004] Specifically, the present invention provides a single-photon avalanche diode, comprising:

[0005] A plurality of avalanche diode units are stacked in sequence along the propagation direction of the incident light to be detected, each of the avalanche diode units having an electric field control module for independently adjusting the bias electric field of each of the avalanche diode units;

[0006] In the propagation direction of the incident light, the avalanche diode unit of the next stage is used to absorb the remaining photons not absorbed by the avalanche diode unit of the previous stage and generate carriers, thereby forming an avalanche current;

[0007] The light absorption wavelength ranges of adjacent avalanche diode units at least partially overlap.

[0008] Optionally, the type of each avalanche diode unit is completely the same, partially the same, or completely different;

[0009] The type of each avalanche diode unit includes any one of a split absorption graded charge multiplication structure, an impact ionization engineered structure, and a PIN structure.

[0010] Optionally, each of the avalanche diode units further comprises an absorption layer and a multiplication layer;

[0011] The material of the absorption layer includes any one of InGaAs and GaAs;

[0012] The material of the multiplication layer includes any one of InP, InGaAs, and InGaAsP.

[0013] Optionally, each of the avalanche diode units further comprises a substrate, a buffer layer, a transition layer, a charge layer and a passivation layer;

[0014] The buffer layer is located between the substrate and the absorbent layer;

[0015] The transition layer and the charge layer are located between the absorption layer and the multiplication layer;

[0016] The passivation layer is at least located on the surface of the multiplication layer;

[0017] The material of the substrate includes any one of InP and GaAs;

[0018] The charge layer includes any one of InP and InAlAs;

[0019] The material of the passivation layer includes any one of SiNx, SiO2, and Al2O3.

[0020] Optionally, each of the avalanche diode units further comprises a Zn diffusion region disposed within the multiplication layer;

[0021] The Zn diffusion region in each multiplication layer is located in the middle of the single photon avalanche diode;

[0022] The areas of the Zn diffusion regions are equal; or, the Zn diffusion region of the avalanche diode unit of the next stage is larger than the Zn diffusion region of the avalanche diode unit of the previous stage.

[0023] Optionally, among the plurality of avalanche diode units, the avalanche diode unit of the first stage further comprises a Zn diffusion region located in the multiplication layer;

[0024] The multiplication layer of the avalanche diode unit of the second stage is arranged adjacent to the Zn diffusion region;

[0025] The width of the avalanche diode unit of the second stage is smaller than the width of the Zn diffusion region.

[0026] Optionally, a guard ring is provided at the periphery of the Zn diffusion region, and the guard ring is located within the multiplication layer.

[0027] Optionally, the thickness of the substrate is 350 μm and the doping concentration is 1e18 cm -3 and / or

[0028] The thickness of the buffer layer is 0.5 μm and the doping concentration is 5e16 cm -3 and / or

[0029] The thickness of the absorption layer is 2 μm and the doping concentration is 1e15 cm -3 and / or

[0030] The thickness of the transition layer is 60 nm and the doping concentration is 2e16 cm -3 and / or

[0031] The thickness of the charge layer is 200 nm and the doping concentration is 1e17 cm -3 and / or

[0032] The thickness of the multiplication layer is 3 μm and the doping concentration is 1e15 cm -3 and / or

[0033] The thickness of the passivation layer is 2 μm.

[0034] Optionally, each of the electric field control modules includes:

[0035] an anode electrode, located at one end of the avalanche diode unit;

[0036] a cathode electrode, located at the other end of the avalanche diode unit;

[0037] The electric field directions of the electric field control modules of two adjacent avalanche diode units are the same; or

[0038] The electric field directions of the electric field control modules of two adjacent avalanche diode units are opposite, and the two electric field control modules share one anode electrode or one cathode electrode.

[0039] On the other hand, the present invention further provides a single-photon detector comprising the single-photon avalanche diode as described in any one of the above items.

[0040] In the single-photon avalanche diode and single-photon detector of the present invention, the single-photon avalanche diode comprises multiple stacked avalanche diode units, each with an independent electric field control module. Therefore, while maintaining a relatively thin absorption layer thickness within each avalanche diode unit, the synergistic effect of multiple stages of single-photon avalanche diode units achieves distributed gain through multiple photon absorption and avalanche multiplication. This reduces the source of dark current. Furthermore, each stage of the single-photon avalanche diode unit can gradually capture remaining photons not absorbed by the previous stage, significantly improving the overall photon capture efficiency. This brings the absorption efficiency of the single-photon avalanche diode to nearly 100%. Furthermore, the multi-stage gain stacking improves the overall detection efficiency of the single-photon avalanche diode. This invention achieves the synergistic optimization of high detection efficiency and low dark current under low bias conditions, resolving the core conflict of "detection efficiency vs. dark current" in the prior art.

[0041] Furthermore, for mixed-wavelength light absorption detection, each level of single-photon avalanche diode unit can adapt to the absorption of specific wavelength photons by adjusting the absorption layer material, and gradually capture the remaining wavelength photons that are not absorbed by the previous level avalanche diode unit, so that the total photon capture efficiency is significantly improved, thereby increasing the absorption efficiency of the single-photon avalanche diode for incident light to nearly 100%.

[0042] Furthermore, the distributed gain of avalanche multiplication avoids the accumulation of post-pulse noise caused by excessive single-stage gain, significantly improves the signal-to-noise ratio, and reduces noise.

[0043] Furthermore, since the multiple avalanche diode units are independent of each other, the first-stage avalanche diode unit can be used as the main avalanche diode unit, and the remaining avalanche diode units can be used as auxiliary avalanche diode units. The dark current of each auxiliary avalanche diode unit can be counted independently without affecting the dark current of the main avalanche diode unit. In other words, the synchronization circuit only accumulates the multi-stage avalanche signal, and the dark current of the auxiliary avalanche diode unit can be excluded from the total dark current. The light supplementary absorption multiplication of the auxiliary avalanche diode unit is included in the total light detection efficiency. Based on this, the present invention can significantly improve the overall detection efficiency while keeping the dark current unchanged.

[0044] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0046] Figure 1 is a schematic structural diagram of a single-photon avalanche diode according to one embodiment of the present invention;

[0047] Figure 2 is a schematic structural diagram of a single-photon avalanche diode according to one embodiment of the present invention;

[0048] Figure 3 FIG. 4 is a schematic structural diagram of a single-photon avalanche diode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] Refer to the following Figures 1 to 3 To describe the single-photon avalanche diode and single-photon detector of the embodiment of the present invention. In the description of this embodiment, it should be understood that the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features, that is, include one or more of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. When a feature "includes or contains" one or some of the features it covers, unless otherwise specifically described, this indicates that other features are not excluded and may further include other features.

[0050] Unless otherwise expressly defined or limited, terms such as "disposed," "installed," "connected," "connected," "fixed," and "coupled" should be broadly interpreted. For example, they may refer to fixed or detachable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two elements or interaction between two elements, unless otherwise expressly defined. A person of ordinary skill in the art should be able to understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0051] In addition, in the description of this embodiment, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact via another feature between them. That is, in the description of this embodiment, the first feature being "above," "above," and "above" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature being "below," "below," or "below" the second feature may mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0052] In the description of the present embodiment, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in any one or more embodiments or examples.

[0053] Figure 1 FIG is a schematic structural diagram of a single photon avalanche diode according to an embodiment of the present invention, as shown in FIG. Figure 1 As shown, and reference Figures 2 to 3 An embodiment of the present invention provides a single-photon avalanche diode, which includes a plurality of avalanche diode units. The plurality of avalanche diode units are stacked in sequence along the propagation direction of the incident light to be detected. Each avalanche diode unit has an electric field control module for independently adjusting the bias electric field of each avalanche diode unit. In the propagation direction of the incident light, the avalanche diode unit of the next level is used to absorb the remaining photons that are not absorbed by the avalanche diode unit of the previous level and generate carriers, thereby forming an avalanche current. The light absorption wavelength ranges of adjacent avalanche diode units at least partially overlap.

[0054] Specifically, in a single-photon avalanche diode, the number of avalanche diode units can be two, three, four, or five or more, and the number can be selected according to a preset detection efficiency set for the single-photon avalanche diode. Each electric field control module can adjust the bias electric field through an independent voltage.

[0055] The working process of the single-photon avalanche diode in this embodiment is as follows: the incident light first enters the first-level avalanche diode unit, whose absorption layer captures part of the photons within a specific wavelength range and generates electron-hole pairs; the remaining photons that are not absorbed are transmitted to the next-level avalanche diode unit, and the next-level avalanche diode unit adjusts the bias electric field through the electric field control module, so that its absorption layer continues to capture the remaining photons (compensation absorption) and triggers avalanche multiplication (compensation multiplication). Each level of avalanche diode unit independently controls the electric field strength to ensure sufficient photon absorption efficiency at a thinner absorption layer thickness, while avoiding the high bias voltage required for a single thick absorption layer. Ultimately, multiple levels work together to absorb photons step by step, accumulate avalanche current signals, and achieve efficient single-photon detection.

[0056] Compared to the existing solution of improving detection efficiency by thickening the absorption layer, this embodiment uses a vertically stacked structure of multiple avalanche diode units and independent electric field control. While maintaining the relatively thin absorption layer thickness of each avalanche diode unit, it utilizes the synergistic effect of multiple single-photon avalanche diode units to achieve distributed gain of multiple photon absorption and avalanche multiplication. On the one hand, the source of dark current is reduced. On the other hand, each level of single-photon avalanche diode unit can gradually capture the remaining photons not absorbed by the previous level of avalanche diode unit, significantly improving the total photon capture efficiency and increasing the absorption efficiency of the single-photon avalanche diode for incident light to nearly 100%. The total detection efficiency of the single-photon avalanche diode is also improved through the superposition of multiple levels of gain. This embodiment can achieve the coordinated optimization of high detection efficiency and low dark current under low bias conditions, solving the core contradiction of "detection efficiency-dark current" that is difficult to balance in the existing technology.

[0057] Furthermore, for mixed-wavelength light absorption detection, each level of single-photon avalanche diode unit can adapt to the absorption of specific wavelength photons by adjusting the absorption layer material, and gradually capture the remaining wavelength photons that are not absorbed by the previous level avalanche diode unit, so that the total photon capture efficiency is significantly improved, thereby increasing the absorption efficiency of the single-photon avalanche diode for incident light to nearly 100%.

[0058] Furthermore, the distributed gain of avalanche multiplication avoids the accumulation of post-pulse noise caused by excessive single-stage gain, and the signal-to-noise ratio is significantly improved.

[0059] Furthermore, since the multiple avalanche diode units are independent of each other, the first-stage avalanche diode unit can be used as the main avalanche diode unit, and the remaining avalanche diode units can be used as auxiliary avalanche diode units. The dark current of each auxiliary avalanche diode unit can be counted independently without affecting the dark current of the main avalanche diode unit. In other words, the synchronization circuit only accumulates the multi-stage avalanche signal, and the dark current of the auxiliary avalanche diode unit can be excluded from the total dark current, and its light supplementary absorption multiplication is included in the total light detection efficiency. Based on this, this embodiment can significantly improve the overall detection efficiency while keeping the dark current unchanged.

[0060] In some optional embodiments of the present invention, adjacent avalanche diode units have the same light absorption wavelength range. For example, the light absorption wavelength of each stage of avalanche diode units is 1550 nm.

[0061] In some optional embodiments of the present invention, the type of each avalanche diode unit includes any one of a separated absorption graded charge multiplication structure (SAGCM), an impact ionization engineered structure (including materials such as InAlAs), and a PIN structure.

[0062] Specifically, the type of each avalanche diode unit can be completely identical, partially identical, or completely different. For example, when the single-photon avalanche diode includes three avalanche diode units: the first-stage avalanche diode unit and the second-stage avalanche diode unit can both be split-absorption gradient charge multiplication structures, and the third-stage avalanche diode unit can be a PIN structure; or the first-stage avalanche diode unit can be a split-absorption gradient charge multiplication structure, and the second-stage avalanche diode unit and the third-stage avalanche diode unit can both be a PIN structure; or all three avalanche diode units can be split-absorption gradient charge multiplication structures.

[0063] In some optional embodiments of the present invention, each avalanche diode unit further includes an absorption layer and a multiplication layer; the material of the absorption layer includes any one of InGaAs and GaAs; the material of the multiplication layer includes any one of InP, InGaAs, and InGaAsP.

[0064] Specifically, each avalanche diode unit is of the SAGCM type, which has the advantages of low noise, high gain-bandwidth product and long wavelength adaptability. The absorption layer is adapted to the optical fiber communication band of 1310 / 1550nm.

[0065] In some optional embodiments of the present invention, each avalanche diode cell further includes a substrate, a buffer layer, a transition layer, a charge layer, and a passivation layer. The buffer layer is located between the substrate and the absorption layer; the transition layer and the charge layer are located between the absorption layer and the multiplication layer; and the passivation layer is located at least on the surface of the multiplication layer. The substrate material includes any one of InP and GaAs; the charge layer includes any one of InP and InAlAs; and the passivation layer material includes any one of SiNx, SiO2, and Al2O3. The transition layer material can be InGaAsP.

[0066] In this embodiment, the substrate provides mechanical support and thermal management, and serves as a lattice matching template. The buffer layer mitigates the lattice mismatch between the substrate and the epitaxial layer through a gradient composition, reducing dislocation density. The transition layer is designed with a band gradient to guide carriers from the absorption layer into the multiplication layer for efficient injection, while also smoothing the electric field distribution to avoid uneven breakdown. The charge layer regulates the peak electric field in the avalanche region through high doping, screening high-energy carriers to trigger controllable avalanches and suppress excessive noise. The passivation layer covers the surface of the multiplication layer, neutralizing defect states and isolating it from the environment, thereby reducing dark current and extending device life. The combined action of these layers significantly improves 1550nm wavelength detection efficiency, reduces dark current density, and improves breakdown voltage uniformity, achieving the beneficial effects of high sensitivity and low noise.

[0067] In some optional embodiments of the present invention, the thickness of the substrate is 350 μm and the doping concentration is 1e18 cm -3 .

[0068] In some optional embodiments of the present invention, the buffer layer has a thickness of 0.5 μm and a doping concentration of 5e16 cm -3 .

[0069] In some optional embodiments of the present invention, the thickness of the absorption layer is 2 μm and the doping concentration is 1e15 cm -3 .

[0070] In some optional embodiments of the present invention, the thickness of the transition layer is 60 nm and the doping concentration is 2e16 cm -3 .

[0071] In some optional embodiments of the present invention, the thickness of the charge layer is 200 nm and the doping concentration is 1e17 cm -3 .

[0072] In some optional embodiments of the present invention, the thickness of the multiplication layer is 3 μm and the doping concentration is 1e15 cm -3 .

[0073] In some optional embodiments of the present invention, the thickness of the passivation layer is 2 μm.

[0074] In the above embodiments, the detection efficiency of each avalanche diode unit is improved by reasonably setting the thickness and / or concentration parameters of each layer structure.

[0075] In some optional embodiments of the present invention, each electric field control module includes an anode electrode and a cathode electrode. The anode electrode is located at one end of the avalanche diode unit, and the cathode electrode is located at the other end of the avalanche diode unit. In this embodiment, the electric field control module of each avalanche diode unit achieves dynamic electric field regulation and precise control of the avalanche process through the coordinated operation of the anode and cathode electrodes.

[0076] In some optional embodiments of the present invention, the electric field control modules of two adjacent avalanche diode units have the same electric field direction. That is, the anodes and cathodes of adjacent units are aligned in the same direction, and the electric fields have the same direction (e.g., both pointing from the anode to the cathode). This embodiment has the advantage of being easy to manufacture.

[0077] In some alternative embodiments of the present invention, the electric field directions of the electric field control modules of two adjacent avalanche diode units are opposite, and the two electric field control modules share an anode electrode or cathode electrode. Specifically, the electric field directions of the adjacent units are opposite (e.g., anode → cathode for unit 1, cathode → anode for unit 2), and the two units share the same electrode (e.g., a common anode or cathode).

[0078] In some optional embodiments of the present invention, each avalanche diode unit cell further includes a Zn diffusion region disposed within the multiplication layer; the Zn diffusion region within each multiplication layer is located in the center of the single-photon avalanche diode. The areas of the Zn diffusion regions are equal; alternatively, the Zn diffusion region of the subsequent avalanche diode unit cell is larger than that of the previous avalanche diode unit cell. This arrangement maximizes the ability of light to transmit from the bottom through the diffusion window to the absorption layer of the subsequent avalanche diode unit cell.

[0079] In some optional embodiments of the present invention, among the multiple avalanche diode cells, the first-stage avalanche diode cells further include a Zn diffusion region within the multiplication layer; and the multiplication layer of the second-stage avalanche diode cells is disposed adjacent to the Zn diffusion region. The first-stage and second-stage avalanche diode cells share a single Zn diffusion region, which can reduce the production cost of the single-photon avalanche diode.

[0080] Furthermore, the width of the second-stage avalanche diode unit is smaller than the width of the Zn diffusion region, which can further reduce production costs while maintaining the photon absorption effect and multiplication effect of the second-stage avalanche diode unit unchanged.

[0081] In some optional embodiments of the present invention, a guard ring is provided around the Zn diffusion region, and the guard ring is located inside the multiplication layer. The guard ring is used to prevent premature breakdown of the electric field.

[0082] The specific structure of the single photon avalanche diode is further described in detail below in conjunction with Examples 1, 2 and 3.

[0083] Example 1

[0084] like Figure 1 As shown, the single photon avalanche diode 10 includes two avalanche diode units, namely a first avalanche diode unit 100 and a second avalanche diode unit 200. The first avalanche diode unit 100 is a first-stage avalanche diode unit, and the second avalanche diode unit 200 is a second-stage avalanche diode unit.

[0085] The first avalanche diode unit 100 is composed of structural components with different functions. Specifically, the first avalanche diode unit 100 includes, from bottom to top, a first anti-reflection layer 101, a first substrate 102, a first buffer layer 103, a first absorption layer 104, a first transition layer 105, a first charge layer 106, a first multiplication layer 107, and a first passivation layer 108. The first avalanche diode unit 100 also includes a first anode electrode 111, a first cathode electrode 112, a first Zn diffusion region 109, and a first guard ring 113. The first anode electrode 111 is disposed on the periphery of the first anti-reflection layer 101. The first anode electrode 111 and the first cathode electrode 112 constitute a first electric field control module and form a first electric field region.

[0086] Specifically, a first substrate 102 is grown epitaxially, a first buffer layer 103 is epitaxially grown on its surface, and a first absorption layer 104 is further grown epitaxially. To reduce the charge accumulation problem caused by the large band gap difference between the first absorption layer 104 and the first multiplication layer 107, a first transition layer 105 is epitaxially grown on the surface of the first absorption layer 104. To control the electric field of the first absorption layer 104 and the first multiplication layer 107, a first charge layer 106 is epitaxially grown on the surface of the first transition layer 105. To achieve a multiplication effect, a first multiplication layer 107 is epitaxially grown on the surface of the first charge layer 106. Through the above epitaxial process, the growth of the first avalanche diode unit 100 epitaxial wafer is achieved. To limit the multiplication region to a specific area, Zn diffusion is performed twice in the first multiplication layer 107 through a Zn diffusion process, forming a first Zn diffusion region 109 with a diffusion depth of 2μm and a doping concentration of 1e18 cm -3 ). A first guard ring 113 is diffused around the periphery of the first Zn diffusion region 109 to prevent premature breakdown of the electric field. In order to reduce light reflection, a first anti-reflection layer 101 is coated on the surface of the incident light region of the first substrate 102. A gold electrode is evaporated on other areas of the first substrate 102 as a first anode electrode 111, a first passivation layer 108 is evaporated on the surface of the first multiplication layer 107, and a metal electrode is evaporated on part of the upper surface of the first Zn diffusion region 109 as a first cathode electrode 112. In the entire epitaxial structure, Figure 1 110 represents the first charge multiplication region, and 701 represents the initial incident light. The first avalanche diode unit 100 with separated absorption gradient charge multiplication effect is manufactured through the above-mentioned epitaxial growth, diffusion, evaporation and other processes.

[0087] The material of the first substrate 102 is InP, with a thickness of 350 μm and a doping concentration of 1e18 cm -3 The first buffer layer 103 is made of InP with a thickness of 0.5 μm and a doping concentration of 5e16 cm-3 The first absorption layer 104 is made of InGaAs with a thickness of 2 μm and a doping concentration of 1e15 cm -3 The material of the first transition layer 105 is InGaAsP, with a thickness of 60nm and a doping concentration of 2e16cm -3 The material of the first charge layer 106 is InP, with a thickness of 200 nm and a doping concentration of 1e17 cm -3 The material of the first multiplication layer 107 is InP, with a thickness of 3 μm and a doping concentration of 1e15 cm -3 The thickness of the first passivation layer is 2 μm. The thickness of the first anode electrode 111 is 100 nm, and the thickness of the first cathode electrode 112 is 100 nm.

[0088] The second avalanche diode unit 200 has a similar structure to the first avalanche diode unit 100, with the corresponding functional layers having the same parameters such as materials, thickness, and concentration. Specifically, the second avalanche diode unit 200 includes: a second back passivation layer 201 (thickness 2μm), a second substrate 202, a second buffer layer 203, a second absorption layer 204, a second transition layer 205, a second charge layer 206, a second multiplication layer 207, a second top passivation layer 208 (thickness 2μm), a second anode electrode 211, a second cathode electrode 212, a second Zn diffusion region 209, a second guard ring 213, and a second charge multiplication region 210. 702 represents incident light that is not absorbed by the first absorption layer 104. The thickness of the second back passivation layer 201 and the second top passivation layer 208 are both 2μm. The second anode electrode 211 and the second cathode electrode 212 constitute a second electric field control module and form a second electric field region.

[0089] In this embodiment, the single-photon avalanche diode 10 operates as follows: initial incident light 701 passes through the first anti-reflection layer 101 and enters the first avalanche diode unit 100 from the back. It is absorbed by the first absorption layer 104, generating electron-hole pairs. The first anode electrode 111 and the first cathode electrode 112 are connected to the positive and negative electrodes, respectively. The high electric field is confined to the first charge multiplication region 110. Under the action of the electric field, holes pass through the first transition layer 105 and the first charge layer 106 to reach the first multiplication layer 107, generating an avalanche effect within the high-field first charge multiplication region 110, thereby generating an avalanche current. Due to the limited light absorption effect of the first absorption layer 104, some light is not absorbed. Incident light 702 not absorbed by the first absorption layer passes through the second avalanche diode unit 200, reaches the second absorption layer 204, and is absorbed there, generating electron-hole pairs. The second anode electrode 211 and the second cathode electrode 212 are connected to the positive electrode and the negative electrode, respectively. The high electric field is confined to the second charge multiplication region 210. Holes generated by the electric field pass through the second transition layer 205 and the second charge layer 206 to the second multiplication layer 207, generating an avalanche current within the second charge multiplication region 210. This achieves compensatory light absorption and charge multiplication, improving the overall light absorption efficiency of the single-photon detector and increasing its detection efficiency.

[0090] In this embodiment, the light absorption efficiency of a single avalanche diode unit is only about 80%. In this embodiment, the overall light absorption efficiency of the single-photon avalanche diode 10 is about 96%. Specifically, the first avalanche diode unit 100 absorbs 80% of the initial incident light. The remaining 20% ​​of light is then absorbed by the second avalanche diode unit 200, which ultimately achieves an absorption rate of 96% of the initial incident light.

[0091] Example 2

[0092] like Figure 2 As shown, the single photon avalanche diode 10 includes two avalanche diode units, namely a first avalanche diode unit 100 and a third avalanche diode unit 300. The first avalanche diode unit 100 is a first-stage avalanche diode unit, and the third avalanche diode unit 300 is a second-stage avalanche diode unit.

[0093] The first avalanche diode unit 100 in this embodiment is substantially identical to the first avalanche diode unit 100 in Example 1 and will not be further described here. The third avalanche diode unit 300 in this embodiment can be viewed as the second avalanche diode unit 200 in Example 1 rotated 180 degrees, with the corresponding functional layers having the same materials, thicknesses, and doping concentrations. Specifically, the third avalanche diode unit 300 includes a third passivation layer 301, a third substrate 302, a third buffer layer 303, a third absorption layer 304, a third transition layer 305, a third charge layer 306, a third multiplication layer 307, a third anode electrode 311, a third cathode electrode 312, a third Zn diffusion region 309, a third guard ring 313, and a third charge multiplication region 310. The third anode electrode 311 and the third cathode electrode 312 constitute a third electric field control module and form a third electric field region.

[0094] When the single-photon avalanche diode 10 of this embodiment is in operation, the incident light 702 that is not absorbed by the first absorption layer passes through the third avalanche diode unit 300, reaches the third absorption layer 304 and is absorbed by it, generating electron-hole pairs. The third anode electrode 311 and the third cathode electrode 312 are connected to the positive electrode and the negative electrode respectively. The high electric field is confined to the third charge multiplication region 310. The holes generated under the action of the electric field pass through the third transition layer 305 and the third charge layer 306 to reach the third multiplication layer 307, generating an avalanche current in the third charge multiplication region 310. This achieves the effect of compensatory absorption of light and compensatory multiplication of charge. This in turn improves the overall light absorption efficiency of the single-photon detector and increases the detection efficiency of the single-photon detector.

[0095] Example 3

[0096] like Figure 3 As shown, the single photon avalanche diode 10 includes two avalanche diode units, namely a first avalanche diode unit 100 and a fourth avalanche diode unit 400. The first avalanche diode unit 100 is a first-stage avalanche diode unit, and the fourth avalanche diode unit 400 is a second-stage avalanche diode unit.

[0097] The first avalanche diode unit 100 in this embodiment is basically the same as the first avalanche diode unit 100 in Example 1. The main difference is that in this embodiment, a first top passivation layer 114 is further provided on the top of the first Zn diffusion region 109, which is located on the periphery of the fourth multiplication layer 407. The remaining structures are not repeated here.

[0098] The width of the fourth avalanche diode unit 400 is less than the width of the upper surface of the first Zn diffusion region 109. The fourth avalanche diode unit 400 includes, from top to bottom, a fourth passivation layer 401, a fourth substrate 402, a fourth buffer layer 403, a fourth absorption layer 404, a fourth transition layer 405, a fourth charge layer 406, and a fourth multiplication layer 407. The fourth avalanche diode unit 400 also includes a fourth anode electrode 411, a fourth cathode electrode 412, and a fourth charge multiplication region 410. The fourth anode electrode 411 is disposed on the side of the fourth passivation layer 401 and on the upper surface of the fourth substrate 402; the fourth cathode electrode 412 is disposed on the upper surface of the first passivation layer 108.

[0099] The fourth multiplication layer 407 and the first multiplication layer 107 are respectively located on either side of the first Zn diffusion region 109. The fourth avalanche diode unit 400 and the first avalanche diode unit 100 share the same first Zn diffusion region 109. The fourth cathode electrode 412 and the first cathode electrode 112 are the same electrode. The first anode electrode 111 and the first cathode electrode 112 constitute a first electric field control module and form a first electric field region. The fourth anode electrode 411 and the fourth cathode electrode 412 constitute a fourth electric field control module and form a fourth electric field region.

[0100] When the single-photon avalanche diode 10 of this embodiment is in operation, the incident light 702 that is not absorbed by the first absorption layer passes through the fourth avalanche diode unit 400, reaches the fourth absorption layer 404 and is absorbed by it, generating electron-hole pairs. The fourth anode electrode 411 and the fourth cathode electrode 412 are connected to the positive electrode and the negative electrode respectively. The high electric field is confined to the fourth charge multiplication region 410. The holes generated under the action of the electric field pass through the fourth transition layer 405 and the fourth charge layer 406 to reach the fourth multiplication layer 407, generating an avalanche current in the fourth charge multiplication region 410. This achieves the effect of compensatory absorption of light and compensatory multiplication of charge. This improves the overall light absorption efficiency of the single-photon detector and increases the detection efficiency of the single-photon detector.

[0101] In summary, to improve the photodetection efficiency of the lnGaAs / lnP single-photon detector, Examples 1, 2, and 3 employ independent structural designs to construct compensating absorption layers and compensating multiplication layers, achieving improvements in incident light absorption efficiency close to 100%. Furthermore, secondary multiplication is achieved to increase the avalanche probability, thereby improving the photodetection efficiency of the lnGaAs / lnP single-photon detector. Furthermore, because the electric field of each avalanche diode unit is independent, the dark current of the second-stage avalanche diode unit has no effect on the dark current of the first-stage avalanche diode unit, thus maintaining the dark current of the first-stage avalanche diode unit unchanged. This significantly improves the overall photodetection efficiency while ensuring that the dark current remains unchanged.

[0102] An embodiment of the present invention further provides a single-photon detector, which includes a readout circuit and a single-photon avalanche diode as described in any one of the above embodiments.

[0103] At this point, those skilled in the art will recognize that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications consistent with the principles of the present invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. A single photon avalanche diode, characterized in that: include: A plurality of avalanche diode units are stacked in sequence along the propagation direction of the incident light to be detected, each of the avalanche diode units having an electric field control module for independently adjusting the bias electric field of each of the avalanche diode units; In the propagation direction of the incident light, the avalanche diode unit of the next stage is used to absorb the remaining photons not absorbed by the avalanche diode unit of the previous stage and generate carriers, thereby forming an avalanche current; The light absorption wavelength ranges of adjacent avalanche diode units at least partially overlap.

2. The single photon avalanche diode according to claim 1, characterized in that The type of each avalanche diode unit is exactly the same, partially the same, or completely different; The type of each avalanche diode unit includes any one of a split absorption graded charge multiplication structure, an impact ionization engineered structure, and a PIN structure.

3. The single photon avalanche diode according to claim 1, wherein: Each of the avalanche diode cells further includes an absorption layer and a multiplication layer; The material of the absorption layer includes any one of InGaAs and GaAs; The material of the multiplication layer includes any one of InP, InGaAs, and InGaAsP.

4. The single photon avalanche diode according to claim 3, characterized in that Each of the avalanche diode units further includes a substrate, a buffer layer, a transition layer, a charge layer and a passivation layer; The buffer layer is located between the substrate and the absorbent layer; The transition layer and the charge layer are located between the absorption layer and the multiplication layer; The passivation layer is at least located on the surface of the multiplication layer; The material of the substrate includes any one of InP and GaAs; The charge layer includes any one of InP and InAlAs; The material of the passivation layer includes any one of SiNx, SiO2, and Al2O3.

5. The single photon avalanche diode according to claim 3, characterized in that: Each of the avalanche diode units further includes a Zn diffusion region disposed within the multiplication layer; The Zn diffusion region in each multiplication layer is located in the middle of the single photon avalanche diode; The areas of the Zn diffusion regions are equal; or, the Zn diffusion region of the avalanche diode unit of the next stage is larger than the Zn diffusion region of the avalanche diode unit of the previous stage.

6. The single photon avalanche diode according to claim 3, characterized in that Among the plurality of avalanche diode cells, the avalanche diode cell of the first stage further comprises a Zn diffusion region located in the multiplication layer; The multiplication layer of the avalanche diode unit of the second stage is arranged adjacent to the Zn diffusion region; The width of the avalanche diode unit of the second stage is smaller than the width of the Zn diffusion region.

7. The single photon avalanche diode according to claim 5 or 6, characterized in that: A guard ring is provided on the periphery of the Zn diffusion region, and the guard ring is located in the multiplication layer.

8. The single photon avalanche diode according to claim 4, characterized in that The thickness of the substrate is 350 μm and the doping concentration is 1e18 cm -3 and / or The thickness of the buffer layer is 0.5 μm and the doping concentration is 5e16 cm -3 and / or The thickness of the absorption layer is 2 μm and the doping concentration is 1e15 cm -3 and / or The thickness of the transition layer is 60 nm and the doping concentration is 2e16 cm -3 and / or The thickness of the charge layer is 200 nm and the doping concentration is 1e17 cm -3 and / or The thickness of the multiplication layer is 3 μm and the doping concentration is 1e15 cm -3 and / or The thickness of the passivation layer is 2 μm.

9. The single photon avalanche diode according to claim 1, characterized in that: Each of the electric field control modules comprises: an anode electrode, located at one end of the avalanche diode unit; a cathode electrode, located at the other end of the avalanche diode unit; The electric field directions of the electric field control modules of two adjacent avalanche diode units are the same; or The electric field directions of the electric field control modules of two adjacent avalanche diode units are opposite, and the two electric field control modules share one anode electrode or one cathode electrode.

10. A single photon detector, characterized in that: Comprising the single photon avalanche diode according to any one of claims 1 to 9.

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