Photodiode structure and photoelectric sensor with dark current indication function

Abstract

The present invention provides a photodiode structure with a dark current indication function, including: a photosensitive photodiode and a reference photodiode; a light-blocking layer is provided on the photosensitive surface of the reference photodiode, and the dark currents of the photosensitive photodiode and the reference photodiode have a fixed multiple relationship. The present invention also provides a photoelectric sensor, including: a processing module and the photodiode structure. Through the structural design of the present invention, the photodiode structure can output two current signals, so that in actual operation, only the two current signals need to be subtracted to obtain an accurate incident photocurrent, ultimately achieving the purpose of eliminating dark current and reducing noise, and the present invention does not need to eliminate the dark current of the photodiode by adding peripheral devices, so the present invention has the advantages of simple structure and low cost, and further improves the photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection equipment, and in particular relates to a photodiode structure and a photoelectric sensor with a dark current indication function. Background Art

[0002] As the core component of photoelectric sensors, photodiodes can be used for distance detection, contact alarms, gesture recognition, etc. In these applications, photodiodes receive scattered signal light and convert the light signal into an electrical signal output. In the entire receiving process, the photodiode's ability to collect scattered signal light and its photoelectric conversion efficiency are two key factors. To improve the above two performances, the most common solution in existing designs is to increase the aperture of the photodiode and the thickness of the absorption layer. However, increasing the aperture and thickening the absorption layer will significantly increase the dark current of the photodiode, thereby increasing the noise. Summary of the invention

[0003] To solve the above technical problems, the present invention provides a photodiode structure and a photoelectric sensor with a dark current indication function. In order to have a basic understanding of some aspects of the disclosed embodiments, a simple summary is given below. This summary is not a general review, nor is it intended to identify key / important components or describe the scope of protection of these embodiments. Its only purpose is to present some concepts in a simple form as a preface to the detailed description that follows.

[0004] The present invention adopts the following technical solution:

[0005] In some optional embodiments, a photodiode structure with a dark current indication function is provided, including: a photosensitive photodiode and a reference photodiode; the reference photodiode is connected in parallel with the photosensitive photodiode through an electrode, a light-blocking layer is provided on the photosensitive surface of the reference photodiode, and there is a fixed multiple relationship between the dark currents of the photosensitive photodiode and the reference photodiode.

[0006] Furthermore, the photosensitive photodiode and the reference photodiode are germanium silicon photodiodes or germanium silicon avalanche photodiodes.

[0007] Furthermore, the photosensitive photodiode and the reference photodiode use silicon as a substrate, use a layer of N-doped silicon as a cathode connection layer, use a layer of P-doped silicon as an anode connection layer, and use germanium as an absorption layer.

[0008] Furthermore, when the light-sensitive photodiode and the reference photodiode are avalanche photodiodes, a layer of intrinsic silicon is used as a photomultiplier layer, and a layer of P-doped silicon is used as a charge layer.

[0009] Furthermore, the anode of the photosensitive photodiode is connected to the anode of the reference photodiode, or the cathode of the photosensitive photodiode is connected to the cathode of the reference photodiode; the connection between the photosensitive photodiode and the reference photodiode refers to sharing the same electrode or being connected by wire bonding.

[0010] In some optional embodiments, a photoelectric sensor is provided, comprising: a processing module and the photodiode structure with dark current indication function; the processing module is used to obtain two current signals output by the photosensitive photodiode and the reference photodiode, and subtract the two current signals to eliminate dark current.

[0011] Furthermore, the dark current Id of the photosensitive photodiode 感光 and the dark current Id of the reference photodiode 参考 There is a fixed multiple relationship between: Id 感光 =N×Id 参考 ;

[0012] The dark current of the photosensitive photodiode and the dark current of the reference photodiode have a fixed multiple relationship, which refers to any situation where the dark current of the photosensitive photodiode can be indicated by the reference photodiode, including but not limited to the following situations:

[0013] The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode does not change with time and environment, and N is an objective fixed constant and is stored in the processing module;

[0014] The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode changes with time and environment, but this change can be ignored. At this time, the processing module presets a fixed constant as the N value;

[0015] The multiple relationship between the dark current of the photosensitive photodiode and the reference photodiode changes with time and environment, and this change cannot be ignored. At this time, the processing module generates and stores table data, and the table data contains N values ​​corresponding to different environments and times.

[0016] The beneficial effects brought by the present invention: through the structural design of the present invention, the photodiode structure can output two current signals, so that in actual work, only the two current signals need to be subtracted to obtain the accurate incident photocurrent, ultimately achieving the purpose of eliminating dark current and reducing noise. Moreover, the present invention does not need to eliminate the dark current of the photodiode by adding peripheral devices. Therefore, the present invention has the advantages of simple structure and low cost, and further improves the photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of a photodiode structure with a dark current indication function of the present invention;

[0018] Figure 2 It is an equivalent circuit diagram of a photodiode structure with a dark current indication function of the present invention. DETAILED DESCRIPTION

[0019] The following description and accompanying drawings fully demonstrate specific embodiments of the present invention so that those skilled in the art can practice them. Other embodiments may include structural, logical, electrical, process and other changes. The embodiments represent possible variations only. Unless clearly required, separate components and functions are optional, and the order of operation may vary. The parts and features of some embodiments may be included in or replace the parts and features of other embodiments.

[0020] Embodiment 1:

[0021] like Figure 1-2 As shown, the present invention provides a photodiode structure with a dark current indication function, including: a photosensitive photodiode 1 and a reference photodiode 2.

[0022] The light-sensitive photodiode 1 receives the signal light through the photosensitive surface 102 and converts the light signal into an electrical signal.

[0023] The light-blocking layer 103 is set on the photosensitive surface of the reference photodiode 2, so the reference photodiode 2 does not receive signal light, and is used to output a dark current reference value to indicate the dark current of the photosensitive photodiode 1 in real time. The light-blocking layer 103 is a layer of material that is opaque in the diode working band, so that stray signal light cannot pass through at all, so as to ensure that the current output by the reference photodiode 2 at any time is its own dark current, so as to ensure that the dark current can be accurately eliminated later.

[0024] The light-proof material used in the light-blocking layer 103 may be any medium, metal or structure that prevents the signal light from passing through, and may be reflective or absorbing.

[0025] The reference photodiode 2 is connected in parallel with the photosensitive photodiode 1 through the electrode 101, and the anode of the photosensitive photodiode 1 is connected to the anode of the reference photodiode 2, or the cathode of the photosensitive photodiode 1 is connected to the cathode of the reference photodiode 2. The connection between the photosensitive photodiode 1 and the reference photodiode 2 means that the two share the same electrode, or that the two are connected by wire bonding.

[0026] There is a fixed multiple relationship between the dark current of the photosensitive photodiode 1 and the reference photodiode 2, that is, Id 感光 =N×Id参考 , where Id 感光 is the dark current of the photodiode 1, Id 参考 is the dark current of reference photodiode 2.

[0027] Figure 2 The case where the cathodes of the photosensitive photodiode 1 and the reference photodiode 2 are connected is shown in FIG. 1 . For the case where the anodes of the photosensitive photodiode 1 and the reference photodiode 2 are connected, the working principle is the same, and therefore it is also within the scope of protection of the present invention. Figure 2 In the example, the voltage of the first port is V1, the voltage of the second port is V2, and the voltage of the third port is V3.

[0028] For the photosensitive photodiode 1, its bias voltage is the potential difference between the second port and the third port, that is, the bias voltage of the photosensitive photodiode is V2-V3, and the current output by the photosensitive photodiode 1 is the sum of the signal photocurrent and its own dark current, that is, I 信号 +Id 感光 , the direction is D→C→E→F.

[0029] For the reference photodiode 2, its bias voltage is the potential difference between the second port and the first port, that is, the bias voltage is V2-V1, and the current output by the reference photodiode 2 is its own dark current, that is, Id 参考 , the direction is D→C→B→A.

[0030] Therefore, the photodiode structure of the present invention can output two groups of current signals: the first group is output from the third port as the signal output terminal, and the output current is I 信号 +Id 感光 The second group is output from the first port as the reference end, and the output current is Id 参考 The two sets of current signals are simultaneously output to the outside of the photodiode structure for subsequent calculations. 感光 =N×Id 参考 , so the current output from the signal output terminal is subtracted from N×Id in real time 参考 The effect of eliminating dark current can be achieved, thereby reducing the noise caused by dark current.

[0031] The photosensitive photodiode 1 and the reference photodiode 2 are germanium silicon photodiodes or germanium silicon avalanche photodiodes and have the following characteristics:

[0032] First, using silicon as a substrate;

[0033] Second, a layer of N-doped silicon is used as the cathode connection layer;

[0034] Third, a layer of P-doped silicon is used as the anode connection layer;

[0035] Fourth, using germanium as the absorption layer;

[0036] Fifth, when the light-sensitive photodiode and the reference photodiode are avalanche photodiodes, a layer of intrinsic silicon is used as a photomultiplier layer, and a layer of P-doped silicon is used as a charge layer.

[0037] The photodiode structure of the present invention is guaranteed to have higher light collection capability and photoelectric conversion efficiency.

[0038] Embodiment 2:

[0039] The present invention provides a photoelectric sensor, comprising: a processing module and the photodiode structure with dark current indication function in embodiment 1.

[0040] The processing module is used to obtain two current signals output by the photosensitive photodiode 1 and the reference photodiode 2, and subtract the two current signals to eliminate the dark current, and finally obtain the accurate signal photocurrent.

[0041] In actual application, the two sets of current signals output by the photodiode structure are collected by the external circuit at the same time and input into the processing module for operation. The processing module can be an operator or a microcomputer processing system. 感光 and the dark current Id of the reference photodiode 2 参考 There is a fixed multiple relationship between: Id 感光 =N×Id 参考 .

[0042] There is a fixed multiple relationship between the dark currents of the photosensitive photodiode 1 and the reference photodiode 2, which refers to any situation where the dark current of the photosensitive photodiode 1 can be indicated by the reference photodiode 2, including but not limited to the following situations:

[0043] In the first case, the multiple relationship between the dark current of the photosensitive photodiode 1 and the reference photodiode 2 does not change with time and environment. At this time, N is an objective fixed constant, which is stored in the processing module and is used when the processing module performs specific calculations.

[0044] In the second case, the multiple relationship between the dark current of the photosensitive photodiode 1 and the reference photodiode 2 changes with time and environment, but the change is very small, so that this change can be ignored in actual calculation. At this time, the processing module presets a fixed constant as the N value, which is stored in the processing module and can be called for use in specific calculations;

[0045] In the third case, the multiple relationship between the dark current of the photosensitive photodiode 1 and the reference photodiode 2 changes with time and environment, and this change cannot be ignored. At this time, the processing module generates and stores table data. The table data contains N values ​​corresponding to different environments and times. This table data is stored in the processing module. During specific calculations, the N value is obtained in real time by looking up the table and then performing subtraction operations.

[0046] The photodiode structure with dark current indication function proposed in the present invention has a photosensitive photodiode 1 and a reference photodiode 2. When working, the photodiode structure outputs two sets of current signals at the same time. In the external circuit, by performing real-time calculations on the current at the signal end and the current at the reference end, the dark current component in the signal end current can be subtracted, thereby achieving the effect of eliminating dark current and reducing noise. Therefore, the structural design of the present invention enables the chip to directly output two current signals, and the dark current elimination effect can be achieved through simple calculations in the external circuit. Under the premise of ensuring the accurate output of the incident photocurrent value, the present invention has the advantages of simple structure and low cost.

[0047] Those skilled in the art will also appreciate that the various illustrative logic blocks, modules, circuits, and algorithmic steps described in conjunction with the embodiments herein can all be implemented as electronic hardware, computer software, or a combination thereof. In order to clearly illustrate the interchangeability between hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above around their functions. Whether such functions are implemented as hardware or software depends on specific applications and the design constraints imposed on the entire system. A skilled person can implement the described functions in an alternative manner for each specific application, but such implementation decisions should not be interpreted as departing from the scope of protection of the present disclosure.

Claims

1. A photodiode structure with dark current indication function, characterized in that: The photodiode comprises: a photosensitive photodiode and a reference photodiode; The reference photodiode is connected in parallel with the photosensitive photodiode through an electrode, a light-blocking layer is provided on the photosensitive surface of the reference photodiode, and there is a fixed multiple relationship between the dark currents of the photosensitive photodiode and the reference photodiode, so that the dark current can be eliminated by subtracting the two current signals output by the photosensitive photodiode and the reference photodiode; The dark current Id of the photosensitive photodiode 感光 and the dark current Id of the reference photodiode 参考 There is a fixed multiple relationship between: Id 感光 =N×Id 参考 ; The fixed multiple relationship refers to any situation where the dark current of the light-sensing photodiode is indicated by the reference photodiode, The case where the dark current of the light-sensitive photodiode is indicated by the reference photodiode includes: The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode does not change with time and environment, and N is an objective fixed constant; The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode changes with time and environment, but this change can be ignored. At this time, a fixed constant is preset as the N value; The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode changes with time and environment, and this change cannot be ignored. At this time, table data is generated and stored, and the table data contains N values ​​corresponding to different environments and times.

2. The photodiode structure with dark current indication function according to claim 1, characterized in that: The light-sensitive photodiode and the reference photodiode are germanium-silicon photodiodes or germanium-silicon avalanche photodiodes.

3. The photodiode structure with dark current indication function according to claim 2, characterized in that: The photosensitive photodiode and the reference photodiode use silicon as a substrate, use a layer of N-doped silicon as a cathode connection layer, use a layer of P-doped silicon as an anode connection layer, and use germanium as an absorption layer.

4. The photodiode structure with dark current indication function according to claim 3, characterized in that: When the light-sensitive photodiode and the reference photodiode are avalanche photodiodes, a layer of intrinsic silicon is used as a photomultiplier layer, and a layer of P-doped silicon is used as a charge layer.

5. The photodiode structure with dark current indication function according to claim 4, characterized in that: The anode of the photosensitive photodiode is connected to the anode of the reference photodiode, or the cathode of the photosensitive photodiode is connected to the cathode of the reference photodiode; the connection between the photosensitive photodiode and the reference photodiode refers to sharing the same electrode or being connected by wire bonding.

6. A photoelectric sensor, characterized in that: The photoelectric sensor comprises: a processing module and a photodiode structure with a dark current indication function as claimed in any one of claims 1 to 5; The processing module is used to obtain two current signals output by the light-sensitive photodiode and the reference photodiode, and subtract the two current signals to eliminate dark current.

7. The photoelectric sensor according to claim 6, characterized in that: The dark current Id of the photosensitive photodiode 感光 and the dark current Id of the reference photodiode 参考 There is a fixed multiple relationship between: Id 感光 =N×Id 参考 .

8. The photoelectric sensor according to claim 7, characterized in that: The fixed multiple relationship refers to any situation where the dark current of the light-sensing photodiode is indicated by the reference photodiode, The case where the dark current of the light-sensitive photodiode is indicated by the reference photodiode includes: The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode does not change with time and environment, and N is an objective fixed constant and is stored in the processing module; The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode changes with time and environment, but this change can be ignored. At this time, the processing module presets a fixed constant as the N value; The multiple relationship between the dark current of the photosensitive photodiode and the reference photodiode changes with time and environment, and this change cannot be ignored. At this time, the processing module generates and stores table data, and the table data contains N values ​​corresponding to different environments and times.

9. A method for eliminating dark current using a photodiode structure, wherein the photodiode structure is the photodiode structure according to any one of claims 1 to 5, The dark current Id of the photosensitive photodiode 感光 and the dark current Id of the reference photodiode 参考 There is a fixed multiple relationship between: Id 感光 =N×Id 参考 ; The method comprises the following steps: Providing a first port, a second port and a third port such that the bias voltage of the reference photodiode is the potential difference between the second port and the first port, and the bias voltage of the light-sensing photodiode is the potential difference between the second port and the third port; The two sets of current signals are simultaneously output from the photodiode structure to the outside of the photodiode structure for subsequent operation, wherein the first set of current signals is output through the third port as the signal output end, and the output current is I 信号 +Id 感光 The second set of current signals is output from the first port as the reference end, and the output current is Id 参考 ; Based on Id 感光 =N×Id 参考 , the current through the output I 信号 +Id 感光 Subtract N×Id in real time 参考 To eliminate the dark current in the output current to obtain the signal photocurrent I 信号 .

10. The method according to claim 9, characterized in that The fixed multiple relationship refers to any situation where the dark current of the light-sensing photodiode is indicated by the reference photodiode, The case where the dark current of the light-sensitive photodiode is indicated by the reference photodiode includes: The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode does not change with time and environment, and N is an objective fixed constant; The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode changes with time and environment, but this change can be ignored. At this time, a fixed constant is preset as the N value; The multiple relationship between the dark current of the photosensitive photodiode and the dark current of the reference photodiode changes with time and environment, and this change cannot be ignored. At this time, table data is generated and stored, and the table data contains N values ​​corresponding to different environments and times.

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