A surface-incident photodiode structure with dark current self-compensation function

Abstract

The present invention provides a surface-incident photodiode structure with a dark current self-compensation function, comprising: a photosensitive photodiode and a compensation photodiode; a light-blocking layer is provided on the photosensitive surface of the compensation photodiode, and the dark currents of the photosensitive photodiode and the compensation photodiode are equal. The present invention can achieve the self-compensation function of the dark current at the chip level without the cooperation of an external circuit operational amplifier; the present invention has both a photosensitive photodiode and a compensation photodiode. During operation, the compensation photodiode can compensate and cancel out the dark current of the photosensitive photodiode, thereby reducing the noise caused by the dark current of the photosensitive photodiode; the bias voltages of the photosensitive photodiode and the compensation photodiode of the present invention are controlled separately and are not restricted, so it can be applied to more usage scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of photodetectors, and particularly relates to a surface-incident photodiode structure with a dark current self-compensation function. Background Art

[0002] As a core device of a photosensor, a photodiode can be used for distance detection, contact alarm, gesture recognition, etc. In these applications, the photodiode receives scattered signal light and converts the optical signal into an electrical signal for output. During the entire reception process, the light collection ability and the photoelectric conversion efficiency of the photodiode are two key factors. To improve the above two performances, the most common solution in the 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. To solve the above technical problems, the patent document with the application publication number CN108829171A discloses a device and method for eliminating the dark current of a monitoring diode, but it is necessary to use an adjustable resistor and an operational amplifier in an external circuit to achieve the elimination of the dark current, and the timeliness is poor. In addition, the two photodiodes used in CN108829171A are directly connected in series with the adjustable resistor and then connected to a 5V bias voltage. Therefore, the two photodiodes are linked during the adjustment process. To achieve the elimination of the dark current, the bias voltage and the working state of the photosensitive diode are limited. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a surface-incident photodiode structure with a dark current self-compensation function. To provide a basic understanding of some aspects of the disclosed embodiments, a simple summary is given below. This summary part is not a general review, nor is it intended to identify key / important constituent elements or delineate the protection scope of these embodiments. Its sole purpose is to present some concepts in a simple form as a preamble to the subsequent detailed description.

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

[0005] In some optional embodiments, there is provided a surface-incident photodiode structure with a dark current self-compensation function, including: a photosensitive photodiode and a compensation photodiode; the compensation photodiode is connected in series with the photosensitive photodiode through an electrode, a light-blocking layer is provided on the photosensitive surface of the compensation photodiode, and the dark currents of the photosensitive photodiode and the compensation photodiode are equal.

[0006] Further, the anode of the photosensitive photodiode is connected to the cathode of the compensation photodiode, or the cathode of the photosensitive photodiode is connected to the anode of the compensation photodiode; the end where the photosensitive photodiode is connected to the compensation photodiode serves as the signal output end of the surface-incident photodiode structure.

[0007] Further, the photosensitive photodiode and the compensation photodiode are silicon-germanium photodiodes or silicon-germanium avalanche photodiodes.

[0008] Further, the photosensitive photodiode and the compensation photodiode use silicon as the substrate, use a layer of N-doped silicon as the cathode connection layer, use a layer of P-doped silicon as the anode connection layer, and use germanium as the absorption layer.

[0009] Further, when the photosensitive photodiode and the compensation photodiode are avalanche photodiodes, an intrinsic silicon layer is used as the photomultiplier layer, and a layer of P-doped silicon is used as the charge layer.

[0010] Further, the dark currents of the photosensitive photodiode and the compensation photodiode being equal refers to all situations where the dark currents of the photosensitive photodiode and the compensation photodiode are equal, including but not limited to the following situations:

[0011] The photosensitive photodiode and the compensation photodiode have the same structure and shape and the same operating bias voltage, and at this time the dark currents are equal;

[0012] The photosensitive photodiode and the compensation photodiode have different structures and shapes, but the differences in structure and shape have no effect on the dark current values of the two at the same bias voltage, and the two have the same operating bias voltage, and at this time the dark currents are equal;

[0013] The photosensitive photodiode and the compensation photodiode have different structures and shapes, and the differences in structure and shape cause the dark currents of the two to be different at the same bias voltage. At this time, the operating bias voltages of each are adjusted to make the dark currents equal.

[0014] The beneficial effects brought by the present invention:

[0015] 1. The present invention does not require the cooperation of an external circuit operational amplifier, and can realize the self-compensation function of the dark current at the chip level, has good timeliness, and can avoid the unstable factors brought by introducing other devices;

[0016] 2. The present invention has both a photosensitive photodiode and a compensation photodiode. During operation, the compensation photodiode can compensate and cancel out the dark current of the photosensitive photodiode, thereby reducing the noise caused by the dark current of the photosensitive photodiode;

[0017] 3. The bias voltages of the photosensitive photodiode and the compensation photodiode of the present invention are controlled separately and are not restricted. Therefore, it can be applied to more usage scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of a surface incident photodiode structure with a dark current self - compensation function according to the present invention;

[0019] Figure 2 is an equivalent circuit diagram of a surface incident photodiode structure with a dark current self - compensation function according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The following description and the drawings fully disclose specific embodiments of the present invention, enabling those skilled in the art to practice them. Other embodiments may include structural, logical, electrical, process, and other changes. The examples represent possible variations. Unless explicitly required, individual components and functions are optional, and the order of operations can vary. Parts and features of some embodiments may be included in or substituted for parts and features of other embodiments.

[0021] As Figure 1-2 shown, in some illustrative embodiments, the present invention provides a surface incident photodiode structure with a dark current self - compensation function, including: a photosensitive photodiode 1 and a compensation photodiode 2.

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

[0023] A light - blocking layer 103 is provided on the photosensitive surface of the compensation photodiode 2. Therefore, the compensation photodiode 2 does not receive signal light and is only used to provide real - time compensation for the dark current. Among them, the light - blocking layer 103 is a substance that is opaque in the working wavelength band of the diode, so that stray signal light cannot pass through at all, ensuring that the current output by the compensation photodiode 2 at any time is its own dark current, so as to ensure that the dark current can be directly and accurately eliminated when the photosensitive photodiode 1 and the compensation photodiode 2 are used in combination.

[0024] The light - blocking layer 103 uses an opaque substance, which can be any medium, metal, or structure that makes signal light unable to pass through. Specifically, it can be reflection or absorption.

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

[0026] The dark currents of the photosensitive photodiode 1 and the compensation photodiode 2 are equal, that is, Id 感光 = Id 补偿 , where Id 感光 is the dark current of the photosensitive photodiode 1, and Id 补偿 is the dark current of the compensation photodiode 2.

[0027] Figure 2 shows the case where the cathode of the photosensitive photodiode 1 is connected to the anode of the compensation photodiode 2. For the case where the anode of the photosensitive photodiode 1 is connected to the cathode of the compensation photodiode 2, the working principle is the same, and it is also within the scope of protection of the present invention. Figure 2 In, 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 first port, that is, the bias voltage of the photosensitive photodiode is V2 - V1. 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 , and the direction is D→C→B→A.

[0029] For the compensation photodiode 2, its bias voltage is the potential difference between the second port and the third port, that is, the bias voltage is V3 - V2. The current output by the compensation photodiode 2 is its own dark current, that is, Id 补偿 , and the direction is F→E→C→D.

[0030] Therefore, for the branch where the second port is located, the dark currents of the photosensitive photodiode 1 and the compensation photodiode 2 are equal in magnitude and opposite in direction, and thus cancel each other out. The total current passing through the second port is I 信号 , thereby eliminating the influence of the self-dark current of the photosensitive photodiode 1 on the signal-to-noise ratio. The end where the photosensitive photodiode 1 is connected to the compensation photodiode 2 can be used as the signal output end of the surface-incident photodiode structure.

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

[0032] First, silicon is used as the substrate;

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

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

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

[0036] Fifth, when the photosensitive photodiode and the compensation photodiode are avalanche photodiodes, use a layer of intrinsic silicon as the photomultiplier layer and a layer of P-doped silicon as the charge layer.

[0037] Ensure that the surface-incident photodiode structure of the present invention has high light collection ability and photoelectric conversion efficiency.

[0038] The dark currents of the photosensitive photodiode 1 and the compensation photodiode 2 being equal refers to all situations where the dark currents of the photosensitive photodiode 1 and the compensation photodiode 2 are equal, including but not limited to the following situations:

[0039] In the first situation, the structures and shapes of the photosensitive photodiode 1 and the compensation photodiode 2 are the same, and their operating bias voltages are also the same. At this time, the dark currents are equal, and the dark current can be completely eliminated;

[0040] In the second situation, the structures and shapes of the photosensitive photodiode 1 and the compensation photodiode 2 are different, but the differences in the structures and shapes have no effect on the dark current values of the two under the same bias voltage, and their operating bias voltages are the same. At this time, the dark currents are equal, and the dark current can be completely eliminated;

[0041] In the third situation, the structures and shapes of the photosensitive photodiode 1 and the compensation photodiode 2 are different, and the differences in the structures and shapes cause the dark currents of the two under the same bias voltage to be different. At this time, the dark currents can be made equal by adjusting their respective operating bias voltages, and the dark current can also be completely eliminated at this time.

[0042] Those skilled in the art should also understand that all the illustrative logical blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the above-described various illustrative components, blocks, modules, circuits, and steps have been generally described in terms of their functions. Whether such a function is implemented as hardware or software depends on the specific application and the design constraints imposed on the entire system. Skilled technicians can implement the described functions in a flexible manner for each specific application. However, such implementation decisions should not be construed as departing from the protection scope of the present disclosure.

Claims

1. A surface-incident photodiode structure with a dark current self-compensation function, characterized in that, Comprising: A photosensitive photodiode and a compensation photodiode; The photosensitive photodiode and the compensation photodiode are silicon-germanium photodiodes or silicon-germanium avalanche photodiodes; The compensation photodiode is connected in series with the photosensitive photodiode through an electrode, and one end where the photosensitive photodiode is connected to the compensation photodiode serves as the signal output end of the surface-incident photodiode structure; A light-blocking layer is provided on the photosensitive surface of the compensation photodiode, and the light-blocking layer enables the current output by the compensation photodiode at any time to be its own dark current; The structures and shapes of the photosensitive photodiode and the compensation photodiode are different, and the differences in their structures and shapes result in different dark currents under the same bias voltage. By adjusting their respective working bias voltages, the dark currents of the two are made equal.

2. The surface incident photodiode structure with dark current self-compensation function according to claim 1, characterized in that, The anode of the photosensitive photodiode is connected to the cathode of the compensation photodiode, or the cathode of the photosensitive photodiode is connected to the anode of the compensation photodiode.

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

4. The surface incident photodiode structure with dark current self-compensation function according to claim 3, characterized in that, When the photosensitive photodiode and the compensation photodiode are avalanche photodiodes, a layer of intrinsic silicon is used as the photomultiplier layer, and a layer of P-doped silicon is used as the charge layer.

Images