An avalanche photodiode focal plane array pixel gain simulation method and device
By applying bias voltages under dark and light conditions, the current response curves of the focal plane array of avalanche photodiodes were obtained. Pixel gain was simulated using photogenerated carriers and collisional ionization models, solving the problems of high fabrication cost and long R&D cycle, and achieving efficient pixel gain acquisition and device optimization design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NO 24 RES INST OF CETC
- Filing Date
- 2026-04-14
- Publication Date
- 2026-07-10
AI Technical Summary
Existing silicon-based avalanche photodiode focal plane array detectors have high fabrication costs and long development cycles, and it is difficult to accurately obtain pixel gain parameters, which affects device performance and development efficiency.
By applying varying bias voltages under dark and light conditions, the dark current response curves and photocurrent response curves of the avalanche photodiode focal plane array are obtained. Simulations are then performed using photogenerated carriers and collisional ionization models to calculate the pixel gain of the pixel unit.
Accurately obtaining pixel gain shortens the R&D cycle, reduces costs, provides a theoretical basis for device optimization design, and improves detector performance and reliability.
Smart Images
Figure CN122361908A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of detector simulation technology, and in particular to a method and apparatus for simulating pixel gain of an avalanche photodiode focal plane array. Background Technology
[0002] With the development of industrial technology, silicon avalanche photodiode (Si-APD) focal plane array detectors have been widely used in astronomical observation, remote sensing mapping, autonomous driving, and quantum communication. These detectors achieve three-dimensional imaging in the visible to near-infrared band (400nm~1100nm), possessing advantages such as high sensitivity, fast response speed, and high integration. They can significantly improve the detection and recognition capabilities of optoelectronic systems in low-light environments while reducing system size and power consumption. However, such devices suffer from high fabrication costs and long development cycles. Therefore, it is urgent to conduct research on process simulation and key parameter modeling for APD focal plane arrays to shorten the development cycle, reduce costs, and support the independent controllability and systematization of these devices.
[0003] Pixel gain is a key parameter characterizing the performance of an APD focal plane detector and an important indicator that must be accurately obtained in design and application, directly affecting the detector's sensitivity and noise level. APD focal plane detectors are based on the collisional ionization and avalanche multiplication mechanism of charge carriers. Under certain bias conditions, they achieve avalanche amplification of photogenerated charge carriers, thereby obtaining significant gain and improving the device's signal-to-noise ratio and weak light signal detection capability. Therefore, accurately obtaining and establishing a pixel gain parameter model is crucial for the optimized design of high-performance, high-reliability APD focal plane detectors. Summary of the Invention
[0004] This invention provides a method and apparatus for simulating pixel gain of avalanche photodiode focal plane array (APD) to solve the technical problems of high design cost and long development cycle of the aforementioned APD focal plane detector.
[0005] In a first aspect, the present invention provides a method for simulating pixel gain of an avalanche photodiode focal plane array, comprising:
[0006] Under dark field and light field conditions, a varying bias voltage is applied to the focal plane array of avalanche photodiodes to obtain the dark current response curve and photocurrent response curve of the anode current of the pixel unit in the focal plane array as a function of the bias voltage. Under different bias voltages, the signal difference between the dark current response curve and the photocurrent response curve is extracted, and the pixel gain of the pixel unit is determined based on the signal difference.
[0007] In one embodiment of the present invention, before applying a varying bias voltage to the avalanche photodiode focal plane array, the simulation method further includes: establishing a detector array structure model and calling a photogenerated carrier model and a collisional ionization model; using the photogenerated carrier model and the collisional ionization model to perform an electrical simulation on the detector array structure model to simulate the collisional ionization characteristics of the avalanche photodiode focal plane array under a strong electric field distribution.
[0008] In one embodiment of the present invention, the step of obtaining the dark current response curve includes: setting a bias voltage step size; gradually increasing the bias voltage from an initial value to a preset voltage threshold using the bias voltage step size, and obtaining the anode current of the pixel unit under each bias voltage; and generating the dark current response curve according to the correspondence between the anode current and the bias voltage.
[0009] In one embodiment of the present invention, after obtaining the dark current response curve, the method further includes: determining the breakdown voltage of the avalanche photodiode focal plane array based on the dark current response curve.
[0010] In one embodiment of the present invention, the step of constructing the light field conditions includes: establishing a light injection model; adjusting the incident light intensity and incident angle of the light injection model according to the position of the avalanche photodiode focal plane array, so that the light source output by the light injection model is perpendicularly incident on the avalanche photodiode focal plane array.
[0011] In one embodiment of the present invention, the step of obtaining the photocurrent response curve includes: using a carrier transport model to obtain the anode current of the pixel unit under each bias voltage; and generating the photocurrent response curve according to the correspondence between the anode current and the bias voltage.
[0012] In one embodiment of the present invention, extracting the signal difference between the dark current response curve and the photocurrent response curve under different bias voltages, and determining the pixel gain of the pixel unit based on the signal difference, includes: determining a preset sampling voltage based on the breakdown voltage; obtaining the anode current corresponding to the dark current response curve and the photocurrent response curve under multiple bias voltages, wherein the multiple bias voltages include the preset sampling voltage; calculating the signal difference between the anode current of the photocurrent response curve and the dark current response curve under each bias voltage; and determining the pixel gain based on the ratio of the signal differences under different bias voltages.
[0013] Secondly, the present invention also provides an avalanche photodiode focal plane array pixel gain simulation device, the device comprising: The characteristic curve determination module is used to apply varying bias voltages to the avalanche photodiode focal plane array under dark field and light field conditions, respectively, to obtain the dark current response curve and photocurrent response curve of the anode current of the pixel unit in the focal plane array as a function of the bias voltage. The gain determination module is used to extract the signal difference between the dark current response curve and the photocurrent response curve under different bias voltages, and determine the pixel gain of the pixel unit based on the signal difference.
[0014] The beneficial effects of this invention are as follows: This invention provides a method and apparatus for simulating pixel gain in an avalanche photodiode focal plane array. The method includes: applying varying bias voltages to the avalanche photodiode focal plane array under dark and light field conditions, respectively; obtaining the dark current response curve and photocurrent response curve of the anode current of the pixel unit in the focal plane array as a function of the bias voltage; extracting the signal difference between the dark current response curve and the photocurrent response curve under different bias voltages; and determining the pixel gain of the pixel unit based on the signal difference. The pixel gain simulation method provided by this invention can accurately obtain pixel gain and is applicable to silicon-based APD focal plane detector arrays with different pixel unit structures. Furthermore, this method can reveal the influence of changes in the internal electric field distribution caused by factors such as bias voltage on the array gain, thereby providing a theoretical basis and technical path for device optimization design in practical applications. Attached Figure Description
[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.
[0016] In the attached diagram: Figure 1 This is a flowchart illustrating the pixel gain simulation method for avalanche photodiode focal plane array provided in this embodiment of the invention. Figure 2 This is a schematic diagram comparing the simulation and measured results of the dark current response curve and photocurrent response curve of the silicon-based APD focal plane detector array provided in the embodiments of the present invention. Figure 3 This is a block diagram of the avalanche photodiode focal plane array pixel gain simulation device provided in an embodiment of the present invention. Detailed Implementation
[0017] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.
[0018] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. The drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0019] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.
[0020] With the development of industrial technology, silicon avalanche photodiode (Si-APD) focal plane array detectors have been widely used in astronomical observation, remote sensing mapping, autonomous driving, and quantum communication. These detectors achieve three-dimensional imaging in the visible to near-infrared band (400nm~1100nm), possessing advantages such as high sensitivity, fast response speed, and high integration. They can significantly improve the detection and recognition capabilities of optoelectronic systems in low-light environments while reducing system size and power consumption. However, such devices suffer from high fabrication costs and long development cycles. Therefore, it is urgent to conduct research on process simulation and key parameter modeling for APD focal plane arrays to shorten the development cycle, reduce costs, and support the independent controllability and systematization of these devices.
[0021] Pixel gain is a key parameter characterizing the performance of an APD focal plane detector and an important indicator that must be accurately obtained in design and application, directly affecting the detector's sensitivity and noise level. APD focal plane detectors are based on the collisional ionization and avalanche multiplication mechanism of charge carriers. Under certain bias conditions, they achieve avalanche amplification of photogenerated charge carriers, thereby obtaining significant gain and improving the device's signal-to-noise ratio and weak light signal detection capability. Therefore, accurately obtaining and establishing a pixel gain parameter model is crucial for the optimized design of high-performance, high-reliability APD focal plane detectors.
[0022] Currently, in order to ensure the pixel gain performance of the device, it is necessary to select devices, redundancy and optimize the design based on experimental data. In the research and development process, multiple tape-out iterations are required, which is time-consuming and costly.
[0023] To solve the above problems, such as Figure 1 As shown, this application provides a method for simulating pixel gain of an avalanche photodiode focal plane array, which includes at least steps S110 to S120: Step S110: Apply varying bias voltages to the avalanche photodiode focal plane array under dark field and light field conditions, respectively, to obtain the dark current response curve and photocurrent response curve of the anode current of the pixel unit in the focal plane array as a function of the bias voltage.
[0024] For example, under dark conditions, the bias voltage of the cathode of the pixel unit in the avalanche photodiode focal plane array is set. During the change of the bias voltage, the change of the anode current of the pixel unit with the bias voltage in the dark field is extracted, and a dark current response curve is plotted based on the dark field change. Similarly, the incident light source and the bias voltage of the cathode of the pixel unit are set. During the change of the bias voltage, the change of the anode current of the pixel unit with the bias voltage in the light field is extracted, and a photocurrent response curve is plotted based on the light field change.
[0025] In detail, before applying a varying bias voltage to the avalanche photodiode focal plane array, the simulation method also includes: establishing a detector array structure model and calling the photogenerated carrier model and the collisional ionization model; using the photogenerated carrier model and the collisional ionization model, performing an electrical simulation on the detector array structure model to simulate the collisional ionization characteristics of the avalanche photodiode focal plane array under a strong electric field distribution.
[0026] Specifically, before applying a varying bias voltage to the cathode of the pixel unit in the avalanche photodiode focal plane array, a detector array structure model is established. The MODEL statement is used to call the photogenerated carrier model (e.g., SRH carrier generation-recombination model), and the IMPACT statement is used to call the collisional ionization model (e.g., SELB local collisional ionization model). Using the photogenerated carrier model and the collisional ionization model, the detector array structure model is electrically simulated to realize the collisional ionization characteristics of the silicon-based APD focal plane array under a strong electric field distribution.
[0027] The MODEL statement is used to define the physical model parameters of a semiconductor device. The Shockley-Read-Hall (SRH) carrier generation-recombination model is one of the core theories describing the nonradiative recombination process in semiconductors, and is particularly applicable to carrier recombination through defect energy levels in indirect bandgap semiconductors (such as silicon and germanium).
[0028] The IMPACT statement is a key command in Silvaco TCAD simulation tools (such as the Atlas module) used to define the physical model of carrier impact ionization. The SELB local impact ionization model refers to the Selberherr impact ionization model, which is often enabled in TCAD (Technology Computer-Aided Design) simulation tools (such as SilvacoAtlas or Medici) via the impact selb or model selb commands to simulate avalanche breakdown processes in semiconductor devices.
[0029] The collisional ionization rate of electrons is shown in expression (1): (1) in, The collisional ionization rate of electrons. It is an exponential function, E is the electric field intensity along the current direction in the detector array structure model, and AN, BN and BETAN are defined by the IMPACT statement.
[0030] The collision ionization rate of a hole is shown in expression (2): (2) in, The collision ionization rate of holes. It is an exponential function, where E is the electric field intensity along the current direction in the detector array structure model. AP, BP, and BETAP are defined by the IMPACT statement.
[0031] In detail, the steps for obtaining the dark current response curve include: setting the bias voltage step size; gradually increasing the bias voltage from the initial value to a preset voltage threshold using the bias voltage step size, and obtaining the anode current of the pixel unit under each bias voltage; and generating the dark current response curve based on the correspondence between the anode current and the bias voltage.
[0032] Specifically, the bias voltage of the cathode of the pixel unit in the avalanche photodiode focal plane array is increased from the initial value (0V) to the preset voltage threshold (140V) using the SOLVE statement, and the bias voltage step size is set to 5V. The anode current of the pixel unit under dark conditions is obtained for each bias voltage. The relationship between the anode current and the bias voltage is extracted, and the dark current response curve is plotted using the TONYPLOT statement.
[0033] The SOLVE statement is the core command used to perform simulation solutions. It instructs the simulator to perform numerical calculations on the current device structure under specified bias or time conditions to solve a set of partial differential equations describing the physical behavior of the device. The TONYPLOT statement is a visualization tool in Silvaco TCAD simulation software (semiconductor process and device simulation software) used to display and analyze the results of semiconductor process and device simulations.
[0034] More specifically, after obtaining the dark current response curve, the process also includes: determining the breakdown voltage of the avalanche photodiode focal plane array based on the dark current response curve. Specifically, after obtaining the dark current response curve, the EXTRACT statement is called to extract the voltage value at the inflection point of the dark current response curve, and this voltage value is recorded as the breakdown voltage of the avalanche photodiode focal plane array, resulting in a breakdown voltage Vbr = 134V.
[0035] The EXTRACT statement is a data extraction and calculation command in the Silvaco TCAD simulation tool. Its core function is to automatically measure and calculate key physical quantities or electrical parameters from simulation results.
[0036] More specifically, the steps for constructing the light field conditions include: establishing a light injection model; adjusting the incident light intensity and incident angle of the light injection model according to the position of the avalanche photodiode focal plane array, so that the light source output by the light injection model is perpendicularly incident on the avalanche photodiode focal plane array. Specifically, the steps for constructing the light field conditions include: calling the light injection model via the BEAM statement; placing the light source directly above the device structure according to the position of the avalanche photodiode focal plane array; adjusting the light incident angle of the light injection model to an incident light wavelength of 800 nm, an incident angle of 90°, and a light intensity of 0.1 W / cm². 2 (watts per square centimeter), enabling the light source emitted by the light injection model to be incident vertically onto the avalanche photodiode focal plane array.
[0037] The BEAM statement is the core command in Silvaco TCAD for defining light sources, used to set various parameters of incident light in optoelectronic device simulations.
[0038] More specifically, the steps for obtaining the photocurrent response curve include: using a carrier transport model to obtain the anode current of the pixel unit under each bias voltage; and generating the photocurrent response curve based on the correspondence between the anode current and the bias voltage.
[0039] Specifically, a carrier transport model related to wavelength and local electric field (such as the Boltzmann transport model) is invoked to realize the function of collecting photogenerated carriers of the avalanche photodiode focal plane array under optical field conditions, wherein the state of the particles is shown in expression (3): (3) Where h is Planck's constant and k is the wave vector of the particle. The coordinates of the particle are represented by q, t represents time, describing the change of the particle's state over time; q represents the electron charge, and B represents the local electric field.
[0040] Under light field conditions, the SOLVE statement is used to increase the cathode bias voltage of the pixel unit in the avalanche photodiode focal plane array from the initial value (0V) to the preset voltage threshold (140V). The anode current of the pixel unit under each bias voltage under light field conditions is obtained. The relationship between the anode current and the bias voltage is extracted, and the photocurrent response curve is plotted using the TONYPLOT statement.
[0041] S120. Under different bias voltages, extract the signal difference between the dark current response curve and the photocurrent response curve, and determine the pixel gain of the pixel unit based on the signal difference.
[0042] More specifically, under different bias voltages, the signal difference between the dark current response curve and the photocurrent response curve is extracted, and the pixel gain of the pixel unit is determined based on the signal difference, including: determining a preset sampling voltage based on the breakdown voltage; obtaining the anode current corresponding to the dark current response curve and the photocurrent response curve under multiple bias voltages, wherein the multiple bias voltages include the preset sampling voltage; calculating the signal difference between the anode current of the photocurrent response curve and the dark current response curve under each bias voltage; and determining the pixel gain based on the ratio of the signal differences under different bias voltages.
[0043] Specifically, using 0.9 times the breakdown voltage as the preset sampling voltage, the EXTRACT statement is used to extract the first and second anode currents from the dark current response curve at a bias voltage of 0V and the preset sampling voltage, respectively. The EXTRACT statement is also used to extract the third and fourth anode currents from the photocurrent response curve at a bias voltage of 0V and the preset sampling voltage, respectively. Subtracting the third anode current from the first anode current yields the first current signal difference I1, where I1 = 1.5 × 10⁻⁶. -8 A (Amperes), subtracting the second anode current from the fourth anode current yields the second current signal difference I2, I2 = 9.25 × 10 -7 A (Ampere), divide the second current signal difference I2 by the first current signal difference I1 to obtain the pixel gain M of the avalanche photodiode focal plane array, M=I2 / I1=61.8.
[0044] It is worth mentioning that, Figure 2This is a schematic diagram comparing the simulation and measured results of the dark current response curve and photocurrent response curve of a silicon-based APD focal plane detector array. The horizontal axis, Cathode Voltage, represents the cathode voltage in volts (V), i.e., the bias voltage; the vertical axis, Anode Current, represents the anode current in amperes. Figure 2 It can be seen that the measured response curve and the simulated response curve have the same trend. The actual measured pixel gain of the avalanche photodiode focal plane array is 59, and the error between the actual and simulated pixel gain is less than 5%.
[0045] like Figure 3 As shown, the present invention also provides a pixel gain simulation device for an avalanche photodiode focal plane array, the device comprising: The characteristic curve determination module 310 is used to apply varying bias voltages to the avalanche photodiode focal plane array under dark field and light field conditions, respectively, so as to obtain the dark current response curve and photocurrent response curve of the anode current of the pixel unit in the focal plane array as a function of bias voltage. The gain determination module 320 is used to extract the signal difference between the dark current response curve and the photocurrent response curve under different bias voltages, and determine the pixel gain of the pixel unit based on the signal difference.
[0046] It should be noted that the avalanche photodiode focal plane array pixel gain simulation device provided in the above embodiments and the avalanche photodiode focal plane array pixel gain simulation method provided in the above embodiments belong to the same concept. The specific way of performing each step has been described in detail in the method embodiments, and will not be repeated here.
[0047] This invention provides a method and apparatus for simulating pixel gain in an avalanche photodiode focal plane array. The method includes: applying varying bias voltages to the avalanche photodiode focal plane array under both dark and light field conditions; obtaining the dark current response curve and photocurrent response curve of the anode current of each pixel unit in the focal plane array as a function of the bias voltage; extracting the signal difference between the dark current response curve and the photocurrent response curve under different bias voltages; and determining the pixel gain of the pixel unit based on the signal difference. The pixel gain simulation method provided by this invention can accurately obtain pixel gain and is applicable to silicon-based APD focal plane detector arrays with different pixel unit structures. Furthermore, this method can reveal the influence of changes in the internal electric field distribution caused by factors such as bias voltage on the array gain, thereby providing a theoretical basis and technical path for device optimization design in practical applications.
[0048] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for simulating pixel gain in a focal plane array of avalanche photodiodes, characterized in that, include: Under dark field and light field conditions, a varying bias voltage is applied to the focal plane array of avalanche photodiodes to obtain the dark current response curve and photocurrent response curve of the anode current of the pixel unit in the focal plane array as a function of the bias voltage. Under different bias voltages, the signal difference between the dark current response curve and the photocurrent response curve is extracted, and the pixel gain of the pixel unit is determined based on the signal difference.
2. The avalanche photodiode focal plane array pixel gain simulation method according to claim 1, characterized in that, The simulation method further includes the following steps before applying a varying bias voltage to the avalanche photodiode focal plane array: Establish a detector array structure model and call the photogenerated carrier model and the collisional ionization model; The detector array structure model is electrically simulated using the photogenerated carrier model and the collisional ionization model to simulate the collisional ionization characteristics of the avalanche photodiode focal plane array under a strong electric field distribution.
3. The avalanche photodiode focal plane array pixel gain simulation method according to claim 1, characterized in that, The steps for obtaining the dark current response curve include: Set the bias voltage step size; The bias voltage is gradually increased from its initial value to a preset voltage threshold using the bias voltage step size, and the anode current of the pixel unit under each bias voltage is obtained; The dark current response curve is generated based on the correspondence between the anode current and the bias voltage.
4. The avalanche photodiode focal plane array pixel gain simulation method according to claim 1, characterized in that, After obtaining the dark current response curve, the process further includes: The breakdown voltage of the avalanche photodiode focal plane array is determined based on the dark current response curve.
5. The avalanche photodiode focal plane array pixel gain simulation method according to claim 1, characterized in that, The steps for constructing the light field conditions include: Establish a light injection model; Based on the position of the avalanche photodiode focal plane array, the incident light intensity and incident angle of the light injection model are adjusted so that the light source output by the light injection model is perpendicularly incident on the avalanche photodiode focal plane array.
6. The avalanche photodiode focal plane array pixel gain simulation method according to claim 1, characterized in that, The steps for obtaining the photocurrent response curve include: Using a carrier transport model, the anode current of the pixel unit under each bias voltage is obtained; The photocurrent response curve is generated based on the correspondence between the anode current and the bias voltage.
7. The avalanche photodiode focal plane array pixel gain simulation method according to claim 4, characterized in that, Extracting the signal difference between the dark current response curve and the photocurrent response curve under different bias voltages, and determining the pixel gain of the pixel unit based on the signal difference, includes: The preset sampling voltage is determined based on the breakdown voltage; Obtain the anode current corresponding to the dark current response curve and the photocurrent response curve under multiple bias voltages, wherein the multiple bias voltages include a preset sampling voltage; Calculate the signal difference between the anode current of the photocurrent response curve and the dark current response curve under each bias voltage; The pixel gain is determined based on the ratio of the signal differences under different bias voltages.
8. A pixel gain simulation device for an avalanche photodiode focal plane array, characterized in that, include: The characteristic curve determination module is used to apply varying bias voltages to the avalanche photodiode focal plane array under dark field and light field conditions, respectively, to obtain the dark current response curve and photocurrent response curve of the anode current of the pixel unit in the focal plane array as a function of the bias voltage. The gain determination module is used to extract the signal difference between the dark current response curve and the photocurrent response curve under different bias voltages, and determine the pixel gain of the pixel unit based on the signal difference.