EDA Model And The Design Of High-efficiency Quenching And Resetting Circuit For SPAD

The single photon detector consisting of single photon avalanche diode can capture the weak optical signal of a single photon with nano-second timing resolution.Single photon avalanche diode detectors are composed of single photon avalanche diode and peripheral circuits.However,in the process of peripheral circuits designing,a precise EDA model must be established for single photon avalanche diode.In this paper,single photon avalanche diode and peripheral circuits are taken as research objects,the establishment of precise EDA model for single photon avalanche diode and the design of highly efficient quenching and resetting circuit are carried out.First of all,from the imaging principle of single photon avalanche diode detector,in the Geiger mode,based on the working principle of single photon avalanche diode,the performance of key parameters and the composition of the peripheral quenching circuit in the single photon avalanche diode are analyzed,which lays a theoretical foundation for the research about subsequent EDA model of single photon avalanche diode and quenching and resetting circuit.Then,an accurate EDA model of single photon avalanche diode is designed for the dark count and after-pulsing characteristics of single photon avalanche diode.In the process of dark count modeling,based on the existing model which have researched on thermal generation,trap-assisted tunneling and band-to-band tunneling mechanisms,the influence of carrier diffusion in region neutral on dark counting is introduced.For the after-pulsing,considering the secondary trap factor in the after-pulsing,the process of the capture and release of carrier is studied.In order to make the parameters used in the model closer to the actual device,the effect of different values of the parameters corresponding to different depths in the depletion region under the same reverse bias voltage is analyzed.Silvaco TCAD tool are used to extract key parameters of avalanche triggering probability and electric field strength.The Verilog-A is used to establish the precise EDA model of single photon avalanche diode,and the Cadence is used to confirm the validity of the established model.The simulation results show that,compared with the existing model,the results of the proposed model are closer to the measured data,the maximum of accuracy increase of dark count in proposed simulation model comes to 31.48% when excess bias voltage equals to 3.5v and temperature equals to 50°C.The after-pulsing model has an exponential decay relationship with the delay-time.Finally,based on the working principle of quenching and resetting circuit,a highly efficient quenching and resetting circuit structure are proposes by changing the traditional quenching mode.In section of the delay circuit,a circuit of double delay module is designed,which can select different delay channels according to different working states of single photon avalanche diode,so that the delay effect is achieved while the resetting time is shorter.Based on the established EDA model of single photon avalanche diode to simulate the characteristics of single photon avalanche diode,the pre-simulation verification of the quenching and resetting circuit is completed by Cadence Spectre.From the simulation results,the quenching and resetting circuit in this paper can shorten the quenching and resetting time to 1.645 ns and reduce the after-pulsing probability by 0.07%,which increases the performance of the quenching and resetting circuit that can be used to reduce after-pulsing probability by 5.11%.The layout of the designed circuit is drawn by Cadence Virtuoso,and post simulation verification is completed by Calibre.The results show that the time of each parameter slightly increases due to the influence of parasitic effects,but the logical time of the post simulation is consistent with the logical time of the pre-simulation,that is,the proposed circuit meets the requirements of circuit design.