Design Of Silicon-based NIR Detection SPAD And Research On The Phenomenon Of SPAD Array Indirect Optical Crosstalk

Single Photon Avalanche Diode(SPAD)and its array has a promising prospect of application in nuclear medicine imaging,laser ranging,quantum communication and other fields due to its excellent single photon resolution,small gain fluctuation and magnetic field anti-interference.Taking 905 nm wavelength photon as the target,the present study designed a SPAD which is applied to its detection to explore the performance of SPAD.In addition,this study analyzed the phenomenon of indirect optical crosstalk when SPAD expands from cell to array and proposed a method to block the occurrence of indirect optical crosstalk,which has been verified by simulation tools.First of all,this study presented the basic requirements for the design of silicon-based near infrared detection SPAD,including target wavelength and detection efficiency,and analyzed the corresponding design difficulties.On this basis,this study proposed the basic structure of silicon-based near infrared detection SPAD,optimized the electric field morphology in the central detection area of the basic structure and detection efficiency with the help of simulation tools.The central electric field was successfully divided into multiplication region and drift region,and the detection efficiency was increased from 0.34% to 6.96%,successfully achieving the design goal of detection efficiency greater than 5%.Secondly,this study designed the procedure of the optimized SPAD structure,which is divided into eight steps,including the whole process from substrate selection to final electrode fabrication.On this basis,this study used simulation tools to simulate those procedures,and compared the differences in structure and electrical characteristics between the devices obtained by process simulation and ideal devices.Finally,this study analyzed the indirect optical crosstalk phenomenon from single SPAD design to SPAD array design,gave the definition and calculation method of indirect optical crosstalk probability and proposed how to establish a model in the simulation tool to simulate indirect optical crosstalk probability.On this basis,this study analyzed the indirect optical crosstalk probability under different SPAD layouts.The simulation results show that the probability of indirect crosstalk caused by a single photon has a great correlation with SPAD array layout,while the probability of indirect crosstalk during an avalanche has little correlation with SPAD array layout.Two methods to reduce the probability of indirect crosstalk are also proposed,and the effectiveness of these two methods is verified by simulation tools.The results show that the two methods of growing germanium layer and forming high doped layer reduce the probability of indirect crosstalk from 10.83% to 6.09% and 5.29% respectively,and achieve good effect of reducing the probability of indirect crosstalk.Finally,this study explored the indirect crosstalk probability of SPAD array with different materials as the substrate to reduce the occurrence of indirect crosstalk from the perspective of changing materials.From the simulation results,the indirect crosstalk probability of gallium phosphide SPAD array is 6.99%,and the indirect crosstalk probability of gallium arsenide SPAD array is 0,both of which are lower than the indirect crosstalk probability of silicon SPAD array of 10.83%.