Research On Some Key Technologies Of Single Photon Avalanche Photodiode

In recent years,with the rapid development of quantum communication system,the study of quantum communication devices has received widespread attention.The single photon detector based on single-photon avalanche photodiode(SPAD)has been valued as a core device for quantum communication receivers.But so far,there still are many challenges about SPAD.In this work,the SPAD has been reaearched from three aspects: circuit model of SPAD,single photon measurement base on SPAD and chip fabrication of SPAD,the specific contents are as follows:(1)In the aspect of SPAD circuit model establishment,we present a new PSpise SPAD circuit model based on reported models.The model adopt continuously differentiable function to describle the I-V characteristics of SPAD to solve the problem of non-convergence in reported models.At the same time,compared with the hardware description language(HDL)based model,this work has advantages in structural simplicity and ease of use.The results of simulation show the model can well simulate the self-quenching,self-sustaining and self-recovering processes of SPAD,which has guiding significance for the design of circuit system.(2)In the aspect of SPAD single photon measurement system implementation,we achieve a 250 MHz single photon measurement system which has chip measurement capability.Through the design of the 52 d B noise suppression filters and two-stage low noise amplifiers,the system can achieve a single-photon avalanche pulse with SNR up to 20 d B,besides,when the detection efficiency is 23%,the dark count probability is 3.5×10-5/gate(8750 cps).(3)In the aspect of SPAD chip fabrication optimization,we study and optimize the SPAD passivation to reduce dark count and dark current.This work compare the effects of different passivation materials on the dark current performance of the device.According to the results of optimized fabrication,this paper prepared some low dark current SPAD chips based on the In Ga As/In Al As wafer designed independently by our lab.The dark current of the fabricated SPAD is 60 n A and gain is 3.5 at 90% of breakdown voltage at room temperature.But the gain of this In Ga As/In Al As chip has to be futher improved.In summary,we study the SPAD from three aspects of circuit model establishment,measurement system optimization and fabrication optimization.This work has guiding significance to the development of SPAD.