An improved active quenching equivalent circuit model for single-photon avalanche photodiodes with avalanche self-sustainability

A single-photon avalanche photodiode (SPAD) is a type of photodiode that operates using the avalanche effect to detect light down to the single photon level. When SPAD detects photons, it generates a massive avalanche of charges which can damage the diode. The quenching circuit prevents these problems by quickly limiting the current flowing through the diode and reducing the avalanche effect. This paper designs an improved SPAD active quenching circuit model. This model introduces an avalanche self-sustaining module to increase the quenching time of SPAD, so that the reverse bias voltage can be well quenched. The simulation results of the improved circuit model and the traditional quenching circuit model are compared in detail by using Cadence PSpice. Set the photon incident time to 500ps, and the reverse bias voltage to 73V. Simulation results show that the improved model can be quenched to 70.051V, unfortunately, the traditional model can only be quenched to 72.848V. Thus, the improved active quenching equivalent circuit model has short recovery time and better quenching effect. It can be used to simulate SPADs with high temporal resolution.