A Compact Active Quenching and Recharge Pixel Circuit for Single Photon Imaging Sensors

This paper presents a compact pixel for single photon imaging applications, comprising of an actively quenched and recharged p+/n-well single photon avalanche diode (SPAD) with $10\ \mu \mathrm{m}$ active area diameter and a novel 8-bit analogue counter. Additionally, the pixel includes a current starved inverter to regulate the hold-off time. Fabricated in $0.18\ \mu \mathrm{m}$ complementary metal oxide semiconductor (CMOS) technology, the pixel occupies an overall area of $21\ \mu \mathrm{m}\times 21\ \mu \mathrm{m}$ which is considerably smaller. Early analytical results demonstrate a fast quenching and recharge time of 120 ps and 4.38 ns respectively. Furthermore, a programmable dead time varying between 4.5 ns to 81 ns can be achieved, hence, leading to a reduction in afterpulsing probability.