A Substrate-Isolated SPAD Integrated with A Fast Active Quench and Reset Circuit in Standard CMOS Process

Single-photon avalanche diodes (SPADs) fabricated in standard CMOS process can be directly integrated with other circuits, making them suitable for cost-effective applications. In this work, a substrate-isolated p-well/deep n-well (DNW) SPAD integrated with a compact and fast active quench and reset (AQR) circuit in standard CMOS process is proposed. The DNW of the SPAD is virtually connected, which makes a deep p-substrate region serve as a guard ring to reduce the edge electric field. In addition, a native MOSFET with a low voltage threshold (VTH) is employed as part of the quench circuit to extend the excess voltage (VEX). Post-layout simulations show that the range of VEX can be extended from 1.7 V to 3.5 V, and a quench time as low as 138 ps can be achieved, which corresponds to a quench slew rate of 25.4 V/ns. Both the quench and the reset time are adjustable, achieving the smallest dead time of 1.2 ns.