Comparative Analysis of SPAD Models for Low-Light Imaging

Single photon avalanche diode (SPAD) plays a vital role in low-light imaging. Process libraries do not have a SPAD device model for simulation. A circuit model that can accurately simulate SPAD's behavior is required. This paper reviews and compares currently available SPAD models. A passive quenching circuit (PQC) is used to characterize SPAD models. 30
$\mu \ \mathrm{m} \ \mathrm{X} \ 30 \mu \mathrm{m}$
square-shaped n-s/p-sub, nwell/p-sub, p-s/nwell/p-sub SPADs without guard rings are designed, and a breakdown voltage of 11.16, 14.78, and 10.22 volts is observed, respectively. The models are compared with SPAD's quenching and recharge time. The n+/p-sub SPAD is used for our study. From this work, we conclude that the most accurate modeling of SPAD can be done by an equation-based model. We also compare the photon detection efficiency (PDE) and dark count rates (DCR). This study is conducted in the TSMC 180 nm process.