Electric Field Line Crowding-Based SPAD for Enhanced Photon Detection Efficiency

This article discusses the front-side illuminated (FSI) single-photon avalanche diode (SPAD) designed for enhancing photon detection efficiency (PDE). The SPAD has an additional electrode (AE) besides the cathode and anode. The two variants of SPAD, one with and without AE, are simulated using the TCAD tool and are compared with the existing architecture in the literature. The SPAD consists of a partially depleted absorption volume with a thickness of 10.4 $\mu $ m. The field strength around the cathode and AE is maintained due to electric field line crowding. By introducing AE, the charge collection and carrier multiplication near the cathode are enhanced. This leads to an improvement in PDE. The peak PDE achieved at a wavelength of 600 nm for SPAD with AE and without AE are 45% and 33.9%, respectively. At a wavelength of 905 nm, the PDE for SPAD with AE is 15.2%, while for SPAD without AE is 11.3%. The dark count rate (DCR), at room temperature and at an excess bias of 3.5 V, for SPAD without AE is 171 cps, and with AE is 151 cps.