Enhancing Photodetection Efficiency of CMOS SiPMs using Virtual Guard Rings in a Standard 0.35 μm Process

In this letter, we introduce a design of virtual guarded SiPMs fabricated in a standard 0.35 μm standard complementary metal oxide semiconductor (CMOS) process. We compare the performance of these virtual guarded cells (VGC) to that of conventional cells with real guard rings, referred to as physical guarded cells (PGC). Specifically, we evaluate the photon detection efficiency (PDE) of both types of SiPMs. Our results demonstrate that the VGC SiPM outperforms the PGC SiPM, exhibiting a true PDE of (22.5 ± 0.5) %, which is significantly higher than the PDE of (10.9 ± 0.3) % obtained for the PGC SiPM. The superior PDE of the VGC SiPM is attributed to a larger active or photosensitive area due to the virtual guard rings and a thinner n-layer in the photosensitive region.