In this paper, two different SPAD structures are designed and fabricated by 0.13μm CMOS technology. For the
structure-1, a guard ring with low implanted p-well is used at the edge of p+ region, which prevents the periphery region
breakdown while for the structure-2 a “virtual” guard ring structure with a p- well under the whole P+ region is designed.
The first structure exhibits a maximum photon detection probability of 15% and a typical dark count rate of 18 kHz at
room temperature while the second structure exhibits a maximum of photon detection probability of 28% and a dark
count rate of 23 kHz. These results would give a help for further advanced SPAD design.