CMOS SPADs with up to 500 μm diameter and 55% detection efficiency at 420 nm

ABSTRACT Many demanding applications require single-photon detectors with very large active area, very low noise, high detection efficiency, and precise time response. Single-photon avalanche diodes (SPADs) provide all the advantages of solid-state devices, but in many applications other single-photon detectors, like photomultiplier tubes, have been preferred so far due to their larger active area. We developed silicon SPADs with active area diameters as large as 500 μm in a fully standard CMOS process. The 500 μm SPAD exhibits 55% peak photon detection efficiency at 420 nm, 8 kcps of dark counting rate at 0°C, and high uniformity of the sensitivity in the active area. These devices can be used with on-chip integrated quenching circuitry, which reduces the afterpulsing probability, or with external circuits to achieve even better photon-timing performances, as good as 92 ps FWHM for a 100 μm diameter SPAD. Owing to the state-of-the-art performance, not only compared to CMOS SPADs but also SPADs developed in custom technologies, very high uniformity and low crosstalk probability, these CMOS SPADs can be successfully employed in detector arrays and single-chip imagers for single-photon counting and timing applications.