Displacement Damage Characterization of CMOS Single-Photon Avalanche Diodes: Alpha-Particle and Fast-Neutron Measurements

We report on alpha and neutron irradiation of 7.8 $\boldsymbol {\mu }\text{m}$ single-photon avalanche diodes (SPADs) manufactured in 40-nm CMOS. Displacement damage leads to persistent dark count rate hot spots, due to carrier generation centers introduced by radiation. Defects are studied as a function of temperature and electrical stress, with live acquisitions evidencing large amounts of short-term annealing of the damage, and sometimes also random telegraph signal. Average damage factors and defect activation energies are consistent with a large field-enhancement of carrier generation. Since some radiation-induced defects lead to out-of-spec behavior, the implications for the reliability of SPAD-based systems are also discussed, by projecting the associated terrestrial failure rates.