Dark Count Rate Distribution in Neutron-Irradiated CMOS SPADs

Dark count rate (DCR) increase in CMOS single-photon avalanche diodes (SPADs) exposed to a nonmonochromatic neutron source is modeled, taking into accountthe source spectrum and the geometry of the device under test. Experimental results from the characterization of SPADs fabricated in a 150-nm technology and irradiated with 1-MeV neutron equivalent fluences up to 1011 cm-2 are found to be in good agreement with the theoretically calculated distribution of the nonionizing energy deposited in the device substrate.