CMOS SPADs for High Radiation Environments

We first characterized large 180 nm CMOS single-photon avalanche diode (SPAD) imagers under 10 and 100 MeV protons irradiation up to a displacement damage dose of 1 PeV/g. We used the dark count rate (DCR) to assess the non-ionizing damage levels created by protons. It is shown that the DCR levels are determined by the number and the type of defects created within the photocollector region of the irradiated SPAD. It is also found that the activation energies correspond to the defect energy levels of oxygen-vacancy, divacancy, and phosphorus-vacancy complexes. After irradiation, a DCR reduction was observed under room temperature, which shows the transient response of DCR induced by ionizing damage. Furthermore, high-temperature annealing was performed to accelerate recovery. We then measured the timing performance of individual SPADs with photons and 180 GeV/c pions employed as minimum ionizing particles (MIP). Both results showed sub-10 ps timing resolution per single detector. Overall, the devices under test retain reasonable DCR after the high dose of radiation, showing SPADs have the potential to be used in long-term space missions or high energy physics applications.