Evaluation of an Operational Concept for Improving Radiation Tolerance of Single-Photon Avalanche Diode (SPAD) Arrays

Silicon (Si) single-photon avalanche diode (SPAD) arrays sensitive to the 400to 900-nm wavelength range have been studied for a number of uses due to their high detection efficiency; zero readout noise; low timing jitter; mechanical robustness; low-voltage(<; 50 V) operation; mass producibility; and low size, weight, power, and cost. As with all solid-state detectors, however, they are susceptible to damage by radiation, with displacement damage by energetic particles being the primary concern for many applications. This article reports the results of low-dose-rate neutron irradiation from an americium-beryllium (AmBe) source on a 256 × 256 array of 10-μm active diameter SPADs, each with live recording of their dark count rate (DCR), up to a cumulative displacement damage dose equivalent to that delivered by a 1-MeV neutron fluence of 5.69·109 cm^-2 in Si (11.59 TeV/g). A small fraction (~2.57%) of the SPADs in the array experienced a significant step increase in their DCR, which we ascribe to displacement damage. The remainder experienced a far more gradual and subdued increase. For this reason, an operational concept for SPAD arrays, whereby SPADs that begin to exhibit a step increase in DCR are disabled, should significantly extend the useful performance of such arrays in radiation environments. We report the surviving proportion of an array implementing such an operational concept per unit dose and its DCR.