Damage generation efficiency of protons and 60Co gammas in III–V infrared semiconductors

Radioisotope (60Co) and particle accelerator (10 s MeV proton) sources are both commonly used to assess the effects of the space radiation environment on electronics and detectors; however, the efficiency of 60Co gammas to generate displacement damage is poorly understood. Here, 60Co and 54.3 MeV proton degradation of the minority carrier lifetime are compared for an InAs/InAsSb superlattice and bulk InAsSb semiconductor infrared detector materials to assess the extent to which 60Co gammas generate displacement damage. It is found that, for equivalent nuclear energy deposition in each sample, the lifetime damage factor for 60Co irradiation is ∼14× higher than anticipated based on the lifetime damage factor from protons. This is explained by the difference in proton and 60Co gamma cascade sizes and dynamics (whereby protons generate large cascades and 60Co gamma-generated electrons generate only isolated Frenkel pairs). This difference drives the smaller damage factor for protons due to the enhanced defect recovery with larger cascades. This efficiency is an important factor to consider when analyzing electronic device performance following 60Co irradiation.