Radiation Damage and Annealing Effects in Photon Coupled Isolators

Photon-coupled isolators with both photodiode and phototransistor detectors were irradiated to a total dose of 108 rads(Si) at a 60Co source and to a fluence of 3.7×lO13 n/cm2 (E > 10 kev) at a TRIGA reactor. Damage constants for both the biased and unbiased cases were obtained. Decreases in the current transfer ratios at the highest dose were from 60 for the isolators using photodiodes to more than 10,000 for the isolators using phototransistors. No changes were noted in the isolation resistance or the capacitance. Rise and fall times decreased by about a factor of seven for the isolators using phototransistors. After irradiation isochronal annealing data was obtained on the recovery of the degraded parameters.