Characteristics of SEU current transients and collected charge in GaAs and Si devices

Results of transient current and charge collection measurements on GaAs and Si devices bombarded with 5-MeV alpha particles are presented. Upper bounds for rise-time and charge collection time of aproximately 120 psec and approximately 300 psec, respectively, were determined for the GaAs devices studied. The observed lack of funneling for lightly doped Si devices is consistent with the long dielectric relaxation time in the substrate material. Slow charge collection in lightly doped Si diodes is interpreted as arising from drift in low electric fields. Measurements of the bias and doping dependence of charge collection by funneling are in good agreement with the predictions of the McLean-Oldham model.