Experiments and modeling of the photocurrent response of GaAs MESFETs

1-μm technology GaAs MESFETs were exposed to a transient radiation environment at the Rensselaer Gaerttner linear accelerator laboratory and modeled by computer simulation using a modified version of the PISCES-IIB semiconductor device simulation code and the TRIGSPICE circuit simulation code. The MESFETs were tested in steady-state conditions, with short (20-ns) radiation pulses and with short pulses on devices that had received a prior dose of gamma, neutron, or neutron-plus-gamma irradiation. Parasitic bipolar action was observed in the short pulse testing in unexposed devices. Previously unreported transient failure was observed in the neutron preirradiated devices only. The threshold for this failure is consistent with the level of severity of prior irradiation. steady-state photocurrent and the parasitic bipolar transistor are modeled and explained on the basis of physical mechanisms