Study of neutron damage in GaAs MESFETs

Implanted channel GaAs MESFETs subjected to neutron irradiation show large modifications of the pinch-off voltage, open-channel saturation current, and transconductance in agreement with previous results. In this work we demonstrate how an experimental technique, based on the frequency dispersion of the transconductance, g/sub m/(f), and output conductance, g/sub D/(f), can identify the deep levels induced by neutron irradiation through measurements performed directly on packaged devices. After irradiation, a frequency dispersion of the transconductance has been observed, while it was flat in the unirradiated device. The g/sub m/(f) curve shape depends on the device bias conditions, and it has permitted for the first time to evaluate the activation energy of different deep levels induced by neutron irradiation in MESFETs.