Degradation of GaAs MESFETs in Radiation Environments

The effects of gamma and neutron irradiation on lownoise, GaAs MESFETs are reviewed, with emphasis on microwave amplifier characterisitics. With gamma irradiation, the amplifier noise figure degrades above 107 rads (Si), without change in signal parameters. With neutron irradiation, amplifier gain and noise figure degrade above 1014 n/cm2. With gamma irradiation, unidentified levels are apparently introduced that respond at microwave frequencies. With neutron irradiation, changes are caused principally by carrier compensation in the graded region between the channel and substrate. Device characterization procedures, experimental results, and degradation mechanisms are discussed.