Transient response of GaAs microwave power FET to X-ray pulses

The GaAs MESFETs, constructed with a 2 micron high mobility low conductivity VPE buffer layer, were exposed at room temperature to the X-ray pulse from a FEBETRON 705 source up to dose rates of 9 x 10(10) rad(Si)/s. Upset of the 2-GHz output signal and its recovery time depended on how well the nominal 50-ohm test circuit lines were matched to 50 ohms. Strong increases in Ids tracked the X-ray pulse, approached peak values of two times IDSS and usually showed a 10% tail which always disappeared in microseconds. Evidence for a backgating effect was not found. No primary photocurrents could be identified.