Safe operating area of GaAs MESFET and PHEMT for amplification in overdrive operating conditions

We present an evaluation of the safe operating area of a GaAs MESFET and a PHEMT operating under overdrive conditions. The methodology, used to define the limit of the device safe operating area, consists in applying accelerated DC step stresses with bias conditions that can be reached by the Vds and Vgs sweeps in overdrive operation. The identified parameter drifts of the MESFET are rather less related to hot electron effects than the PHEMT ones as the stress bias conditions correspond to a conduction regime where the impact ionization rate is weaker for the MESFET than for the PHEMT. Specific DC life-tests summarised in this work have allowed to orientate the technology choice for overdrive operating conditions in a satellite mission, preferably towards the MESFET instead of the PHEMT under test.