Drain Corrosion in RF Power GaAs PHEMTs

We have investigated drain degradation in a set of experimental RF power GaAs PHEMTs. Drain degradation was observed in the form of an increase in R_D and a reduction in I_max in a variety of conditions. We found that both forms of degradation arise from surface corrosion that takes place on different locations on the drain and dominate in different regimes of operation. Specifically, the increase in R_Dwas prominent in the ON-state and was found to be associated with corrosion on the drain n+GaAs ledge. The reduction in I_max, in contrast, was prominent in the OFF-state and was associated with corrosion on the exposed AlGaAs barrier close to the gate. A significant finding is that in both cases, the drain-to-gate voltage emerges as a significant accelerating factor of drain corrosion.