In this paper, we carry out a 2-D transient analysis of field-plate GaAs metal-semiconductor field-effect transistors (FETs) by taking surface states into account. Quasi-pulsed currentvoltage curves are derived from the transient characteristics. We show that drain lag and current slump (power slump) due to surface states are reduced by introducing a field plate because the fixed potential at the field plate mitigates the trapping effects of the surface states. The dependence of lag and current slump on the field-plate length and the SiO2 passivation layer thickness is also studied. We show that it is possible to reduce the current slump and maintain the high-frequency performance of GaAs FETs at optimum values of the field-plate length and the SiO2 layer thickness.
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