Physics-based simulation of field-plate effects on substrate- and surface-related current slump in GaAs FETs

Two-dimensional transient simulation of GaAs FETs with a field plate is performed in which substrate traps and surface states are considered. Quasi-pulsed I-V curves are derived from the transient characteristics. It is studied how the existence of field plate affects slow current transients and current slump due to substrate traps and surface states. It is shown that both the substrate-related and surface state-related transients and current slump are reduced by introducing a field plate. It is suggested that there are optimum values for field-plate length and insulator thickness under the field plate to reduce the current slump and also to maintain high frequency performance of GaAs FETs.