The performance of submicrometer gate length GaAs MESFET's

The influence of gate length, active layer thickness, and buffer layer current upon the steady-state and RF parameters of short gate length GaAs MESFET's is investigated using a two-dimensional model that accounts for electron energy relaxation effects. For devices of similar pinchoff voltage, the saturation currents are approximately the same, but the presence of substrate conduction in a device greatly reduces its transconductance and gain-bandwidth product. The effect upon frequency response due to gate length, donor profile, gate resistance, and source inductance is numerically evaluated. The model is shown to be in reasonable agreement with measured submicrometer device characteristics.