Variable Threshold Heterostructure FET Studied by Monte Carlo Simulation
We investigate the influence on the performance of self-aligned n-type GaAs/AIGaAs Heterostructure Field Effect Transistors (HFETs) of using a threshold voltage that is allowed to vary with lateral position. We use a self-consistent ensemble Monte Carlo technique for this study of Variable Threshold HFETs (VTHFETs). For a gate length of 0.5 μm, we show that we are able to manipulate the velocity profile in the channel so as to increase the mean electron velocity in the source end of the channel by up to 50%. This figure also gives directly the improvement of the drain current and the transconductance. Despite this transconductance rise, the intrinsic cutoff frequency fT remains constant or even falls slightly. However, fT of a loaded device may still substantially increase.
KeywordsThreshold Voltage Gate Voltage Drain Current Electron Velocity Doping Density
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