Simulation of Ultra-Small GaAs MESFET's Using Quantum Moment Equations—II: Velocity Overshoot

The physical effects inherent in the operation of ultra-small devices are based on the fact that the critical length (e.g., the gate length or the depletion length) becomes so small that it approaches the coherence length of the electrons that provide the operation, which suggests that such small devices must be treated as quantum-mechanical objects. In a previous paper, we described the accurate simulation of ultra-small devices, which requires quantum effects such as tunneling and quantum repulsion (complementary to barrier penetration) to be included. This numerical model is based upon a full quantum description based upon moments of the Wigner distribution function. Numerical simulation of ultrasmall MESFET's has been carried out using this model. Here, we emphasize the velocity overshoot and other hot-carrier effects and the change of these due to the quantum effects.