Ballistic phenomena in GaAs MESFETs: modelling with quantum moment equations

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. The accurate simulation of ultra-small devices requires quantum effects such as tunnelling and quantum repulsion (complementary to barrier penetration) to be included. The authors have developed a numerical model based upon a full quantum description-the moments of the Wigner distribution function. Numerical simulation of ultra-small MESFETs has been carried out using this model. Here, they emphasize the hot carrier effects such as ballistic transport and velocity overshoot. They also investigate the change of the velocity due to the quantum effects.