Poisson-Schroedinger-Continuity two-dimensional analysis of both short (ballistic) and long (drift-diffusion) III–V FETs

Abstract

It was recently shown that the quantum mechanical results of the Landauer theory of conduction, applied to a simple one-layer channel FET, can be recast in the traditional drift-diffusion form but with the mobility and injection velocity redefined in a new context. Based on that, we have performed two-dimensional Poisson-Schrödinger-Continuity calculations for both long drift-diffusion and short ballistic quantum well FETs. Very good agreement with many-layer, state-of-the-art InGaAs devices has been achieved provided that only one parameter, the saturation velocity υsat of the mobility function, is rescaled so that our calculated drain current agrees with the experimental value at very large gate voltages VG. This single value of υsat has been used at all other VG. Our calculations are not only a test of the equivalence described above but valuable information about the sub-threshold regime and especially the leakage currents is obtained. This information is usually absent in rigorous Landauertype-or equivalently non-equilibrium Green functions-calculations which are performed in simplified FET systems.