COMPARISON OF NON-PARABOLIC HYDRODYNAMIC SIMULATIONS FOR SEMICONDUCTOR-DEVICES

Parabolic drift-diffusion simulators are common engineering level desi gn tools for semiconductor devices. Hydrodynamic simulators, based on the parabolic band approximation, are becoming more prevalent as devic e dimensions shrink and energy transport effects begin to dominate dev ice characteristics. However, band structure effects present in state- of-the-art devices necessitate relaxing the parabolic band approximati on. This paper presents simulations of ballistic diodes, a benchmark d evice, of Si and GaAs using two different non-parabolic hydrodynamic f ormulations. The first formulation uses the Kane dispersion relationsh ip in the derivation of the conservation equations. The second model u ses a power law dispersion relation {(hk)(2)/2m = xW(y)}. Current-volt age relations show that for the ballistic diodes considered, the non-p arabolic formulations predict less current than the parabolic case. Ex planations of this will be provided by examination of velocity and ene rgy profiles. At low bias, the simulations based on the Kane formulati on predict greater current flow than the power law formulation. As the bias is increased this trend changes and the power law predicts great er current than the Kane formulation. It will be shown that the non-pa rabolicity and energy range of the hydrodynamic model based on the Kan e dispersion relation are limited due to the binomial approximation wh ich was utilized in the derivation. Copyright (C) 1996 Elsevier Scienc e Ltd.