Band-to-Band Tunneling in SiGe: Influence of Alloy Scattering

An improved band-to-band tunneling (BTBT) model for SiGe random alloy is presented. The model takes into account the coherent transition through the direct band gap as well as the phonon and alloy scattering induced transitions to the indirect conduction band valleys. The complex valence and conduction band structures obtained from the 6-band k · p and from the multi-valley effective mass models are combined to compute the non-parabolic imaginary dispersions for the direct and indirect BTBT transitions, which agree well with the full band calculations. The present model is validated against the atomistic quantum simulation based on the empirical tight binding method. Simulation results show that the alloy scattering plays an important role in the indirect BTBT of SiGe alloy and should not be neglected.