Si–SiO2 interface band-gap transition – effects on MOS inversion layer

Density functional theory simulation results of the atomic structure at the Si–SiO2 interface implies a non-abrupt transition of the band-gap within the oxide. The depth of the transition, 2–6 Å, is comparable to the approximately 1 nm oxide thickness in nano-CMOS devices, and is expected to affect their characteristics. Using hierarchical simulation approach, we combine for the first time ab-initio density functional theory simulations of the interface, with self-consistent Poisson– Schrödinger one-dimensional device simulations, and estimate the impact of interface band-gap transition on the inversion layer quantisation, capacitance, and tunnelling characteristics of a metal–oxide–semiconductor structure.