From ab initio properties of the Si-SiO2 interface, to electrical characteristics of metal-oxide-semiconductor devices

The gradual transition of the band-gap at the Si-SiO2 interface affects quantisation and leakage characteristics of MOS inversion layer. We establish a link between first principles DFT simulations of the interface, and continuum simulations in the effective mass approximation, in order to obtain a realistic description of the band-gap transition for device modelling. The simplistic approach of obtaining real-space-dependent band-gap profile from the ab initio calculated electronic structure results in uncertainty of the simulated device characteristics. This uncertainty is small however, when compared to the magnitude of the simulated impact of the transition layer. A linear transition of the band-gap over 6 - 7 A in the oxide approximates well the effects simulated with the realistic band-gap profile from DFT.