Paramameterization and Application of DFTB theory to the modelling of Fully Depleted Si-on-insulator MOSFETs

Abstract

We present a recent parametrisation of DFTB for Si and O aiming at the modelling and simulation of transport properties of ultra-scaled Si-based field-effect transistors. With this parametrisation, we first evaluate the electronic and dielectric properties of oxidised Si films in the range of 0.8 to 10 nm thickness, which is very relevant for contemporary and future Si-on-insulator technology. We obtain very good agreement with available experimental data for the thickness dependence of the Band-gap, conduction and valence band offsets, as well as the dielectric constant of the Si film. We then couple DFTB to the non-equilibrium Greens' function formalism and calculate the drain current characteristics of an extremely thin planar Si-on-insulator MOSFET. The simulated atomic model of the transistor includes explicitly en essential part of the gate- and buried oxides, and yields very good agreement with similar experimental device - without involving any further parameters, at least in the sub-threshold region, where electrostatics and band-structure determine the current-voltage characteristics.