Tight-binding investigation of electron tunneling through ultrathin SiO2gate oxides

We investigate electron tunneling through ultrathin gate oxides using scattering theory within a tight-binding framework. We employ Si100]/SiO₂/Si100] model junctions with oxide thicknesses between 7 and 18 Å. This approach accounts for the three-dimensional microscopic structure of the model junctions and for the three-dimensional nature of the corresponding complex energy bands. The equilibrium positions of the atoms in the heterostructure are derived from first-principles density-functional calculations. We show that the present method yields qualitative and quantitative differences from conventional effective-mass theory.