Tunneling through ultrathin SiO₂ gate oxides from microscopic models

We investigate theoretically coherent electron tunneling through three-dimensional microscopic Si[100]/SiO₂/Si[100] model junctions with oxide thicknesses between 0.4 and 4.6 nm. The transmission probabilities of these structures were calculated using a semiempirical tight-binding scattering method. Our calculations provide a basis for the microscopic understanding of the observed independence of tunneling transmission on the orientation of the bulk silicon and on the nature of inelastic defect-assisted tunneling. We document significant differences between transmission coefficients obtained with the present scheme and with the popular effective-mass-based approaches. The energy dependence of the effective tunneling mass in bulk silicon dioxide is predicted.