Oscillations in MOS tunneling

Oscillatory deviations from classical Fowler-Nordheim tunneling were measured in MOS capacitor structures with dry oxides ranging in thickness from 30 to 75 Å. The silicon was p type, the metallization chrome-gold, and the direction of tunneling that corresponding to electrons being injected from the metal into the SiO2 conduction band. The observed variation of oscillation phases and amplitudes with oxide thickness suggests the following conclusions. The Si-SiO2 interface is independent of oxide thickness only for thicknesses greater than 65 Å. At lower thicknesses, the barrier height at the interface decreases slowly with oxide thickness at a rate on the order of 10 mV/Å. At higher thicknesses, the barrier height is 4.08 eV. The interface is abrupt to within a few angstroms. The energy dispersion relationship within the SiO2 conduction band is parabolic, at least up to 3 eV above the band edge, with an effective-mass–to–free-electron-mass ratio of unity. The mean free path within the SiO2 conduction band is on the order of 13 Å.