Tunneling in thin MOS structures

Recent results on tunneling in thin MOS structures are described. Thermally grown SiO2 films in the thickness range of 22–40 A have been shown to be effectively uniform on an atomic scale and exhibit an extremely abrupt oxide-silicon interface. Resonant reflections are observed at this interface for Fowler-Nordheim tunneling and are shown to agree with the exact theory for a trapezoidal barrier. Tunneling at lower fields is consistent with elastic tunneling into the silicon direct conduction band and, at still lower fields, inelastic tunneling into the indirect conduction band. Approximate dispersion relations (E-k, E-κ) are obtained over portions of the silicon-dioxide energy gap and conduction band.