Unification of three multiphonon trap-assisted tunneling mechanisms

Abstract

There are three basic multiphonon trap-assisted tunneling (TAT) mechanisms in the gate leakage current of a metal-oxide-semiconductor (MOS) structure: the short-ranged trap potential, nonadiabatic interaction and electric field induced trap-band transitions. In this paper, a comparison of these three mechanisms is made for the first time in a single (Schenk’s model) MOS structure. A properly box-normalized electron wave function in the SiO2 conduction band in an electric field is used to calculate the field ionization rate of a deep neutral trap. It is found that capture and emission rates of a deep neutral trap are almost the same in the short-ranged trap potential and nonadiabatic interaction induced TAT processes, so the two mechanisms give a similar contribution to the total TAT current. The calculated TAT current and the average relaxation energy (∼1.5 eV) due to these two mechanisms are in good agreement with the experimental results. In contrast, capture and emission rates in Schenk’s model are several orders smaller. The TAT current induced by this mechanism is also much smaller and can be ignored.