Enhanced Tunneling through Dielectric Films due to Ionic Defects

Abstract

The theoretical shape of the potential barrier for a dielectric film interposed between two metals is discussed, with particular emphasis on the effects arising from ionic defects, interfacial dipoles, and field penetration of the electrodes. It is shown that both ions and the extension of their electric fields penetrating the electrodes have a significant effect on barrier shape. By applying Stratton's theory of tunneling, an analytic expression is obtained for the increase of tunnel current due to ion penetration of the barrier. For ion concentrations of the order of one per unit area equal to the film thickness square, the tunnel current increases by an order of magnitude. Numerical results are also presented for an Al–Al₂O₃–Al barrier, where the analytic solution is only marginally valid.