Electron tunneling through a double barrier in a reverse-biased metal-oxide-silicon structure

Abstract

A number of effects in metal/(tunnel-thin SiO2)/p+-Si structures associated with electron tunneling from the valence band of bulk Si into a metal have been studied. The tunneling occurs through two successively arranged tunnel-transparent barriers: that of the depleted space charge region in Si and the SiO2 barrier, with the possible intermediate involvement of a quantum well formed by the Si conduction band. The current-voltage characteristics of the structures are calculated in terms of a simple model that considers these mechanisms for the purely depletion mode, i.e., with the inversion layer charge neglected. The relationship between the structure parameters (p-Si doping level and oxide thickness) and the relative contributions of nonresonant and resonant (via quantum-well levels in the Si conduction band) tunneling to the overall current through an MOS structure is discussed. The conditions most favorable for the observation of resonance effects are formulated.