Creation and termination of substrate deep depletion in thin oxide MOS Capacitors by charge tunneling

Abstract

Deep depletion in both p-type and n-type substrates can be induced by minority carriers tunneling away from the substrate. When this occurs, tunneling current becomes saturated at the rate of carrier generation in the substrate, with the excess applied voltage dropped across the deep-depletion region. We present a quantitative model for this phenomenon based on balancing the tunneling current and the space-charge generation current. Conversely, the usual transient deep depletion in n-type substrate MOS capacitors can be terminated by tunneling-induced electron-hole pair generation, except for those with ultrathin oxides (<40 Å).