Current and capacitance characteristics of a metal–insulator–semiconductor structure with an ultrathin oxide layer

Abstract

By self-consistently solving the Schrödinger and Poisson equations, we have studied theoretically the current and capacitance characteristics of a metal–oxide–semiconductor structure consisting of an ultrathin oxide layer embedded between an n-silicon substrate and n+-polycrystalline silicon gate. It has been shown that due to the finite doping level in the polycrystalline silicon gate and the complication of the energy sublevels in the accumulation layer, self-consistent calculation of Schrödinger and Poisson equations is of vital importance. Decreasing the oxide layer thickness drastically increases the conduction current density from the substrate to the polycrystalline silicon gate. The capacitance increases monotonically as a function of the gate bias, it gradually saturates. The theoretical results explain well our experimental data.