Effects of double Schottky barrier on the electric properties of ceramic semiconductors

Abstract

Effects of the interface states at the grain boundaries on the applied voltage dependence of the double Schottky barrier (DSB) are theoretically discussed. Based on the simplified models of rectangular density distributions for the interface states, effects of the energy level, density of states, and the distribution width of the interface states are quantitatively calculated. The I-V characteristics of DSB's are also calculated and the nonlinear I-V relations are discussed. The nonlinear exponent (alpha) of the I-V relation was found to be determined mainly by the barrier height and the total charge of the interface states. The observed ICTS spectra and other electric properties of ZnO varistors and PTC thermistors are discussed on the basis of the above DSB model.