Temperature Dependence of ac Hopping Conductivity

Previous work on ac hopping conductivity in semiconductors has shown that when the impurity concentration is relatively high, the temperature dependence of the conductivity is considerably more pronounced than the theory accounts for. At the same time, the frequency dependence becomes weakened at the higher temperatures. It is proposed that multiple hops can account for these phenomena. An approximate analysis of the effect of multiple hops on the conductivity is presented. The results of this analysis are compared with some experimental results and are found to be capable of explaining the observed deviations from previous theories.