The Meyer-Neldel Rule in Semiconductors

Two explanations are given for the Meyer-Neldel rule in inorganic semiconductors. First it is shown that the freezing-in of donor acceptor-type defects can lead to this rule both for band conductors and for small-polaron hopping conductors. Next it is shown that a Gaussian distribution of defect energy levels or a Gaussian distribution of hopping energies, under specific conditions of defect interactions, can also lead to this rule. As an example of a small-polaron hopping conductor experimental results are described of conductivity measurements on a vanadium garnet single crystal. The first-mentioned model leads to a freezing-in temperature which corresponds well with the value known from other experiments. 0 1984 Academic Press, Inc. 1. Introduction In A = aE, + /3. (3) The temperature dependence of the elec- This relation is called the Meyer-Neldel trical conductivity of solids is given by the rule. formula The same phenomenon was found later u = A exp(-EJkT)