CONCENTRATION-DEPENDENCE OF CARRIER MOBILITY AND DIFFUSIVITY IN DILUTED HOPPING SYSTEMS

The distribution of nearest neighbours in dilute hopping systems is shown to be determined completely by positional disorder. As a result, there is no interplay between the energy and distance as far as the easiest jump is concerned and the distribution in energy of hopping neighbours parallels the density-of-state distribution function. As a result the dependence of the charge carrier mobility on concentration and temperature can be factorized into terms dependent on concentration and temperature only. These dependences are calculated for the case of a completely random spatial distribution of localized states. The temperature dependence of the transport coefficients in dilute systems is shown to coincide with that in systems with a high concentration of hopping sites.