ON THE DESCRIPTION OF HOPPING-ENERGY RELAXATION AND TRANSPORT IN DISORDERED-SYSTEMS

Some recent theoretical approaches to the hopping of electrons through localized band-tail states are discussed. Particular attention is giv en to the approximation in which energy relaxation of non-equilibrium electrons is treated as diffusion in energy space and to the approxima tion based on the averaging of hopping rates. It is shown that both ap proaches lend to results different from those based on Mott's semiquan titative technique with averaging hopping distances, not the rates. De tailed analysis shows that both diffusion approximation and averaging of hopping rates are inapplicable to hopping relaxation and transport of carriers in band tails.