Electric-field-induced hopping transport in superlattices

A strong electric field applied parallel to the superlattice axis leads to Wannier-Stark localization. There are two formally equivalent pictures for the drift velocity and the diffusion coefficient, the hopping model, which is most suitable for localized states, and the band picture, which is applicable to extended states. Complete localization of carriers is achieved by strong electric and magnetic fields. In these molecule-like systems, there is a strong interdependence between the carrier spectrum and its statistical properties, the description of which requires a new approach. The related double-time character of the transport gives rise to interesting quantum effects in the current-voltage characteristics. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.