Theory of high-field transport in semiconductor superlattice structures

Abstract

The authors present a theoretical framework for the transport of charge carriers in semiconductor multiple-quantum-well structures for motion perpendicular to the layers. The formalism is derived on the basis of strong electric fields but they allow the possibility of describing the low-field ohmic region by using a simple scaling argument. Stark localisation in narrow energy bands implies that the transport phenomena are a superposition of phonon-assisted hopping and intra-band tunnelling. The transport equations and transition rates are derived and discussed in relation to experimental results. In addition they also consider the influence of an external magnetic field both parallel and perpendicular to the layers. The influence of disorder is considered and it is found that it can considerably modify the nature of the physical effects predicted on the basis of the 'pure' eigenstates. Recent experiments on magneto-transport perpendicular to the layers are discussed in the light of this theoretical formalism.