No abstract

This article reviews the transport properties of electrons in semiconductor heterojunction structures, in which the degrees of freedom for motion of the charge carriers are reduced by confining potentials, thereby producing low-(i.e. two-, one-or even zero-) dimensional electronic structures. A theoretical treatment of quantisation effects due to two-dimensional (2D) and one-dimensional (1D) confinement, with and without an applied magnetic field, will be given, and used to interpret a range of experimental results obtained from GaAs/Al,Ga,_,As 2D and 1D heterojunction structures. For 2D samples, these results cover low-field mobility measurements, which give information on the scattering mechanisms present, and high-field magnetotransport studies, including the quantum Hall effect and parallel conduction processes. In 1D structures, quantum and ballistic transport processes will be discussed.

A new model is proposed to explain some important experimental results on the * * * We want t o thank J. M. LAGEMAAT, J. A. PALS and M. F. H. SCHUURMANS for stimulating discussions.

No abstract