V. The Hall effect in impurity bands and inversion layers

Abstract

Abstract Results are presented on transport processes when carriers are localized in impurity bands and inversion layers. For impurity bands, the evidence of conduction by excitation to a mobility edge is reviewed, and contrasted with the Hall effect which shows the Hall mobility to be thermally activated. Evidence from the literature is presented showing how magnetic-field-induced localization of carriers can give rise to a Hall effect close to that expected for excitation to a mobility edge. Some points on transport in inversion layers are summarized, in particular the variation of the temperature dependence of conductance on sample preparation treatment. It is hoped that this will clarify the literature on these, often referred, sample variations. Results are presented showing how it is possible to obtain a transport process in which 1/R H is activated or one in which μH is activated. Where 1/R H is activated, delocalization by impact ionization is demonstrated. It is concluded that the mechanism deter...