The Hall mobility in amorphous semiconductors in the presence of long-range potential fluctuations

Abstract

We have recently proposed that, for an amorphous semiconductor, the ‘activated’ behaviour of Q(T) = ln [sgrave](T) + e/kS(T), where [sgrave] is the conductivity and S the thermopower, can be understood on the basis of diffusive transport above a mobility edge, if this mobility edge is affected by the static random potential caused by charged centres. This activated behaviour for Q(T) is found in many amorphous systems including, and best documented for, glow-discharge (gd) deposited Si : H. The model is extended to a calculation of the Hall mobility in the presence of the random field. The treatment is based on the random phase model, i.e. the Hall mobility is independent of temperature for an undisturbed mobility edge. Comparison with experimental data for doped gd Si : H is made and satisfactory agreement is obtained.