ELECTRONS, HOLES, AND THE HALL-EFFECT IN AMORPHOUS-SILICON

The double sign anomaly in hydrogenated amorphous silicon,observed by LeComber et al. [1] in 1977, has remained puzzling ever since. Recentl y we attacked this problem from two different directions using the equ ation-of-motion method. Calculations reproduce the double sign anomaly and were rationalised in terms of the behaviour of the spectral funct ion. in a new type of calculation the motion of a 'wave packet' was st udied in an applied field. Behaviour characteristic of positive and ne gative effective masses was found in the same ranges of energy for cry stalline and a-Si. A perturbation theory is given for reconciling thes e results.