It has recently been proposed that the electron microscopic mobility in hydrogenated amorphous silicon is of the order of 100 cm2V-lS-l, and that the observed lower mobility values result from scattering by potential fluctuations arising from defect centres which have a negative effective correlation energy. We show that such potential fluctuations cannot lower the mobility to its observed value of 10 cm2V-lS-lMoreover, we find that the experimental evidence used to support the claim of a higher mobility can be adequately explained by the lower of the accepted values.
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We gratefully acknowledge clarifying discussions with R. A. Street, M. Hack, E. A. Schiff and J. M. Marshall. This research is supported by the Solar Energy Research Institute.