Determination of the extended-state electron mobility in a-Si

Abstract

The multi-trapping transport model has been applied, with widely differing results, to deduce the extended-state electron mobility μc in a-Si from the measured drift mobility μe. The interpretation of the data is discussed in the light of experimental information on the tail-state distribution. It is concluded that the observable transit signal represents a coherent group of drifting carriers which interact predominantly with a narrow range of tail states, 0·13-0·14 eV below εc. Measurements of μc have been extended to 450 K and it is shown that, with the above approximation, the multi-trapping model provides an excellent fit to μc(T) between 150 and 450 K. Analysis of the high-temperature data leads to μe=(10 ± 5) cm2V−1s−1 for undoped a-Si, consistent with the tail-state distribution.