Nanoscopic inclusions in high-deposition-rate a-Si:H

Hole drift mobility measured in a-Si:H deposited by expanding thermal plasma method at growth rates higher than 2nm/s fails to show the electric field dependence normally seen in the case of dispersive transport in ´standard´ a-Si:H, i.e. material prepared by plasma-enhanced chemical vapor deposition at ∼250°C. A Gaussian component in the density of valence-band tail states, superimposed to the generally accepted exponential one, can account for such behavior for the hole transients. The presence of randomly sized nanocrystallites in the amorphous matrix is thought to generate the Gaussian density of states contribution.