Band-edge conduction in amorphous semiconductors.

Numerous experiments indicate that the conduction process near the band edges of amorphous semiconductors differs from that in crystals. Three possible explanations for the anomalies have been proposed: long-range potential fluctuations, hopping in band tails, and polaron formation. In this paper the transport energy description will be used to show in a transparent way how band-tail hopping may cause the anomalous transport. Transient measurements provide important evidence for this phenomenon. In this description the mobility edge plays no direct role in transport phenomena.