Study Of Conduction Band Tail States In A-Si,Ge:H,F Alloys By Electron Time-Of-Flight

The electron time-of-flight characteristics of un-alloyed a-Si:H and of a-Si,Ge:H,F alloys were studied. The log I -log t characteristics of the alloys are highly dispersive and include anomalous features. The characteristics depend strongly on measurement temperature, becoming more regular as the temperature increases. Substantial differences between low-gap alloys with comparable optical gaps are observed. Computer simulation suggests that an extra density of deep tail states, or the midgap states, are responsible for the anomalous characteristics.