Optical and electronic properties of sputtered hydrogenated amorphous silicon-tin alloys

Hydrogenated amorphous silicon-tin alloys (a-Si1−xSnx:H), in the composition range 0≤x≤0.51, have been prepared by rf sputtering. It is shown that the addition of Sn moves the conduction-band edge, thereby closing the optical band gap. The dc dark conductivity increases less than expected, with increasing Sn content, based on a simple decrease in band gap. This and the temperature dependence of the dark conductivity suggest a transition from extended-state free-carrier conduction to localized-state hopping conduction. Photoluminescence measurements show the presence of defect-state radiative recombination.