Light-induced effects on transport in hydrogenated amorphous silicon-sulfur alloys at different temperatures

초록

The effect of light illumination on the electronic transport in hydrogenated amorphous silicon-sulfur alloys (a-SiS <inf>x</inf>:H) has been investigated at various temperatures. The light-induced effects were monitored using photoconductivity and dark conductivity measurements, including subgap defect density by the constant photocurrent method. The light-induced changes in the dark conductivity, as illumination temperature increases, reveal a transition from normal to inverse Staebler-Wronski (S-W) behavior at a critical temperature (T <inf>c</inf>) that decreases with increasing sulfur concentration. On the other hand, the changes in the photoconductivity reveal normal S-W behavior at all the observed temperatures, but those are significantly reduced with increasing temperature and sulfur concentration. Correlation between subgap defect density and photoconductivity indicates that the defects created at temperatures higher than T <inf>c</inf> act as inefficient recombination centers as compared with those created at temperatures lower than T <inf>c</inf>. Two competing reaction processes, controlled by hydrogen diffusion, for light-induced defect generation are proposed to account for the experimental results. © 2002 American Institute of Physics.