Effect of deposition temperature on the structural and electrical properties of laser-crystallized hydrogenated amorphous silicon films

The deposition temperature of hydrogenated amorphous silicon films deposited by dc glow discharge was found to affect the crystallinity, hydrogen content, and silicon-hydrogen bonding after laser crystallization of the film. This in turn affected the electrical properties of the crystallized film. The crystallinity of the film after laser annealing was always higher than that of the corresponding furnace-crystallized films, for the same deposition temperature, and it increased with decreasing deposition temperature, similar to that observed in furnace crystallized films (650 °C, 30 h). However, the dark and photoconductivity, photoresponse (defined as the ratio of photo to dark conductivity), and the carrier diffusion length increased with increasing deposition temperature (150-350 °C). This was due to both an increase in hydrogen content and the SiH and SiH₂ bonding, as shown by evolved gas analysis and infrared spectroscopy. Carrier transport measurements indicated that the dominant transport mechanism changed from localized hopping to extended state transport with increasing deposition temperature for the laser-crystallized films.