Low temperature (<100 °C) fabrication of thin film silicon solar cells by HWCVD

Amorphous silicon films have been made by HWCVD at a very low substrate temperature of <= 100 degrees C (in a dynamic substrate heating mode) without artificial substrate cooling, through a substantial increase of the filament-substrate distance (similar to 80 mm) and using one straight tantalum filament. The material is made at a reasonable deposition rate of 0.11 nm/s. Optimized films made this way have device quality, as confirmed by the photosensitivity of > 10(5). Furthermore, they possess a low structural disorder, manifested by the small Gamma/2 value (half width at half maximum) of the transverse optic (TO) Si-Si vibration peak (at 480 cm(-1)) in the Raman spectrum of similar to 30.4 cm(-1), which translates into a bond angle variation of only similar to 6.4 degrees. The evidence gathered from the studies on the structure of the HWCVD grown film by three different techniques, Raman spectroscopy, spectroscopic ellipsometry and transmission electron microscopy, indicate that we have been able to make a photosensitive material with a structural disorder that is smaller than that expected at such a low deposition temperature.