The influence of hydrogen dilution and substrate temperature in hot-wire deposition of amorphous and microcrystalline silicon with filament temperatures between 1900 and 2500 degrees C

The effect of hydrogen dilution and substrate temperature on the optoelectronic and structural properties of thin films deposited by hot-wire chemical vapor deposition with filament temperatures between 1900 and 2500 degrees C from silane and hydrogen are studied. Amorphous silicon films are obtained at high deposition rates for hydrogen dilutions below 90%. The deposition rate scales approximately linearly with the filament temperature in this regime. Microcrystalline films are obtained for hydrogen dilution above 90%, independently of the filament temperature and substrate temperature, with much lower growth rates. The Raman spectrum of these films shows high crystalline fraction and small grain size. High conductivity films, typical of microcrystalline silicon, with high growth rates were achieved by either increasing the substrate temperature at low hydrogen dilution, or by using a hydrogen dilution just at the amorphous to microcrystalline transition point.