Dependence of optical constants of a-GaAsN thin films on sputtering pressure

Amorphous GaAsN (a-GaAsN) films have been deposited at room temperature by reactive magnetron sputtering on glass substrates at different sputtering pressure. The deposition rate decreased as the sputtering pressure increased. Transmittance and reflectance of the as-deposited films were obtained by spectrophotometric measurement. The sputtering pressure influence on the optical band gap (E
_g
), refractive index (n), the dispersion parameters (E
_o
, E
_d
) have been investigated. An analysis of the absorption coefficient revealed a direct optical transition characterizing the as-deposited films. The refraction index dispersion of the as-deposited a-GaAsN films fitted well to the Cauchy dispersion relation and Wemple's model.