Effect of Annealing on the Optical Properties of AgGa0.5In0.5Te2 Thin Film

AgGa_0.5In_0.5Te₂ thin films were deposited, by thermal evaporation of presynthesised bulk ingot material, onto a Corning 7095 glass substrates. EDXS studies on the prepared films show that the as-deposited films are nearly stoichiometric. Also, XRD studies on the as-deposited and annealed films revealed an amorphous-to-crystalline phase transition at Ta ≈ 473 K. The optical constants (n, k) of the amorphous and crystalline AgGa_0.5In_0.5Te₂ films, were determined from the transmittance and the reflectance data at normal incidence in the spectral range 400-2500 nm. The high frequency dielectric constant and the carrier concentration and the effective mass ratio were determined from the analysis of the refractive index at long wavelengths. The analysis of the absorption spectra of the investigated films revealed non-direct energy gaps, characterizing the amorphous films, in contrary to the crystalline films which exhibited only direct energy gaps.