Spectral features of Ge50−ySbxTe50−x+y alloys where 0⩽x⩽15 and 0⩽y⩽30 in thin film state

Optical spectral features of Ge50−ySbxTe50−x+y alloys where 0⩽x⩽15 and 0⩽y⩽30 in the thin film state were measured. The transmittance and reflectance have been measured at normal incidence at room temperature in the spectral range 190–2500 nm for all compositions with different thicknesses. Refractive index and extinction coefficient have been evaluated in the above spectral range. Band tail width and the band edge parameter were almost constant for all samples with different compositions. Absorption band spectrum on the basis of the imaginary parts of the dielectric constant, ε2, was applied in evaluating the optical band gap.