Impact of Se and Te addition on optical characteristics of ternary GeInSb chalcogenide films as promising materials for optoelectronic applications

Abstract

Abstract The present study investigates the linear and non-linear optical characteristics of non-crystalline quaternary Ge15In5Sb5Se75 (GIS-Se) and Ge15In5Sb5Te75 (GIS-Te) chalcogenide thin films. The amorphous nature of the studied compositions was confirmed by x-ray diffraction (XRD). The values of transformation temperatures determined by differential thermal analysis (DTA), such as glass transition T g and crystallization T c temperatures, are 524.3 and 639.6 K for GIS-Se and 503.6 and 542.0 K for GIS-Te. The calculated values of glass forming ability ( G F A ) and thermal stability ( H ) for GIS-Se are higher than those for GIS-Te. The transmittance T ( λ ) and reflectance R ( λ ) spectrophotometric measurements in the UV–vis. wavelength range (400–2500 nm) are used to estimate the index of refraction n and extinction coefficient k . The obtained values of n and k are found to be thickness independent in the investigated range. Tauc’s extrapolation model was used to determine both Urbach tail ( E U ) and optical band gap ( E g o p t ) energies. The values of ( E U ) are 0.416, 0.526 eV and ( E g o p t ) are 1.83, 1.31 eV with indirect allowed transitions for GIS-Se and GIS-Te, respectively. The optical conductivity σ o p t increased as photon energy ( h ν ) increased, and it was enhanced in the presence of Te than Se addition. The analysis of the index of refraction ( n ) is used to evaluate the dispersion energy E d , the high frequency dielectric constant ε ∞ , the oscillator strength S 0 , the lattice dielectric constant ε L , the ratio N / m * and the optical electronegativity ∅ o p t , which were found to be higher in GIS-Te than those in GIS-Se composition. The volume ( V E L F ) and surface ( S E L F ) energy loss functions were found to be increased with increasing ( h ν ) and the presence of Te. Furthermore, the calculated values of nonlinear optical susceptibility χ ( 3 ) and nonlinear index of refraction n 2 for GIS-Se and GIS-Te are 0.195 × 10−12, 2.44 × 10−11 esu and 0.868 × 10−12, 10.19 × 10−11 esu, respectively. The detailed outcomes show that the studied film samples are suitable for various optical applications such as phase-change optical rewritable disks, optical sensors, optoelectronic devices and high-speed optical fibers.