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

The present study investigates the linear and non-linear optical characteristics of non-crystalline quaternary Ge 15 In 5 Sb 5 Se 75 (GIS-Se) and Ge 15 In 5 Sb 5 Te 75 (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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"