Optical and electrical properties of amorphous thin films in Gex Te1-x system

Ge_xTe_1-x thin films of different compositions are prepared on glass substrates by sputtering deposition. The optical transmittance, reflectance, electrical resistivity of the thin films axe measured as a function of composition,x. The optical energy gap and the electrical resistivity is highest when Ge_xTe_1-x enters the GeTe₂ phase due to its very ordered network structure resulting in narrow localized states in the amorphous energy band structure. Also, the refractive index and the extinction coefficient are lowest at the GeTe₂ composition since the absorption tailing near the band edge is minimum.