The hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon-germanium (a-SiGe:H) alloys have been prepared by the plasma enhanced chemical vapor deposition (PECVD) method. The films were grown on corning #1737 glass from the gas mixture of silane and germane. Superlattice thin films consisted of a-Si:H/a-SiGe:H multilayer structure. The UV-VIS Spectrometer analysis of a-SiGex:H alloys and superlattices thin films showed that the bandgap absorption spectra of a-SiGex:H alloys shift to lower photon energy with an increase in the GeH4 flow rate [0-300 sccm] and various a-Si:H [2-10 nm]/a-SiGex:H [2 nm] thickness. The optical bandgap had decreased by between 1.24 similar to 1.71 eV in regards to a-SiGe:H and superlattice thin films.