Thin films of Te46-xAs32+xGe10Si12 (x = 0, 5) of different thicknesses are deposited on glass substrate by vacuum evaporation. X-ray diffraction revealed the formation of amorphous films. The value of the optical band gap, E(g), is found to increase with the thickness of the films and with increasing As content. The films are heat treated at different elevated temperatures from 298 to 423 K. The values of E(g) are found to decrease with increasing temperature of heat treatment. The band tail, E(e), obey Urbach’s empirical relation.