OPTICAL INVESTIGATIONS ON INXSE1-X THIN-FILMS .1.

Measurements of absorbance and transmittance in In0.05Se0.95 thin films in the spectral range approximately 1.1 to approximately 3.9 eV at room temperature were carried out. The effect of the annealing temperature is considered. It has been noticed that the absorption coefficient for In0.05Se0.95 films exhibits exponential dependence on photon energy, following Urbach's rule in the absorption edge for this film. Therefore, the optical gap E(g)opt as well as the high-frequency dielectric constant epsilon(infinity)' both depend on the film composition and hence on the annealing temperature. The observed increase of E(g)opt with annealing temperature was explained on the basis of the Mott and Davis model for the density of states in amorphous solids and free carrier absorption.