Optical properties of indium doped CdS thin films

Thin films of polycrystalline In doped CdS with a wide range of indium concentrations (1017−1021cm−3) have been deposited by indium and CdS coevaporation. Their optical properties in the visible and near-infrared region have been determined by optical transmission measurements and correlated to the indium concentration and substrate temperature. The refractive index presents a maximum at an indium concentration in the range 1019−1020cm−3 The energy dependence of the absorption edge on indium concentration is due to the Burnstein-Moss shift. The width of the exponential tail in the absorption coefficient increases with indium concentration and softens the abrupt abrorption edge of the CdS thin films.These dependences have been correlated with the incorporated quantity of indium into the CdS crystallites.