Optical properties of some sol-gel-derived gallium-doped ZnO films

摘要

Gallium-doped zinc oxide (ZnO) films with different concentrations have been prepared by sol-gel technique. The films are optically transparent and electrically conducting. The optical transmission and reflection data for the films have been analyzed. The optical absorption coefficient (α) and hence the refractive index (n), extinction coefficient (k) and the band gap (E_g) have been determined for these films using different methods. It has been observed that band gap initially increases with gallium doping from 3.281 to 3.328 eV up to a doping concentration of 2 at.%. Further doping has an adverse effect with respect to both electrical and optical properties. The width of the band tail states, which is connected to localized states in the band gap, also increases with slight doping and is maximum for 4 at.% doped samples.