Effect of dopant concentration and crystalline structure on the absorption edge in ZnO:Y films

. We study the crystalline structure and absorption spectra for the zinc oxide films with different levels of yttrium doping. The films are deposited on glass substrates, using radio-frequency magnetron sputtering. We estimate the concentration of free charge carriers and show that the ‘blue’ shift of the fundamental absorption edge in ZnO:Y films with increasing doping level (up to 4.7 wt. %) is explained by Burstein–Moss effect. At higher concentrations of yttrium, behaviour of the fundamental absorption edge is described by a known empirical Urbach rule.