The effect of annealing processes on electronic properties of sol-gel derived Al-doped ZnO films

Al-doped ZnO films with high transmittance and low resistivity were prepared by sol-gel method with a three-step annealing. By investigating the relative effect of the Al∕Zn ratio to the annealing on electrical and optical properties, the origin of electrical conduction is verified as the combining effect of the high temperature annealing which enhances crystal quality that provides higher mobility of electrons and the reduction annealing which releases the localized electrons caused by oxygen absorption. Varying the Al∕Zn ratio causes a small Burstein–Moss shift and a slight change in carrier concentration. In contrast, the annealing procedure produces significant changes in the carrier concentration and mobility.