Effect of Ga Doping on Transparent and Conductive Al-Doped ZnO Films Prepared Using Magnetron Cosputtering

Al-doped ZnO (AZO) films with various Ga contents were prepared by magnetron co-sputtering in order to investigate the effect of Ga additions on the structural and optoelectronic characteristics of AZO films. The appropriate Ga doping level improved the crystallinity of the AZO films, investigated by X-ray diffraction analysis. The resistivity of AZO films decreased from 3.5 x 10(-3) to 8.1 x 10(-4) Omega cm by Ga doping at 2.1 at. %. The Hall mobility was improved by enhancing the polycrystalline growth of the films. The carrier concentration was increased by Ga doping, which was activated as an extrinsic donor. At a further increase in the Ga content of more than 2.1 at. %, the crystallinity and resistivity of the Ga-doped AZO films deteriorated. The optical band gap was increased, and the transmittance in the visible region was increased from 86.7 to 91.0% using the same level of Ga doping at 2.1 at. %. (C) 2010 The Japan Society of Applied Physics