Effect of Al doping on the DC reaction sputtered ZnO thin films

ZnO films with c-orientation and high transmission were grown by dc reaction sputtering with Zn and Al element targets. In the initial stage of Al doping, the inter-planar distance, the optical refractive index and the band-gap changed significantly. Then, as Al content increases, the optical refractive index and the band-gap change slowly, and the inter-planar distance reaches a stable value of 0.266 nm. The analyses reveal that all of doped Al atoms provide carries as donors, and the results also indicate that the conductivity of the films mainly depends on the carrier localization caused by the lattice defects.