Effect of Ga Doping Concentration on Electrical and Optical Properties of Nano-ZnO:Ga Transparent Conductive Films

Transparent conductive nano ZnO thin films with different Ga doping concentrations (1, 3, 5, 7 at.%) were prepared on glass substrate by RF magnetron sputtering. The influence of Ga doping concentration on the structural, electrical and optical properties of ZnO:Ga films was investigated by XRD, SEM, Hall measurement and optical-transmission spectroscopy. It shows that the nano ZnO:Ga films are dense and flat, and have polycrystalline structure with preferential (002) and weak (101) orientation. The grain sizes, carrier concentration and Hall mobility changes non-linearly with the increase of Ga-content. The lowest resistivity of 1.44×10⁻³ Ωcm appears at 3 at.% Ga doping concentration. The average transmittance of the films is about 80∼90% in the visible range. The optical band gap obtained for these films is larger than for pure ZnO (∼3.37 eV).