Co-doping effects of Mg and Be on properties of ZnMgBeGaO UV-range transparent conductive oxide films prepared by RF magnetron sputtering

In this work, the Zn0.96-x−yMgxBeyGa0.04O films co-doped with different Mg and Be doping levels of 3 ∼10 at.% were prepared using an RF magnetron sputtering, and the correlation between the film properties and the doping levels was investigated. With an increase in Mg or Be doping level, the film crystal quality gradually deteriorated and the ZnO c-axis parameter was contracted or expanded due to the difference in ionic radii of Mg and Be ions, resulting in the shift of the ZnO (0 0 0 2) XRD peak position to lower 2θ or higher 2θ values and the broadening of the ZnO (0 0 0 2) XRD peak. All the grown films were highly transparent with a transmittance above 85% in the visible wavelength region and the band-gap widened from 3.74 eV to 3.88 eV at high doping level of 5 at.% Mg and 10 at.% Be, whereas the resistivity was degraded from 1.6 × 10−3 Ω cm at low doping level to 1-4 × 10−1 Ω cm at high doping level. In the Zn0.88Mg0.05Be0.03Ga0.04O film post growth annealed at 400 °C in Ar + H2 mixture ambient, the lowest resistivity of 8.17 × 10−4 Ω cm, the highest electron concentration of 5.26 × 1020 cm−3, and the large band-gap of 3.8 eV were obtained, which is attributed to the hydrogen incorporation in film during annealing and the improved film crystal quality.