Comparative study of group-II alloying effects on physical property of ZnGaO transparent conductive films prepared by RF magnetron sputtering

•Alloying effects of group-II elements into ZnGaO were compared with each other.•Physical properties of the deposited films were strongly dependent on the alloying elements.•The wide band-gap of 3.76 eV could be achieved with Be alloying.•The lowest resistivity was attained by Mg alloying.•Local vibration modes related to Ca or Sr doping were found in the Raman spectra.

The alloying effects of group-II elements on the properties of the Zn0.86X0.1Ga0.04O (X: Be, Mg, Ca, Sr) films were investigated and compared with each other. Mg alloying into ZnGaO resulted in the best quality of film, whereas Ca or Sr incorporation significantly deteriorated the properties of the resultant films. The lowest resistivity of 1.07 × 10−3 Ω cm was achieved from the film alloyed with Mg and while, the wide band-gap of 3.76 eV was reached by Be doping in ZnGaO. It was suggested that the film property was strongly dependent on the alloying elements and critically affected by the mismatch of ionic radii between alloying elements and Zn. Additional phonon modes were found in the Raman spectra of Ca and Sr doped films and these phonons were suggested to be due to the local vibration modes related to Ca or Sr doping.