Gallium codoping for high visible and near-infrared transmission in Al-doped ZnO thin films for industrial-scale applications

Transparent conductive oxide (TCO) materials have been constantly studied and developed in laboratory research scale, but few of them were successfully connected to the industrial production. One of main reasons is a lack of reproducibility of the high TCO performance due to the completely different fabrication conditions, equipment, and scale between academic science and industry. In this work, the authors report high visible and near-infrared transmission in Zn(Al,Ga)O thin films that were fabricated under suitable industrial conditions by using a large-scale, high-throughput in-line sputtering system. Zn(Al,Ga)O exhibits sheet resistance of ∼8.05 Ω/sq. and average optical transmittance of 92.07% in the visible region, with a figure of merit that is three times higher than that of ZnAlO. Zn(Al,Ga)O also shows high near-infrared transmittance tunability of more than 10% without significant change in the visible light transmittance, where the difference is <1%. The authors reveal the significant roles of Ga in both compensating for the degradation in the film crystallinity and suppressing the creation of crystal defects such as Al interstitials, ZnAl2O4 nanocluster precipitations, and grain boundaries. These results suggest high optoelectrical properties of Zn(Al,Ga)O thin film for industrial applications.