Effect of gas ambient and varying RF sputtering power for bandgap narrowing of mixed (ZnO:GaN) thin films for solar driven hydrogen production

Abstract

The ZnO and mixed (ZnO:GaN) thin films are synthesized by (RF) magnetron sputtering in Ar and mixed O2 and N2 gas ambient at 100 °C, followed by post-annealing at 500 °C in ammonia for 4 h. The mixed (ZnO:GaN) thin films deposited under Ar gas ambient failed to reduce the bandgap, whereas (ZnO:GaN) thin films grown under mixed O2 and N2 gas ambient showed bandgap reduction. The (ZnO:GaN) films deposited under mixed O2 and N2 gas exhibited enhanced crystallinity, with shifting the optical absorption into the visible light regions. The bandgap reduction in mixed (ZnO:GaN) thin films is realized by varying the RF power. As a result, mixed (ZnO:GaN) films grown under mixed O2 and N2 showed higher photocurrents than the mixed (ZnO:GaN) thin films deposited under Ar gas ambient. Our results indicate that reduced bandgap with enhanced PEC response can be attained using the appropriate gas ambient and by varying the RF power using mixed (ZnO:GaN) films.