Novel gallium oxynitride thin film photoanodes for photoelectrochemical water oxidation

Abstract

Gallium oxynitride (GaON) is an emerging semiconductor with tunable band structures and promising band positions for photoelectrochemical (PEC) water oxidation. Here, we report a bottom-up approach for the growth of GaON thin films on Ti substrates via e-beam evaporation of Ga2O3 followed by thermal nitridation under a controlled NH3 flow. This method yields wurtzite-phase GaON with a narrowed band gap (1.7–2.0 eV), ideally positioned for visible-light-driven water oxidation. Analysis of systematic variations in nitridation temperature and precursor thickness confirmed that the crystallinity, charge-carrier transport, and light absorption characteristics of GaON collectively determine its overall PEC performance, with optimum activity achieved at 700 °C and a Ga2O3 thickness of approximately 300 nm. These findings establish clear design principles for GaON-based photoanodes.