Valence-band electronic structure of As-terminated GaN(0001) surfaces

Surface engineering in GaN-based technology is essential for enhancing existing devices and exploring new opportunities, potentially turning GaN surfaces into platforms for devices incorporating two-dimensional crystals. In this article, we show the impact of arsenic termination on the electronic properties of GaN (0001)-oriented crystals. For this purpose, photoemission experiments and density functional theory (DFT) calculations were conducted. As atoms were vapour-deposited using an As-cracker source onto a clean GaN(0001) surface maintained at a temperature of 300 °C under ultra-high vacuum conditions. This preparation procedure allowed to obtain an As coverage of about one monolayer. The presence of As atoms on the GaN(0001) surface alters the valence-band electronic structure, with surface states positioned near the valence band maximum being evident, as confirmed by UV photoelectron spectroscopy (UPS) as well as DFT calculations. DFT was utilized to explain the origins of these features, examining various configurations of As atoms on the GaN(0001) surface.