Surface Contamination with Si and O Impurities for GaN Single-Crystalline Layers Grown by Ultra-High-Vacuum Sputter Epitaxy

Abstract

In this study, we demonstrated a GaN surface contamination and cleaning technique focused on O- and Si-based compounds generated by an exposure to the atmosphere. The GaN single-crystalline layers were grown on sapphire (0001) substrates using the ultra-high-vacuum radio-frequency sputter epitaxy technique. During X-ray photoelectron spectroscopy (XPS) measurements, O1s and Si2p XPS signals were detected on the as-grown GaN layer surface. Thermal treatment was performed in order to remove these impurities, and the results of the XPS measurements indicated a significant decrease in the O–Ga bonds on the GaN layer surface. Following the buffered hydrogen fluoride etching treatment, a decrease in the Si compounds on the GaN layer surface was confirmed by a significant decrease in the Si2p/Ga3d XPS signal intensity ratio.