Effects of nitrosyl fluoride based gas treatment on fluorination and redox reaction at GaN surface and Pt/GaN interface

The effects of nitrosyl fluoride (FNO) gas treatment on the surface of GaN(0001) and its interface with sputtered Pt were investigated by hard x-ray photoelectron spectroscopy (HAXPES). Annealing GaN and Pt/GaN samples in an FNO gas atmosphere resulted in the appearance of prominent F 1s peaks in the HAXPES spectra, indicating the efficient formation of Ga–Fx bonding states not only in bare-GaN but also in Pt/GaN, even when the FNO gas treatment was performed after Pt deposition. In addition, the chemical shifts of the Ga 2p3/2 and N 1s peaks corresponded to a Fermi level shift toward the valence band. The FNO gas treatment induced greater oxidation of the GaN surface than the Pt/GaN interface. By contrast, at the Pt/GaN interface, the unintentionally formed oxide GaOx was reduced, resulting in an improvement of the electrical properties. The results of this study suggest that FNO gas treatment is an effective post-processing method for the fluorination of GaN-based systems after metal deposition.