NF3 and F2 gas fluorination of GaN surface and Pt/GaN interface analyzed by hard X-ray photoelectron spectroscopy

The effects of NF3 or F2 gas annealing on epitaxially grown GaN and its interface with sputter-deposited Pt were investigated using hard X-ray photoelectron spectroscopy. Annealing GaN and Pt/GaN samples in an NF3 atmosphere led to the emergence of prominent F 1s peaks and chemically shifted Ga 2p peaks, indicating the efficient formation of Ga–Fx species not only in the bare GaN surface but also in the Pt/GaN interface, even when the NF3 treatment was performed after the Pt was deposited. By contrast, F2 annealing also led to the fluorination of the GaN surface and nonfluorination of the Pt/GaN interface. Although the plasma sputtering process removed F from the surface, band shifts were observed when the treatment conditions were varied. The findings in this study suggest that NF3 treatment is an effective post-processing method for fluorinating GaN-based systems before or after metal deposition.