X-ray photoelectron spectroscopy and x-ray diffraction study of the thermal oxide on gallium nitride

The oxidation of single crystal gallium nitride in dry air has been investigated. X-ray photoelectron spectroscopy (XPS) revealed minimal oxide growth at 450 and $\text{750\hspace{0.17em}°}$ C for up to 25 h. However, at $\text{900\hspace{0.17em}°}$ C the growth of an oxide approximately 5000 Å thick was observed after 25 h. This oxide was determined to be the monoclinic $\beta$ -Ga${}_2{\mathrm{O}}_3$ using glancing angle x-ray diffraction. XPS spectra of the Ga $\text{3d}$ and Ga $\text{2p}$ core levels indicated peak shifts of 1.2 and 1.3 eV, respectively, from Ga–O to Ga–N bonding. The Ga $L_3{M}_{45}{M}_{45}$ core level binding energy was also investigated and $\beta$ -Ga${}_2{\mathrm{O}}_3$ and GaN each presented a characteristic peak shape.