Bulk Single Crystalline β-Ga2O3 (001) Surface Analyzed by XPS

A 2-inch β-Ga2O3 (beta-gallium oxide) single crystal wafer of (001) orientation was diced into 5 × 5 mm² specimens, and its surface was characterized via X-ray photoelectron spectroscopy (XPS). Both ex situ and in situ pretreatments were conducted prior to XPS to eliminate surface contamination. Comprehensive spectra were acquired, including a wide survey scan and high-resolution core level scans of Ga 3d, Ga 3p, Ga 3s, Ga 2p, O 1s, and C 1s, along with the valence band spectra and Ga LMM and O KLL Auger transitions. The oxidation state observed across all gallium and oxygen core levels corresponds to Ga³⁺, which, when combined with the quantitative analysis results, supports the presence of a stoichiometric β-Ga2O3 phase. Carbon contamination was found to be negligible, indicating a clean surface with minimal adventitious carbon. The presence and spectral features of the Ga and O Auger lines further substantiate the oxidation state assignments and provide complementary insights into the surface chemical environment.