Surface analysis of bulk monocrystalline β-Ga2O3(2¯01) via x-ray photoelectron spectroscopy

A (2¯01)-oriented β-Ga2O3 (beta-gallium oxide) single crystal wafer, 2 in. in diameter, was diced into 5 × 5 mm2 specimens for surface chemical analysis using x-ray photoelectron spectroscopy (XPS). To ensure accurate surface characterization, both ex situ and in situ pretreatment methods were employed to effectively remove surface contaminants. XPS data collection included a comprehensive survey spectrum and high-resolution core-level scans of Ga 2p, Ga 3s, Ga 3p, Ga 3d, O 1s, and C 1s, along with valence band spectra and Ga LMM and O KLL x-ray induced Auger electron spectroscopy (XAES) transitions. The oxidation state identified in all gallium and oxygen photoelectron lines corresponds to Ga3+, indicating the presence of the β-Ga2O3 phase. Additionally, organic oxides and hydrocarbons were detected after 300 °C UHV annealing, which indicates the presence of strongly bonded species and an elevated number of dangling bonds on the (2¯01) surface. The Ga and O Auger features further corroborate the oxidation state assignments and offer additional insight into the surface chemical environment of the β-Ga2O3 specimens.