Photoelectron Holographic Study for Atomic Site Occupancy for Si Dopants in Si-Doped κ-Ga₂O₃(001)

We investigated atomic site occupancy for the Si dopant in Si-doped κ-Ga₂O₃(001) using photoelectron spectroscopy (PES) and photoelectron holography (PEH). From PES and PEH, we found that the Si dopant had one chemical state, and three types of inequivalent Si substitutional sites (Si_Ga) were formed. The ratios for the inequivalent tetrahedral, pentahedral, and octahedral Si_Ga sites were estimated to be 55.0%, 28.1%, and 16.9%, respectively. Higher (lower) ratios for the three inequivalent Si_Ga sites may come from a lower (higher) formation energy. The Tetra (Octa) Si_Ga site has the highest (lowest) ratio of the three Si_Ga sites since it has the lowest (highest) formation energy. We suggest that the tetrahedral Si_Ga site is due to the active dopant site, whereas the pentahedral and octahedral Si_Ga sites can be attributed to the inactive dopant sites for Si-doped κ-Ga₂O₃(001).