High-resolution X-ray photoemission study of photo-grown Ga₂O₃ in GaN/AlGaN/GaN heterostructures on Si substrates

For GaN/AlGaN/GaN heterostuructures grown on Si substrates, we investigated the changes in the chemical compositions during photochemical oxidation. We utilized synchtrotron-based high-resolution X-ray photoemission spectroscopy to precisely analyze the stoichiometry change. Epitaxially-grown GaN/AlGaN/GaN multilayer films showed a single-crystalline structure and the dominant bonding character of Ga-N near the surface. After photoelectrochemical oxidation with deionized water, the Ga-N bonding transformed into the Ga-O bonding, in which the stoichiometry was confirmed to be Ga₂O₃. Thus, photoelectrochemical oxidation with water may be a good candidate for fabricating the gate dielectric layer, Ga₂O₃, for GaN-based power transistors.