Twin-induced phase transition from β-Ga₂O₃ to α-Ga₂O₃ in Ga₂O₃ thin films

We deposited a 300-nm-thick Ga₂O₃ thin film on an amorphous SiO2/Si substrate via pulsed laser deposition. X-ray diffraction patterns revealed the formation of β-Ga₂O₃ phase at a substrate temperature of 700 °C. X-ray photoelectron spectra indicated that the degree of oxidation increased after annealing at 700 °C. Further annealings at higher temperatures led to a transition of the β-Ga₂O₃ phase to the α-Ga₂O₃ phase; this transition was caused by the twin structure formed during the crystallinity improvement process. In addition, we discuss the mechanism of the transition from the β phase to the α phase in the β-Ga₂O₃ thin films.