Fe-induced stabilization of corundum α-(Fe _x Ga_1-x )₂O₃ thin films: phase transformation and thermodynamic insights

Gallium oxide (Ga₂O₃) is an ultrawide-bandgap semiconductor with strong potential for electronic and optoelectronic applications. The metastable corundum α-phase is particularly attractive for alloying and bandgap engineering but suffers from limited thermal stability. In this work, the phase stability of α-(Fe _x Ga_1-x )₂O₃ thin films grown by mist chemical vapor deposition is systematically studied using experiments and density functional theory. Increasing Fe content suppresses the α → β transformation, shifts the transition to higher temperatures, and reduces the bandgap due to electronic hybridization. DFT results show that Fe incorporation lowers the energy difference between α- and β-phases, stabilizing the corundum structure through strain effects, defect interactions, and reduced cation mobility. These findings provide insight into phase control in Ga₂O₃-based alloys and a pathway to stabilize metastable oxide phases for high-temperature applications.