Self‐Trapped Hole Migration and Defect‐Mediated Thermal Quenching of Luminescence in α‐ and β‐Ga ₂ O ₃

Abstract Gallium oxide (Ga 2 O 3 ) is a promising ultrawide bandgap semiconductor for next‐generation power electronics and optoelectronic devices. Here, temperature‐dependent and polarization‐resolved photoluminescence excitation spectroscopy data, complemented by hybrid‐functional first‐principles calculations, are presented, and a microscopic model is derived that explains the interplay of hole migration, defect trapping, and carrier recombination at defects underlying thermal quenching phenomena in α‐ and β‐Ga 2 O 3 . In α‐Ga 2 O 3 , the UV emission is attributed to self‐trapped holes, while the blue luminescence arises from defect‐related processes, including gallium split vacancies and their defect complexes. Calculations reveal an energy barrier of 88 meV for self‐trapped hole migration in α‐Ga 2 O 3 , consistent with activation energies from temperature‐dependent photoluminescence. This enables efficient trapping by defects, enhancing blue luminescence and quenching UV emission. In β‐Ga 2 O 3 , a higher migration barrier of 0.36 eV reduces the defect trapping, allowing the UV self‐trapped hole emission to remain intense, with blue luminescence emerging only at elevated temperatures. These results establish a direct link between self‐trapped hole migration, defect trapping, and thermal quenching of emission in both phases. The insights advance the understanding of carrier dynamics in ultrawide bandgap oxides and may guide defect engineering for high‐performance functional devices.