Correlating photoluminescence spectra with electrical transport properties in defect-dependent β -Ga2O3 films

In this study, β-Ga2O3 thin films were fabricated on c-plane Al2O3 substrates using magnetron sputtering. As the film thickness increases from 80 to 380 nm, the in-plane crystalline domains show 120° rotation twinning, accompanied by an increase in the defect density. The defect competition among gallium vacancies, oxygen interstitials, and oxygen vacancies modulates the optical bandgap and carrier transport. Quantitative analysis using the Huang–Rhys model reveals a pronounced increase in electron–phonon coupling and local lattice relaxation in films thicker than 300 nm. This change occurs in the same thickness range as the transition from nearly Ohmic behavior to trap-assisted transport, indicating a close correlation between the evolution of defect-related optical states and carrier trapping. The nonmonotonic evolution of defect states directly governs the bandgap narrowing and interfacial conductivity. The metal–semiconductor–metal detectors exhibit a distinct wavelength-dependent temporal response, enabling solar-blind deep-ultraviolet detection. This work provides a defect-informed strategy for designing β-Ga2O3-based optoelectronic devices beyond steady-state photoresponse.