Comprehensive Spectroscopic Study of Competing Recombination Channels and Thermal Quenching Mechanisms in β-Ga2O3 Single Crystals

This work investigates a comprehensive temperature-dependent photoluminescence (PL) study (7–300 K) of β-Ga2O3 single crystals under 250 nm excitation. The emission consists of three competing bands at ~3.55 eV (J1), ~3.37 eV (J2), and ~3.07 eV (J3), exhibiting a redshift, band broadening, and a crossover near ~140 K with increasing temperature. The novelty of this study lies in the first quantitative investigation of the temperature-dependent photoluminescence of undoped β-Ga2O3 single crystals, revealing activation, trap-release, and phonon-coupling parameters that define the competition between STE (Self-trapped exciton)- and DAP-related emission channels. A two-channel Arrhenius analysis of global thermal quenching at Emax (at maximum PL), J1, and J2 reveals a common shallow barrier (E1 = 7–12 meV) alongside deeper, band-specific barriers (E2 = 27 meV for J1 and 125 meV for J2). The J3 band shows non-monotonic intensity (dip–peak–quench) reproduced by a trap-assisted generation model with a release energy Erel = 50 meV. Linewidth analysis yields effective phonon energies (Eph ≈ 40–46 meV), indicating strong electron–phonon coupling and a transition to multi-phonon broadening at higher temperatures. These results establish a coherent picture of thermally driven redistribution from near-edge STE-like states to deeper defect centers and provide quantitative targets (activation and phonon energies) for defect engineering in β-Ga2O3-based optoelectronic and scintillation materials.