Ultra-wide-bandgap (ScGa)2O3 alloy thin films and related sensitive and fast responding solar-blind photodetectors

Although β-Ga2O3 is considered an excellent candidate for solar-blind photodetectors (PDs) owing to its direct bandgap (4.9 eV) and high stability, the cut-off wavelength often oversteps the DUV region, reducing the rejection ratio of the PD. Moreover, oxygen vacancies, which always appear in β-Ga2O3 films, act as trap centers hindering carrier recombination and significantly lowering response speed. To disentangle these issues, we propose in this work to modify β-Ga2O3 by incorporating Sc to form ternary (ScGa)2O3 alloys. Thanks to the wider bandgap of Sc2O3 (∼5.7 eV) than Ga2O3 and stronger Sc–O bonding than Ga–O, the (ScGa)2O3 alloy films exhibit a wider bandgap (5.17 eV) with fewer oxygen vacancies compared with pure-Ga2O3, as expected, which eventually lead to an ultra-low dark current (0.08 pA at 10 V) and faster response times (τrise: 41/149 ms; τdecay: 22/153 ms) of the alloy film-based PDs. Furthermore, the peak and cut-off response wavelengths of the (ScGa)2O3 PD are blue shifted relative to the pure Ga2O3 PD, resulting in a higher rejection ratio (>500 vs ∼317). The Sc-alloying strategy, taking advantage of wider bandgap of Sc2O3 and stronger Sc–O bonding to widen the bandgap while reducing the intrinsic carriers and oxygen vacancies in the (ScGa)2O3 alloy, is expected to be generally applicable to the design of other wide-bandgap oxide alloys for developing high-performance UV photodetectors with a low dark current and high response speed.