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

Although beta-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 beta-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 beta-Ga2O3 by incorporating Sc to form ternary (ScGa)(2)O-3 alloys. Thanks to the wider bandgap of Sc2O3 (-5.7 eV) than Ga2O3 and stronger Sc-O bonding than Ga-O, the (ScGa)(2)O-3 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 (tau(rise): 41/149 ms; tau(decay): 22/153 ms) of the alloy film-based PDs. Furthermore, the peak and cut-off response wavelengths of the (ScGa)(2)O-3 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)(2)O-3 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. (C) 2020 Elsevier B.V. All rights reserved.