Anion Engineering Enhanced Response Speed and Tunable Spectral Responsivity in Gallium-Oxynitrides-Based Ultraviolet Photodetectors

Most of the currently developed Ga2O3-based solar blind photodetectors exhibit unexpected high persistent photoconductive gain at the expense of low response speed, and thus, the suppression of carrier trapping remains challenging. In this work, we demonstrated amorphous gallium-oxynitride-based (GaON) ultraviolet photodetectors with tunable spectral response and enhanced response speed by in situ anion engineering with a reactive sputtering technique. The tunable spectral response from 4.95 to 4.37 eV is a result of a bandgap narrowing effect, attributed to the elevation of the valence band maximum (VBM) by the hybridization of N 2p and O 2p states and the enhanced p-d repulsion. The constructed GaON PDs with a proper nitrogen composition exhibit remarkably reduced dark current and a fast response time of about 100 μs. Oxygen vacancies are deactivated by the lift-up of VBM so that slow carrier detrapping processes are suppressed, resulting in the reduced persistent photoconductivity and improved response speed. Meanwhile, nitrogen introduction increases the recombination and scattering probabilities of photoexcited carriers, which results in the reduced photoresponsivity. Thus, the rational design through anion engineering allows a flexibility in bandgap modulation and suppression of carrier trapping in oxynitrides, which provides an alternative strategy to achieve high-speed ultraviolet photodetectors.