High-performance (Al0.4Ga0.6)2O3/Al0.32Ga0.68N-based UVC/UVB tunable dual-band photodetectors

Abstract

The detection of ultraviolet B (UVB) and UVC radiation is of paramount importance, and has expanding applications in industrial, scientific, environmental and biomedical fields. In this work, high-Al-content β-(Al_0.4Ga_0.6)₂O₃/Al_0.32Ga_0.68N films prepared via a thermal oxidation process from AlGaN layers are employed to fabricate UVC/UVB dual-band photodetectors (PDs). The PDs achieve two responsivity peaks at ∼200 nm and 305 nm, and also exhibit tunable dual-band photodetection, which can operate in separate UVB-dominated, UVC/UVB broadband and UVC-dominated detection modes by modulating the bias voltage from 10 V to 25 V. In particular, the PDs exhibit a responsivity (R) of 0.35 A W⁻¹, detectivity of 2.46 × 10¹² Jones, UVC/UVA rejection ratio (R₂₀₀/R₃₆₅) of 70 and UVC/visible rejection ratio (R₂₀₀/R₅₀₀) of 106 with an external quantum efficiency of 219% under 200 nm light illumination at 25 V bias, demonstrating good comprehensive performance over the UVC band. The tunable dual-band detection capability can be ascribed to the effect of increasing bias voltage on lowering the barrier height between electrodes and the (Al_xGa_1−x)₂O₃ layer, promoting the photogenerated electrons in (Al_xGa_1−x)₂O₃ films to easily cross over the reduced barrier height and contributing to the UVC detection. In addition to providing a facile, economical and feasible way to fabricate UVC/UVB tunable dual-band PDs via bias voltage regulation, this work is also expected to inspire further exploration on developing versatile and high-performance multi-band PDs.