High-Performance Self-Powered <i>c</i> -MgZnO-Based Schottky and PIN Far-UVC Photodetectors

Self-powered far-ultraviolet C (far-UVC, 200 < λ < 240 nm) photodetectors are highly desired due to their wide-ranging applications. Cubic-phase Mg_<i>x</i>Zn_1-<i>x</i>O (<i>c</i>-MgZnO), an ultrawide bandgap ternary semiconductor alloy with high Mg composition derived from MgO and ZnO, offers tunable wide bandgap (∼4.5-7.8 eV), low-temperature process compatibility, and environmentally benign characteristics, making it highly promising for far-UVC photodetection. Herein, self-powered far-UVC photodetectors based on a Pt/<i>c</i>-MgZnO/ZnO Schottky junction and NiO/<i>c</i>-MgZnO/ZnO PIN heterojunction were designed and successfully fabricated for the first time. At zero bias, both the Schottky and PIN devices exhibit excellent intrinsic far-UVC photodetection capability with ultrafast response speeds (10-90% rise time: ∼30 ns; 90-10% decay time: ∼450 ns). The superior performance of these photodiodes arises from the efficient dissociation of photoexcited electron-hole pairs, a process enabled by the built-in electric field within the depletion region at the junction interfaces. This mechanism will be thoroughly analyzed through energy band diagrams and carrier transport investigations. More interestingly, the PIN junction device demonstrates superior responsivity, higher rectification ratio, and lower dark current compared to the Schottky device, owing to its enhanced built-in potential and larger effective space-charge region area. At zero-bias operation with 222 nm illumination, the fabricated PIN heterojunction device exhibits a responsivity of ∼3.43 mA/W that escalates to ∼96 mA/W under high-temperature operation at 200 °C.