Quantum‐Confinement‐Effect‐Tuned Cascade AlQDs/β‐Ga₂O₃ Heterojunctions for Ultrasensitive Solar‐Blind Photodetection and Interference‐Resistant Imaging

Abstract Solar‐blind photodetection plays a crucial role in environmental monitoring, corona detection, and covert battlefield communication due to its unique high signal‐to‐noise ratios in the UVC band. Aluminum quantum dots (AlQDs) emerge as promising optical materials owing to their extended photoresponse in the ultraviolet region, along with their low cost and compatibility with optoelectronic devices. Herein, an AlQDs‐based cascade solar‐blind photodetector is presented with enhanced sensitivity, achieved through the quantum confinement effect. By employing a gradient double‐layer AlQDs stack integrated with β ‐Ga₂O₃, the heterojunction demonstrates a significantly suppressed dark current, reduced from 3 nA to 2 pA, and a spectral noise density of 2.8 × 10 −11 A Hz⁻ 1 / 2 compared to the single‐layer device. The optimized photodetector achieves a high UV–vis rejection ratio ( R 250 / R 400 ) of 2.5 × 10 3 , a specific detectivity of ≈2.3 × 10 1 2 Jones, a relatively fast response time of 25 ms, and a responsivity of 35.1 mA W −1 under a 1 V bias. Furthermore, the device demonstrates robust interference‐resistant imaging capabilities, enabling ultra‐weak photodetection down to 23 nW cm −2 . These results highlight the potential of AlQDs‐based cascade devices for advanced solar‐blind photodetection applications.