Ultra-sensitive flexible Ga₂O₃ solar-blind photodetector array realized via ultra-thin absorbing medium

The quest for solar-blind photodetectors with outstanding optoelectronic properties and weak signals detection capability is essential for their applications in the field of imaging, communication, warning, etc. To date, Ga₂O₃ has demonstrated potential for high-performance solar-blind photodetectors. However, the performance usually decays superlinearly at low light intensities due to carrier-trapping effect, which limits the weak signal detection capability of Ga₂O₃ photodetectors. Herein, a Ga₂O₃ solar-blind photodetector with ultra-thin absorbing medium has been designed to restrain trapping of photo-generated carriers during the transporting process by shortening the carrier transport distance. Meanwhile, multiple-beam interference is employed to enhance the absorption efficiency of the Ga₂O₃ layer using an Al/Al₂O₃/Ga₂O₃ structure. Based on the ultra-thin absorbing medium with enhanced absorption efficiency, a 7 × 7 flexible photodetector array is developed, and the detectivity can reach 1.7 × 10¹⁵ Jones, which is among the best values ever reported for Ga₂O₃ photodetectors. Notably, the performance of the photodetector decays little as the illumination intensity is as weak as 5 nW/cm², revealing the capacity to detect ultra-weak signals. In addition, the flexible photodetector array can execute the functions of imaging, spatial distribution of light source intensity, real-time light trajectory detection, etc. Our results may provide a route to high-performance solar-blind photodetectors for ultra-weak light detection.