High-Sensitivity and Fast-Speed UV Photodetectors Based on Asymmetric Nanoporous-GaN/Graphene Vertical Junction.

GaN-based photodetectors are strongly desirable in many advanced fields, such as space communication, environmental monitoring, etc . However, the slow photo-response speed in currently reported high-sensitivity GaN-based photodetectors still hinders their applications. Here, we demonstrate a high-sensitivity and fast-speed UV photodetector based on asymmetric Au/nanoporous-GaN/graphene vertical junctions. The nanoporous GaN-based vertical photodetector shows an excellent rectification ratio up to ∼10 5 at +4 V / -4 V. The photo-responsivity and specific detectivity of the device is up to 1.01 × 10 4 A/W and 7.84 × 10 14 Jones, respectively, more than three orders of magnitude higher than the control planar photodetector. With switching light on and off, the repeatable on/off current ratio of the nanoporous GaN-based vertical photodetector is ∼4.32 × 10 3 , which is about 1.51 × 10 3 times to that of the control planar device. The measured rise/decay time is 12.2 μs/14.6 μs, which is the fastest value for the high-sensitivity GaN-based photodetectors to date. These results suggest that the asymmetric Au/nanoporous-GaN/graphene structure can improve the sensitivity and the photo-response speed of GaN-based PDs simultaneously.