Dual-wavelength ultraviolet photodetector based on vertical (Al,Ga)N nanowires and graphene

Due to the wide application of UV-A (320 nm-400 nm) and UV-C (200 nm-280 nm) photodetectors, dual-wavelength (UV-A/UV-C) photodetectors are promising for future markets. A dual-wavelength UV photodetector based on vertical (Al,Ga)N nanowires and graphene has been demonstrated successfully, in which graphene is used as a transparent electrode. Both UV-A and UV-C responses can be clearly detected by the device, and the rejection ratio (R_{254 nm}/R_{450 nm}) exceeds 35 times at an applied bias of -2 V. The short response time of the device is less than 20 ms. Furthermore, the underlying mechanism of double ultraviolet responses has also been analyzed systematically. The dual-wavelength detections could mainly result from the appropriate ratio of the thicknesses and the enough energy band difference of (Al,Ga)N and GaN sections.