Surmounting the interband threshold limit by the hot electron excitation of multi-metallic plasmonic AgAuCu NPs for UV photodetector application

Multi-metallic alloy NPs composed of various elemental compositions can surmount the interband threshold limit of mono-metallic NPs and thus can offer a promising route to boost up the performance limit of conventional ultraviolet photodetectors (PDs). In this work, a hybrid UV-PD configuration has been demonstrated by combining the multi-metallic plasmonic alloy NPs of AgCu, AuCu, and AgAuCu on a GaN photoactive layer in order to exploit the improved photo carrier injection by the strong hot electrons and LSPR. Among various devices, the tri-metallic AgAuCu NP PD demonstrates the highest performance with a remarkably high photocurrent of 1.47 x 10(-2) A at 1 V with fast rise (T-r) and fall (T-f) times of 170 and 700 ms with a very stable current. This leads to the superior figure-of-merit parameters of the PD with a photoresponsivity of 4.3 x 10(6) mA W-1, detectivity of 3.52 x 10(12) Jones and EQE of 1.39 x 10(6)%, which is similar to 16 times higher than the bare GaN PD. This ranks the AgAuCu PD as one of the best GaN based UV photodetectors. The photocurrent enhancement and excellent figure-of-merit can be attributed to the significantly increased photo carrier injection by the efficient hot electron generation via the LSPR and improved interfacial barrier characteristics by the tri-metallic elemental synergy.

Automated summary

In this work, a hybrid UV photodetector was constructed by combining multi-metallic plasmonic alloy NPs on a GaN photoactive layer, leading to a significant enhancement in photocurrent and excellent performance parameters. Among the various devices, the tri-metallic AgAuCu NP photodetector demonstrated the highest performance with superior photoresponsivity, detectivity, and EQE.