Investigation on External Quantum Efficiency Droops and Inactivation Efficiencies of AlGaN-Based Ultraviolet-C LEDs at 265-285 nm.

The temperature-dependent external quantum efficiency (EQE) droops of 265 nm, 275 nm, 280 nm, and 285 nm AlGaN-based ultraviolet-c light-emitting diodes (UVC-LEDs) differed in Al contents have been comprehensively investigated. The modified ABC model (R=An+Bn2+Cn3) with the current-leakage related term, f(n)=Dn4, has been employed to analyze the recombination mechanisms in these UVC-LED samples. Experimental results reveal that, at relatively low electrical-current levels, the contribution of Shockley-Read-Hall (SRH) recombination exceeds those of the Auger recombination and carrier leakage. At relatively high electrical-current levels, the Auger recombination and carrier leakage jointly dominate the EQE droop phenomenon. Moreover, the inactivation efficiencies of 222 nm excimer lamp, 254 nm portable mercury lamp, 265 nm, 280 nm, and 285 nm UVC-LED arrays in the inactivation of E. coli have been experimentally investigated, which could provide a technical reference for fighting against the new COVID-19.