A prominent source of charge carrier losses due to non-radiative recombination in AlGaN QWs, caused by the presence of charged centers localized at disordered hetero interfaces, has been experimentally revealed. It was found out that the spectral density of current low-frequency noise, which carries integral information about single defects and a defect system, is an order of magnitude higher in AlGaN QWs than in effective blue InGaN/GaN QWs. Thus, non-radiative recombination losses are still the source responsible for the low quantum efficiency of ultraviolet LEDs.