278 nm deep ultraviolet LEDs with 11% external quantum efficiency

III-Nitride based deep ultraviolet (DUV) light emitting diodes (LEDs) offer smaller size, wider choice of peak emission wavelengths, lower power consumption and reduced cost compared to mercury vapor lamps and other UV light sources. Increasing efficiency of DUV LEDs accelerates their applications in bio-agent detection, analytical instrumentation, phototherapy, disinfection, biotechnology and sensing. We report on 278 nm DUV LEDs with external quantum efficiency exceeding 10 % achieved by improvements of material quality and light extraction.