White light generation using 280 nm light emitting diode pumps

High power 250–280 nm deep ultraviolet (UV) light emitting diode (LED) structures were grown by migration-enhanced metal organic chemical vapour deposition (MEMOCVD) approach allowing for very high material quality for high aluminum composition AlxGa1–xN layers (x up to 70%). Standard square geometry devices with CW power up to 0.5 mW at 80 mA and pulse power more than 3 mW at 200 mA were fabricated. These high power UV LEDs were mounted into TO type package with phosphor-coated windows. This approach yielded cold white (x = 0.26, y = 0.26) LED with corrected colour temperature of about 15000 K and averaged color rendering index as high as 90. Due to using of deep UV LED as a pump source excellent stability of CIE 1931 chromaticity coordinate and average colour rendering is achieved. The power conversion efficiency of about 20 % and luminous efficacy of about 210 lm/W was also measured. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)