Highly efficient broad-area blue and white light-emitting diodes on bulk GaN substrates

Highly efficient light emitting diodes (LEDs) with peak emission wavelengths of normally 450 nm were grown fabricated and tested. The performed by metal organic chemical vapour deposition on. The LEDs were grown on c-plane (0001) bulk GaN substrates and fabricated into broad area devices with active area 0.01 cm. Considerations were made to improve extraction efficiency including transparent contacts suspended mirror-less packaging and encapsulation in a truncated pyramid optic. These factors resulted in LEDs with high peak external quantum efficiency and reduced efficiency droop. The output power and external quantum efficiency at 20 mA were 38.5 mW and LEDs were fabricated by application of a yellow phosphor to the blue LEDs. The white LED luminous flux and efficacy at 20 mA was 9.6 lm and 12.8 lm/W. The chromaticity coordinates and correlated colour temperature were (0.34 K-0.378 K) and 4998 K. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim