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

Abstract

AbstractHighly efficient light emitting diodes (LEDs) with peak emission wavelengths of nominally 450 nm were grown, fabricated and tested. The growth was performed by metal organic chemical vapour deposition. The LEDs were grown on c ‐plane (0001) bulk GaN substrates and fabricated into broad‐area devices with active area 0.01 cm2. 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 68.9%. At 100 mA, they were 170 mW and 60.9%. White 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 128 lm/W. The chromaticity coordinates and correlated colour temperature were (0.348 K, 0.378 K) and 4998 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)