Enhancement of external quantum efficiency in GaN-based light emitting diodes using a suspended geometry

Abstract

Using a transparent and mirror-less chip mounting technique we have increased the total external efficiency by 26%. This increase in the external quantum efficiency for a light-emitting diode (LED) was based on c-plane (0001) bulk GaN employing a suspended geometry. A small size LED (200 x 550 μm 2) affixed to a Ag header is compared to an LED die lifted off the header. The output power for the LED in the suspended geometry was 30.4 mW, a 13% increase over the conventional placement and the EQE increased from 49% to 56% at a forward current of 20 mA under pulsed conditions. The suspended die was then placed into a cone optic and its output power and EQE improved to 34 mW and 62%, respectively. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.