Optical design of GaN resonant cavity LEDs emitting at 510nm for use in plastic optical fibre applications

ABSTRACT The optimized optical design of GaN resonant cavity light emitting didoes (RCLEDs) emitting at 510nm for maximum extraction efficiency into numerical apertures (NAs) of 1.0 (total emission) and 0.5 (typical plastic optical fiber NA) are determined using a modeling tool based on the simulation of dipole emission in a multilayer structure. The optimization is performed for a metal-AlGaN/GaN DBR cavity structure as functions of the aluminum fraction in the DBR and the internal quantum well (QW) emission linewidth. The optimum number of DBR pairs is shown to depend on both these parameters together and the emission NA, and varies between 3 and 14. The maximum calculated extraction efficiency for a metal-AlN/GaN cavity structure, assuming a QW emission linewidth of 30nm, is 0.18 (0.055) into an emission NA of 1.0 (0.5). The position of the QW relative to the metal mirror is shown to be the crucial device parameter in determining the extraction efficiency of the RCLED. Simulations show farfield measurements should provide information on the position of the QWs in the cavity. The reduction in the spectral emission linewidth of the RCLED due to the cavity is also modeled.