Light Extraction in GaInN Light-Emitting Diodes using Diffuse Omnidirectional Reflectors

A theoretical and experimental analysis of light extraction in GaInN light-emitting diodes (LEDs) employing diffuse omnidirectional reflectors is presented. The diffuse omnidirectional reflector consists of GaN, a current spreading layer, a layer roughened by Ar ion etching, and a Ag layer. Randomly distributed polystyrene spheres are used as an etch mask. The diffusely reflected power is enhanced by two orders of magnitude for a roughened reflector surface compared with a planar surface. The GaInN LEDs with diffuse omnidirectional reflectors show a higher light output and a lower angular dependence of emission than LEDs with specular reflectors. The enhancement is attributed to reduced trapping of light within the high-index GaN semiconductor.