Surface-plasmon-enhanced GaN-LED based on the quasi-symmetrical planar waveguide structure

The surface-plasmon-enhanced GaN-LED based on the quasi-symmetrical planar waveguide structure is proposed. This structure contains a dielectric/metal/dielectric multilayer coated on the GaN-layer. The uppermost layer with the optimized thickness and polished sapphire substrate make sure that the light extraction efficiencies in top- and bottom-emission are high enough, respectively. The effective indexes of surface-plasmon-waveguides and Purcell factor in this structure are investigated. Compared with the reference structure covered by a single metal-film, the light extraction efficiency and surface-plasmon extraction efficiency in this structure are effectively improved. The photoluminescence experiments reveal that its peak intensity of top (bottom) emission is about 2.5 (1.8) times greater than that from the reference structure.