Performance enhancement of GaN-based light-emitting diodes by surface plasmon coupling and scattering grating

Using the analysis of the evanescent surface plasmon polariton (SPP) mode at the GaN/Ag interface as basis, we propose a light-emitting diode (LED) structure with a plasmonic Ag nanostructure and sapphire grating to enhance external quantum efficiency. The 2D finite-difference time-domain method is used to study the spectral properties of the hybrid structure and the effects of structural parameters on light emission enhancement. The plasmonic Ag nanostructure couples recombination energy to the SPP modes at the GaN/Ag interface, whereas the sapphire grating scatters photons out of the LED chips with high extraction efficiency. Under optimal parameters, external quantum efficiency enhancement increases to approximately eighteen times the original value at a relatively long wavelength.