Light extraction enhancement of GaN-based light emitting diodes using MgF2/Al omnidirectional reflectors

We report on the enhancement of the light extraction of GaN-based light emitting diodes (LEDs) by using MgF2/Al omnidirectional reflectors (ODRs). The ODRs consisting of a quarter-wavelength-thick MgF2 having a refractive index of 1.39 and Al metal produce a high-angle-integrated reflectivity of 96.6%. To optimize the electrical injection and light reflection, the MgF2/Al ODRs are combined with Pd/Ag metallic reflectors using mesh configuration. Compared to reference LEDs, LEDs fabricated with the MgF2/Al ODRs show an enhanced output power by 23% and a slight increase in the forward voltage by 0.18 V, leading to the improvement in power efficiency by 17%.