MgO nano-pyramids structure for enhancement of light extraction efficiency in vertical light-emitting diodes

We demonstrate novel method for improving light extraction efficiency for n-side-up vertical InGaN/GaN light-emitting diodes (V-LEDs) using MgO nano-pyramids and ZnO refractive-index modulation layer. The MgO nano-pyramids structure is successfully fabricated on n-GaN/ZnO surface using electron-beam evaporation. The light output power of n-GaN/ZnO/MgO V-LEDs is enhanced by 49% compare to that of n-GaN V-LEDs. The angular-dependent far-field emission shows the significant increase of side emission for the n-GaN/ZnO/MgO V-LEDs due to the increase of critical angle for total internal reflection as well as the roughened surface by MgO pyramids structure. These experimental results indicate the critical role of surface texturing in improving the light extraction efficiency of the V-LEDs for solid-state lighting.