Effect of nano-patterning of p-GaN cladding layer on photon extraction efficiency

Various sized nano-patterns, ranging from 0.8 μm × 0.4 μm to 2.0 μm × 1.0 μm were formed on the p-GaN top cladding layer of green LED, in order to increase photon extraction efficiency by suppressing total internal reflection. Fabrication of nano-patterns was done by UV nanoimprint lithography and reactive ion etching of p-GaN using SiCl4 and Ar gases using SiO2 as an etch mask. The effect of various nano-patterns on top p-GaN layer was investigated by photoluminescence. Compared to LED structure without nano-patterns on top cladding layer, the LED structures with sub-micron sized nano-patterns exhibit up to four times stronger emission intensity. This implies that the photon extraction efficiency of LED structures was increased by nano-patterns on top p-GaN layer. However, the luminescence intensity of LED structures with patterns greater than a micron, was less increased.