Light extraction from gallium nitride-based light emitting diodes with a noninvasive two-dimensional photonic crystal

A noninvasive fabrication process involving soft nanoimprint lithography is used to pattern a photonic crystal (PhC) in titania film for enhanced light extraction from a GaN light emitting diode (LED). This technique avoids damaging the LED structure by the etching process, while photoluminescence measurements show extracted modes emitted from the quantum wells which agree well with modeling. A light extraction improvement of 1.8 times is measured using this noninvasive PhC. Contacts are made on the LED structure without PhC. The device works properly and shows good electrical properties. A drop in the external quantum efficiency is observed under high forward bias and is attributed to Auger recombination processes.