Simulation and fabrication of highly efficient InGaN-based LEDs with corrugated interface substrate

The external efficiency of normal LEDs is reduced by total internal reflection, which typically causes 50 to 80 percent of the emitted photons to be trapped in guided modes. We have increased the external quantum efficiency by using the corrugated interface substrate (CIS) texturing on the sapphire substrates to scatter light out of the nitride film. In order to maximize the outcoupling efficiency of the corrugation, we stimulated the outcoupling efficiency by varying the diameter, the period and the depth of the corrugations. With the use of the optimized corrugation pattern, the external quantum efficiency of 34% was achieved experimentally, without detriment to the forward and reverse electrical characteristics of LEDs.