Large Enhancement of Extraction Efficiency in Thin-Film Photonic Crystal InGaN Light-Emitting Diode Structures

Abstract
The light extraction efficiency in thin-film InGaN light-emittingdiode (LED) structures having photonic crystal patterns is studiedtheoretically based on three-dimensional finite-differencetime-domain (FDTD) simulations. The thin-film InGaN LED structuresconsist of $p-i-n$ GaN/InGaN hetero-structures placed on ahigh-reflectance mirror. The extraction efficiency of an unpatternedLED structure has been found to be as high as 20 \% at anappropriate quantum-well position for a GaN/InGaN film thickness of1 $mu$m. When square-lattice photonic crystal patterns areintroduced in the optimized thin-film LED structure, a largeincrease in the extraction efficiency is observed as the air-holedepth increases. It is found that the extraction efficiency can beenhanced by more than 4 times, corresponding to an extractionefficiency of greater than 80 \%.
Keywords: GaN LED, Photonic crystal, FDTD

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