Large enhancement of extraction efficiency in thin-film photonic crystal InGaN light-emitting diode structures

초록

Light extraction efficiency in thin-film InGaN light-emitting diode (LED) structures having photonic crystal patterns is studied theoretically based on the three-dimensional finite-difference time-domain (FDTD) simulation. The thin-film InGaN LED structures consist of p-i-n GaN/InGaN heterostructures placed on a high-reflectance mirror. When the GaN/InGaN film thickness is 1 m, the extraction efficiency of an unpatterned LED structure has been found to be as high as 20% at appropriate quantum-well position. When square lattice photonic crystal patterns have been introduced in the optimized thin-film LED structure, large enhancement extraction efficiency is observed as air-hole depth increases. It is found that the extraction efficiency can be enhanced by more than 4 times, corresponding to the extraction efficiency of >80%. In particular, even at relatively shallow air-hole depth of ~200 nm, the extraction efficiency is obtained to be >60%, indicating promising practical application of photonic crystal patterning to thin-flim InGaN LED structures.