Enhanced light extraction in nitride light-emitting diodes by epitaxially grown photonic-crystal nanopyramid arrays

A photonic crystal has been created on the p-layer of an InGaN light-emitting diode wafer by selective area growth, thus avoiding the etch processes that are detrimental to the active region. Nanopyramid arrays with either hexagonal or Archimedian lattices were grown in apertures defined by nanoimprint lithography. Electroluminescence measurements show that the pyramids improve the on-axis light output by up to 1.9–2.0 times. This technique could be extended to higher aspect ratio nanostructures that will have stronger coupling between the guided modes and the photonic crystal.