Interactions of Diffraction Modes Contributed From Surface Photonic Crystals and Nanoholes in a GaN-Based Light-Emitting Diode

Photonic crystals (PhCs) were typically fabricated on the mesa surface of an LED to improve light extraction, which is regarded as the weak coupling between the laterally propagated light in the epilayers and the surface nanostructure. Here, we report GaN-based LEDs with the PhC structure on the mesa surface and nanohole reflectors surrounding the light-emitting mesa. The output power of the new LED structure is higher than that of the device with only surface PhCs due to the enhanced diffraction of low-order modes propagated in the lateral direction, in addition to the higher order mode light diffraction from the surface PhCs. From the relative angular spectra, the interaction of in-plane optical wave with the nanoholes (which are etched through multiple quantum wells) is much stronger than that with surface PhCs, suggesting an efficient light diffraction to the surface normal by nanoholes.