Double Photonic Quasi-Crystal Structure Effect on GaN-Based Vertical-Injection Light-Emitting Diodes

GaN-based thin-film vertical-injection light-emitting diodes (VLEDs) with a double 12-fold photonic quasi-crystal (PQC) structure formed using nanoimprint lithography (NIL) and inductively coupled plasma reactive-ion etching (ICP-RIE) are fabricated and presented. At a driving current of 20 mA and with a chip size of $350 \times 350$ μm2, our thin-film LED with a double-12-fold-PQC structure gave a light output power of 40.5 mW, which is an increase of 77% when compared with the output power of a VLED without a PQC structure at a peak wavelength of 460 nm. In addition, the corresponding light radiation patterns show a narrow beam shape due to the strong guided light extraction on the n-GaN surface and the reflected light effect of the PQC structure formed in the vertical direction on the p-GaN surface.