Laser Liftoff GaN Thin-Film Photonic Crystal GaN-Based Light-Emitting Diodes

We fabricated a thin-film vertical-injection light-emitting diode (LED), which uses a highly efficient coherent external scattering of trapped light by photonic crystal (PhC). The PhC patterns ( ${\rm a}=1200$ nm) were formed on top of the n-GaN surface after laser liftoff of the sapphire substrate. This light extraction structure just above micron scale was prepared by a conventional photolithography ($\lambda_{\rm c} = 405$ nm). The Si-gel- encapsulated thin-film LED with PhC patterns (${\rm a} = 1\ 200$ nm), which had a depth of 500 nm, demonstrated up to 76% improvement in light output power at a forward current of 60 mA, compared with the nonpatterned thin film LED.