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 (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_c = 405 nm). The Si-gel-encapsulated thin-film LED with PhC patterns (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.