Photonic crystal light-emitting diodes fabricated by microsphere lithography
– WN Ng, CH Leung, PT Lai, and HW Choi

PhC LED (bottom) driven at 1.5 mA.
Nanotechnology, vol. 19, 25, pp. 255302 (2008)
Instead of using conventional electron lithography, a two-dimensional photonic crystal consisting of a hexagonal array of triangular air-holes was created on the surface of a GaN LED substrate using microsphere lithography. The microspheres self-assemble into a single-layered hexagonal-close-packed array acting as an etch mask. A significant enhancement in photoluminescence intensity was recorded from the PhC LED structure. A twofold increase in electroluminescence was observed from the PhC LED compared to an as-grown LED with identical geometry. Besides geometrical factors due to surface roughening, the dispersive nature of PhCs and diffractive properties of the PhC as a grating contribute to the enhancement of light extraction from the LED.