Scientists from the University of Hong Kong used a nanopatterned mask to etch the surface on an LED. According to the researchers, the mask is composed of air holes between hexagonal-close-packed microspheres and could be a low-cost alternative to e-beam writers.
As the researchers explain, the introduction of a photonic crystal structure on the surface of an LED can improve light extraction by diffracting waveguided modes out of the semiconductor. Choi and his colleagues use a dry etching process to transfer the pattern of air holes onto the LED wafer. The silica particles are subsequently removed from the substrate by sonification to reveal an array of triangular-shaped voids spaced at intervals of 290 nm along the semiconductor surface.