Photonic crystal light-emitting diodes fabricated by microsphere lithography

Abstract

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.

Bottom-Up Assembly and Applications of Photonic Materials

“…They reported a twofold enhancement of the light emission from the fabricated LEDs with the photonic crystal. This increase was attributed to the light dispersion of the photonic crystal, light diffraction through the photonic crystal grating and the scattering of light due to the roughened surface [142]. Li et al described the use of nanosphere lithography to pattern a close-packed array of nanopillars that is embedded within an InGaN/GaN LED structure.…”

Nanosphere Lithography for Nitride Semiconductors

“…Amongst different kinds of materials, silica-made nanosphere is especially suitable for etching process, since the good etch resistivity of silica renders the patterned monolayer of nanosphere a naturally good hard mask. One of the most popular 'secondary' nanostructures derived from nanosphere lithography is the nanopillar array (Cheung et al, 2006;Li et al, 2007;Ng et al, 2008). After coating a monolayer of nanospheres onto a sample, the circular hexagonal close-packed pattern can be easily transferred to the sample by a subsequent dry etch.…”

“…For instance, one major issue with GaN devices is the limited efficiency of light extraction. To tackle this problem, texturing of the surface in a regular manner has been adopted at the micrometer and nanometer scales (David et al, 2008;Han et al, 2006;Ng et al, 2008;Noda & Fujita, 2009). Therefore in this chapter, we will demonstrate the potential applications of nanosphere lithography including photonic crystals and surface plasmons.…”

Enhancement of light extraction efficiency in InGaN/GaN vertical blue light emitting diodes by surface patterning: Design and simulation

“…Various methods have been projected to improve the light extraction efficiency of LEDs such as micro-patterning [5,6], nanopatterning [7], micro-cavity LED design [8], surface roughing [9,10], coating of porous films [11], photonic crystals [12], and many more. Patterning the surface is one of the most efficient ways to improve the light output power because of multiple chances of light escape from the surface.…”