InGaN light-emitting diodes with indium-tin-oxide sub-micron lenses patterned by nanosphere lithography

Close-packed micro-lenses with dimensions of the order of wavelength have been integrated onto the indium-tin-oxide (ITO) layer of GaN light-emitting diodes employing nanosphere lithography. The ITO lens arrays are transferred from a self-assembled silica nanosphere array by dry etching, leaving the semiconductor layer damage-free. An enhancement of up to 63.5% on optical output power from the lensed light-emitting diode (LED) has been observed. Lens-patterned LEDs are also found to exhibit reduced emission divergence. Three-dimensional finite-difference time-domain simulations performed for light extraction and emission characteristics are found to be consistent with the observed results.