Enhancement of light extraction in GaN based LED structures using TiO2 nano-structures

TiO2 nano-patterns were formed on the indium-tin-oxide (ITO) layer of GaN based light emitting diodes (LEDs) without a residual layer using a sol-imprinting process. A polydimethylsiloxane mold replicated from a Si master was used as the imprint stamp for the sol-imprinting process. The light extraction efficiency of LEDs was enhanced by the TiO2 nano-patterns formed on the ITO layer because the TiO2 nano-patterns locally modulated the refractive index of the ITO layer and enhanced the scattering of light at the ITO layer. Consequently, directly fabricated TiO2 nano-patterns on the ITO layer can esoln hance the light extraction efficiency of LEDs without plasma-induced damage.