Enhancement of light extraction efficiency for GaN-based light emitting diodes using ZrO₂ high-aspect-ratio pattern as scattering layer

We developed the direct patterning process of the ZrO₂ high-aspect-ratio (HAR) pattern for light-extraction efficiency of GaN-based blue light-emitting diodes (LEDs). ZrO₂ HAR pattern, which has relatively high refractive index and acts as scattering layer, was formed on GaN-based blue LEDs using ultraviolet-nanoimprint lithography (UV-NIL) with mixture of ZrO₂ nanoparticle and monomer. The photons generated from the multi-quantum well layer can escape the ITO (Indium Tin Oxide) layer more easily due to gradual refractive index and optical path that increased via waveguide mode. The ZrO₂ patterned LED with high pattern density showed the high brightness in same input current. The patterned LED with pitch of 1 µm showed the 25.7% higher light output power than a un-patterned LED at a driving current of 20 mA.