Strong Light-Extraction Enhancement In Gainn Light-Emitting Diodes Patterned With Tio2 Micro-Pillars With Tapered Sidewalls

An effective method to enhance the light extraction for GaInN light-emitting diodes (LEDs) is reported. The method employs TiO2 micro-pillars with tapered sidewalls, which are refractive-index-matched to the underlying GaN. The tapered micro-pillars are fabricated by using reflowed photoresist as mask during CHF3-based dry etch, with O-2 added in order to precisely control the taper angle. LEDs patterned with TiO2 micro-pillars with tapered sidewalls show a 100% enhancement in light-output power over planar reference LEDs. The measured results are in good agreement with ray-tracing simulations, showing strong potential of optical surfaces that are controlled in terms of refractive index and lateral structure. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4756797]