Coherent vertical beaming using Bragg mirrors for high-efficiency GaN light-emitting diodes

Opt Express. 2013 Jun 17;21(12):14566-72. doi: 10.1364/OE.21.014566.

Abstract

We propose a dielectric Bragg mirror that utilizes coherent coupling with multiple quantum wells (MQWs) to significantly enhance light extraction from GaN light-emitting diode (LED). Full vectorial electromagnetic simulation showed that, under constructive interference conditions, the Bragg mirror consisting of two dielectric (SiO(2)/TiO(2)) stacks and a silver layer led to >30% enhancement in light extraction, as compared to a single silver mirror. Such significant enhancement by a pre-designed Bragg/metal mirror was ascribed to the vertically oriented radiation pattern and reduced plasmonic metal loss. In addition, the gap distance between the MQWs and a Bragg mirror at which the constructive interference takes place could be controlled by modulating the thickness of the first low-refractive-index layer. Moreover, a two-dimensional periodic pattern was incorporated into an upper GaN layer with the designed Bragg mirror and it was shown that a lattice constant of ~800 nm was optimal for light extraction. We believe that tailoring the radiation profile of light emitters by coherent coupling with designed high-reflectivity mirrors will be a promising route to overcome the efficiency limit of current semiconductor LED devices.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Equipment Design
  • Equipment Failure Analysis
  • Gallium / chemistry*
  • Lenses*
  • Lighting / instrumentation*
  • Refractometry / instrumentation*
  • Semiconductors*

Substances

  • gallium nitride
  • Gallium