Mechanism of enhanced light output in InGaN-based microlight emitting diodes

H. W. Choi, C. W. Jeon, M. D. Dawson, P. R. Edwards, R. W. Martin, S. Tripathy

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Micro-light emitting diode (LED) arrays with diameters of 4 to 20 mum have been fabricated and were found to be much more efficient light emitters compared to their broad-area counterparts, with up to five times enhancement in optical power densities. The possible mechanisms responsible for the improvement in performance were investigated. Strain relaxation in the microstructures as measured by Raman spectroscopy was not observed, arguing against theories of an increase in internal quantum efficiency due to a reduction of the piezoelectric field put forward by other groups. Optical microscope images show intense light emission at the periphery of the devices, as a result of light scattering off the etched sidewalls. This increases the extraction efficiency relative to broad area devices and boosts the forward optical output. In addition, spectra of the forward emitted light reveal the presence of resonant cavity modes [whispering gallery (WG) modes in particular] which appear to play a role in enhancing the optical output.
Original languageEnglish
Pages (from-to)5978-5982
Number of pages5
JournalJournal of Applied Physics
Issue number10
Publication statusPublished - 9 May 2003


  • indium compounds
  • gallium compounds
  • light emitting diodes
  • quantum well devices
  • semiconductor quantum wells
  • III-V semiconductors
  • wide band gap semiconductors
  • Raman spectra
  • cathodoluminescence
  • electroluminescence
  • optical microscopy

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