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Title: The impact of trench defects in InGaN/GaN light emitting diodes and implications for the “green gap” problem

The impact of trench defects in blue InGaN/GaN light emitting diodes (LEDs) has been investigated. Two mechanisms responsible for the structural degradation of the multiple quantum well (MQW) active region were identified. It was found that during the growth of the p-type GaN capping layer, loss of part of the active region enclosed within a trench defect occurred, affecting the top-most QWs in the MQW stack. Indium platelets and voids were also found to form preferentially at the bottom of the MQW stack. The presence of high densities of trench defects in the LEDs was found to relate to a significant reduction in photoluminescence and electroluminescence emission efficiency, for a range of excitation power densities and drive currents. This reduction in emission efficiency was attributed to an increase in the density of non-radiative recombination centres within the MQW stack, believed to be associated with the stacking mismatch boundaries which form part of the sub-surface structure of the trench defects. Investigation of the surface of green-emitting QW structures found a two decade increase in the density of trench defects, compared to its blue-emitting counterpart, suggesting that the efficiency of green-emitting LEDs may be strongly affected by the presence of these defects.more » Our results are therefore consistent with a model that the “green gap” problem might relate to localized strain relaxation occurring through defects.« less
Authors:
; ; ; ; ; ;  [1] ; ;  [2] ; ;  [3] ; ;  [4] ; ;  [5]
  1. Department of Materials Science and Metallurgy, University of Cambridge, 22 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)
  2. Photon Science Institute, School of Physics and Astronomy, Alan Turing Building, University of Manchester, Manchester M13 9PL (United Kingdom)
  3. Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich GmbH, Leo-Brandt- Straße, D-52425 Jülich (Germany)
  4. Monash Centre for Electron Microscopy, Monash University, Clayton Campus, VIC 3800 (Australia)
  5. Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY (United Kingdom)
Publication Date:
OSTI Identifier:
22303516
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CRYSTAL DEFECTS; CRYSTAL GROWTH; CURRENTS; DENSITY; EFFICIENCY; ELECTROLUMINESCENCE; EXCITATION; GALLIUM NITRIDES; INDIUM COMPOUNDS; LAYERS; LIGHT EMITTING DIODES; PHOTOLUMINESCENCE; POWER DENSITY; QUANTUM WELLS; RECOMBINATION; RELAXATION; STRAINS; SURFACES