Degradation of structural and optical properties of InGaN/GaN multiple quantum wells with increasing number of wells

S. Pereira, M. R. Correia, E. Pereira, K. P. O'Donnell, E. Alves, N. P. Barradas, A. D. Sequeira, N. Franco, I. M. Watson, C. Liu

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Abstract

We compare the structural and spectral properties of two multi quantum wells (MQWs), grown by metal organic chemical vapour deposition under the same nominal conditions, with a different number of periods. The MQWs, each with 20% InN and containing 8 and 18 wells, respectively, grew on-axis and coherent to GaN, as revealed by X-ray diffraction reciprocal space mapping (RSM) analysis. Comparison of the asymmetrical (105) RSMs indicates an overall structural deterioration and greater well-barrier intermixing for the MQW with the larger number of wells. Moreover, the composition of the MQWs was depth-profiled by grazing incidence Rutherford backscattering spectrometry (RBS). RBS further evidences strong intermixing in the 18-well heterostructure. The deleterious effects of intermixing on the emission spectrum are revealed by low temperature photoluminescence spectroscopy. Despite similar peak emission energies (ΔE < 45 meV) the 8-well structure shows a more symmetric and narrow peak (FWHM ≈ 100 meV) in comparison with that of the 18-well sample (FWHM ≈ 170 meV). Surface analyses by atomic force and scanning electron microscopy show an increased density, size and depth of V-pit defects on the 18-well structure. These results suggest that dislocations and pitting result from a larger elastic strain energy accumulated in the thicker MQW stack and are a fundamental intermixing mechanism for InGaN/GaN MQWs.

Original languageEnglish
Pages (from-to)302-306
Number of pages5
JournalPhysica Status Solidi C - Current Topics in Solid State Physics
Volume0
Issue number1
DOIs
Publication statusPublished - 1 Dec 2002
Event2nd International Workshop on Nitride Semiconductors, IWN 2002 - Aachen, Germany
Duration: 22 Jul 200225 Jul 2002

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Keywords

  • multi quantum wells (MQWs)
  • emission spectroscopy
  • metallorganic chemical vapor deposition
  • mixing
  • nitrides
  • optical properties
  • photoluminescence spectroscopy
  • rutherford backscattering spectroscopy
  • scanning electron microscopy
  • x ray diffraction

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