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Lee, K. B. and Parbrook, P. J. and Wang, T. and Ranalli, F. and Martin, T. and Balmer, R. S. and Wallis, D. J.;
Journal of Applied Physics
Optical investigation of exciton localization in AlxGa1-xN
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The optical properties of AlxGa1-xN epilayers with x ranging from 0.08 to 0.52 have been studied by photoluminescence (PL). The temperature dependent PL of the AlxGa1-xN epilayers shows a classical ``S-shape'' behavior. This behavior is attributed to exciton localization due to compositional fluctuations in the AlxGa1-xN layers. The localization parameter sigma extracted from temperature dependent PL, which gives an estimate of degree of localization, is found to increase with Al composition, up to a value of 52 meV at the highest Al composition studied. Several phonon replicas are observed at the lower energy side of the main excitonic emission peak in these epilayers at low temperature. In all cases, the Huang-Rhys parameter has been estimated. The Huang-Rhys parameter is found to increase with x indicating that the degree of localization again increases with x. In addition, the Huang-Rhys parameter is found to increase with higher order phonon replicas. (c) 2007 American Institute of Physics.
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