Localization of excitation in InGaN epilayers

Kachkanov, V. and O'Donnell, K. P. and Pereira, S. and Martin, R. W. (2007) Localization of excitation in InGaN epilayers. Philosophical Magazine, 87 (13). pp. 1999-2017. ISSN 1478-6435 (https://doi.org/10.1080/14786430701342164)

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Abstract

Energy scalability of the excitation-emission spectra of InGaN epilayers, quantum wells and light-emitting diodes provided indirect evidence for a fundamental common cause of the remarkable optical properties of this commercially important semiconductor alloy. Phase segregation on the nanoscale ( accidental quantum dot formation) has generally been accepted as the mechanism of the spectral energy scaling ( K. P. O'Donnell, R. W. Martin and P. G. Middleton, Phys. Rev. Lett. 82 237 ( 1999)). Recently, however, the downsizing of the InN bandgap, from 2 to about 1 eV, has prompted a re-examination of the observations. Here, we present new structural evidence of InGaN nanostructure, obtained from a comparative analysis of Ga and In K-edge EXAFS ( extended X-ray absorption fine structure) of a wide range of InxGa1-xN epilayer samples. The mean In-Ga and Ga-In next-nearest-neighbour ( NNN) separations are found to be unequal in length for InN-poor ( 0.1 < x < 0.4) samples. The degree of inequality increases with decreasing InN fraction, x, and therefore correlates with luminescence efficiency in this range of alloy composition. We propose that the breakdown of In/Ga randomicity in InGaN alloys is associated with efficient excitation-emission in blue-green light-emitting devices. Although non-randomicity may lead to a weak quasi-localization of excitation, through the suppression of energy back-transfer, the issue of strong exciton localization in InGaN is not directly addressed by these results.

  • Item type:Article
    ID code:31044
    Dates:
    Date
    Event
    2007
    Published
    17 May 2007
    Published Online
    Subjects:Science > Physics > Optics. Light
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:21 Jun 2011 12:34
    Last modified:08 Apr 2024 19:04
    URI:https://strathprints.strath.ac.uk/id/eprint/31044
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