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 1478-6435Full text not available in this repository. (Request a copy from the Strathclyde author)
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.
|Keywords:||luminescence, excitation, emissions, absorption, Optics. Light|
|Subjects:||Science > Physics > Optics. Light|
|Department:||Faculty of Science > Physics|
|Depositing user:||Pure Administrator|
|Date Deposited:||21 Jun 2011 12:34|
|Last modified:||29 Jul 2016 02:35|