Journal
SUPERLATTICES AND MICROSTRUCTURES
Volume 36, Issue 4-6, Pages 791-798Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.spmi.2004.09.035
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We present theoretical calculations of the variation of exciton energies in truncated conical InGaN quantum dots (QDs) in a GaN matrix with dot size and indium composition. We compute the builtin strain-induced and spontaneous piezoelectric fields using a surface integral method that we have recently derived, and confirm that the built-in fields can be of the order of a few MV/cm, resulting in a spatial separation of the electrons and holes. The ground state wavefunctions of the exciton (X-0), biexciton (2X(0)) and the two charged excitons (X- and X+) are then calculated in the Hartree approximation, using a self-consistent finite difference method. We find that the electron-hole recombination energy is always blue-shifted for the charged excitons X- and X+, with a further blue-shift for the biexciton, and this blue-shift increases with increasing indium content. We describe the trends in interband transition energy and the scale of the blue-shift with dot size, shape and composition. We conclude that spectroscopic studies of the exciton, charged excitons and biexciton should provide a useful probe of the structural and piezoelectric properties of GaN-based QDs. (C) 2004 Elsevier Ltd. All rights reserved.
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