Large quantum dots with small oscillator strength

Søren Stobbe, T.W. Schlereth, S. Höfling, A. Forchel, Jørn Märcher Hvam, Peter Lodahl

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

We have measured the oscillator strength and quantum efficiency of excitons confined in large InGaAs quantum dots by recording the spontaneous emission decay rate while systematically varying the distance between the quantum dots and a semiconductor-air interface. The size of the quantum dots is measured by in-plane transmission electron microscopy and we find average in-plane diameters of 40 nm. We have calculated the oscillator strength of excitons of that size assuming a quantum-dot confinement given by a parabolic in-plane potential and a hard-wall vertical potential and predict a very large oscillator strength due to Coulomb effects. This is in stark contrast to the measured oscillator strength, which turns out to be so small that it can be described by excitons in the strong confinement regime. We attribute these findings to exciton localization in local potential minima arising from alloy intermixing inside the quantum dots.
Original languageEnglish
JournalPhysical Review B Condensed Matter
Volume82
Pages (from-to)233302
ISSN0163-1829
DOIs
Publication statusPublished - 2010

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