GaAsSb-capped InAs quantum dots: From enlarged quantum dot height to alloy fluctuations

J.M. Ulloa Herrero, R. Gargallo-Caballero, M. Bozkurt, M. Moral, del, A. Guzman, P.M. Koenraad, A. Hierro

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Abstract

The Sb-induced changes in the optical properties of GaAsSb-capped InAs/GaAs quantum dots (QDs) are shown to be strongly correlated with structural changes. The observed redshift of the photoluminescence emission is shown to follow two different regimes. In the first regime, with Sb concentrations up to ~12%, the emission wavelength shifts up to ~1280 nm with a large enhancement of the luminescence characteristics. A structural analysis at the atomic scale by cross-sectional scanning tunneling microscopy shows that this enhancement arises from a gradual increase in QD height, which improves carrier confinement and reduces the sensitivity of the excitonic band gap to QD size fluctuations within the ensemble. The increased QD height results from the progressive suppression of QD decomposition during the capping process due to the presence of Sb atoms on the growth surface. In the second regime, with Sb concentrations above ~12%, the emission wavelength shifts up to ~1500 nm, but the luminescence characteristics progressively degrade with the Sb content. This degradation at high Sb contents occurs as a result of composition modulation in the capping layer and strain-induced Sb migration to the top of the QDs, together with a transition to a type-II band alignment.
Original languageEnglish
Article number165305
Pages (from-to)165305-1/7
Number of pages7
JournalPhysical Review B
Volume81
Issue number16
DOIs
Publication statusPublished - 2010

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