Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement: The Sb-induced changes in the optical properties of GaAsSb-capped InAs/GaAs quantum dots ͑QDs͒ 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 ϳ12%, the emission wavelength shifts up to ϳ1280 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 ϳ12%, the emission wavelength shifts up to ϳ1500 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.

Pronounced Purcell enhancement of spontaneous emission in CdTe/ZnTe quantum dots embedded in micropillar cavities Appl. Phys. Lett. 101, 132105 (2012) Fabrication and photoluminescence of SiC quantum dots stemming from 3C, 6H, and 4H polytypes of bulk SiC Appl. Phys. Lett. 101, 131906 (2012) Radiative transitions in stacked type-II ZnMgTe quantum dots embedded in ZnSe J. Appl. Phys. 112, 063521 (2012) Anomalous temperature dependence of photoluminescence in self-assembled InGaN quantum dots Appl. Phys. Lett. 101, 131101 (2012) Optical properties of multi-stacked InGaAs/GaNAs quantum dot solar cell fabricated on GaAs (311)B substrate J. Appl. Phys. 112, 064314 (2012) Additional information on J. Appl. Phys. The origin of the modified optical properties of InAs/GaAs quantum dots (QD) capped with a thin GaAs 1Àx Sb x layer is analyzed in terms of the band structure. To do so, the size, shape, and composition of the QDs and capping layer are determined through cross-sectional scanning tunnelling microscopy and used as input parameters in an 8 Â 8 kÁp model. As the Sb content is increased, there are two competing effects determining carrier confinement and the oscillator strength: the increased QD height and reduced strain on one side and the reduced QD-capping layer valence band offset on the other. Nevertheless, the observed evolution of the photoluminescence (PL) intensity with Sb cannot be explained in terms of the oscillator strength between ground states, which decreases dramatically for Sb > 16%, where the band alignment becomes type II with the hole wavefunction localized outside the QD in the capping layer. Contrary to this behaviour, the PL intensity in the type II QDs is similar (at 15 K) or even larger (at room temperature) than in the type I Sb-free reference QDs. This indicates that the PL efficiency is dominated by carrier dynamics, which is altered by the presence of the GaAsSb capping layer. In particular, the presence of Sb leads to an enhanced PL thermal stability. From the comparison between the activation energies for thermal quenching of the PL and the modelled band structure, the main carrier escape mechanisms are suggested. In standard GaAs-capped QDs, escape of both electrons and holes to the GaAs barrier is the main PL quenching mechanism. For small-moderate Sb (<16%) for which the type I band alignment is kept, electrons escape to the GaAs barrier and holes escape to the GaAsSb capping layer, where redistribution and retraping processes can take place. For Sb contents above 16% (type-II region), holes remain in the GaAsSb layer and the escape of electrons from the QD to the GaAs barrier is most likely the dominant PL quenching mechanism. This means that electrons and holes behave dynamically as uncorrelated pairs in both the type-I and type-II structures. V C 2012 American Institute of Physics.[http://dx

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