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: We report a combined experimental and theoretical analysis of Sb and In segregation during the epitaxial growth of InAs self-assembled quantum dot structures covered with a GaSbAs strain-reducing capping layer. Cross-sectional scanning tunneling microscopy shows strong Sb and In segregation which extends through the GaAsSb and into the GaAs matrix. We compare various existing models used to describe the exchange of group III and V atoms in semiconductors and conclude that commonly used methods that only consider segregation between two adjacent monolayers are insufficient to describe the experimental observations. We show that a three-layer model originally proposed for the SiGe system ͓D. J. Godbey and M. G. Ancona, J. Vac. Sci. Technol. A 15, 976 ͑1997͔͒ is instead capable of correctly describing the extended diffusion of both In and Sb atoms. Using atomistic modeling, we present strain maps of the quantum dot structures that show the propagation of the strain into the GaAs region is strongly affected by the shape and composition of the strain-reduction layer.
This work explores the strain dependence of the piezoelectric effect in GaAs and InAs zinc blende crystals. We write the polarization in terms of the internal anion-cation displacement and the ionic and dipole charges. We then use ab initio density functional theory to evaluate the dependence of all quantities on the strain tensor. We investigate which aspects of the elastic and dielectric response of zinc blende crystals are sources of non-linearities in the piezoelectric effect. We observe that the main source of non-linearities is the response to elastic deformation and, in particular, the internal sublattice displacement of the interpenetrating cation and anion sublattices. We show that the internal sublattice displacement dependence on the diagonal stress components is neither symmetric nor antisymmetric in the strain. Therefore, non-linear coefficients of order higher than quadratic are needed to correctly describe non-linear effects. Using a fitting procedure of the ab initio data, we also determine all non-linear piezoelectric coefficients up to the third power in the diagonal components of the strain tensor. We can report that non-linear effects up to third order can be significant in precisely determining the magnitude of the piezoelectric polarization if compressive or tensile strains larger than 10% are present. We notice however that, in nanostructures such as quantum dots, the optical properties are less sensitive to the third order non-linear piezoelectric effect and that third order coefficients can therefore be neglected. V
In this work we show that tetragonal strain can be used to create a sign reversal of the piezoelectric field in InAs/GaAs semiconductor heterostructures. The strain dependence of the internal displacement of the cation-anion pairs and of the bond polarity are taken into account, beyond the linear model, within an ab initio scheme. The reported tunability of the piezoelectric field is a concept that can be exploited in optoelectronic devices.
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