Kinetic Monte Carlo simulations and cross-sectional scanning tunneling microscopy as tools to investigate the heteroepitaxial capping of self-assembled quantum dots

J.G. Keizer, P.M. Koenraad, P. Smereka, J.M. Ulloa, A. Guzman, A. Hierro

Research output: Contribution to journalArticleAcademicpeer-review

13 Citations (Scopus)
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Abstract

In the last decade, an ever increasing understanding of heteroepitaxial growth has paved the way for the fabrication of a multitude of self-assembled nanostructures. Nowadays, nanostructures such as quantum rings,1 quantum wires,2 quantum dashes,3 quantum rods,4 and quantum dots (QDs)5 can be grown with relative ease. Among these, QDs have, due to their 0-dimensional nature, received the most attention and are applied or suggested in QD lasers,6,7 single-photon emitters,8 single-electron transistors,9 and spin manipulation.10,11 As the electronic properties of QDs strongly depend on their size, shape, and chemical composition, a detailed knowledge of the growth process and the resulting QD morphology is needed in order to understand the involved physics and tune their properties. A large variety of imaging techniques are available to study the morphology, the dimensions, and the chemical composition of self-assembled QDs, e.g., scanning/ transmission electron microscopy,12 x-ray diffraction,13 atomic force microscopy,14,15 atom probe tomography,16,17 and cross-sectional scanning tunneling microscopy (X-STM).18 However, all the existing imaging techniques can only provide snapshots of the QDs after the growth is completed. At the moment, only a few techniques, e.g., reflection highenergy electron diffraction (RHEED),19 in situ accumulated stress measurements,20 and spectroscopic ellipsometry,21 can give real-time information during the growth and thereby help monitoring the growth. But, if such techniques provide valuable information about the growth surface, the averaging nature of the techniques makes them of little use when studying atomic-scale processes such as intermixing or segregation. In this respect, kinetic Monte Carlo (KMC) simulations of the heteroepitaxial growth process can be of great value and provide further insight on the growth dynamics. However, such KMC simulations are computationally challenging22,23 and still need validation by an experimental imaging technique. In this paper, we presentKMCresults using recent developments in computational methods.24 The KMC simulations are compared to atomically precise QD morphologies extracted from experimental X-STM images. These two techniques are used in conjunction to study strain engineering of the capping layer25,26 as a method to control the height of quantum dots, an important parameter determining the QDs emission wavelength. We show that KMC simulations not only are in good agreement with the X-STM study, but also provide valuable details of the growth process that hitherto could not be obtained.
Original languageEnglish
Article number155326
Pages (from-to)155326-1/8
Number of pages8
JournalPhysical Review B
Volume85
Issue number15
DOIs
Publication statusPublished - 2012

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