X-ray atomic mapping of quantum dots

Arka B. Dey, Milan K. Sanyal, Denis T Keane, Gavin P. Campbell, Bo Hong Liu, Ian Farrer, David A. Ritchie, Michael J. Bedzyk

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


We report a model-independent atomic-mapping technique for quantum dots (QDs) by combining Bragg reflection x-ray standing wave (XSW) and grazing incidence diffraction (GID) measurements. In this study, we choose GaAs capped InGaAs QDs/GaAs(001) as a model system to show the locations and arrangements of indium atoms within the QDs along various [hkl] directions. This technique directly reveals the actual amount of positional anisotropy and ordering fraction of indium atoms within the QDs by probing the (1¯11), (111), (311), (1¯31), (113), and (1¯13) crystallographic planes. We find that indium atoms are outwardly shifted along the [001] direction by small fractions of the lattice constant, 0.04aGaAs and 0.06aGaAs from Ga sites for 50- and 150-Å GaAs capped InGaAs QDs, respectively. We observe that an improved coherency factor of the indium atoms within the QDs by 45-60% along the [001] and [011] directions reduces the photoluminescence linewidth by 22%, thus making the QDs efficient for QD-laser and optoelectronic device applications. We also find that the position and ordering of In atoms along the (113) and (1¯13) planes are most sensitive to the thickness of the GaAs cap layer. Our XSW-based results are supported by numerical calculations using a QD-macroscopic structural model based on our GID study. We thus show that this atomic-mapping technique will be useful for studying various quantum structures and tuning their properties.

Original languageEnglish (US)
Article number056002
JournalPhysical Review Materials
Issue number5
StatePublished - May 2020

ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)


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