Institute of Fundamental Technological Research
Polish Academy of Sciences


W. Neumann

Humboldt-Universität zu Berlin (DE)

Recent publications
1.  Dimitrakopulos G.P., Kalesaki E., Kioseoglou J., Kehagias T., Lotsari A., Lahourcade L., Monroy E., Häusler I., Kirmse H., Neumann W., Jurczak G., Young T.D., Dłużewski P., Komninou Ph., Karakostas T., Morphology and strain of self-assembled semi-polar GaN quantum dots in (1112) AlN, JOURNAL OF APPLIED PHYSICS, ISSN: 0021-8979, DOI: 10.1063/1.3506686, Vol.108, pp.104304-1-9, 2010

GaN quantum dots (QDs) grown in semipolar (11-22) AlN by plasma-assisted molecular-beam epitaxy were studied by transmission electron microscopy (TEM) and scanning transmission electron microscopy techniques. The embedded (11-2)-grown QDs exhibited pyramidal or truncated-pyramidal morphology consistent with the symmetry of the nucleating plane, and were delimited by nonpolar and semipolar nanofacets. It was also found that, in addition to the (11-22) surface, QDs nucleated at depressions comprising {10-11} facets. This was justified by ab initio density functional theory calculations showing that such GaN/AlN facets are of lower energy compared to (11-22). Based on quantitative high-resolution TEM strain measurements, the three-dimensional QD strain state was analyzed using finite-element simulations. The internal electrostatic field was then estimated, showing small potential drop along the growth direction, and limited localization at most QD interfaces.

Quantum dots, Transmission electron microscopy, III-V semiconductors, High resolution transmission electron microscopy, Epitaxy

Dimitrakopulos G.P. - Aristotle University of Thessaloniki (GR)
Kalesaki E. - Aristotle University of Thessaloniki (GR)
Kioseoglou J. - Aristotle University of Thessaloniki (GR)
Kehagias T. - Aristotle University of Thessaloniki (GR)
Lotsari A. - Aristotle University of Thessaloniki (GR)
Lahourcade L. - CNRS (FR)
Monroy E. - CNRS (FR)
Häusler I. - Humboldt-Universität zu Berlin (DE)
Kirmse H. - Humboldt-Universität zu Berlin (DE)
Neumann W. - Humboldt-Universität zu Berlin (DE)
Jurczak G. - IPPT PAN
Young T.D. - IPPT PAN
Dłużewski P. - IPPT PAN
Komninou Ph. - Aristotle University of Thessaloniki (GR)
Karakostas T. - Aristotle University of Thessaloniki (GR)

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