Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 43: Poster Session: Quantum Dots and Wires - Preparation and Characterization / Devices (incl. Laser) / Ultrafast Phenomena
HL 43.13: Poster
Dienstag, 27. März 2012, 09:30–12:30, Poster D
TEM-Investigation of strain fields in In(Ga)As quantum dots — •Moritz Hartwig1, Tore Niermann1, André Strittmatter2, Tim David Germann2, Gernot Stracke2, Jan-Hindrik Schulze2, Udo W. Pohl2, and Michael Lehmann1 — 1Institut für Optik und Atomare Physik, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany — 2Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
In Stranski-Krastanov growth-mode the strain of the wetting layer is relaxed by growth of 3D islands. This is exploited in the self-organized growth of In(Ga)As quantum dots (QD) on GaAs substrate. These QDs are buried under a further GaAs layer. The remaining strain fields have an effect on the optoelectronic properties of these nanostructures. TEM dark-field images in the light of strong reflections (like {400} in GaAs) are extremely sensitive to strain fields. In order to investigate only the strain fields of single QDs, dark field images of the chemically sensitive {200}-reflection are utilized under large specimen tilt angle preventing imaging of QDs, which are not isolated. The strain components in in-plane and in growth direction are investigated individually. A change in the symmetry of the strain fields in growth direction is observed in specimen with an additional strain-reducing layer. Furthermore, a slight asymmetry of the in-plane component is found, possibly caused by a distorted shape of the QDs.
This work is supported by the DFG Collaborative Research Centre 787 "Semiconductor Nanophotonics".