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HL: Fachverband Halbleiterphysik
HL 32: Quantum dots and wires: preparation and characterization I
HL 32.8: Vortrag
Mittwoch, 27. Februar 2008, 16:15–16:30, ER 270
Formation, atomic structure, and electronic properties of GaSb/GaAs quantum rings — •Rainer Timm1, Andrea Lenz1, Lena Ivanova1, Holger Eisele1, Ganesh Balakrishnan2, Diana L. Huffaker2, Ian Farrer3, David A. Ritchie3, and Mario Dähne1 — 1Institut für Festkörperphysik, Technische Universität Berlin, Germany — 2Center for High Technology Materials, University of New Mexico, Albuquerque, USA — 3Cavendish Laboratory, University of Cambridge, UK
The growth of semiconductor quantum dots (QDs) and their transition into quantum rings (QRs) upon overgrowth have attracted large interest during the last years. In the GaSb/GaAs material system, which is very promising for charge storage devices due to its type-II band alignment [1], a spontaneous transition of QDs into QRs during fast overgrowth has been observed.
Using cross-sectional scanning tunneling microscopy and spectroscopy [2], we were able to study the atomic structure, chemical composition, and electronic properties of GaSb/GaAs QRs grown by MBE using various growth conditions. Typical QR baselengths vary between 10 and 20 nm with inner diameters amounting to about 40% of the outer ones, at densities of up to 9 × 1010 cm−2.
A strong Sb segregation upon GaAs overgrowth is observed, which is assumed to be the driving force for ring formation together with the large strain within the nanostructures.
[1] M. Geller et al., Appl. Phys. Lett. 82, 2706 (2003).
[2] R. Timm et al., Appl. Phys. Lett. 85, 5890 (2004).