Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 49: Quantum dots: preparation and characterization
HL 49.3: Vortrag
Freitag, 27. März 2009, 10:45–11:00, BEY 81
Strain and critical thickness of the 2D→3D transition during GaSb/GaAs quantum dot growth — •Holger Eisele1,2, Rainer Timm1, Andrea Lenz1, Lena Ivanova1, and Mario Dähne1 — 1Institut für Festkörperphysik, Technische Universität Berlin, Hardenberstr. 36, D-10623 Berlin — 2The University of Texas at Austin, Austin, TX 78712, USA
While for InAs/GaAs the critical thickness of 2D→3D transition is independent of the growth conditions within a small range of 1.5 – 1.8 monolayer (ML), for the GaSb/GaAs system extremely different values are reported up to now, ranging from about 0.5 ML to 4.0 ML. Therefore, we investigated differently grown GaSb/GaAs samples using cross-sectional scanning tunneling microscopy to study the amount of GaSb material in the wetting layer and the quantum dots. For these samples we found a critical thickness in the range of 1.0 ML to 1.5 ML of accumulated GaSb on the GaAs (001) surface. To support this experimental finding we calculated the strain energies of 1 ML InAs and GaSb on GaAs. Even if the lattice mismatch increases only from 7.2% (for InAs/GaAs) to 7.8% (for GaSb/GaAs), the strain energy is about 34% higher in the latter system due to the differences of the elastic moduli. Assuming similar surface energies for both systems, the critical thickness for the 2D→3D transition gets theoretically reduced by the same factor from about 1.65±0.15 ML for InAs to 1.2±0.1 ML for GaSb on GaAs.