Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 46: Quantenpunkte und -dr
ähte: Herstellung und Charakterisierung I

HL 46.1: Vortrag

Montag, 7. März 2005, 16:45–17:00, TU P164

Atomistic investigation of InAs quantum dots at different growth stages — •Thomas Hammerschmidt, Peter Kratzer, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

Recent experiments suggest that InAs quantum dots (QD’s) grown on GaAs (001) undergo a shape transition during growth from ’hut’ to ’dome’-like shapes, similar to Ge QD’s on Si. From a thermodynamic point of view, QD formation is governed by the balance between the energy gain due to strain relief and the energy cost due to formation of QD side facets and edges. In order to account for both contributions, we have developed a carefully parameterized Abell-Tersoff bond-order potential. It reproduces the elastic constants as well as properties of both GaAs and InAs (001) surface reconstructions obtained from density-functional theory calculations with good accuracy and is transferable to the higher-index facets of QD’s. Based on recent STM studies, we set up several detailed atomic structures of InAs QD’s along the shape-transition path from a flat QD dominated by {137} facets to a fully developed QD dominated by {110} facets, some with partially grown facets. After relaxation with our potential we analyzed changes in the total energy and the strain-field. We find that small QD’s favor the ’hut’ shape and that the facets preferably grow from bottom to top, in agreement with experiment.