Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 56: Quantum dots and wires: Preparation and characterization III

HL 56.1: Vortrag

Freitag, 31. März 2006, 11:00–11:15, POT 51

Understanding Growth of InAs/GaAs Quantum Dot Nanostructures in Atomic Detail — •Thomas Hammerschmidt, Peter Kratzer, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

The experimental and theoretical investigations of the last decade lead to a good understanding of many aspects of quantum dot (QD) growth. One of the remaining challenges is the discrimination of kinetic and thermodynamic effects. We focus on the question which aspects of QD growth can be understood within thermodynamic reasoning. In particular, we identify the driving force for the experimental findings of a sequence of shapes with increasing QD size, and of growth correlations in QD stacks.
Recently, we developed an interatomic potential of the Abell-Tersoff type that accounts for the energetic balance of strain relief and QD side-facet formation during QD growth, and enables us to systematically study the energetics and atomic structure of realistic QD nanostructures. Based on recent atomically resolved STM images we set up InAs QD nanostructures in atomic detail, apply our potential to relax them, and compare the resulting total energies. We find that the experimentally observed critical coverage for the 2D to 3D growth transition and the shape sequence of ‘hut’-like QD’s dominated by {317} facets and ‘dome’-like QD’s dominated by {101} can be attributed to three distinct stability regimes. Furthermore, we can explain the vertical growth correlations in QD stacks by quantitatively calculating the size of the critical nucleus in different lateral positions.