Dresden 2006 – scientific programme

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SYSS: Structure Formation and Self-Organization in non-equilibrium Systems

SYSS 3: Structure Formation and Self-Organization in non-equilibrium Systems - Poster

SYSS 3.8: Poster

Thursday, March 30, 2006, 16:00–18:00, P1

Interplay between thermodynamics and kinetics in the capping of InAs/GaAs(001) quantum dots — •Paola Acosta — Max-Planck-Institute for Solid State Research

Three-dimensional islands grown by Stranski-Krastanov heteroepitaxy have been the subject of an intensive study over the last decade. In order to be employed as quantum dots (QDs) these islands must be overgrown with a wider energy band gap material. The capping typically produces strong changes in their morphology and composition, determining the final QD optoelectronic properties. A clear understanding of this process is therefore of fundamental importance. We have thoroughly analyzed the GaAs overgrowth of InAs self-organized islands by means of in-situ STM, as well as, ex-situ AFM. The most evident result is that two well-defined capping regimes can be distinguished. The first is characterized by a rapid partial dissolution of the pristine islands, and is governed by a fast dynamics (diffusion on strained regions, alloying, low energy facets). As a consequence in this regime the morphological transformations are almost independent of the cap deposition rate and the resulting morphologies are close to thermodynamic equilibrium. The second regime is marked by a true overgrowth of the remaining structures, and is essentially controlled by atomic diffusion processes.