Regensburg 2002 – wissenschaftliches Programm

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O: Oberflächenphysik

O 38: Epitaxie und Wachstum (III)

O 38.7: Vortrag

Freitag, 15. März 2002, 12:45–13:00, H43

Surface stress and phase diagram of the wetting layer inInAs/GaAs(001) heteroepitaxy — •Evgeni Penev, Peter Kratzer, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4–6, 14195Berlin-Dahlem

Formation of a pseudomorphic wetting layer (WL) is the first stage of the Stranski-Krastanov growth of self-assembled quantum dots in the InAs/GaAs(001) material system. As the WL plays an active role in the mechanism of self-assembly it is of ultimate importance to achieve detailed understanding of its energetics.

We have carried out first-principles density-functional theory calculations to address the thermodynamic stability of the (2× 3) and (2× 4) reconstructions of the WL surface as a function of the arsenic chemical potential, µ_As, the amount of InAs deposited, θ, and elastic strain ε. Our atomistic results provide evidence for at least three possible phases in the WL phase diagram depending on µ_As and θ. Under very As-rich growth conditions and low θ the (2× 3) phase is favorable. With both θ and As deficiency increasing, the latter retracts and the β 2(2× 4) and α 2(2× 4) phases become dominant. Comparison with the experimentally relevant clean GaAs(001) and InAs(001) surfaces is made as well. While these clean surfaces are under tensile surface stress, we find that compressive stress dominates for the WL surfaces.