Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 70: Quantum Dots and Wires: Theory

HL 70.9: Vortrag

Donnerstag, 17. März 2011, 12:30–12:45, POT 151

Exciton fine structure splitting in self-assembled semiconductor QDs: Intrinsic and extrinsic effects — •Ranber Singh and Gabriel Bester — Max-Planck-Institut f\"{u}r Festk\"{o}rperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany

There are ongoing efforts to understand excitonic fine structure splitting (FSS) in self-assembled strained (InGaAs/GaAs) and unstrained (GaAs/AlGaAs) quantum dots (QDs). We investigate the excitonic FSS in InGaAs/GaAs and GaAs/AlGaAs QDs of different shapes and sizes using the atomistic pseudopotential approach. We consider the effects of the growth direction, alloy ordering, charged point defects and uniaxial strain. We find that the growth direction, alloy ordering and uniaxial strain affect the FSS quite significantly. However, charged point defects have a rather small effect on the FSS. We obtain a large FSS in small QDs, when the single particle wavefunctions of electrons and/or holes spread into the interface regions between the QD and the barrier. In such a case a small elongation along [110] or [1$\bar{1}$0] in the circular QD base increases the FSS quite significantly. However, if the QD is large enough (which represents the ``conventional" case) so that $S$ single particle wavefunctions of electrons and holes are well confined in the center region of the QD, the elongation of the QD has a marginal effect on the FSS.