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HL: Fachverband Halbleiterphysik

HL 37: Quantum Dots and Wires: Optical Properties III

HL 37.1: Vortrag

Mittwoch, 24. März 2010, 09:30–09:45, H15

Vanishing Excitonic Fine Structure Splitting in In(Ga)As/GaAs Quantum Dots Grown on (111) GaAs Substrates — •Murat Öztürk¹, Erik Stock¹, Jan A. Töfflinger¹, Till Warming¹, Irina Ostapenko¹, Sven Rodt¹, Andrei Schliwa¹, Aleksandr I. Toropov², Sergej A. Moschenko², Dimitry V. Dmitriev², Vladimir A. Haisler², and Dieter Bimberg¹ — ¹Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany — ²Institute of Semiconductor Physics, Lavrenteva av 13, Novosibirsk 630090, Russia

Non-classical correlated photons are of largest importance for quantum key distribution. A source of entangled photon pairs can be based on the biexciton (XX)→exciton (X)→0 recombination cascade, if the fine structure splitting (FSS) of the exciton bright states is below the homogeneous linewidth. Symmetrically shaped In(Ga)As/GaAs quantum dots (QDs) grown on GaAs (111) substrates are expected to exhibit zero FSS due to the C_3V symmetry of the confinement potential. Here, we present In(Ga)As/GaAs QDs grown on GaAs (111) substrates with a low spatial density (<10⁹ cm⁻²). Single photon emission is proved with a g²(0)≤0.3. Micro-photoluminescence from a number of single QDs reveals similar luminescence line patterns for several QDs and therefore allows the assignment to transitions of specific excitonic complexes. Polarization dependent measurements reveal the FSS down to less than 10 µeV, limited by the spectral resolution of our setup. The nonzero splitting is understood in terms of shape and strain as symmetry of the QDs. This work is partly funded by the SFB 787.