Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 64: Quantum Dots and Wires: Optical Properties VI
HL 64.5: Vortrag
Freitag, 26. März 2010, 11:15–11:30, H14
Cascaded exciton emission of an individual strain-induced quantum dot — •Florian J. R. Schülein1, A. Laucht2, M. Mattila3, J. Riikonen3, M. Sopanen3, H. Lipsanen3, J. J. Finley2, A. Wixforth1, and H. J. Krenner1 — 1Lehrstuhl für Experimentalphysik I, Universität Augsburg, Universitätsstr. 1, 86159 Augsburg, Germany — 2Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching, Germany — 3Department of Micro and Nanosciences, Micronova, Helsinki University of Technology, P.O. Box 3500, FIN-02015 TKK, Finland
Individual strain-induced quantum dots defined by InP stressors in an InGaAs/GaAs quantum well are isolated by electron beam lithography and selective wet chemical etching of stressors from an ensemble. Single exciton (1X) and biexciton (2X) are identified by power-dependent photoluminescence spectroscopy and do not show any finestructure splitting. Time-resolved PL spectroscopy performed at different excitation powers shows clear indications of cascaded emission of unpolarized photons in the transition from the triexciton back to the crystal ground state: The onset of the 1X emission is delayed with respect to the laser excitation pulse and the decay of the higher exciton levels at higher excitation powers. The decay time of one transition agrees with the rising time of the next lower transition of the cascade. This observation is characteristic for a the cascaded emission of single photons. Furthermore, we can reproduce this behavior using a rate equation model for a three-step cascade. Our system is a potential candidate for a source of polarization entangled photon pairs.