Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 55: Quantum dots: Interaction with environment

HL 55.1: Talk

Wednesday, March 18, 2015, 15:00–15:15, EW 203

Influence of crossed excitons on the carrier dynamics in dot-in-well structures — •Mirco Kolarczik, Nina Owschimikow, Yücel Kaptan, Nicolai Grosse, and Ulrike Woggon — Institut für Optik und Atomare Physik, Technische Universität Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany

Quantum dots (QDs) embedded in a quantum well (QW), the so-called DWELL system, are an important class of active media in opto-electronic devices. In addition to strain relaxation, the well provides an efficient way of injecting carriers into the QDs. We investigate the energy level structure formed by the combination of zero-, two- and three-dimensional confinement in an In(Ga)As-based DWELL system embedded in a GaAs matrix by ultrafast two-color pump-probe spectroscopy. We find that "crossed excitons", a Coulomb-correlated electron-hole pair with one carrier localized in the QD, and the complementary carrier in either the QW or the bulk, are formed in these systems [1]. The crossed excitons play an important role in the response of the system to an optical excitation as well as in the lateral coupling between QDs mediated by the well. They create an additional localized density of states around the QDs, that significantly modifies capture and escape processes between QDs and surrounding QW and bulk material.

[1] N. Owschimikow, M. Kolarczik, Y. Kaptan, N. Grosse, and U. Woggon, Appl. Phys. Lett. 105, 101108 (2014)