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DS: Fachverband Dünne Schichten

DS 6: Nanophotonics - Theory of Nanophotonic Devices II

DS 6.3: Talk

Monday, March 23, 2009, 15:00–15:15, GER 38

Control of the Linear Polarization of Excitonic Emission from Group-III-nitride Quantum Dots — •Momme Winkelnkemper, Gerald Hönig, Andrei Schliwa, and Dieter Bimberg — Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany

Control of the polarization of emission from single QDs is of major importance for applications, such as QD-based single-photon emitters for quantum cryptography. The properties of excitonic emission from bulk wurtzite group-III nitrides are governed by the valence band (VB) structure of these materials. A, B, and C excitons can be unambiguously identified analyzing the linear polarization of their emission in different detection geometries. Order and character of the VBs can be altered if the material is strained. Here, we show that a structural anisotropy of InGaN/GaN quantum dots (QDs) leads to a linear polarization of confined A- and B-type excitonic states in orthogonal directions. Moreover, we predict a similar polarization effect for GaN/AlN QDs and show that it is, in fact, evoked by an anisotropy of the strain field within the QDs. Using strain-dependent eight-band k.p theory we calculate the polarization of the optical transitions in either elongated QDs or QDs under externally applied stress. For both cases a pronounced linear polarization is found. By performing a quantitative study we show that the polarization of the ground state transition can be effectively controlled by externally applied uniaxial stresses.