Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 44: Poster Session: Quantum Dots and Wires - Transport & Optical Properties
HL 44.11: Poster
Dienstag, 27. März 2012, 09:30–12:30, Poster D
Phonon-assisted relaxation and linewidth enhancement of exciton states in double quantum dots — •Jonas Daniels1, Tilmann Kuhn1, and Pawel Machnikowski2 — 1Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — 2Institute of Physics, Wrocław University of Technology, 50-370 Wrocław, Poland
Here we consider theoretically excitons in a pair of lens-shaped vertically aligned InAs/GaAs QDs in the presence of an external electric field. Single-particle wave functions of the confined carriers are calculated using a variational multicomponent envelope function scheme, while Coulomb interaction is included within the standard configuration-interaction to determine the exciton states. In dependence of the applied field, we study the optical spectrum for different geometries. Changing the applied field leads to a transition of various exciton states from a direct type, where the carriers are mainly localized in the same dot, to an indirect type, where they are mainly localized in different dots. These changes are accompanied by different hole and electron related anticrossings, visible in absorption spectra. The lines of the exciton transitions are broadened due to phonon-related processes such as phonon-assisted relaxations and tunneling. We calculate the linewidths due to deformation potential and piezoelectric coupling of the excitons to acoustic phonons. We show that the linewidths strongly depend on the spatial overlap and the energy separation of the involved electron and hole states and thus both the interdot distance and the applied field.