Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 9: Semiconductor Nanophotonics: Materials, Models, Devices - GaN based Photonics II

DS 9.4: Talk

Monday, February 25, 2008, 17:00–17:15, H 2032

Recombination Kinetics of Localized Excitons in InGaN/GaN Quantum Dots — •Momme Winkelnkemper, Mattias Dworzak, Till Bartel, Axel Hoffmann, and Dieter Bimberg — Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstraße 36, D-10623 Berlin, Germany

The suitability of InGaN/GaN heterostructures for optoelectronic devices is sensitively affected by the built-in piezo- and pyroelectric fields, which affect the emission wavelengths as well as recombination dynamics via the quantum-confined Stark effect. In the present work, we study the photoluminescence (PL) decay of InGaN/GaN quantum dots (QDs) and its dependence on the built-in piezo- and pyroelectric fields. The decay of the ensemble photoluminescence (PL) is found to be strongly non-exponential, while all single-QD measurements yield exponential decays. We show that the non-exponential decay of the ensemble PL is well explained with a broad distribution of excitonic lifetimes within the QD ensemble. Using an inverse Laplace transformation, we derive an energy-dependent decay-time distribution function, which agrees well with the single-QD decay times. Within the framework of eight-band k.p theory, we calculate the dependence of the radiative excitonic lifetimes on structural parameters, such as QD height, lateral diameter, and chemical composition. The built-in piezo- and pyroelectric fields cause a sensitive dependence of the radiative lifetimes on the exact QD geometry and composition, resulting in a broad lifetime distribution even for moderate variations of the QD structure.