Dresden 2003 – scientific programme

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HL: Halbleiterphysik

HL 35: Quantenpunkte und -dr
ähte: Optische Eigenschaften I

HL 35.3: Talk

Wednesday, March 26, 2003, 18:00–18:15, BEY/154

Many-particle effects in InGaAs/GaAs-Quantum dots — •Cornelia Sing, Florian Guffarth, Robert Heitz, Roman Sellin, and Dieter Bimberg — TU Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10629 Berlin, Germany

The impact of the many-particle Coulomb interaction on the electronic properties of a large number of excitons localized in self-organized InGaAs/GaAs quantum dots (QDs) is investigated. Photoluminescence (PL) measurements on mesa structures evidence at high excitation densities a pronounced renormalization of the exciton transition energies in neutral QDs. The population of the QDs is estimated based on detailed modeling accounting for the independent recombination in different QDs in a master equations of micro states (MEM) approach. The intensity ratios in the saturation regime allow extracting the relative radiative lifetimes of the exciton transitions.

Low energy shifts as large as 35 meV are observed for the ground state transition, whereas the excited states exhibit first a blue turning into a red shift, when the respective state is completely filled. A comparison of the renormalization in QDs with different number of excited states and structures with and without wetting layer indicate, the renormalization to result mainly from the Coulomb interaction of the localized carriers, though the interaction with delocalized carriers contributes too, but much weaker. A pronounced broadening of the inhomogeneous QD emission with increasing excitation density cannot be completely explained with the statistical population distribution but indicates Coulomb and Auger scattering to reduce the phase relaxation time.