Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 36: Quantenpunkte und -dr
ähte: Optische Eigenschaften I

HL 36.4: Vortrag

Donnerstag, 11. März 2004, 11:00–11:15, H17

Structure Dependent Few-particle Effects in InAs Quantum Dots — •Andrei Schliwa, Sven Rodt, Florian Guffarth, Robert Heitz, Robert Seguin, and Dieter Bimberg — Institut für Festkörperphysik, Technische Universität Berlin

Interaction between strongly localized charge carriers in zero-dimensional systems like quantum dots (QDs) depend sensitively on their geometrical properties. Few-particle properties, like the biexciton binding energies, may vary not only in size but also in sign. Based on the configuration interaction method those properties are calculated for realistic InAs QDs as function of their structural properties. The wavefunctions are obtained from eight-band k·p calculations including strain and piezoelectric effects.

The problem of correlating calculated and measured spectra can be circumvented exploiting the monolayer splitting in photoluminescence (PL) -spectra in appropriately grown samples. Detailed analysis of those spectra shows that (i) the QDs are very flat, (ii) the QDs have well-defined interfaces and (iii) each peak represents a subensemble of QDs sharing the same height. With decreasing transition energy the height of the related QD-ensemble increases subsequently by one monolayer. Single dot spectra revealing details of few-particle effects are obtained by cathodoluminescence measurements with shadow masks. Transition from positive to negative biexciton binding energy with increasing exciton energy due to decreasing dot size is observed and understood in the framework of the above theory.