Hamburg 2001 – scientific programme

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HL: Halbleiterphysik

HL 26: Symposium: Spectroscopy of Single Quantum Dots

HL 26.4: Fachvortrag

Thursday, March 29, 2001, 12:00–12:30, S2

Few-particle effects in self-organized quantum dots — •Robert Heitz, Volker Türck und Oliver Stier — Institut für Festkörperphysik der Technischen Universität Berlin

Single quantum dot (QD) spectroscopy provides a powerful tool to study exchange and correlation effects in zero-dimensional systems. The present understanding neglects the actual complex confining potentials provided by inhomogeneously strained self-organized QD’s. Few-particle effects are, e.g., sensitive to the asymmetry of the electron and hole wavefunctions in such QD’s. Few-particle states in self-organized QD’s are calculated taking into account the full structural properties. Based on realistic single-particle wave functions obtained from eight-band k·p calculations neutral and charged exciton and bi-exciton states are calculated by a configuration interaction approach. The influence of the structural properties is discussed for the InAs/GaAs model system. For example, the piezoelectric effect causes an anti-binding bi-exciton state in pyramidal QD’s, whereby decreasing the size of or truncating the pyramid stabilizes the bi-exciton. The calculations are extended to the CdSe/ZnSe material system and compared to recent spot-cathodoluminescence results. Neutral and charged exciton and bi-exciton states are identified. The source of the often pronounced interaction of epitaxial II-VI QD’s with the matrix, causing spectral-diffusion, is identified based on the calculations. Additionally, time-resolved measurements reveal lateral energy transfer processes within the CdSe QD-layer.