Regensburg 2002 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 15: Quantenpunkte und -dr
ähte: Optische Eigensch. I

HL 15.4: Vortrag

Dienstag, 12. März 2002, 11:45–12:00, H14

Time-Resolved Spectroscopy on Single CdSe/ZnSe Self-Assembled Quantum Dots — •Brian Patton, Wolfgang Langbein, and Ulrike Woggon — Exp. Physik IIb, Universität Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund

Single-dot spectroscopy in systems of semiconductor quantum dots often relies on the ability to isolate the features of one dot from a spectrum containing multiple dots. In these systems statistical variations in the E-field in the vicinity of the dot by carrier trapping processes cause jitter in the spectral position of excitonic features. We use this effect to identify transitions from individual dots in a CdSe/ZnSe system. We can then remove the effects of jitter components with a frequency of less than 1Hz.
Theory predicts that anisotropy in the shape of quantum dots leads to a polarisation-splitting in the spectrum. We measure and use this splitting to isolate the spectral features of individual dots, allowing us to assign them to exciton, biexciton and charged exciton (trion) transitions. Time-resolved analysis of these features presents an insight into the processes governing the decay of these multi-particle systems and confirms the assignations made above. We present data on the lifetimes of these transitions, including a trion lifetime comparible to the exciton lifetime and, in contrast to [1], a biexciton lifetime approximately half that of the exciton. Furthermore, we find a trion binding energy comparible to that of the biexciton.
We are grateful to K. H. Leonardi and D. Hommel (University of Bremen) for providing the samples.
G. Bacher et al., Phys. Rev. Lett. 83, 4417 (1999).