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Ultrafast Dynamics in Semiconductor Quantum Wells

Chris Hall

Centre for Atom Optics and Ultrafast Spectroscopy

3:30 pm Friday, 9 September 2011, EN101, EN Building, Hawthorn.

ZnO is a good candidate for use in UV light emitting devices. In the first half of the seminar I will present our work on c-axis grown ZnO/MgZnO quantum wells (QW). In this orientation the QWs have a built in electric field which spatially separates the confined electrons and holes, dramatically altering the properties of the QW compared to QWs with no built in field. The time-dependent properties of the quantum well are revealed by pump-probe spectroscopy, time-resolved photoluminescence and modelling. By structuring the barriers of QWs that have a built in electric field we show that the overlap integral of the wavefunctions for the lowest energy electron and hole states may be predictably controlled.

In the last half of the seminar I will present the first examination of coherently coupled and spatially separated excitons in an asymmetric double quantum well system. Calculations and experimental results suggest that the two lowest energy and bright heavy-hole excitons are localised to opposite QWs for barrier widths = 4 nm. We observe coherent coupling between these excitons for barrier widths of 4, 6 and 20 nm.

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