Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 9: Heterostrukturen I
HL 9.3: Vortrag
Montag, 8. März 2004, 15:45–16:00, H17
Dynamics of Excitons in Coupled Quantum Well Structures — •Andreas Gärtner1, D. Schuh2, and J. P. Kotthaus1 — 1CeNS und Sektion Physik der LMU, München — 2Walter Schottky Institut, TU München
The experiments to learn more about motion and interaction of long-living excitons in coupled quantum wells (QW) [1] are carried out in semiconductor heterostructures at low temperatures (4 K). These epitaxially grown samples contain two GaAs-QWs which are separated by a thin tunnelling barrier.
Metallic gates applied to a sample generate an electrical field
perpendicular to the QW layers.
This causes the transition from direct to spatially indirect excitons,
i.e. electron
and hole are located
in different QWs. Thus, the overlap of their wave functions
is reduced and the excitonic life time increases.
By means of the quantum confined stark effect (QCSE) the vertical electric
field affects the effective
excitonic potential [2].
It can be modulated by interdigitated gate structures [3] leading
to in-plane dift phenomena.
In our experimental pump-and-probe-setup we observed these effects on photo generated excitons by analyzing their emitted photoluminescence spatially, temporally and spectrally. An intensified CCD-Camera featuring a temporal resolution in the sub-nanosecond regime allows further detailed studies on the dynamics of excitonic drift.
[1] Butov et al., Nature 417, 47 (2002)
[2] S. Zimmermann et al., Phys. Rev. B 56, 13414 (1997)
[3] J. Krauß et al., Phys. Rev. Lett. 88, 036803 (2002)