Regensburg 2004 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 12: Poster I
HL 12.15: Poster
Montag, 8. März 2004, 16:30–19:00, Poster A
Energy dependent optical selection rules for spin orientation in quantum wells — •Tobias Nowitzki1, Stefan Pfalz1, Roland Winkler1, Daniel Hägele1, Andreas Wieck2, and Michael Oestreich1 — 1Universität Hannover, Institut für Festkörperphysik, Abteilung Nanostrukturen, Appelstraße 2, 30167 Hannover — 2Ruhr-Universität Bochum, I. Institut für Experimentalphysik, Universitätsstraße 150, 44780 Bochum
Spin-polarized charge carriers are generated in a quantum well by optical excitation with circularly polarized light. By analyzing the degree of polarization of the time resolved photoluminescence (PL), we determine the initial degree of spin polarization of the excited electrons. We measure the initial polarization degree in the PL of a GaAs/AlGaAs sample with quantum well thicknesses between 5 nm and 20 nm for different photon energies of the exciting laser beam. Commonly, such initial degree of polarization is calculated using the angular momentum selection rules for optical transitions between different band edge electron and hole states in a bulk semiconductor. However, due to Coulomb interaction and coupling between heavy and light holes, the generated excitons usually contain substantial contributions from electron and hole states with different angular momentum components. We compare the experimental spectra with calculated spectra that fully take into account Coulomb interaction and heavy-hole light-hole coupling.