Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster 1

HL 13.36: Poster

Monday, March 26, 2007, 15:00–17:30, Poster A

Photoluminescence and ultrafast spectroscopy on GaAs quantum wells close to a GaMnAs layer — •Robert Schulz, Tobias Korn, Andreas Maurer, Dominik Stich, Ursula Wurstbauer, Dieter Schuh, Werner Wegscheider, and Christian Schüller — Institut für Experimentelle und Angewandte Physik II, Universität Regensburg, 93040 Regensburg, Germany

We study nonmagnetic GaAs quantum wells (QW) embedded in an AlGaAs/GaAs heterostructure close to a ferromagnetic GaMnAs layer. We present photoluminescence (PL) data of two QWs at different distances to the GaMnAs layer measured at 4 K: one QW is close (3 to 10 nm) to the GaMnAs layer, the other one is 120 nm away and used as a reference. The PL signal of the QW close to the Ga(Mn)As layer shows a significant broadening and quenching depending on the barrier width. This may be due to two effects: (i) Backdiffusion of Mn through the barrier into the upper QW during sample growth. (ii) Tunnelling of photoexcited charge carriers through the barrier into the low-bandgap Ga(Mn)As layer.

Additionally, time-resolved pump-probe experiments show that the carrier lifetime in the upper QW in comparison with the reference QW is significantly reduced. In contrast, the spin lifetime is four times larger, which we attribute to the D’Yakonov-Perel mechanism: Mn ions within the upper QW act as momentum scattering centers und thus increase the spin lifetime.

We acknowledge support by the DFG via project SCHU1171/1 and SFB 689 TP B4.