Dresden 2003 – scientific programme

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MA: Magnetismus

MA 7: Spin-Elektronik

MA 7.6: Talk

Monday, March 24, 2003, 16:30–16:45, HSZ/401

Spin Relaxation in InGaAs Heterostructures — •Lars Schreiber¹, Thomas Rohleder¹, Marcus Heidkamp¹, Bernd Beschoten¹, Gernot Güntherodt¹, and R. Hey² — ¹RWTH Aachen, 2. Physikalisches Institut, 52056 Aachen — ²Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin

Determination of electrical spin injection efficiency from ferromagnets into semiconductors in a spin LED depends upon both carrier and spin lifetime in the LED quantum well [1]. Therefore, we investigated spin dephasing and spin coherence in undoped In_xGa_1−xAs/GaAs quantum wells with different In concentration using time-resolved Kerr rotation (TRKR). Electron spins were optically excited by a circularly polarized pump puls and probed using Kerr rotation in Voigt geometry at various magnetic fields and temperatures. For TRKR the laser energy was tuned to the lowest quantum well interband transition energy at all temperatures as deduced from photoluminescence spectra. At high temperatures, the spin relaxation times decrease with increasing temperature for all In concentrations in good agreement to values obtained by time-resolved photoluminescence (TRPL) [1]. Spin lifetimes are virtually independent of magnetic field. For samples with low In concentration, an additional component with long spin lifetime (> 1 ns) was observed at low temperatures (<12 K). This component was not found using TRPL.

[1] M. Ramsteiner et al., in Advances in Solid State Physics, Vol. 42 (Springer, Berlin, 2002) Supported by BMBF FKZ01BM160 and 13N8244