Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 17: Poster I

HL 17.39: Poster

Monday, February 25, 2008, 16:30–19:00, Poster D

Photoluminescence and ultrafast spectroscopy on diffusion barriers between GaAs quantum wells and GaMnAs layer — •R. Schulz, A. Wagner, T. Korn, U. Wurstbauer, D. Schuh, W. Wegscheider, and C. Schüller — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, 93040 Regensburg, Germany

GaMnAs is a highly interesting material system for future spintronic devices. We present a study of nonmagnetic GaAs quantum wells (QW) embedded in AlGaAs barriers, close to a ferromagnetic GaMnAs layer. The samples were grown on semi-insulating GaAs(001) and contain two QWs, where one QW is close (between 3 and 10 nm) to the GaMnAs layer and the other one is farther away (120 nm), and serves as a reference. We studied the influence of different types and widths of the barrier material (AlGaAs layer and a short-period AlAs/GaAs superlattice) as well as post-growth annealing. The photoluminescence (PL) of the upper quantum wells shows a significant broadening and quenching depending on barrier width. Additionally, time-resolved Faraday rotation (TRFR) reveals that the spin lifetime in the upper QW is up to 50 times longer than that in the lower QW. We attribute these observations to backdiffusion of Mn into the QW during and after growth. Both, the PL and the TRFR, are highly sensitive to small quantities (below 0.05 %) of Mn and allow us to study the efficiency of barrier layers in suppressing Mn diffusion.
We acknowledge support by the DFG via project SCHU1171/1 and SFB 689 TP B4.