Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 19: Symposium Spin Effects in Semiconductors of Reduced Dimensionality
HL 19.4: Hauptvortrag
Dienstag, 26. Februar 2008, 12:00–12:30, ER 270
Electrical spin injection into single InGaAs quantum dots — •Michael Hetterich1, Wolfgang Löffler1, Thorsten Passow1, Dimitri Litvinov2, Dagmar Gerthsen2, and Heinz Kalt1 — 1Institut für Angewandte Physik and DFG Center for Functional Nanostructures (CFN), Universität Karlsruhe (TH), D-76128 Karlsruhe, Germany — 2Laboratorium für Elektronenmikroskopie and CFN, Universität Karlsruhe (TH), D-76128 Karlsruhe, Germany
In the context of a potential future quantum information processing we investigate the simultaneous initialization of electronic spin states in InGaAs quantum dot (QD) ensembles via electrical injection from diluted magnetic ZnMn(S)Se spin aligners. Metallic nano-apertures on top of our spin-injection light-emitting diodes enable us to individually address and optically read-out spin states in single QDs. A reproducible spin polarization degree close to 100% is observed for a subset of the QD ensemble although injection takes place into the upper Zeeman level of the dots, thus confirming the robustness of spin states in the latter. However, the ensemble-averaged polarization degree shows a strong drop with increasing QD emission wavelength. Our measurements suggest that spin relaxation processes outside the QDs as well as the energetic position of the electron Fermi level play a crucial role in the explanation of this effect (e.g. formation of a 2D electron gas at the III–V/II–VI interface). A further contribution is defect-related spin scattering at the interface. Improved structures with optimized Fermi level position and lattice-matched ZnMnSSe spin aligners are currently under development.