Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 19: Symposium Spin Effects in Semiconductors of Reduced Dimensionality

HL 19.4: Invited Talk

Tuesday, February 26, 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.