Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 7: Quantum dots: Optical properties I

HL 7.3: Talk

Monday, March 23, 2009, 14:00–14:15, BEY 118

Time-resolved studies of pulsed electrical spin initialization in single InGaAs quantum dots — •P. Asshoff, W. Löffler, J. Zimmer, H. Flügge, H. Füser, M. Hetterich, and H. Kalt — Institut für Angewandte Physik, Universität Karlsruhe (TH), and DFG Center for Functional Nanostructures, CFN, D-76128 Karlsruhe

For spin-injection light-emitting diodes with a diluted magnetic semiconductor as spin aligner, we have recently demonstrated that the achievable spin-injection fidelity in quantum dots ranges from near-unity to even negative values depending on the individual dot. To study the origin of this phenomenon, we investigated the temporal behavior of the spin-injection fidelity using ns-pulses for the electrical injection into the dots. In quantum dot ensemble measurements, we clearly see that the polarization degree drops within the first nanoseconds of the electrical pulse. Measurements concerning the temporal evolution of the polarization degree for single quantum dots as well as approaches to theoretically model the observed dynamics will be presented. The latter should open up the possibility to relate the spin-injection fidelity of individual quantum dots to scattering mechanisms, which may allow for improved designs to enhance spin injection significantly. Furthermore, our time-resolved studies of the pulsed spin initialization process are a first step towards future spin manipulation experiments.