Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 74: Quantum dots: Optical properties

HL 74.2: Vortrag

Donnerstag, 14. März 2013, 09:45–10:00, H16

Spin-flip Raman scattering on Γ-X mixed excitons in indirect band-gap (In,Al)As/AlAs quantum dots — •Dennis Kudlacik¹, J. Debus¹, D. Dunker¹, V. F. Sapega², T. S. Shamirzaev¹, E. L. Ivchenko², D. R. Yakovlev^1,2, and M. Bayer¹ — ¹Experimentelle Physik 2, Technische Universität Dortmund, 44227 Dortmund, Germany — ²Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia

We studied the fine structure of the indirect exciton in self-assembled (In,Al)As/AlAs quantum dots (QDs) by means of spin-flip Raman scattering (SFRS). The QDs are characterized by a type-I band alignment, wherein, dependent on the dot size, a crossover between the energetically lowest conduction-band states of the Γ- and X-valley occurs. This Γ-X mixing of the electron levels is used to optically study the indirect in momentum-space exciton. It has a long recombination lifetime and longitudinal spin relaxation time of up to several milliseconds. Using the resonant SFRS the g-factor tensors of the indirect exciton, Γ-valley heavy-hole, and X-valley electron are determined. The spin-flip scattering mechanisms are based on acoustic phonon interaction in tilted magnetic field geometries. The efficiencies of the electron and heavy-hole spin scattering strongly depend on the excitation energy across the inhomogeneously broadened QD ensemble. The Γ-valley electron cannot be observed because of its short lifetime and the broad dispersion of its g-factor corresponding to the strong variation in the QD sizes, which is evidenced in experiment and theory.