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HL: Halbleiterphysik

HL 18: Ultrakurzzeitph
änomene I

HL 18.8: Talk

Tuesday, March 27, 2001, 12:15–12:30, S9/10

Two-color femtosecond spectroscopy of self organized InGaAs/AlGaAs quantum dots — •M. Betz¹, A. Leitenstorfer¹, F. Findeis², E. Duijs², A. Zrenner², and G. Böhm² — ¹Physik-Department E11, Technische Universität München, D-85748 Garching — ²Walter-Schottky-Institut, Technische Universität München, D-85748 Garching

InGaAs/AlGaAs quantum dots with a ground state transition energy of 1.42 eV have been fabricated via the Stranski-Krastanov growth mode and a subsequent annealing procedure. Employing a special two-color Ti:sapphire laser, highly sensitive nonlinear studies with femtosecond time resolution are performed. We demonstrate time correlated luminescence experiments on quantum dot ensembles at low temperatures (T_L = 3 K): two independently tunable pulse trains

with durations between 50 fs and 500 fs resonantly create carriers within the dots, in the GaAs substrate or in the wetting layer. The variation of the ground state luminescence with pump-probe delay time provides detailed information on the relaxation dynamics of carriers generated in

excited states of the quantum dots and the capture process of carriers from the surroundings. Polarization dependent measurements give insight into the ultrafast coherent dynamics of these zero-dimensional electron-hole systems.