Dresden 2006 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
HL: Halbleiterphysik
HL 52: Quantum dots and wires: Optical properties IV
HL 52.3: Vortrag
Freitag, 31. März 2006, 11:30–11:45, POT 151
Direct Observation of Inter-level Phonon Relaxation in Individual Quantum Dot Molecules — •T. Nakaoka1,2, H. J. Krenner1, E. C. Clark1, M. Sabathil1, M. Bichler1, Y. Arakawa2, G. Abstreiter1, and J. J. Finley1 — 1Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 3, D-85748 Garching, Germany — 2RCAST, University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo, 153-8505, Japan
We present an optical study of relaxation between tunnel coupled excitonic states in individual self-assembled InGaAs/GaAs QD-molecules embedded in Schottky photodiodes. Radiative lifetimes and temperature evolution of the emission intensities of the coupled states are probed close to the point of maximum coupling. The interdot coupling (2E) is tuned by detuning (Δ) away from the anticrossing [Edirect−Eindirect= (Δ2 + (2E)2)1/2] using static electric field perturbations. The results obtained clearly demonstrate that the radiative lifetimes of the coupled excitonic states can be tuned from τ = 0.3 ns to 1.3 ns, as the fraction of direct character of the exciton wavefunction is varied. Furthermore, close to the anticrossing (Δ ∼ 0) where the electron component of the wavefunction hybridizes into symmetric and antisymmetric orbitals, the lifetimes of both transitions tend to the same value confirming the fully mixed nature of the states. Temperature dependent measurements demonstrate that relaxation from the antibonding to bonding state can occur during the radiative lifetime. Analysis of the temperature dependent data indicates that such inter-level relaxation proceeds over timescales faster than ∼ 100 ps for 2E = 3.1 meV mediated by acoustic phonon scattering.