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Physical Review Letters

Ultralong Dephasing Time in InGaAs Quantum Dots

Paola Borri, W. Langbein, Stephan Schneider, U. Woggon, Paul J Sellin, D. Ouyang, D. Bimberg

Published Sep 1, 2001• 996 citations
Publisher

Abstract

We measure a dephasing time of several hundred picoseconds at low temperature in the ground-state transition of strongly confined InGaAs quantum dots, using a highly sensitive four-wave mixing technique. Between 7 and 100 K the polarization decay has two distinct components resulting in a non-Lorentzian line shape with a lifetime-limited zero-phonon line and a broadband from elastic exciton-acoustic phonon interactions.

DOI
10.1103/physrevlett.87.157401

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Abstract We measure the dephasing time of the first optically‐active excited‐state excitonic transition in strongly confined InGaAs quantum dots using transient four‐wave mixing. The optically‐driven excited‐state polarization shows a bi‐exponential decay with a significant fraction of the probed excited states exhibiting a very long dephasing time, in the nanosecond range at 10 K. The full time‐dependent four‐wave mixing polarization is microscopically calculated by taking into account both virtual and real acoustic phonon‐assisted transitions. The bi‐exponential decay is qualitatively explained by a model of two‐bright excitonic excited states non‐degenerate in the absence of in‐plane cylindrical symmetry. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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We measure the dephasing time of the exciton ground-state transition in ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}\mathrm{As}$ quantum dots using a sensitive four-wave mixing technique. We find experimental evidence that the dephasing time is given only by the radiative lifetime at low temperatures. We demonstrate the tunability of the radiatively limited dephasing time from 400ps400\phantom{\rule{0.3em}{0ex}}\mathrm{ps}400ps up to 2ns2\phantom{\rule{0.3em}{0ex}}\mathrm{ns}2ns in a series of annealed ${\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}\mathrm{As}$ quantum dots with increasing quantum-confinement energy from 69meVto330meV69\phantom{\rule{0.3em}{0ex}}\mathrm{meV}\phantom{\rule{0.5em}{0ex}}\text{to}\phantom{\rule{0.5em}{0ex}}330\phantom{\rule{0.3em}{0ex}}\mathrm{meV}69meVto330meV.