We study the carrier capture and relaxation in self-assembled InAs/ GaAs quantum dots ͑QDs͒ using bleaching rise time measurements as a function of the excitation density, at 5, 77, and 293 K. We observe that the bleaching rise time and the carrier lifetime of the first excited state are longer than the bleaching rise time of the QD ground state, indicating that the excited state does not act as an intermediate state. For high excitation density, we observe a temperature-dependent plateau in the initial bleaching rise time, contradicting an Augerscattering-based relaxation model. Both these experimental results point toward a relaxation through the continuum background, followed by a single LO-phonon emission toward the QD ground state. The relaxation through the continuum background is governed by Coulomb or acoustic phonon coupling between the continuum and the discrete QD energy levels.

Prasanth, R.; Haverkort, J.E.M.; Deepthy, A.; Bogaart, E.; van der Tol, J.J.G.M.; Patent, E.; Zhao, G.; Gong, Q.; Veldhoven, van, P.J.; Nötzel, R.; Wolter, J.H.

The energy and excitation density dependence of the carrier dynamics in self-assembled InAs∕InP quantum dots (QDs), emitting in the 1.55μm wavelength region, is investigated by means of time-resolved pump-probe differential reflection spectroscopy at room temperature. We observe ultrafast carrier capture and subsequential carrier relaxation into the QD ground state within 2.5 ps. The carrier lifetime in the QDs strongly depends on the QD optical transition energy within the QD ensemble as well as the carrier density, and ranges from 560 up to 2600 ps.

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Polarization-resolved reflection measurements are performed on nearly circular InAs/ GaAs quantum dots ͑QDs͒ by means of time-resolved differential reflection spectroscopy. We observe linear polarization anisotropy of the differential absorption, revealing the dichroic character of the QD reflection. The observed magnitude of the dichroism is ⌰ ͓110͔ / ⌰ ͓110͔ = 1.07. The polarization has a preferential direction orientated along the ͓110͔ crystal axis, which is confirmed by polarization-resolved photoluminescence. We observe that the polarization anisotropy of the reflectivity is strongly dependent on the pump excitation density, decreasing from = 0.14 at low excitation to = 0.06 at high excitation. The pump power dependence is described by a binomial model taking into account the statistics of carrier capture into a limited number of QDs.