Dichroic reflection of InAs∕GaAs quantum dots

Abstract

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.

Circular dichroism inInAs∕GaAsquantum dots: Confinement-induced magnetism

“…A similar behavior is observed for TRDR measurements in which linear polarized probe light is used, see Ref. 19. Also here, we ascribe the onset of the saturation to the finite density of states of the QD ensemble.…”

“…The 30 nm GaAs spacer layers are inserted to prevent electronic coupling of the QDs. Atomic force microscopy images of uncovered QDs show the formation of nearly circular quantum dots 19 with a density of 2.8 ϫ 10 10 cm −2 per layer. We emphasize that the sample is undoped.…”

“…19, a binomial model is developed which describes the level population as a function of the excitation density. The differential signal as a function of the carrier density can be expressed by a binomial series:…”

Extended electron states in lateral quantum dot molecules investigated with photoluminescence

“…The excitation power density was varied from 0.01 to 1000 W / cm 2 , the latter resulting in a QD occupation by approximately one electron-hole pair, as deduced from time-resolved differential reflection spectroscopy. 12 The PL signal was dispersed by a single monochromator and detected by a cooled ͑In,Ga͒As linear photodiode array. For micro-PL, a low number of QDMs were selected through aluminum masks with 1 ϫ 1 m 2 square openings fabricated by electron-beam lithography.…”

Power dependent photoluminescence of lateral quantum dot molecules: Indication of extended electron states

“…The samples were excited by a cw Ti:sapphire laser operating at 800 nm with excitation power densities varied from 0.01 to 1000 (P 0 ) W/cm 2 . Each QD is occupied with approximately 1 electron-hole pair for excitation density P 0 , deduced from time-resolved differential reflection spectroscopy [6].The diameter of the excited area on the sample surface was about 50 µm, probing around 20000 QDMs. The PL signal was dispersed by a single monochromator and recorded by a cooled InGaAs charge coupled device.…”