Publications de Daniel Oberli | EPFL Graph Search

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We investigated the optical properties of excitons in quasi-one-dimensional semiconductor quantum structures by photoluminescence and photoluminescence excitation: High-quality GaAs/AlxGa1-xAs heterostructures were grown using low-pressure organometallic chemical vapour deposition (OMCVD) on non-planar substrates. The experimentally observed subband separations are in good agreement with a theoretical calculation of the quantum-confined eigenstates, which includes the mapping of the crescent-shaped wire obt

The effect of the miscut angle of vicinal substrate on the optical and morphological properties of GaAs/AlxGa1-xAs quantum wells grown by metalorganic vapor phase epitaxy is studied by means of photoluminescence (PL) and atomic force microscopy. Within small changes of the miscut angle, we observe strong variations of the PL linewidth, energy, and lineshape, as well as transitions between the morphology of the sample's surface and interface. The relation between these features is discussed, and the particul

The emission pattern of charged excitons in a semiconductor quantum dot (QD) is composed of a quadruplet of linearly polarized lines when a magnetic field is applied in a Voigt configuration. The orientation of the linear polarization of exciton emission i ...

We present a theoretical analysis of experimental photoluminescence spectra in highly excited semiconductor quantum wires. We show that the inclusion in the theory of electron-hole correlations strongly modifies the shape of emission spectra at any density. We discuss the role of these correlations in the evaluation of the band gap renormalization. The calculated energy- and density-dependence of the broadening agree qualitatively with the experimental results. The broadening is also comparable in magnitude

We have studied the effect of disorder on the radiative properties of semiconductor quantum wires by time-resolved photoluminescence spectroscopy. The dependence of the radiative lifetimes is measured over a temperature range extending from 8 to 150 K. At low temperatures we find that the measured dependence does not conform to the theoretical prediction for recombination of free excitons in a quasi-one-dimensional system due to the major influence of disorder. An extension of the theory is developed in ord

We present an experimental signature of the Anderson localisation of microcavity polaritons, and provide a systematic study of the dependence on disorder strength. We reveal a controllable degree of localisation, as characterised by the inverse-participati ...

We demonstrate efficient, regulated single-photon operation from site-controlled InGaAs quantum dots (QDs) grown on a prepatterned substrate. Under nonresonant optical excitation, carriers trapped at structural or compositional defects of the adjacent nano ...

We have studied the effect of valence band mixing on the optical properties of semiconductor quantum wires by analyzing the luminescence polarization. Large polarization anisotropy is observed and directly compared to the effects predicted by a k . p model calculation of the valence band structure.

The results of a group theoretical analysis of the excitonic fine structure are presented and compared with spectroscopic data on single quantum dots. The spectral features reveal the signatures of a symmetry higher than the crystal symmetry (C-3v). A cons ...

We present results on the polarization-resolved photoluminescence emitted from InGaAs/AlGaAs single quantum dots (QDs) grown in inverted tetrahedral pyramids. The emitted light was detected for two mutually perpendicular linear polarization directions in t ...

The diffusivity of photogenerated electron-hole pairs in weakly disordered GaAs/AlGaAs V-groove quantum wires was measured using a photoluminescence (PL) time-of-flight technique. It is shown that the electron-hole pair diffusion is thermally activated above about 50 K. Exciton localization is observed in micro-PL (mu PL) spectra at low temperature. A reduction in the Stokes shift is found to accompany the increase in the diffusion coefficient. Nevertheless, localization-related features in the mu PL spectr

Pyramidal, site-controlled InGaAs/AlGaAs quantum dots (QDs) are studied by micro-photoluminescence (PL) spectroscopy in a magnetic field. The light-hole (LH) excitonic transitions exhibit diamagnetic shifts similar to those of their heavy-hole (HH) counterparts. From the evolution of the excitonic lines, effective g-factors of g = 1.7 and 0.4 for HH and LH neutral excitons are inferred. (c) 2007 Elsevier B.V. All rights reserved.

We have performed low-density (< 10(5) cm(-1)) time-resolved photoluminescence experiments that probe the relaxation of photo-excited carriers in a quantum wire. Our results show that carrier-carrier collisions are dominant at very short times both for intra- and for inter-subband scattering as only expected if non-Markovian effects are taken into account. (C) 1999 Elsevier Science B.V. All rights reserved.

A systematic and simple theoretical approach is proposed to analyze true degeneracies and polarized decay patterns of exciton complexes in semiconductor quantum dots. The results provide reliable spectral signatures for efficient symmetry characterization, ...

The dynamics of charging and recombination of photoexcited, site-controlled semiconductor quantum dots (QDs) are investigated using microphotoluminescence (PL) and photon-correlation spectroscopy combined with rate equation modeling. Several species of neu ...

We report on the observation of negatively and positively charged excitons in the photoluminescence spectra of V-groove quantum wires. The charged exciton binding energy increases with the strength of the quantum confinement. We demonstrate that the charged excitons are localized by the fluctuations of the confinement potential and estimate a minimal value of the localization length. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.

Evidence of tunneling and electronic coupling in a one-dimensional system is reported. This is accomplished by comparing low-temperature photoluminescence and photoluminescence excitation spectra of GaAs double quantum wires of different barrier widths with a full 4 x 4 k . p calculation of coupled interband transitions. [S0163-1829(98)01228-4].

The interaction between coherent polaritons and incoherent excitons plays an important role in polariton physics. Using resonant pump-probe spectroscopy with selective excitation of single polariton branches, we investigate the different dephasing mechanis ...

Daniel Oberli

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Optical spectroscopy of semiconductor quantum wires

Optics, morphology, and growth kinetics of GaAs/Al_{x}Ga_{1-x}As quantum wells grown on vicinal substrates by metalorganic vapor phase epitaxy

Coulomb correlations of charged excitons in semiconductor quantum dots

Excitonic corrections and band gap renormalization in quantum wires

Effect of disorder on the temperature dependence of radiative lifetimes in V-groove quantum wires

Anderson localisation in steady states of microcavity polaritons

Optimization of the efficiency of single photon sources based on quantum dots under optical excitation

Polarization anisotropy and valence band mixing in semiconductor quantum wires

Symmetry Elevation and Symmetry Breaking: Keys to Describe and Explain Excitonic Complexes in Semiconductor Quantum Dots

Excited excitonic states observed in semiconductor quantum dots using polarization resolved optical spectroscopy

Diffusion of electron-hole pairs in disordered quantum wires

Magneto-photoluminescence of heavy- and light-hole excitons in site-controlled pyramidal quantum dots

Single-photon emission from pyramidal quantum dots: The impact of hole thermalization on photon emission statistics

Intrasubband and intersubband scattering in semiconductor quantum wires

Symmetries and the Polarized Optical Spectra of Exciton Complexes in Quantum Dots

Quantum Dot Exciton Dynamics Probed by Photon-Correlation Spectroscopy

Observation of charged excitons in V-groove quantum wires

Tunneling and coupling between one-dimensional states in double quantum wires

Coherent and incoherent aspects of polariton dynamics in semiconductor microcavities

Sub-meV Photoluminescence Linewidth and >106 cm2/Vs Electron Mobility in AlGaAs/GaAs Quantum Wells Grown by Metallorganic Vapor Phase Epitaxy on Slightly Misoriented Substrates