Jean-Daniel Ganière

Chattez avec Graph Search

Posez n’importe quelle question sur les cours, conférences, exercices, recherches, actualités, etc. de l’EPFL ou essayez les exemples de questions ci-dessous.

AVERTISSEMENT : Le chatbot Graph n'est pas programmé pour fournir des réponses explicites ou catégoriques à vos questions. Il transforme plutôt vos questions en demandes API qui sont distribuées aux différents services informatiques officiellement administrés par l'EPFL. Son but est uniquement de collecter et de recommander des références pertinentes à des contenus que vous pouvez explorer pour vous aider à répondre à vos questions.

Advantages and remaining issues of state-of-the-art m-plane freestanding GaN (FS-GaN) substrates grown by halide vapor phase epitaxy (HVPE) for m-plane InGaN epitaxial film growth by metalorganic vapor phase epitaxy are described. Because of the low threading dislocation and basal-plane stacking fault densities, improved quantum efficiency and short radiative lifetime are achieved for the near-band-edge emission of 200–250 nm thick m-plane pseudomorphic InGaN epilayers. As the surface flatness is greatly im

We have recently shown that in II-VI/III-V heterojunctions and related devices fabricated by molecular beam epitaxy, the II/VI flux ratio employed during the early stages of II-VI growth can be used to control the local interface composition and the band alignment. Here we demonstrate that the local interface composition in pseudomorphic, strained ZnSe/GaAs(001) heterostructures as well as lattice-matched ZnSe/In0.04Ga0.96As(001) heterostructures also have a dramatic effect on the nucleation of native stack

We report on the realization of InGaAs-lnGaAsP separate confinement heterostructure multiple quantum well lasers grown by chemical beam epitaxy. We discuss key growth parameters and characterization by secondary-ion mass spectroscopy, transmission electron microscopy, electron-beam-induced current, and x-ray diffraction. Threshold current densities as low as 450 A/cm(2) are obtained on lasers with five strained InGaAs quantum wells, along with internal quantum efficiencies of 90% and optical losses of 5 cm(

Light dispersing device comprising a slit element having a slit for exposure to electromagnetic radiation, wherein the slit element is configured and disposed for turning the slit between at least two positions. The light dispersing device is used together ...

Photoluminescence lifetimes of the n = 2 level in a large quantum well show a clear nonmonotonic dependence on the density of optically generated carriers. Varying the power density over five orders of magnitude we prove directly the high efficiency of carrier-carrier interaction for intersubband scattering when longitudinal-optical phonon emission is suppressed. For low densities, the observed n = 2 decay times get shorter (from 40 down to 5 ps) as the density is increased. At high densities Pauli blocking

We investigated the interdiffusion of InGaAs/InP quantum wells (QWs) due to rapid thermal annealing (RTA) by photoluminescence (PL) spectroscopy and wedge transmission electron microscopy (WTEM). After RTA at temperatures between 650 and 900 degrees C (annealing time 1 min) we observed large emission energy shifts of up to 210 meV. From the temperature dependence of the PL emission energy shifts, the interdiffusion lengths, interdiffusion coefficients and activation energies (e.g. of 2 eV) were determined u

The observation of a wedge-shaped semiconductor specimen by transmission electron microscopy (WTEM) is an interesting alternative to conventional TEM. Information on chemical composition, layer thickness down to atomic resolution, spatial extension of the interfaces can be obtained. Secondary ion mass spectrometry (SIMS) is a complementary technique used to gain information on impurity concentration present in the semiconductor material.

We explored the degradation in electron beam pumped Zn1-xCdxSe/ZnSe laser structures by combining cathodoluminescence measurements in a scanning electron microscope with transmission electron microscopy. We found that degradation occurred via the formation of dark spot and dark line defects, and that it involved the formation of a characteristic type of defect, namely dislocation loops within the ZnCdSe quantum well, which grew to form a characteristic network as degradation progressed.

We report on the mechanism of hopping for bound excitons under an energy gradient. By means of a Monte-Carlo simulation, we show that this mechanism explains the movement of bound excitons observed experimentally. We show that the speed of the excitons dec ...

We studied the formation of buried heterostructures obtained in a single growth step over nonplanar substrates patterned with ridges. When the ridge dimensions are large enough, the growth on the mesa top is similar to that on a planar substrate. In contrast, ridge spacings below almost-equal-to 10 mum influence the composition of the alloys grown on the ridge as well as those grown in the valley centre. The possible surface mechanisms which may explain this behaviour are discussed.

Using time-resolved photoluminescence, we have investigated the radiative behavior of neutral and negatively charged excitons in CdTe-based quantum wells. We find that the photoluminescence of negatively charged excitons can be well reproduced by a model of delocalized and thermalized three-particle complexes. A large radiative zone in k-space results from the transfer of the charged exciton momentum to the remaining electron (recoil effect). On the other hand, the photoluminescence decay of excitons is not

We explore the defect distribution and the degradation in electron beam pumped Zn1-xCdxSe/ZnSe laser structures by combining cathodoluminescence measurements in a scanning electron microscope with transmission electron microscopy. We found that degradation occurs via the formation of [100]-oriented dark line defects, and that it involves the formation of a characteristic type of defect, namely dislocation loops within the ZnCdSe quantum well, which grow to form a characteristic network as degradation proces

Quantitative nondispersive cathodoluminescence (CL) measurements and dispersive CL experiments are performed at room temperature on n(+)-InP substrates as a function of the accelerating voltage (Eo). The results are explained in terms of band-to-band recombination. The red shift of the CL spectrum observed when increasing Eo, as well as the large value of the measured diffusion length with respect to the radiative one are interpreted on the basis of a high efficiency of the photon recycling process.

We report on the direct observation of biexcitons in a III-nitride based multiple quantum well microcavity operating in the strong light-matter coupling regime by means of nonresonant continuous wave and time-resolved photoluminescence at low temperature. ...

We study the dynamics of the charged and neutral excitons in a modulation-doped GaAs quantum well by time-resolved photoluminescence under a resonant excitation. The radiative lifetime of the charged exciton is found to be surprisingly short, 60 ps. This time is temperature independent between 2 and 10 K, and increases by a factor of 2 at 6 T. We discuss our findings in view of present theories of exciton radiative decay. [S0163-1829(98)03143-9].

Modern transmission electron microscopes offer imaging capabilities down to the atomic lattice resolution, as well as crystallographic and chemical microanalysis with 2-nanometer diameter probes in thin foils. These analytical microscopes are powerful tools for surface, interface and thin films studies.

The optical properties of low pressure metal organic vapor deposition grown GaAs/AlxGa1-xAs (x = 0.5) single quantum well structures (SQW) with grown-in dislocations (GD) were studied by low temperature cathodoluminescence (CL) and photoluminescence (PL). High luminescence efficiency around the GD was observed and attributed to impurity decoration. CL spectra show a region surrounding the GD that consists of Si impurities and native defects in the SQW and barrier layers. The diameter of this region was foun

To study the mechanism of zinc diffusion in GaAs, we diffused zinc from a ZnAs2 source into Si-doped GaAs samples (n almost-equal-to 1.3 X 10(18) cm-3) at different temperatures (from 575-degrees-C up to 700-degrees-C) in sealed evacuated quartz tubes. The samples are characterized by the depth profile of the photoluminescence at different temperatures. The photoluminescence spectra show characteristic emission associated to deep levels of gallium and arsenic vacancies. A detailed analysis of the spectra de

We report on time-resolved photoluminescence studies of charged and neutral excitons in a modulation doped GaAs quantum well under resonant excitation and high magnetic field. The radiative lifetime of the charged exciton is rather short, 60 ps at zero held, and is found to increase by a factor of similar to 2 up to 7 T. The short lifetimes suggest that, under magnetic field, the exciton bound in the trion is delocalized. (C) 1998 Elsevier Science B.V. All rights reserved.

The formation dynamics of charged excitons is studied in CdTe-based quantum wells by picosecond time-resolved photoluminescence. The formation time is obtained by an analysis of temporal behavior of photoluminescence signal after excitation in resonance with either neutral or charged exciton. It is shown that the formation time varies strongly when changing the electron concentration. We also demonstrate that the localization of neutral excitons has strong impact on the formation time of charged exciton and

Jean-Daniel Ganière

Chattez avec Graph Search

Advantages and remaining issues of state-of-the-art m-plane freestanding GaN substrates grown by halide vapor phase epitaxy for m-plane InGaN epitaxial growth

Local interface composition and extended defect density in ZnSe/GaAs(001) and ZnSe/In0.04Ga0.96As(001) heterojunctions

Chemical Beam Epitaxy of 1.55-Mu-M Separate-Confinement Heterostructure Multiple-Quantum-Well Laser-Diodes

Time-resolved spectroscopic measurement apparatus

Density dependence of carrier-carrier-induced intersubband scattering in GaAs/AlxGa1-xAs quantum wells

Investigation of InGaAs/InP Interdiffusion by Simultaneous Transmission Electron-Microscopy and Photoluminescence Analysis

Characterization of Semiconductor-Materials by Wtem and Sims

Degradation of electron-beam-pumped Zn1-xCdxSe/ZnSe GRINSCH blue-green lasers

Hopping process of bound excitons under an energy gradient

One-Step Growth of Buried Heterostructures by Chemical Beam Epitaxy over Patterned InP Substrates

Negatively charged excitons in CdTe-based quantum wells: A time-resolved study

Degradation and defects in electron-beam-pumped Zn1-xCdxSe/ZnSe GRINSCH blue-green lasers

Band-to-band recombination in N+ InP substrate: Evidence of photon recycling

Impact of biexcitons on the relaxation mechanisms of polaritons in III-nitride based multiple quantum well microcavities

Charged exciton dynamics in GaAs quantum wells

Transmission Electron-Microscopy of Surfaces and Interfaces

Cathodoluminescence and Photoluminescence Studies of Dislocations in Gaas/Algaas Quantum-Wells

A Model for the Zn Diffusion in Gaas by a Photoluminescence Study

Dynamics of charged excitons in GaAs quantum wells under high magnetic field

Formation time of negatively charged excitons in CdTe-based quantum wells