Benoît Marie Joseph Deveaud

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Elastic strain engineering is an important way to reversibly tune the properties of micro/nanoscale semiconductors for promising applications in the emerging advanced nanotechnologies, such as the strain enhanced high-mobility transistors, nanogenerators, ...

A detailed study of excitons in unstrained GaN nanocolumns grown by plasma assisted molecular beam epitaxy on silicon substrates is presented. The time-integrated and time-resolved photoluminescence spectra do not depend significantly on the (111) or (001) ...

Low-frequency noise measurements have been performed in the linear range of the I-V characteristics of pseudomorphic Al0.3Ga0.7As/In0.25Ga0.75As/GaAs high electron mobility transistors (HEMTs) grown by molecular beam epitaxy with different channel thicknesses. The results obtained show that the 1/f noise in such devices depends greatly on channel thickness. It is controlled by the penetration of the electron wavefunction into the barrier as well as by Coulombic effects for thin channels and by the increase

We investigate the charge current that is optically injected by interference between one- and two-photon excitation in the presence of excitonic effects. We consider a realistic V-shaped quantum wire excited slightly below the band gap by two simultaneous ...

The design of cost-effective standards for the quality of nano-objects is currently a key issue toward their massive use for optoelectronic applications. The observation by photoluminescence of narrow excitonic and biexcitonic emission lines in semiconduct ...

This article presents the dynamics of excitons in a-plane (Al,Ga)N/GaN single quantum wells of various thicknesses grown on bulk GaN substrates. For all quantum well samples, recombination is observed to be predominantly radiative in the low-temperature ra ...

We have measured the ultrafast simultaneous cross-gain and laser mode dynamics in a gain-clamped semiconductor amplifier perturbed by an intense detuned 150 fs pump pulse. Besides relaxation oscillations, we demonstrate the instantaneous formation of a dark pulse in the laser mode that repeats itself with a period given by the cavity round-trip time. The dark pulse sequence subsequently decays into two-mode beating and is shown to weakly cross modulate the amplifier gain. To describe dark-pulse formation a

Coherent manipulation of spin ensembles is a key issue in the development of spintronics. In particular, multivalued spin switching may lead to new schemes of logic gating and memories. This phenomenon has been studied with atom vapours 30 years ago, but is still awaited in the solid state. Here, we demonstrate spin multistability with microcavity polaritons in a trap. Owing to the spinor nature of these light-matter quasiparticles and to the anisotropy of their interactions, we can optically control the sp

The crossover from an exciton gas to an electron-hole plasma is studied in a GaN/(Al,Ga)N single quantum well by means of combined time-resolved and continuous-wave photoluminescence measurements. The two-dimensional Mott transition is found to be of continuous type and to be accompanied by a characteristic modification of the quantum well emission spectrum. Beyond the critical density, the latter is strongly influenced by band-gap renormalization and Fermi filling of continuum states. Owing to the large bi

We have studied experimentally the radiative lifetimes of negatively charged excitons (X-) and neutral excitons (X) in GaAs and CdTe quantum wells. Despite the different optical properties (e.g. trion binding energies) and the different quantum well structures of the studied samples, we find quite similar X- lifetimes in the range of 45 to 60 ps. On the other side, the X lifetimes are very different and influenced by the material. For relatively low electron concentrations, the X- lifetime is found to be co

Time-resolved measurements of the resonant Rayleigh scattering from quantum well excitons are shown to provide information on the energy-level statistics of the localized exciton states. The signal transients are reproduced by a microscopic quantum model of the exciton two-dimensional motion in presence of spatially correlated disorder. This model allows quantitative determination of the average energy separation between the localized states. Here this quantity turns out to be only a few times smaller than

Bose-Einstein condensates (BECs), the "fifth state of matter," have in fact been discovered by chance both in liquid helium and in superconductors. Since these early encounters, BECs have been sought for, both in atom vapors and in solids. Here we report o ...

Near-field optical spectroscopy is used to investigate the effects of disorder in the optical processes in semiconductor quantum wires. We observe photoluminescence emissions from extended, delocalized excitons at low temperatures (5 K) and low excitation densities. Combining high spectral and spatial resolution, we isolate homogeneous emission lines from excitons delocalized over distances up to 600 nm in the fundamental state. The energies of the emissions are consistent with different quantum spatial con

We present the optical tomography of the probability density of microcavity polaritons, confined in three dimensions by cylindrical traps of various sizes. Collecting the photoluminescence emitted by the quasimodes under continuous nonresonant laser excita ...

We present a comparative study of time-integrated four-wave-mixing and femtosecond emission under resonant excitation on excitons in weakly disordered GaAs quantum wells. At highest exciton densities when dephasing dominates the spectral width (homogeneous broadening), we find that the rise time of the incoherent luminescence signal is given by T-2/2. At lowest densities, optical coherence times approach the exciton radiative lifetime (15 to 20 ps). This confirms our previous result that coherent resonant R

We investigate polariton-polariton interactions in a semiconductor microcavity through two-dimensional Fourier transform (2DFT) spectroscopy. We observe, in addition to the lower-lower and the upper-upper polariton self-interactions, a lower-upper cross in ...

Properties of carrier-induced ferromagnetism in modulation-doped quantum wells of p-type (Cd,Mn)Te are assessed by photoluminescence (PL) and PL excitation spectroscopy. Well-chosen illumination makes it possible to deplete the quantum well and thus to control the strength of the ferromagnetic interactions. Spontaneous local magnetization is proportional to the hole concentration p but the Curie temperature T-C varies little over a wide p range, in agreement with the mean-field model for 2D systems. The spa

We develop a dynamical theory for the optical injection of charge and spin current originating from the interferences between two coherent laser pulses of frequencies omega and 2omega. Multiband Bloch equations which include one- and two-photon interband transitions are derived. They also account for ac Stark shifts and intersubband two-photon transitions. The model is used to describe the case of time-dependent charge and spin current injection in a symmetric GaAs/AlGaAs quantum well. A comparison to the b

We present a systematic study of the oscillator strength of the positively charged excitons (X+) in Cd1-xMnxTe quantum wells. CW-absorption and time-resolved photoluminescence measurements were combined as two approaches for the determination of the oscillator strength. By varying (in a small magnetic field) the spin subband hole distribution at constant total concentration, we observe an increase of the oscillator strength in absorption, proportional to the hole concentration in one spin subband (the one w

Control of the wave function of confined microcavity polaritons is demonstrated experimentally and theoretically by means of tailored resonant optical excitation. Three dimensional confinement is achieved by etching mesas on top of the microcavity spacer l ...

Benoît Marie Joseph Deveaud

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Temperature Dependent Exciton Funnel Dynamics in Uniform Strain Gradient Field Observed by Time-Resolved Photoluminescence

Time-resolved spectroscopy on GaN nanocolumns grown by plasma assisted molecular beam epitaxy on Si substrates

Low-Frequency Noise Measurements of Alxga1-Xas/Inyga1-Y as/Gaas High-Electron-Mobility Transistors

Optical injection of charge current in quantum wires: oscillations induced by excitonic effects

Biexciton emission and crystalline quality of ZnO nano-objects

Temperature-Dependence of Exciton Radiative Recombination in (Al,Ga)N/GaN Quantum Wells Grown on a-Plane GaN Substrates

Observation of dark-pulse formation in gain-clamped semiconductor optical amplifiers by cross-gain modulation

Multistability of a coherent spin ensemble in a semiconductor microcavity

High-temperature Mott transition in wide-band-gap semiconductor quantum wells

Radiative lifetime of negative trions in GaAs and CdTe quantum wells

Optical signatures of energy-level statistics in a disordered quantum system

On the condensation of polaritons

Near-field imaging of one-dimensional excitons delocalized over mesoscopic distances

Probability density tomography of microcavity polaritons confined in cylindrical traps of various sizes

Relevance of dephasing processes for the ultrafast rise of emission from resonantly created excitons in quantum wells

Two-dimensional Fourier transform spectroscopy of exciton-polaritons and their interactions

Light controlled and probed ferromagnetism of (Cd,Mn)Te quantum wells

Dynamics of optical injection of charge and spin currents in quantum wells

Oscillator strengths of charged excitons: combining magnetoabsorption and photoluminescence dynamics in semimagnetic quantum wells

Coherent optical control of the wave function of zero dimensional exciton polaritons