Jean-Daniel Ganière

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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

Annealing in excess arsenic vapor at 650-degrees-C introduces thermal conversion of n-type Si-doped GaAs samples (n = 1.3 X 10(18) cm-3) into p type. The observations are made by current-voltage and electron-beam induced current measurements. The donor concentration on the n side near the junction decreases after annealing. We present a comparison between the photoluminescence spectra of samples annealed under different conditions and an analysis of depth profile of the photoluminescence spectra. Our result

GaAs/AlxGa1-xAs multiple-quantum-well structures with identical well thicknesses (almost-equal-to 119 angstrom) but with different Al contents x in the barrier (x almost-equal-to 0. 1, 0.2, 0.45, and 1) were grown by molecular-beam epitaxy. We report the characterization of the structures by a combination of different techniques. The x-ray-diffraction technique allows us to estimate the Al content x and to measure the period of the structure with good accuracy. Using the photographs given by high-resolution

This paper reports on single quantum well characterization by means of luminescence excited with a laser (photoluminescence) and an electron beam (cathodoluminescence) at liquid helium temperatures. Small quantum well regions with smaller confinement were observed. They seem to be associated with dislocations originated at the substrate. The observed shift of the X (e-hh) peak position versus the excitation level can be explained by luminescence generation in different lateral regions of the quantum well.

GaAlAs/GaAs and GaInAs/InP thick layers, single and multiple quantum wells were grown by atmospheric pressure metalorganic vapor phase epitaxy. Auger electron spectroscopy, wedge transmission electron microscopy, x-ray diffraction, low-temperature photoluminescence, and scanning electron microscopy were used to analyze the crystal quality. These analysis techniques show that layers grown using high vapor pressure metalorganic sources present fluctuations in the ternary alloy composition. We propose that the

We present a detailed study of the luminescence at 3.42 eV usually observed in a-plane epitaxial lateral overgrowth (ELO) GaN grown by hydride vapor phase epitaxy on r-plane sapphire. This band is related to radiative recombination of excitons in a commonl ...

Using reflectivity and picosecond time-resolved photoluminescence, we have studied the intrinsic optical properties of negatively charged excitons in modulation doped CdTe quantum wells. In emission, we observe simultaneously a low energy exponential tail in the charged exciton spectral line and a linear increase of its radiative lifetime with temperature. In absorption, we find a consistent decrease of the charged exciton oscillator strength with temperature. For low electron concentrations these observati

The fluorescence lifetime tau and quantum yield eta(f) of isolated red polydiacetylene chains dispersed in their monomer single crystal matrix were measured between 10 and 100 K. tau increases up to 120 ps at 40 K, then rapidly decreases at higher T. eta(f) is a continuously decreasing function of T. The radiative lifetime tau(r) is proportional to rootT in the whole T range studied. This is the expected behavior for a purely one-dimensional system without localization, a behavior which is not usually obser

Time-resolved cathodoluminescence at 27 K has been performed on a-plane GaN grown by epitaxial lateral overgrowth. We detail the relaxation and recombination mechanisms of excitons [free or bound to neutral donors, or bound to I1-type basal stacking faults ...

We have observed marked oscillations in the time-resolved photoluminescence of a semiconductor microcavity under non-resonant excitation conditions. Hot excitons, created with an ultrashort light pulse, rapidly relax into polaritons in the cavity with a large in-plane momentum K. Shortly after illumination, above a certain excitation power, the polaritons accumulate into an energy trap at the bottom of the dispersion and the light emission, governed by final-state stimulated scattering, starts at K similar

We use the cathodoluminescence mode of a scanning electron microscope to investigate the depth and lateral dependencies of the electron-hole pairs generation by the electron beam in Al0.4Ga0.6As semiconducting material. A multiquantum well structure acts as a detector to measure the relative number of generated minority carriers by their radiative recombination, allowing a direct assessment of the generation volume in the sample. In contrast to electron-beam induced current which was used in former studies,

The effects of hydrogen diffusion on p-n GaAs junctions have been studied by electron beam induced current (EBIC) and cathodoluminescence (CL) at room temperature. Hydrogen passivates both the acceptors in the p-side of the junction and the donors in the n-side of the junction. As a consequence the diffusion lengths increase, the surface recombination velocities decrease, and, finally, the CL intensity increases after the hydrogen treatment. The observation of hydrogen effects on both sides of the junction

We have investigated the optical and structural properties of tensile-strained GaxIn1-xP/InP heterojunctions by cathodoluminescence (CL) in the scanning electron microscope and by transmission electron microscopy (TEM). The lattice mismatch of the samples is ranging from 0.4% (x=5.5%) to 0.84% (x=11.8%). We show, in agreement with previous studies, that the relaxation of tensile-strained epilayers occurs by the emission of partial and perfect dislocations. The numerous twins and stacking faults which are fo

We examine the room-temperature dispersive and non-dispersive cathodoluminescent (CL) signals produced by an n-InP/n(+)-InP homojunction as a function of excitation beam energy. The non-intentionally doped epilayer of the homojunction is thick enough (2.5 mu m) that it can be investigated independently of the substrate by choosing beam energies lower than 25 keV. The red-shift of CL peak, as well as the drastic change of the shape of the CL spectra, observed when increasing the beam energy, are explained in

In situ cathodoluminescence experiments have been performed to follow the time dependence of the UV luminescence in epitaxial lateral overgrowth GaN specimens. The decrease of the observed intensity and red-shift of the UV peak are interpreted in terms of non-radiative defect introduction and diffusion. This leads to strain relaxation of the GaN epilayer, which is initially under compressive strain. Monochromatic UV and yellow CL images show that dislocations act as efficient non-radiative recombination cen

The fluorescence yield, eta approximate to 0.30, and Lifetime, tau approximate to 52 ps, of recently discovered 'red' polydiacetylene isolated chains [R. Lecuiller, J. Berrehar, C. Lapersonne-Meyer, M. Schott, Phys. Rev. Lett. 80 (1998) 4068] have been measured at 15 K. These values show that the relaxation scheme of the 'red-chain' exciton is very different from that of the usual 'blue chains', and that excited states of A, symmetry are not present in the optical gap of red chains. Moreover, the radiative

We describe the first stage of the evolution of CL spectra, intensity and dislocation contrast under low keV electron beam for ELO-GaN with a low dislocation density. The UV and yellow intensities are decreased by beam irradiation. We have observed a broadening of the UV peak towards low energies followed by a red shift. This is explained in terms of an electron beam activation of non-radiative centers which relax partially the compressive strain, The dislocation contrast is lowered, but the dislocations be

The cathodoluminescence mode of the scanning electron microscope is used for the first time to investigate the lateral dependence of the electron-hole pair generation by the electron beam of the scanning electron microscope m semiconducting material. A multiple-quantum-well structure acts as a detector to measure the relative number of generated carriers by their radiative recombination. The method, which avoids the effect of carrier diffusion, enhances the resolution of the measurement to 50 nm and should

In a recent paper we measured the lateral hole diffusion in a GaAs/AlGaAs single quantum well (SQW) by a novel method. At helium temperature, we estimate a lateral hole diffusion length in the QW of 1.5 mum. However, the assumption that diffusion takes place mainly in the, SQW needs to be checked, as the measured diffusion length is the result of two competing processes: (i) hole diffusion in the SQW plane itself and (ii) hole diffusion in the barrier followed by recombination in the SQW. We present here a

Jean-Daniel Ganière

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

Radiative lifetime of negative trions in GaAs and CdTe quantum wells

Thermal-Conversion of N-Type Gaas-Si to P-Type in Excess Arsenic Vapor

Influence of Al Content in the Barrier on the Optical-Properties of Gaas/Alxga1-Xas(X=0.1-1) Multiple-Quantum-Well Structures

Luminescence Peculiarities on (Alga)as Single Quantum-Well

Growth and Characterization of Gaalas Gaas and Gainas Inp Structures - the Effect of a Pulse Metalorganic Flow

Exciton localization on basal stacking faults in a-plane epitaxial lateral overgrown GaN grown by hydride vapor phase epitaxy

Radiative behavior of negatively charged excitons in CdTe-based quantum wells: A spectral and temporal analysis

Fluorescence yield and lifetime of isolated polydiacetylene chains: Evidence for a one-dimensional exciton band in a conjugated polymer

Low-temperature time-resolved cathodoluminescence study of exciton dynamics involving basal stacking faults in a-plane GaN

Oscillatory behaviour in the nonlinear emission of semiconductor microcavities

Cathodoluminescence study of the spatial distribution of electron-hole pairs generated by an electron beam in Al0.4Ga0.6As

Cathodoluminescence and Electron-Beam Induced Current Study of Hydrogen Treatment of P-N GaAs Junction

Transmission electron microscopy and cathodoluminescence of tensile-strained Ga/sub x/In/sub 1-x/P/InP heterostructures. I. Spatial variations of the tensile stress relaxation

Photon recycling as the dominant process of luminescence generation in an electron beam excited n-InP epilayer grown on an n(+)-InP substrate

Defect diffusion and strain relaxation in epitaxial GaN laterally overgrown on (0001) sapphire under low energy electron beam irradiation

Fluorescence quantum yield and lifetime of 'red' polydiacetylene chains isolated in their crystalline monomer matrix

Cathodoluminescence intensity and dislocation contrast evolutions under electron beam excitation in epitaxial GaN laterally overgrown on (0001) sapphire

Determination of the Lateral Distribution of Electron-Hole Pairs Generated by an Electron-Beam in Al0.4Ga0.6As by Cathodoluminescence

Comparison of the Lateral Carrier Transport between a Gaas Single-Quantum-Well and the Algaas Barrier During Cathodoluminescence Excitation