Showing papers by "Jean Massies published in 1995"
TL;DR: In this paper, two classes of non-reactive and reactive surfactants effective during homoepitaxy and hetero-epitactic, respectively, are presented.
40 citations
TL;DR: This work has shown that through repeated treatment with Na6(CO3)(SO4)2, Na3(SO4), Na2SO4, and Na2CO3 (Na2CO4) during the first week of intoxication, Na2Co3 can be modelled on a surface-based basis and show similar properties to that of a drug-free environment.
Abstract: Photoluminescence, reflectivity, and thermally detected optical-absorption (TDOA) experiments have been performed at liquid-helium temperatures on two strained ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs quantum-well (QW) structures grown by metalorganic molecular-beam epitaxy (MOMBE). The QW thicknesses vary from 3--15 ML and 4--16 ML by two monolayer (ML) steps. It is demonstrated that the MOMBE technique allows the thickness to be controlled with an accuracy of 1 ML. The electron--heavy-hole excitonic transitions (${\mathit{e}}_{1}$${\mathrm{hh}}_{1}$) are detected for all the QW's. TDOA enables the light-hole excitonic transition to be observed for the thinnest well in the second sample. The QW excitonic absorption energies are compared with calculations within the framework of the envelope-function approximation by taking into account the strain effects and the indium segregation phenomenon. An accurate determination of the strain conduction-band offset is derived (${\mathit{Q}}_{\mathit{c}}$=0.64\ifmmode\pm\else\textpm\fi{}0.01) and it is found that the indium segregation is very weak at the QW interfaces compared to structures grown by MBE. The light-hole band configuration is type I for the evaluated alloy composition (x=0.21--0.22). Under low excitation intensity, intermediate photoluminescence emissions appear between the ${\mathit{e}}_{1}$${\mathrm{hh}}_{1}$ lines corresponding to nominal thicknesses; they can be associated with fluctuations of 1 ML thickness, which are reported, to our knowledge, for the first time, in this type of QW system. Efficient thermally activated interwell transfer of excitons is also in evidence from photoluminescence experiments. A simple model is used to account for the transfer from narrower to broader wells when the temperature is increased.
22 citations
Abstract: The evolution of surface roughness and the subsequent plastic relaxation mechanisms have been studied by transmission electron microscopy (TEM) as a function of the thickness of highly strained In0.30Ga0.70As layers on GaAs(001). The following stages have been observed: formation of coherent islands, coalescence of islands, and nucleation of dislocations at the troughs of the surface ripples. Dislocations are thus systematically generated where the highest stress concentrations are expected, according to recent theoretical predictions. It is the first time such a plastic relaxation mechanism has been observed in highly strained semiconductor heterostructures.
16 citations
TL;DR: In this paper, the photoluminescence energy of strained (Ga, In) quantum wells is linked to a blue shift of intrinsic ground state excitonic transition energies, which is studied as a function of substrate misorientation angle, well width and indium surface segregation level.
Abstract: The photoluminescence energy of strained (Ga, In)As quantum wells grown on (001) GaAs slightly misoriented (2 degrees-6 degrees) towards (111)A exhibits a blue shift when compared to quantum wells grown on perfectly oriented substrates. It is shown that this observation is linked to a blue shift of intrinsic ground state excitonic transition energies. This effect is studied as a function of substrate misorientation angle, well width and indium surface segregation level. In order to understand its origin, various hypotheses were examined: regular shrinkage of well width due to terrace edges, additionnal stress of the well material at the step edges, and orientation dependent In segregation. It appears that the first two combined effects provide the best description of the experimental tendency.
12 citations
TL;DR: In this paper, a combined application of in-situ reflection high-energy electron diffraction, X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy, the state of the Si(001) surface, the structure of GaN grown on this surface and the orientation relationship between substrate and layer were determined.
Abstract: Electron cyclotron resonance plasma-assisted molecular-beam epitaxy has been used to grow hexagonal and cubic GaN crystal layers on Si(100). By a combined application of in-situ reflection high-energy electron diffraction, X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy, the state of the Si(001) surface, the structure of GaN grown on this surface and the orientation relationship between substrate and layer were determined. Substrate cleaning, surface reconstruction and carbon surface contamination were found to have a strong effect on GaN growth in the early stage of epitaxy (up to 2000 Angstrom). While polycrystalline GaN in its hexagonal phase is obtained on a clean Si(001) surface, cubic GaN grows epitaxially on a Si(001)c(4 x 4) surface covered by small three-dimensional cubic beta-SiC crystallites.
9 citations
TL;DR: The high sensitivity of the magnetoluminescence to the modifications of the wave function, even on the scale of a single monolayer, has been used to deduce experimentally the dependence of the effective reduced mass on the well width.
Abstract: The wave-function localization on a single-monolayer length scale is studied by magnetophotoluminescence in GaSb quantum wells of thickness ranging between 5 and 40 ML. The excitonic effects are found to be important only in the low-field range (B2 T), whereas free-carrier localization dominates at higher field values. Variational calculations of the excitonic transverse extension provide a quantitative description of the experimental data. The high sensitivity of the magnetoluminescence to the modifications of the wave function, even on the scale of a single monolayer, has been used to deduce experimentally the dependence of the effective reduced mass on the well width.
5 citations
TL;DR: In this paper, the wave function on the scale length of a single monolayer has been studied by magnetophotoluminescence in GaSb/AlGaSb quantum wells.
Abstract: The localization of the wave function on the scale length of a single monolayer has been studied by magnetophotoluminescence in GaSb/AlGaSb quantum wells. The studied range of well width includes the direct-indirect transition involvingL-point conduction states and Γ-point valence states induced by quantum size effects. Separate carrier localization dominates at higher field values (B>2T), whereas the excitonic effects are important only in the low field range. Variational calculations of the excitonic transverse extension provide a quantitative description of the experimental data. The dependence of the effective reduced mass on the well width has been obtained experimentally by magnetoluminescence that is highly sensitive to the modifications of the wave function, even on the scale of a single monolayer.