21 research outputs found
Design of a lattice-matched III-V-N/Si photovoltaic tandem cell monolithically integrated on silicon substrate
International audienceIn this paper, we present a comprehensive study of high efficiencies tandem solar cells monolithically grown on a silicon substrate using GaAsPN absorber layer. InGaAs(N) quantum dots and GaAsPN quantum wells have been grown recently on GaP/Si susbstrate for applications related to light emission. For photovoltaic applications, we consider the GaAsPN diluted nitride alloy as the top junction material due to both its perfect lattice matching with Si and ideal bandgap energy for current generation in association with the Si bottom cell. Numerical simulation of the top cell is performed. The effect of layer thicknesses and doping on the cell efficiency are evidenced. In these structures a tunnel junction (TJ) is needed to interconnect both the top and bottom sub-cells. We compare the simulated performances of different TJ structures and show that the GaP(n+)/Si(p+) TJ is promising to improve performances of the current-voltage characteristic
Revue des nouvelles revues marocaines
Benhlal Mohamed. Revue des nouvelles revues marocaines. In: Revue de l'Occident musulman et de la Méditerranée, n°38, 1984. pp. 195-196
Analyse descriptive d'un phénomène de mobilité scolaire descendante au sein de l'enseignement secondaire général bruxellois
"Des élèves, en nombre relativement important, ayant eu un parcours complet dans l'enseignement général et dans des établissements "bien placés" dans la hiérarchie, décident d'effectuer leur dernier degré (les deux années ou seulement la dernière) dans un estimé "moins bien placés". Autrement dit, ils effectuent une sorte de "mobilité descendante"Master [120] en sciences de l'éducation, Université catholique de Louvain, 2018La diffusion de ce mémoire n'est pas autorisée par l'institutio
Revue des nouvelles revues marocaines
Benhlal Mohamed. Revue des nouvelles revues marocaines. In: Revue de l'Occident musulman et de la Méditerranée, n°38, 1984. pp. 195-196
Transport perpendiculaire et propagation guidee dans les superreseaux GaAs-AlAs de courte peride
SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Le collège d'Azrou et la formation d'une élite berbère civile et militaire au Maroc (1927-1956)
AIX-MARSEILLE1-BU Lettres (130012101) / SudocPARIS-CDEM (751075217) / SudocSudocFranceF
An attempt to model the dielectric function in II-VI ternary compounds Hg
The dielectric function ε of II-VI ternaries is described by fitting experimental
results at room temperature to three different models. For each individual composition,
ε variations with photon energy E are well reproduced with only four harmonic
oscillators. The model dielectric function (MDF) of Adachi which is linked to the band
structure does not give better results in the description of and its
derivatives are not correctly reproduced. The MDF model of Kim et al. lead to good
descriptions both of and its derivatives in all the spectral range considered,
and it appears the most powerful model at the present time. We have not fully succeeded in
building a composition dependent model for these bulk semiconductors. The analysis of this
failure reveals that, though the materials appear good, their unknown densities of defects
appear uncorrelated with the composition of the ternaries. These non controlled defect
densities lead mainly to erratic deviations of the broadenings near critical transitions. Though
relatively small these erratic deviations on the broadenings prevent the set up of a
precise composition dependent model. variations are also calculated below
the fundamental gap in HgZnTe and CdZnTe. Zero frequency values are
compared with known experimental results. The large variation of
with composition x in prevents the revealing of the part of ε due to the
defects. In return, the effect of the defects on the crystal polarizability is evidenced in
where the variation of with x is small. This leads us to propose
that the most probable values of are near 7.1 for CdTe and 6.75 for ZnTe
Optical properties and temperature dependence of critical transitions in ZnSe
The dielectric function ε of ZnSe has been deduced from ellipsometric
measurements between 20 K and 380 K. ε is analysed around each critical
point with the standard critical point model. The variations of the different
parameters characterising each transition with temperature are presented and analysed.
The temperature coefficients of the energies of the critical transitions are given.
ε is essentially governed by the Coulomb interaction near the fundamental
gap. Thanks to the high binding energy of the exciton and the low spectral width of
the ellipsometer, the fundamental state of the exciton is found completely separated
from the first excited states and the continuum at low temperature. In return the
strong transition E1 near the L points of the Brillouin zone can be described
equally well with a 2D or an excitonic transition
Dielectric Function and Interband Transitions in HgZnTe Solid Solutions
The dielectric function in HgZn Te is found, for the first time, at 293 K. It is deduced from spectroscopic ellipsometry measurements for the entire composition range and for photon energies ranging from 0.75 eV to 5.7 eV. A detailed analysis of the chemical treatments leading to the best surfaces which correspond to the highest values of at the peak is presented. The oxydation of the surface after the last stripping is also studied. The pseudodielectric function is analysed for the critical point model. The variation, with of the parameters describing the main critical transitions and are obtained. The results are discussed in relation to the band structure and to the properties of these compounds.La fonction diélectrique des solutions solides HgZnTe est donnée, pour la première fois, à 293 K. Ces résultats sont déduits de mesures d'ellipsométrie spectroscopique dans tout le domaine de composition et pour des énergies de photon allant de 0,75 eV à 5,7 eV. Les traitements chimiques permettant d'obtenir les meilleures surfaces correspondant aux plus fortes valeurs de au pic sont analysés en détail. De même, l'oxydation de la surface est suivie par ellipsométrie. La fonction pseudodiélectrique est analysée avec le modèle de points critiques. Les variations des paramètres définissant les principales transitions et sont données en fonction de la composition . Ces résultats sont discutés en relation avec la structure de bande et les propriétés de ces solutions solides
STUDY OF VERTICAL TRANSPORT IN A SUPERLATTICE GaAs/AlAs BY TIME-RESOLVED PHOTOLUMINESCENCE
En mesurant le comportement temporel de la luminescence d'un puits quantique en fonction de l'épaisseur du super-réseau qui le sépare de la surface de l'échantillon, nous déterminons le coefficient de diffusion dans le super-réseau. Nous montrons que les excitations qui diffusent sont des excitons du super-réseau.By measuring the luminescence time behaviour of an enlarged quantum well as a function of the superlattice thickness, we determine the diffusion coefficient in the superlattice. We show that very likely the excitations which diffuse are excitons