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 $\varepsilon (E)$ and its derivatives are not correctly reproduced. The MDF model of Kim et al. lead to good descriptions both of $\varepsilon (E)$ 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. $\varepsilon (E)$ variations are also calculated below the fundamental gap in HgZnTe and CdZnTe. Zero frequency $(\varepsilon_{\infty})$ values are compared with known experimental results. The large variation of $\varepsilon_{\infty}$ with composition x in $\mathrm{Hg}_{1-x}\mathrm{Zn}_{x}\mathrm{Te}$ 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 $\mathrm{Cd}_{1-x}\mathrm{Zn}_{x}\mathrm{Te}$ where the variation of $\varepsilon_{\infty}$ with x is small. This leads us to propose that the most probable values of $\varepsilon_{\infty}$ 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 Hg1−x_{\bf 1-x}Znx_{\bf x}Te Solid Solutions

The dielectric function $\epsilon_{\rm r} + i\epsilon_{\rm i}$ in Hg$_{1-x}$Zn$_x$ 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 $\epsilon_{\rm i}$ at the $E_2$ 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 $x$ of the parameters describing the main critical transitions $E_0,\,E_0 + {\rm \Delta}_0,\, E_1,\,E_1 + {\rm \Delta}_1$ and $E_2$ are obtained. The results are discussed in relation to the band structure and to the properties of these compounds.La fonction diélectrique $\epsilon_{\rm r} + i\epsilon_{\rm i}$ des solutions solides Hg$_{1-x}$Zn$_x$Te 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 $\epsilon_{\rm i}$ au pic $E_2$ 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 $E_0,\,E_0 + {\rm \Delta}_0,\, E_1,\,E_1 + {\rm \Delta}_1$ et $E_2$ sont données en fonction de la composition $x$. 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