Theoretical study of optical properties of anti phase domains in GaP

International audienceIII-V/Si heterostructures are currently investigated for silicon photonics and solar energy conversion. In particular, dilute nitride alloy GaAsPN grown on a GaP/Si platform exhibits lattice match with Si and an optimal band gap configuration for tandem solar cell devices. However, monolithic "coherent" growth of the GaP thin layer on Si suffers from the nucleation of extended structural defects, which can hamper device operation as well as the GaP/Si interface level and through their propagation inside the overall heterostructure. However, the effect of such structural defects on optical and transport properties is actually not well understood in details. In this letter, we investigate the anti phase domains defect (also called inversion domains) by means of ab initio calculations giving insights into the alteration of optical and transport properties of GaP due to the defective GaP/Si interface

High domain wall velocity at zero magnetic field induced by low current densities in spin-valve nanostripes

Current-induced magnetic domain wall motion at zero magnetic field is observed in the permalloy layer of a spin-valve-based nanostripe using photoemission electron microscopy. The domain wall movement is hampered by pinning sites, but in between them high domain wall velocities (exceeding 150 m/s) are obtained for current densities well below 10^{12} \unit{A/m^2}, suggesting that these trilayer systems are promising for applications in domain wall devices in case of well controlled pinning positions. Vertical spin currents in these structures provide a potential explanation for the increase in domain wall velocity at low current densities.Comment: Published version, Applied Physics Express 2, 023003 (2009) http://dx.doi.org/10.1143/APEX.2.02300

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

Hot Carrier Solar Cell: From Simulation to Devices

International audienceSingle junction III-V heterostructures based devices could overtake the Shockley-Queisser limit if thermalisation of photogenerated carriers can be strongly limited as in the hot carrier solar cell concept. Previous modelling and experiments have shown the interest of Multiple Quantum Wells heterostructures in the antimonide system and the importance of very thin structures. In this paper we report new data on the thermalisation rates in antimonide and phosphide heterostructures measured at ambient temperature. For the first time electrical control of hot carrier population is performed on hot carrier heterostructures device

Déplacement de parois magnétiques par injection d'un courant polarisé en spin

Cette thèse est consacrée à l étude expérimentale du déplacement de parois magnétiques par injection d un courant polarisé en spin. Le mécanisme mis en jeu est le transfert de spin. Ces expériences ont été réalisées dans des barreaux nanométriques de vanne de spin de Co/Cu/CoFeB ou Co/Cu/NiFe. Le mouvement d une paroi est étudié dans la couche ferromagnétique douce : CoFeB ou NiFe, par des mesures électriques, via l effet de magnétorésistance géante. A champ nul ou faible, la paroi est déplacée sous l action d un courant CIP (quelques 106 A/cm2), et ce dans deux directions opposées pour des courants opposés. Ces faibles valeurs de courants sont dues aux structures de vannes de spin, dans lesquelles l accumulation de spin crée des courants verticaux agissant localement sur la paroi. Des fluctuations de parois ont été observées lorsque le champ et le courant ont des effets opposés sur la paroi. Des vitesses de parois de 170 m/s ont été mesurées, par imagerie XMCD-PEEM.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Simulation électrique et optique de nanofils de Silicium en géométrie radiale pour des applications photovoltaïques

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Simulation électrique et optique de nanofils de Silicium en géométrie radiale pour des applications photovoltaïques

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Toward a III-V/Si tandem solar cell : characterization and modeling

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Ab initio investigation of defect nucleation at III-V/Si heterointerface for tandem solar cells applications

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