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Dive into the research topics where Marie-Pierre Chauvat is active.

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Featured researches published by Marie-Pierre Chauvat.


Journal of Applied Physics | 2008

Ga kinetics in plasma-assisted molecular-beam epitaxy of GaN(112¯2): Effect on the structural and optical properties

L. Lahourcade; J. P. Renard; B. Gayral; E. Monroy; Marie-Pierre Chauvat; P. Ruterana

GaN directly deposited on m-sapphire by plasma-assisted molecular-beam epitaxy settles into two main crystalline orientation domains: GaN﴾112¯2﴿ and GaN{101¯3}. The dominant phase is GaN﴾112¯2﴿ with GaN║ sapphire and GaN║ sapphire in-plane epitaxial relationships. Deposition of GaN on top of an AlN﴾112¯2﴿ buffer layer and growth under slightly Ga-rich conditions reduce GaN{101¯3} precipitates below the detection limits. Studies of Ga adsorption demonstrate that it is possible to stabilize up to one Ga monolayer on the GaN﴾112¯2﴿ surface. The presence of this monolayer of Ga excess on the growth front reduces the ﴾112¯2﴿ surface energy and hence minimizes the surface roughness. Photoluminescence from two-dimensional GaN﴾112¯2﴿ layers is dominated by a near-band-edge emission, which is assigned to excitons bound to stacking faults, present with a density around 3x105 cm−1.


IEEE Transactions on Applied Superconductivity | 2009

Epitaxial Growth of Sputtered Ultra-Thin NbN Layers and Junctions on Sapphire

J.-C. Villegier; S. Bouat; Paul Cavalier; R. Setzu; R. Espiau de Lamaestre; Corentin Jorel; P. Odier; Bruno Guillet; Laurence Méchin; Marie-Pierre Chauvat; P. Ruterana

High crystalline quality of ultra-thin NbN layers and of NbN-MgO-NbN tri-layers, epitaxially grown by DC-magnetron sputtering in the superconducting B1-cubic phase has been achieved in a reproducible way on three different orientations of sapphire substrates i.e. R-, A- and M-planes. Significant improvements such as higher Tc, higher Jc and lower resistivity have been obtained by growing un-twined (110) oriented NbN layers on M-plane orientation of sapphire. Uniform, low roughness, 3-5 nm thick films with Tc above 12 K and Jc above 5 MA/cm2 at 4.2 K were obtained. Characterizations by TEM, AFM and X-Ray diffraction evidence that growth of un-twined NbN on M-plane lead to a better epitaxy in comparison with twinned films observed on other sapphire orientations. We observe that the reduction of the substrate temperature from 600degC to 300degC during the deposition of NbN or NbN-MgO-NbN layers thicker than 20 nm prevents the nucleation of the competing HCP NbN phase. Moreover, 1.5 nm thick AlN or MgO over-layers sputtered in-situ prevent ultra-thin NbN films degradation through aging. The formation of Nb2NyO5-x ( ~ 2.2 nm) at the unprotected NbN surface and of interfacial NbO ( ~ 0.7 nm) native oxides has been observed by XPS. It is forecasted that such improvements in ultra-thin NbN films deposited uniformly on 3 and 4 inch sapphire wafers is a key in the future development of superconducting single photon detectors, THz HEB mixers and also in low noise quantum analogical and digital Josephson devices.


Journal of Applied Physics | 2014

High In-content InGaN layers synthesized by plasma-assisted molecular-beam epitaxy: Growth conditions, strain relaxation, and In incorporation kinetics

S. Valdueza-Felip; E. Bellet-Amalric; A. Núñez-Cascajero; Yi Wang; Marie-Pierre Chauvat; P. Ruterana; S. Pouget; K. Lorenz; E. Alves; E. Monroy

We report the interplay between In incorporation and strain relaxation kinetics in high-In-content InxGa1-xN (x = 0.3) layers grown by plasma-assisted molecular-beam epitaxy. For In mole fractions x = 0.13–0.48, best structural and morphological qualities are obtained under In excess conditions, at In accumulation limit, and at a growth temperature where InGaN decomposition is active. Under such conditions, in situ and ex situ analyses of the evolution of the crystalline structure with the layer thickness point to an onset of misfit relaxation after the growth of 40 nm, and a gradual relaxation during more than 200 nm, which results in an inhomogeneous strain distribution along the growth axis. This process is associated with a compositional pulling effect, i.e., indium incorporation is partially inhibited in presence of compressive strain, resulting in a compositional gradient with increasing In mole fraction towards the surface.


Journal of Physics: Condensed Matter | 2010

Defect structure in heteroepitaxial semipolar (11\bar {2} 2 ) (Ga, Al)N

Y. Arroyo Rojas Dasilva; Marie-Pierre Chauvat; P. Ruterana; L. Lahourcade; E. Monroy; G. Nataf

The defect structures in semipolar (1122)-GaN, AlN layers grown on m-sapphire by metal organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) are characterized by transmission electron microscopy. The epitaxial relationships are identified as [1010](GaN) || [1120]sap and [1213](GaN) || [0001]sap. Defects are identified as mostly partial dislocations, I1-basal and prismatic stacking faults. The density of dislocations is of the order of 5.5 × 10(9) cm(-2). They are Frank-Shockley partial dislocations with b = 1/6<2023> (90%), Shockley partial dislocations with b = 1/3<1010> (8%) and perfect dislocations of a-type with b = 1/3<1120> (2%). This is in contrast with the growth in c- or a-orientations, where the large majority of extended defects consists of perfect dislocations. Upon MBE regrowth of GaN on MOVPE GaN, no additional defects are generated, although the defects in the substrate propagate through the overgrown layer. However, in the case of MBE deposition of AlN on MOVPE GaN, new threading dislocations of the type b = 1/3<1123> are generated taking stepped and curved structures along their lines.


Journal of Applied Physics | 2013

Systematic study of near-infrared intersubband absorption of polar and semipolar GaN/AlN quantum wells

H. Machhadani; M. Beeler; S. Sakr; E. Warde; Y. Kotsar; M. Tchernycheva; Marie-Pierre Chauvat; P. Ruterana; G. Nataf; Ph. de Mierry; E. Monroy; F. H. Julien

We report on the observation of intersubband absorption in GaN/AlN quantum well superlattices grown on (112¯2)-oriented GaN. The absorption is tuned in the 1.5–4.5 μm wavelength range by adjusting the well thickness. The semipolar samples are compared with polar samples with identical well thickness grown during the same run. The intersubband absorption of semipolar samples shows a significant red shift with respect to the polar ones due to the reduction of the internal electric field in the quantum wells. The experimental results are compared with simulations and confirm the reduction of the polarization discontinuity along the growth axis in the semipolar case. The absorption spectral shape depends on the sample growth direction: for polar quantum wells the intersubband spectrum is a sum of Lorentzian resonances, whereas a Gaussian shape is observed in the semipolar case. This dissimilarity is explained by different carrier localization in these two cases.


Applied Physics Letters | 2011

Efficient blocking of planar defects by prismatic stacking faults in semipolar (112¯2)-GaN layers on m-sapphire by epitaxial lateral overgrowth

B. Lacroix; Marie-Pierre Chauvat; P. Ruterana; G. Nataf; P. de Mierry

For the next-generation solid state lighting, the production of high quality semipolar (112¯2) GaN layers on sapphire obtained using asymmetric epitaxial lateral overgrowth (ELO) method has been investigated. This type of ELO leads to efficient blocking of the basal stacking faults (BSFs) in the bulk, and enables the formation of nondefective layers at the surface. The BSFs terminate due to generation of prismatic stacking faults along a well defined boundary. The corresponding intensity of GaN band edge photoluminescence emission is increased by more than four orders of magnitude in comparison to that from semipolar templates.


Applied Physics Letters | 2009

Mg doping and its effect on the semipolar GaN(112¯2) growth kinetics

L. Lahourcade; Julien Pernot; A. Wirthmüller; Marie-Pierre Chauvat; P. Ruterana; A. Laufer; M. Eickhoff; E. Monroy

We report the effect of Mg doping on the growth kinetics of semipolar GaN(112¯2) synthesized by plasma-assisted molecular-beam epitaxy. Mg tends to segregate on the surface, inhibiting the formation of the self-regulated Ga film which is used as a surfactant for the growth of undoped and Si-doped GaN(112¯2). We observe an enhancement of Mg incorporation in GaN(112¯2) compared to GaN(0001). Typical structural defects or polarity inversion domains found in Mg-doped GaN(0001) were not observed for the semipolar films investigated in the present study.


Journal of Physics D | 2011

The high sensitivity of InN under rare earth ion implantation at medium range energy

B. Lacroix; Marie-Pierre Chauvat; P. Ruterana; K. Lorenz; E. Alves; A Syrkin

In this work, the damage formation in InN layers has been investigated subsequent to europium implantation at 300 keV and room temperature. The layers of several micrometres were produced by hydride vapour phase epitaxy and used as matrices for ion implantation experiments due to their good crystalline quality. From this investigation, it is shown that InN exhibits a low stability under rare earth ion implantation. Starting at a low fluence of around 5 × 1012 Eu cm−2, an extensive modification of the surface layer takes place. The dissociation of InN and the presence of misoriented nanograins are observed in the damaged area. Analysis by electron diffraction indicates that the nanograins correspond to indium oxide In2O3.


Nanotechnology | 2014

Influence of nanoscale faceting on the tunneling properties of near broken gap InAs/AlGaSb heterojunctions grown by selective area epitaxy

Ludovic Desplanque; Maria Fahed; Xiang-Lei Han; Vinay Kumar Chinni; David Troadec; Marie-Pierre Chauvat; P. Ruterana; Xavier Wallart

We report on the selective area molecular beam epitaxy of InAs/AlGaSb heterostructures on a GaSb (001) substrate. This method is used to realize Esaki tunnel diodes with a tunneling area down to 50 nm × 50 nm. The impact of the size reduction on the peak current density of the diode is investigated, and we show how the formation of the InAs facets can deeply affect the band-to-band tunneling properties of the heterostructure. This phenomenon is explained by the surface-dependent incorporation of Si dopant during growth.


Semiconductor Science and Technology | 2015

Rare earth ion implantation and optical activation in nitride semiconductors for multicolor emission

P. Ruterana; Marie-Pierre Chauvat; K. Lorenz

In order to understand the behavior of nitride semiconductors when submitted to ion implantation, we have used 300 keV europium at fluences from 1012 to above 1017 ions cm−2. Subsequently, Rutherford backscattering (RBS), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to investigate the evolution of damage. The optical properties were investigated prior to and after annealing. It was found that the behavior of the three compounds (AlN, GaN InN) under ion implantation is rather different: whereas InN breaks down at very low fluences (~1012 ions cm−2), the damage formation mechanisms are similar in AlN and GaN. In both compounds, extended defects such as stacking faults play a critical role. However, they exhibit different stability, as a consequence, GaN transforms to nanocrystalline state from the surface at a fluence of around 2.5 × 1015 ions cm−2, whereas AlN undergoes a chemical amorphization starting at the projected range (Rp), when implanted to extremely high Eu fluences >1017 ionscm−2. As for the optical activation, the formation of highly stable extended defects in these compounds constitutes a real challenge for the annealing of heavily doped layers, and it was noticed that for a substantial optical activation, the implantation fluences should be kept low (<1015 Eu at cm−2).

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Dive into the Marie-Pierre Chauvat's collaboration.

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P. Ruterana

Centre national de la recherche scientifique

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K. Lorenz

Instituto Superior Técnico

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E. Monroy

Centre national de la recherche scientifique

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L. Lahourcade

Centre national de la recherche scientifique

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Laurence Méchin

Centre national de la recherche scientifique

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E. Alves

Instituto Superior Técnico

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M. Morales

Centre national de la recherche scientifique

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B. Lacroix

Centre national de la recherche scientifique

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G. Nataf

Centre national de la recherche scientifique

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M. Tordjman

Centre national de la recherche scientifique

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