Hybrid MBE-CBE Growth and Characterization of undoped In 0,53 Ga 0,47 As on Fe-InP(001) for avalanche photodiodes (APDs)

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Enzyme immobilised novel core–shell superparamagnetic nanocomposites for enantioselective formation of 4-(R)-hydroxycyclopent-2-en-1-(S)-acetate

Lipase immobilized novel high surface area core–shell superparamagnetic nanoparticles have been fabricated and used as efficient reusable catalysts for the selective production of pharmaceutically important chiral isomers from meso-cyclopent-2-en-1,4-diacetate

Préparation d’un tampon poreux pour accommoder les contraintes mécaniques dans une hétérostructure épitaxiale de Ge/Si

Dans cette thèse, nous avons investigué le potentiel d’un tampon poreux à accommoder la contrainte mécanique qui se développe en épitaxie, lors de la croissance d’une couche en désaccord de mailles avec le substrat hôte. La transmission de l’ordre cristallin du substrat à la couche est l’essence de l’épitaxie dont le siège est la surface du substrat. Ses deux éléments qui sont le paramètre de maille et l’état de surface mettent l’accent sur le rôle important du substrat en hétéroépitaxie. Un substrat conventionnel est massif comparé à une couche mince. Ce rapport force en grande partie la contrainte épitaxiale dans la couche qui s’adapte élastiquement en début de croissance, mais atteint rapidement un seuil où la création de défauts cristallins de types dislocations devient inévitable pour relaxer plastiquement l’excès de la contrainte infligée à la couche par le substrat. C’est ainsi que nous avons étudié un pseudosubstrat formé d’une combinaison de nanocristallites en silicium enveloppées par un enrobage en pseudographène. Grâce à une revue détaillée de l’état de l’art, une caractérisation structurale par diffraction des rayons X et une simulation du comportement mécanique de la structure étudiée par la méthode des éléments, nous avons confirmé que le traitement plasma de la surface, développé dans cette thèse, préserve les propriétés élastiques souples du tampon poreux en même temps que sa stabilité thermique vis-à-vis des températures de croissance typiques en épitaxie. En parallèle, nous avons amorcé des travaux dans notre laboratoire et en collaboration externe pour tester ultimement le potentiel du tampon poreux dans un système épitaxial. Tous les résultats obtenus dans le cadre de cette thèse mettent en valeur le tampon poreux comme un candidat potentiel pour la croissance hétéroépitaxiale

Surface preparation of porous Si-graphene nanocomposites for heteroepitaxy

International audienceWe have investigated the fabrication process of an alternative approach for a direct integration of epitaxial structures onto a foreign substrate. Our approach is based on the synthesis of a nanocomposite made of graphene-like carbon and porous silicon (GPSi). The nanocomposite was produced by anodization etching of a silicon substrate, followed by a thermal carbonization step. The main study focused on the preparation of the nanocomposite surface for subsequent epitaxial deposition. While the nanocomposite must retain its carbon content for thermal stability at epitaxial temperatures, the surface must be stripped of its residual carbon to expose the silicon crystal and support the layer nucleation. Our results show that the porous silicon (PSi) substrate, carbonized at 750 • C and subjected to an O 2 plasma treatment of 20W during 12s, presented a carbon-free surface, while the bulk porous structure retained its carbon coating. Subsequent growth of a crystalline GaAs thin film demonstrated the substrate ability to support epitaxy

Growth of Ge epilayers using iso-butylgermane (IBGe) and its memory effect in an III-V chemical beam epitaxy reactor

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Uprooting defects to enable high-performance III–V optoelectronic devices on silicon

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Hybrid epitaxy technique for the growth of high-quality AlInAs and GaInAs layers on InP substrates

International audienceThe quality and properties of epitaxial films are strongly determined by the reactor type and the precursor source phase. Such parameters can impose limitations in terms of background doping, interface sharpness, clustering, phase separation, and homogeneity. The authors have implemented a hybrid epitaxy technique that employs, simultaneously, vapor and solid sources as group III precursors. The system combines the high throughput and the versatility of gas sources as well as the high purity of solid sources. Using this technique, the authors successfully demonstrated epitaxial growth of Al0.48In0.52As and Ga0.47In0.53As layers on Fe-doped semi-insulating InP (001) substrates with interesting properties, compared with the epilayers grown by more standard techniques (chemical beam epitaxy, metal-organic chemical vapor deposition, and MBE). For AlInAs growth, trimethylindium and solid aluminum were used as In and Al precursors, respectively. In the case of GaInAs, triethylgallium and solid indium were used, respectively, as Ga and In precursors. Thermally cracked arsine (AsH3) was used as an As (group V) precursor for both alloys. The AlInAs and GaInAs epilayers grown at a temperature of 500 °C exhibited featureless surfaces with RMS roughness of 0.2 and 1 nm, respectively. Lattice mismatch is of 134 ppm, for AlInAs, and −96 ppm, for GaInAs, which were determined from high-resolution x-ray diffraction (HR-XRD) patterns and showed a large number of Pendellösung fringes, indicating a high crystalline quality. An FWHM of 18.5 arcs was obtained for GaInAs epilayers, while HR-XRD mapping of a full 2-in. wafer confirmed a viable lattice mismatch homogeneity (standard deviation of 0.026%) for as-grown layers. The authors observed room-temperature background doping values as low as 3 × 1015 cm−3, for AlInAs, and 1 × 1015 cm−3, for GaInAs. Analysis of the PL spectra at 20 K showed an FWHM of 8 meV, for AlInAs, and 9.7 meV, for GaInAs, demonstrating a very good optical quality of the epilayers. In addition, they have investigated the effects of the growth temperature and of the arsine pressure on epilayer properties. They also discuss the optimum conditions for the growth of high-quality Al0.48In0.52As and Ga0.47In0.53As layers on InP (001) substrates using this hybrid epitaxy technique