Croissance de semi-conducteurs à grand gap

La modélisation et la simulation des procédés de croissance tel que le transport physique en phase vapeur (PVT), le dépôt chimique en phase vapeur (CVD ou HTCVD) et les techniques hybrides (CFPVT), sont suffisamment au point pour être utilisées comme des outils de compréhension des phénomènes physiques couplés et comme des outils de conception de nouveaux procédés et d'optimisation de procédés existants. La modélisation des procédés d'élaboration rassemble plusieurs voies physico-chimiques de complexité variable, depuis des études thermodynamiques et/ou cinétiques jusqu'aux transferts simultanés de matière et de chaleur couplées avec les bases de données et propriétés thermodynamiques et/ou cinétiques et de transport. Différentes voies de modélisation sont utilisées, thermodynamiques, cinétique ou transfert de masse, de façon couplée ou découplée, permettant de visualiser l'évolution de la croissance et ainsi comprendre le rôle complexe et fortement couplé des phénomènes

Overview of SiC bulk growth processes

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Vapor Phase vs. Liquid Phase: What is the Best Choice for the Growth of Bulk 3C-SiC Crystals?

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Cristallogenèse des semi-conducteurs à grand gap : contexte et enjeux

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Application of an axial next-nearest-neighbor Ising model to the description of Mn+1AXn phases

International audienceWe show that some important features characterizing the M(n+1)AX(n) phases, a family of hexagonal-structure ternary carbides and nitrides (X) including a transition metal (M) and an A-group element (A), can be reproduced by modifying the spin model known as the axial next-nearest-neighbor Ising model into a form where pseudospin inversion changes the system energy and requires the inclusion of single- and three-spin products. We describe the various MAX phases in terms of M-A or M-X bilayer stacking along the c axis. We discuss the dependence of the cohesive energy and phase stability on coupling parameters which characterize the first-and second-neighbor interactions between those bilayers. We also address the case of "hybrid" MAX phases

Micropipe-induced birefringence in 6H silicon carbide

International audienceThe micropipe-induced birefringence of 6H silicon carbide (SiC) is measured and quantitatively modelled. A good agreement can be obtained between theory and experiment, provided that background residual stress is added to the local dislocation-induced stress. Observations are compatible with or predictable from the Burgers vector values, and birefringence is shown to be an interesting tool for probing the nature of the dislocations associated with e. g. micropipes; it is also faster than and complementary to the more involved techniques of transmission electron microscopy or X-ray topography

Morphological instabilities induced by foreign particles and Ehrlich-Schwoebel effect during the two-dimensional growth of crystalline Ti3SiC2

International audienceAtomic step edges can exhibit a morphological instability under step-flow conditions (the so-called Bales-Zangwill instability). Such instabilities are ascribed to the fact that adatoms approaching a step from opposite directions do not see the same energy barrier to step incorporation (Ehrlich-Schwoebel or ES effect). Due to the very low solubility of carbon in the melt, Ti3SiC2 grown from a Ti-Si liquid phase is an experimental example of two-dimensional (2D) growth. In addition, the ratio between the incorporation rates at a step from the lower terrace and from the upper terrace is probably very high. The latter particularity makes the steps lying below a terrace including an unstable step independent from the forming instability, so that an instability front may appear just on one terrace, whereas the neighboring steps remain stable. Besides, foreign-particle-assisted growth can result in the production of extremely elongated islands or peninsulas on a given terrace, which then form very long grooves between the island edge and the upper terrace step. This provides the ability to test the respective stability of lines and grooves on a single terrace, and to verify that shrinking grooves are more stable than simple steps, as recently demonstrated by another author