A thermodynamical model of molecular beam epitaxy, application to the growth of II VI semiconductors
We present a model of molecular beam epitaxy based on thermodynamics. The equilibrium between a compound or a ternary alloy with the gas phase is illustrated in the case of HgTe and CdHgTe. The meaning of equilibrium pressure is analysed and we make the assumption that the fluxes leaving the actual growing compound are linked by the mass action law where the pressures are transformed into the equivalent fluxes. A detailed balance of the species leaving or arriving at the surface is then possible and leads to a set of equations which can be solved to predict the growth rate, the x value of a ternary alloy, the excess of one of the species, the incorporation coefficient. Examples of calculation are shown for CdTe and Cd x Hg 1−x Te and are compared with experimental results and show a good agreement. The main interest of this model resides in its ability to predict the effects of the modification of one of the growth parameter. Nevertheless it predicts only the limit conditions which are not necessary reach due to the kinetic of the reactions Presentation d'un modele thermodynamique de l'epitaxie par jets moleculaires. Illustration par les cas de HgTe et CdHgTe. La comparaison avec les resultats experimentaux montre la validite des previsions du modele, dont l'interet principal est de permettre d'evaluer l'influence de la modification d'un parametre de croissance. La validite de ce modele est cependant limitee si la cinetique des reactions ne permet pas d'atteindre l'equilibre; ce n'est pas le cas pour les alliages II-VI etudies ici
Composition and thickness distribution of HgCdTe molecular beam epitaxy wafers by infrared microscope mapping
A technique based on infrared microscopy and the automatic fitting of the transmissivity curves has been developed to measure the composition and thickness distributions of HgCdTe wafers grown by molecular beam epitaxy (MBE). This technique has the ability to handle many measuring points, provides high spatial resolution, and can be used for the routine characterization of the uniformity of HgCdTe grown on CdZnTe and Si-based substrates. The mapping measurements both are helpful for infrared detector fabrication and can help MBE growers adjust growth conditions and optimize equipment configurations to grow large area uniform HgCdTe material. The reason that limits the enhancement of uniformity was also discussed.
The Origins of Jewish Guilt: Psychological, Theological, and Cultural Perspectives
The idea that guilt and Judaism are closely interlinked has a long historical legacy. After discussing recent work on anthropology and emotion focusing on shame and guilt, we examine three theories purporting to account for this link: psychoanalytic, theological, and guilt as a cultural stereotype particularly the notion of the Jewish mother.