Etude ab initio de composés et d'alliages ternaires II-IV à base de béryllium

Abstract : The electronic structure of alloys has gained renewed interest during recent years because of the growing technological importance of wide-band-gap semiconductors. In this study, we have noticed novel II-VI materials containing beryllium chalcogenides which have considerable potential to overcome life time problems encountered in conventional II-VI based alloys. Thus our study aims to investigate beryllium chalcogenides and Zn1-xBexSe alloy with beryllium contents over the full composition range. The first part of this work is devoted to the study of the properties of the beryllium chalcogenides compounds. The ab initio simulation is able to predict the effect of the pressure on these compounds, their structural stability, the nature of the band gap as well as the ionic character of atomic bonding. In the second part we report the results of a self-consistent pseudopotential study including structural, optoelectronic and thermodynamic properties of cubic Zn1-xBexSe semiconductor alloy. The use of a 64 atoms supercell makes possible to underline the beryllium incorporation influence on the band gap evolution. The bowing parameter which characterizes the nonlinear dependence of the direct band gap on the alloy composition was derived for the Zn1-xBexSe alloy system. The investigation of the origin of the optical bowing shows a strongest contribution due to the structural effect. The way in which structural relaxation is carried out is illustrated by the first and second nearest neighbors distances behavior reported according to the beryllium molar fraction. Besides, a regular solution model was used to investigate the thermodynamic stability of Zn1-xBexSe, which mainly indicates a wide phase miscibility of gap
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Abid Berghout. Etude ab initio de composés et d'alliages ternaires II-IV à base de béryllium. Matière Condensée [cond-mat]. Université Paul Verlaine - Metz, 2007. Français. ⟨NNT : 2007METZ002S⟩. ⟨tel-01775486⟩

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