Modeling of structural properties of $Ge_{1-x} Sn_x$ alloys

Background. The literature indicates the possibility of creating interesting optoelectronic devices on the basis of semiconductor solid solutions of elements of group IV of the periodic system with the prospect of integration into silicon technology. The $Ge_{1-x} Sn_x$ alloy seems to be the most promising for this purpose and is intensively studied experimentally and theoretically. The aim of this work is to model the alloy's structural properties: restructuring of the crystal lattice, lengths of atomic bonds, angles between bonds depending on the composition. Materials and methods. The author investigated a $Ge_{1-x} Sn_x$ solid solution both for the practically important range of tin fraction $0 < x < 0,2$, and for any theoretically interesting value of $x$. There was simulated a cluster of about 4 thousand atoms, which was investigated by molecular dynamics (MD) using the Tersoff potential. Results. The researcher has obtained dependences of lattice parameters, bond lengths, angles between bonds on the composition, as well as compared with experimental and calculated (ab initio) results. There has been discovered a deviation from the Vegard law, as well as significantly different contributions of Ge-Ge, Ge-Sn, Sn-Sn bonds in the lattice distortion when changing the composition of the alloy. Conclusions. The obtained results can be used in evaluation of the elastic-stress state of GeSn films grown on various substrates. The study of the $Ge_{1-x} Sn_x$ alloy by the MD method allows to conduct researches on much larger clusters than by quantum-mechanical calculations and to obtain comparable results