Model of the local structure of random ternary alloys: Experiment versus theory

Abstract

We have performed an extended x-ray-absorption fine-structure (EXAFS) measurement of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te solid solutions for various concentrations x in the single-phase range 0\ensuremath{\le}x\ensuremath{\le}0.7. Data have been collected on the Mn K, Cd ${L}_{\mathrm{III}}$, and Te ${L}_{\mathrm{III}}$ edges. We have found well-defined different nearest-neighbor Cd-Te and Mn-Te distances almost independent of x. A model of the microscopic structure of the zinc-blende-type ${A}_{1\mathrm{\ensuremath{-}}x}$${B}_{x}$C ternary alloys based on a random distribution of cations has been developed. The model describes the bimodal distribution of near-neighbor distances in terms of distortion of the anion sublattice (the cation sublattice is assumed to remain fixed) with use only of the lattice constants of the alloy and the bond-stretching constants of each binary component. Its application to ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te and ${\mathrm{In}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Ga}}_{\mathrm{x}}$As alloys is proved to be in good agreement with the EXAFS results. Within the framework of this model we also consider the problem of the structural stability of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te.