Statistical model for atomic distances and site occupation in zinc-blende diluted magnetic semiconductors (DMSs)

The statistical strained-tetrahedra model is applied to describe the behaviour of zinc-blende ternary diluted magnetic semiconductors (DMSs) with manganese. Validation is confirmed by comparing calculated and published extended X-ray absorption fine structure (EXAFS) measurements relative to average nearest-neighbour and next nearest-neighbour inter-ion distances in zinc blende DMSs at different Mn contents. The sizes, shapes and site occupation preferences (SOPs) with respect to random, of elemental-configuration tetrahedra, are fully defined for ZnMnSe, ZnMnS and ZnMnTe. For CdMnTe and HgMnTe, all the tetrahedra are defined, with the exception of the configuration with a central Te ion and two cations of each kind at the vertices, which remains inaccessible due to lack of relative experimental data. It is shown that SOPs can normally be derived from EXAFS observation of the variation either of distance or of coordination-number measurements as a function of dilution, with both sets giving results in good agreement.