Statistical model for site occupation preferences and shapes of elemental tetrahedra in the zinc-blende type semiconductors GaInAs, GaAsP, ZnCdTe

A seven-axiom statistical strained-tetrahedra model is developed to describe zinc-blende ternary compound local structures. Validation is obtained 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 such compounds at different ion contents. The elemental configuration tetrahedron sizes and shapes derived and their site occupation preferences with respect to random are presented fully determined for GaAsP and GaInAs. Retrieved experimental data for ZnCdTe, though limited, allow definition of all the tetrahedra except that of the configuration with a central Te ion and two cations of each kind at the vertices (Cd or Zn). It is shown that site occupation preferences can normally be derived from EXAFS observation of variation in either distance in co-ordination number measurements as a function of dilution, both sets giving results in good agreement.