Three atomic shell cluster of SiC is treated as a set of chemical bonds with tetrahedral coordination. Chemical bonds energies are determined in tight binding approximation taking into account second neighbors interaction and relaxation of atomic positions. Correlations in behavior of Al and N atoms in Si-C-Al-N system determine the quasibinary character (SiC) 1-x (AlN) x alloys. Inhomogeneous regions in (SiC) 1-x (AlN) x system were evaluated using the condition of mixing free energy minimum. We assumed that doping does not change the vibration spectra of the crystal.
A model has been developed to calculate the solubility of nitrogen in conventional binary III-V compounds. The model takes into account internal deformations due to relaxation of atoms and the statistical origin of alloys. It is shown that the dispersion of bond lengths in III-V-N solid solutions plays an important role and cannot be neglected. The solubility limit increases by more than three orders of magnitude if both sublattices relax to distances greater than the sixth nearest neighbor position.
We have investigated the influence of near-order on the electronic properties of III-V-N solutions. In nitride-containing solutions, the clustering of identical atoms as second neighbors leads to an increase in the stress energy and a strong decrease in the width of the forbidden zone. On the other hand, the electronic properties of GaInAs depend very weakly on the near-order. The reason for this is the localization of the wave function of the states of the zone edges around certain atoms.
