Thermodynamic properties of ternary semiconducting alloys

Using the new information supplied by EXAFS fine structure measurements and the results of our structural model, we compute the bond probability of a few ternary semiconducting III-V and II-VI alloys as a function of temperature and composition in the framework of a modified quasi-chemical approximation. We derive the thermodynamic functions of mixing, considering both elastic and chemical contributions to the bond energies. We examine how the deviation from the full randomness affects the ordering of such alloys and we construct the phase diagrams in the region of phase separation. Possible formation of ordered compounds at low temperatures is predicted.