Calculations of homogeneous region in Ga1−xAlxAs and GaAs1−xPx ternary solid solutions

Ternary solid solutions of A^IIIB^V compounds are considered as pseudobinary A(x)^IIIB(x)^v compounds, where the behaviour of A(x)^III and B(x)^v pseudoatoms is quite similar to A^III and B^v atoms in a binary A^IIIB^v crystal. Weak dependence of point defect contribution into Gibb's energy of A^IIIB^v crystal on its defect nature, random character of ternary solid solutions of A^IIIB^v compounds allow to use already for binary compounds developed formalism in the determination of component thermodynamic potentials of solid solution. Basing on literature data for the equilibrium solidus of AlAs the approximation for the temperature dependence of thermodynamic potential of an AB quasimolecule in A^IIIB^v crystal is revised. This result together with the well-known parameters for the equilibrium liquidus in Ga–P, Ga–As, and Al–As systems were used for calculations of the nonstoichiometric factor at the boundary of a homogeneous region in Ga_1−xAl_xAs and GaAs_1−xP_x ternary solid solutions. The results are compared with the known literature data.