Thermodynamic analysis of the short-range clustering in III V solid solutions

Abstract

An extension of the « D.L.P. » theory of Stringfellow taking clustering into account has been applied both to pseudobinary, pseudoternary and pseudoquaternary III V alloys. For alloys with two sites sublattices, this clustering tendency is introduced in each sublattice of the zinc blende through a positive short-range order parameter αi-j depending on temperature and composition. It is shown that clustering increases in the GaxIn 1-xX serie (X = Sb, As, P) from the antimonide (αGa-In(1/2, 700°C) = 0.04) to the phosphide (αGa-In(1/2, 700°C) = 0.08) whereas GaASyP1-y and mainly InAs yP1-y have quite random As-P distribution. For pseudoquaternaries the model predicts a linear variation of α i-j versus the composition of the other sublattice. The calculated miscibility gaps are in good agreement with known experimental results for GaxIn1- xP and GaxIn1-xAs yP1-y (the critical temperatures are respectively 750 and 880 °C), whereas the model does not explain an asymmetrical shape of miscibility gap as in the case of GaAsySb 1-y if the excess entropy reduces only to a configurational one