Ordering and decomposition in semiconductor alloys

The stability of ordered semiconductor alloys has been studied, using total energy pseudopotential calculations. The ordered alloys are found to be stabilized with respect to disordered alloys via reduction of the internal strain and by chemical interactions. The Si–C and Si–Ge systems are used as illustrations, finding that ordered Si_x Ge_1−x should be a metastable alloy, in agreement with experimental observations.