Strain relaxation in LT-GaAs by the agglomeration of As antisites

Investigations on the lattice distortion caused by point defects in As-rich GaAs have been performed employing a self-consistent-charge density-functional-based tight-binding method. While both probable defects in As-rich material, the As antisite and the As interstitial, are causing significant lattice distortion, only the isolated As antisite leads to lattice strain in agreement with experiment. Agglomerations of As antisites always show a negative binding energy, which is growing with size of the precipitate. We show that already for the smallest agglomerates of two and three antisites the induced lattice strain is slightly relaxed.