Structural, electronic and energetic properties of self-interstitial clusters in GaAs by tight-binding molecular dynamics

Intrinsic interstitials in GaAs are characterized by a remarkable formation energy that makes them unlikely to be present in as-grown materials and therefore commonly neglected. However, the role of interstitials must be considered in implanted GaAs, where collision cascades by energetic ions produce a large amount of these point defects. This paper reports on semiempirical tight-binding molecular dynamics simulations of interstitial defects in GaAs. The adopted parametrization has been initially applied to the simulation of isolated selfinterstitials, on the basis of previous state of the art density-functional theory results, showing good performances. Then di-interstitial properties have been addressed, showing that self-interstitials have a remarkable tendency to aggregate in bigger structures. The binding energy of these clusters has been calculated on the basis of a simple algebraic model that does not require the calculation of the formation energy of the compound. This work will lay the ground work for a subsequent study of larger aggregates.