Nucleation and first-stage growth processes of extrinsic defects in GaAs triggered by self-interstitials

Abstract

The growth process of small self-interstitial clusters ${I}_{n}$ $(n\ensuremath{\le}7)$ in crystalline GaAs has been addressed by semi-empirical tight-binding molecular-dynamics technique. The ${I}_{n}$ ground-state structures have been found among many possible choices of topological properties and stoichiometric compositions. The stable structure have been fully characterised concerning the structural, electronic, energetic, and elastic properties; some remarkable findings emerged concerning, among the others, the stability scenario of the ground-state structures, the possible low-energy reaction paths involved in the growth process, the electrostatic and the elastic capture volumes and the Fermi-level pinning. It is demonstrated that compact geometries are no longer energetically favoured for $n\ensuremath{\ge}5$ and that the ${I}_{n}$ growth proceeds via capture processes involving either isolated interstitials or di-interstitials. An extended pentainterstitial $({I}_{5})$ ground-state structure has been identified as the possible core-basic structure of extrinsic linear defects along the {111} direction of the GaAs lattice.