Atomic structure of defect complexes containing carbon and hydrogen in GaAs.

Abstract

We study the hydrogen passivation of carbon acceptors and the stability of defect complexes containing carbon and hydrogen in GaAs through first-principles pseudopotential calculations. A carbon-hydrogen ${\mathrm{C}}_{\mathrm{As}}^{\mathrm{\ensuremath{-}}}$-(${\mathrm{HC}}_{\mathrm{As}}$${)}^{0}$ complex with two ${\mathrm{C}}_{\mathrm{As}}$ atoms at second-neighbor As sites is found to be energetically more favorable than the isolated configuration of ${\mathrm{C}}_{\mathrm{As}}^{\mathrm{\ensuremath{-}}}$ and H-${\mathrm{C}}_{\mathrm{As}}$. We also find that a (H-${\mathrm{C}}_{\mathrm{As}}$${)}_{2}$ complex containing two H atoms is more stable than two isolated H-${\mathrm{C}}_{\mathrm{As}}$ pairs. Hydrogen dissociation from the ${\mathrm{C}}_{\mathrm{As}}^{\mathrm{\ensuremath{-}}}$-(${\mathrm{HC}}_{\mathrm{As}}$${)}^{0}$ center upon annealing leads to the formation of a ${\mathrm{C}}_{\mathrm{As}}$-${\mathrm{C}}_{\mathrm{As}}$ pair, and the ${\mathrm{C}}_{\mathrm{As}}$-${\mathrm{C}}_{\mathrm{As}}$ complex subsequently dissociates into two isolated ${\mathrm{C}}_{\mathrm{As}}$ acceptors. Here we propose a dissociation process that involves a C-C split-interstitial complex at an As site and a second-neighbor As vacancy, with an energy barrier of about 1.7 eV, which is similar to that for Zn diffusion. \textcopyright{} 1996 The American Physical Society.