Di-Carbon Defects in Annealed Highly Carbon Doped GaAs

Formation of bonded dicarbon C-C centers is deduced from the observation of Raman lines at 1742, 1708, and $1674\mathrm{cm}{}^{-1\mathrm{}}$ in GaAs codoped with ${}^{12}$C and ${}^{13}$C after annealing at 850 °C with concomitant loss of vibrational scattering from ${\mathrm{C}}_{\mathrm{As}}$. The frequencies agree with results of ab initio theory for a C-C split interstitial (deep donor) formed by the trapping of a mobile interstitial C (displaced ${\mathrm{C}}_{\mathrm{As}}$) atom by an undisplaced ${\mathrm{C}}_{\mathrm{As}}$ acceptor. Other mechanisms of carrier loss are inferred since a weaker Raman triplet is detected at 1859, 1824, and $1788\mathrm{cm}{}^{-1\mathrm{}}$ from a different C-C complex.