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 1674cm^-1 in GaAs codoped with ¹²C and ¹³C after annealing at 850 ^∘{}C with concomitant loss of vibrational scattering from CAs. 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 CAs) atom by an undisplaced CAs acceptor. Other mechanisms of carrier loss are inferred since a weaker Raman triplet is detected at 1859, 1824, and 1788cm^-1 from a different C-C complex.