DI-CARBON DEFECTS IN ANNEALED HIGHLY CARBON-DOPED GAAS

Formation of bonded dicarbon C-C centers is deduced from the observati on of Raman lines at 1742, 1708, and 1674 cm(-1) in GaAs codoped with C-12 and C-13 after annealing at 850 degrees C with concomitant loss o f vibrational scattering from C-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 C-As) atom by an undisplaced C-As acceptor. Other mechanisms of carrier loss are infer red since a weaker Raman triplet is detected at 1859, 1824, and 1788 c m(-1) from a different C-C complex.