Structural investigation of the C-O complex in GaAs

A carbon-oxygen complex occurring in gallium arsenide crystals after annealing at around 700 °C is studied. Fourier transform infrared absorption measurements on the associated vibrational band at 2060 cm-1 under uniaxial stress reveal that the center has tetragonal symmetry. From the intensity of the 18O-related satellite band it is concluded that four oxygen atoms are involved. Ab initio local density calculations show that a tetragonal CO4 molecule forms a stable entity in the gallium arsenide lattice.