GaAs and BAs antisite defects in gallium arsenide

Samples of p-type Ga-rich non-stoichiometric undoped liquid-encapsulated Czochralski GaAs have been subjected to 2 MeV electron irradiation, carried out in stages, to cause the Fermi level to move upwards from the valence band. At each stage, infrared absorption measurements were made of the strengths of electronic transitions from levels at 78 meV and 203 meV and vibrational absorption at 601 cm-1 from 11BAs. The results are consistent with an assignment of the three signatures to 11BAs0, BAs-, and BAs2-, in agreement with previous proposals but in disagreement with other recently published results. The commonly held view that the 78/203 meV defect is due to GaAs antisites cannot therefore be considered to be established.