The lattice-site distribution of B in doped melt-grown material was studied by means of photoluminescence and local vibrational mode spectroscopy. The samples were cut from nominally Si- or Ge-doped crystals, grown under stoichiometric or Ga-rich conditions. In GaAs:Si, the B behaved like an amphoteric dopant. Formation of the antisite, BAs, was favoured by growth from a Ga-rich melt. In Ge-doped GaAs, only the isovalent B defect, BGa, was observed. Apart from infra-red absorption spectra, measured using established Fourier-transform techniques, the BAs-related radiative recombination and local Raman modes of B species were reported. The results demonstrated that photoluminescence and near-infrared Raman spectroscopy were useful tools for detecting substitutionally incorporated B in GaAs.