[en] Nitrogen (N) ions having energy as low as 20 eV were impinged onto the epitaxially growing GaAs surface using combined ion beam and molecular beam epitaxy (CIBMBE) method. Experiments were made as a function of N ion acceleration energy (E/sub a/) and N/sub +/ ion beam current density (I/sub N). E/sub a/ was varied from 20 eV to 30 keV and IN from 900 pA/cm2 to 75 nA/cm2. GaAs growth rate was fixed to 1 mm/h. Photoluminescence (pol) spectra at 2 k exhibited the formation of two sharp emissions at 1.58 eV(x) and 1.495 eV (x2), that are described to the emissions of excitons bound to isolated N atoms. The results show that nitrogen (n) atom in GaAs becomes optically active as an isoelectronic impurity. For samples impinged with relatively high IN, a broad emission together with multiple sharp ones was observed when furnace annealing at 750 degree centigrade was made for the impinged samples. These emissions were found to be due to excitons bound to nitrogen-nitrogen (N-N) pairs. (author)