The great bowing parameter of GaAsN makes this material hopeful for the fabrication of 1.3 and 1.55 mum laser diodes and detectors. However, the effect of energetic nitrogen ion bombardment during growth may have a deleterious effect on the material quality. To avoid the bombardment effect of energetic nitrogen ions, a modified mode for GaAsN growth using dispersive nitrogen is reported. High-quality GaAsN epilayers and abrupt GaAsN/GaAs interfaces were demonstrated using this growth mode. For the first time, a GaAsN/GaAs double quantum well sample was grown with dispersive nitrogen source. Under our annealing conditions of 750degreesC from 10 s to 10 min, no significant evidence of nitrogen out-diffusion from the material was found. The improvement in optical quality due to annealing is attributed to the annihilation of nitrogen-related defects through atomic rearrangement of the lattice, the effect of which on the observed blueshift in the photoluminescence peak needs further investigation. (C) 2002 Elsevier Science B.V. All rights reserved.