Self-organized GaxIn1-xNyAs1-y quantum dots (QDs) were fabricated on GaAs (001) substrates by atomic hydrogen-assisted molecular beam epitaxy with a radio frequency nitrogen plasma source (RF-MBE). By adjusting the amount of lattice mismatch between GaxIn1-xNyAs1-y and GaAs to be almost the same as that of In0.4Ga0.6As and GaAs, we were able to fabricate Ga0.53In0.47N0.02As0.98 QDs with densities up to similar to1.1 x 10(11) cm(-2) on GaAs (001) by atomic H-assisted RF-MBE. Further, we have studied the effect of atomic H irradiation on QDs' growth dynamics and their optical properties. Based on the atomic force microscope and photoluminescence measurements, we found that there exists an optimum range of H-2 flow rates for a uniform and high quality Ga0.53In0.47N0.02As0.98 QDs formation on GaAs substrates. (C) 2003 Elsevier B.V. All rights reserved.