High quality layers ofGaAs1−xNxwere grown on (001)GaAs by metal–organic molecular beam epitaxy. The growth conditions, and especially the nitrogen to arsenic flux ratio, were carefully explored to assure epitaxial crystal growth. We show well behaved and reproducible growth of single phaseGaAs1−xNxwith the GaN mole fraction as high asx=0.10.The nitrogen content of epitaxial layers was determined directly by secondary ion mass spectroscopy and high resolution x-ray diffraction. ©1997 American Institute of Physics.