Thick GaAsN layers and GaInNA/GaAs multiple quantum wells (MQWs) were successfully grown on semi-insulating GaAs substrates by gas-source molecular beam epitaxy equipped with a nitrogen radio frequency (rf) activated plasma source. High resolution x-ray rocking curves indicate that the nitrogen content in the GaAsN layer is increased from 0.7% to 3% with increasing rf cavity pressure. Room temperature photoluminescence measurements show that the emission wavelength decreases when the nitrogen content is increased. The evolution of the strained band gap with nitrogen composition is in quantitative agreement with calculations as well as with other spectroscopic studies, allowing complete characterization of the alloy for a small nitrogen fraction. Furthermore, the influence of the growth temperature and the V-III ratio on the optical and structural properties of the GaInNAs MQWs has been carefully examined. We found that the material properties are optimal at a growth temperature of 400 degreesC and a V-III ratio of 3.