Nitrogen incorporation in the growth of epitaxial GaNxAs(1-x) by chemical beam epitaxy (CBE) using 1,1-dimethylhydrazine (DMHy) was compared, for the first time, when using each of 2 sources of arsenic. Each of cracked arsine (AsH3) and uncracked tris(dimethylamino) arsine were used with triethylgallium as Group III source, at a growth temperature of 490(+/-5)degreesC. Different incorporations were found at high flow pressures of DMHy in the two cases. Nitrogen compositions of fully-strained GaNxAs((1-x)) epilayers from 0.01% to 4.2% were measured by X-ray diffractometry (XRD) on the assumption that Vegard's law applies. Higher nitrogen compositions, up to 7(+/-2)%, were measured by cross-sectional high resolution electron microscopy (HREM) to yield structural information and a measurement of the lattice parameter. Collation of the secondary ion mass spectrometry (SIMS), XRD and HREM data showed that there is good agreement between the nitrogen composition inferred from the lattice parameter and the chemical content, suggesting that the nitrogen is incorporated substitutionally in GaNxAs(1-x) grown under these conditions by CBE. Using trimethylindium and ethyldimethylaminealane with AsH3 and TEGa, the nitrogen incorporations into both 15% InGaAs and. for the first time. into 30% AlGaAs were also measured. Distinctly different nitrogen incorporation efficiencies were observed for the three alloys. particularly at high nitrogen percentages. Unintentional hydrogen incorporation was measured by SIMS for layers grown with AsH3 and found to be at around 10% of the nitrogen level for all three alloys studied. Crown Copyright