We have investigated the dependence of impurity incorporation of GaInNAs on the In concentration, substrate orientation, and growth temperature by secondary ion mass spectroscopy (SIMS). GaInNAs films were grown by low-pressure metalorganic vapor-phase epitaxy (MOVPE) on GaAs substrates. It was found that H and C concentrations were strongly related to the N concentration in the solid and the dimethylhydrazine (DMHy) flux at the surface. Furthermore, intentional Si-doping study revealed that incorporated H was stable, which is most likely a consequence of neutral bonding N, although the activation energy of H was as large as 197kcal/mol derived from the observed growth-temperature dependence.