With the continued importance of 1.3 mum wavelength fiber optic communication, devices based on GaAsN materials are becoming increasingly important components due to their inherent integration capability and their temperature stability. In this paper, we report on the characterization of a radio frequency (RF) plasma source using a dilute nitrogen (N) in argon gas mix, to understand the production of atomic nitrogen and its effect on GaAsN growth. Optical emission intensity was used to characterize nitrogen production, and was found to predict the percentage of nitrogen in an as-grown GaAsN film over a wide range of gas flow and RF power conditions. The RF plasma source was also characterized for the production of ionic species. We found that the number of ions produced, and their energy, varies significantly depending on the RF power, the gas flow rate, and the source gas used (Ar, dilute N in Ar, pure N-2). This data allows for the optimization of RF conditions, which minimize damage from ionic species independently from nitrogen production. (C) 2002 Published by Elsevier Science B.V.