The radio frequency (rf) plasma and its operating conditions play a large, if not dominant role, in the differences of characteristics of molecular beam epitaxy-grown dilute-nitride samples between various research groups. Optimization of the rf plasma itself has become more important due to recent discoveries that ions cause significant damage to the optical quality of the material. An investigation on the effects of different nitrogen gas flows into the rf plasma cell was conducted. GaInNAs quantum wells were grown with different flow rates and their optical quality was examined using photoluminescence. A Langmuir probe was used to qualitatively analyze the ion flux originating from the plasma. We find that lower gas flow rates lead to a "sparse" operating condition and to higher ion counts which degrade the optical quality of the material. Higher flow rates are necessary to minimize ion counts and obtain higher quality materials. (c) 2005 American Vacuum Society.