In this study we report the growth behavior of GaNxP1−x by chemical beam epitaxy using triethylgallium, tertiarybutylphosphine, and a RF-plasma N radical beam source. We demonstrate that the N radical beam source is an effective N source for the growth of GaNxP1−x, compared to ammonia (NH3) with co-injection of phosphine (PH3) or tertiarybutylphosphine (TBP). At a growth temperature of 640°C, the N composition increases slowly from 2.5 to 2.8% even though the N2 flow rate is doubled. When the N2 flow rate is increased further, the reflection high-energy electron diffraction pattern (RHEED) becomes spotty. The N composition, however, shows a strong dependence on the growth temperature. For a fixed N plasma radical beam flux, the lower the substrate temperature is, the higher the N incorporation. The N composition can be adjusted from 0.7 to 10.2% by lowering the growth temperature from 690 to 400°C.