(AlyGa1-y)(0.52)In-0.48 P (y = 0.0, 0.2 and 0.7) was grown by MBE using either GaP or phosphine as the phosphorus source material. SIMS measurements reveal that phosphide semiconductor material grown by using GaP contains significantly more oxygen impurities compared to gas source material. A SIMS measurement of a phosphide laser grown by gas source MBE shows low oxygen contamination in the quaternary regions of the device, but interestingly, a significant oxygen spike occurs in the active region.