We report on the morphology of heavily phosphorous doped silicon films grown by ultra high vacuum chemical vapor deposition at temperatures of ∼550° C. The effects of PH3 on epitaxial films have been examined for silicon deposited using SiH4 and Si2H6. It is found that films grown using silane experience an increase in surface roughness with increasing phosphine partial pressure. AFM and RHEED studies indicate 3-D growth. As epitaxy progresses, it is believed that phosphorus segregation on the growing film surface greatly diminishes the adsorption and surface mobility of the silicon bearing species. Initial Si deposition results in a pitted surface, but as growth advances and the phosphorus coverage increases, growth within the pits decreases the surface roughness. In contrast to SiH4, it is found that Si2H6 provides excellent quality, smooth films even at high PH3 partial pressures.