An open‐tube vapor deposition process has been used to grow GaP epitaxially on GaAs seeds. The overgrowths generally contain large numbers of defects including dislocations, stacking faults, impurity striae, and local strains. The stacking faults and impurity striae may be eliminated by growing on (1¯1¯1¯)‐plane seeds under carefully controlled conditions. The mobility of electrons inn‐type GaP is found to increase from approximately 120 cm2/V sec at 300°K to approximately 600 cm2/V sec at 77°K. Undoped GaP layers are invariablyn‐type with carrier concentration in the range 1015–1017/cm3.