GaP/Si heterostructures were grown under different growth conditions by molecular beam epitaxy in order to obtain single-phase GaP on Si. The growth results were examined by reflective high-energy electron diffraction, anisotropic etching, atomic force microscopy, and x-ray diffraction. The results showed that high quality, single-phase GaP was grown on Si at a high growth temperature, about 500 degreesC, with a low P/Ga flux ratio of 2.5x, while at a lower temperature, a second phase with a 90degrees in-plane rotation was grown. (C) 2004 American Vacuum Society.