In the paper, the influence of growth factors and silicon surface condition on the epitaxial formation of single-domain GaP buffer layers on Si (001) has been studied. A novel two-stage growth technique for the epitaxial building-up of this structure has been put forward and developed. In contrast to using the migration enhanced epitaxy technique, the proposed technology allows one to separate the nucleation and growth stages, to control the doping profile of the GaP buffer layers. The latter is important for further functional applications. The main factors determining the orientation of GaP crystalline lattice when it nucleates on the Si vicinal surface were found. The structural perfection of the grown buffer layers at both stages was proved through careful control by TEM, RHEED, AFM, and HRXRD. These findings have important implications for further functional applications.