In order to improve the structural quality of CdTe/Si composite substrates, we have investigated the MBE growth mechanisms of CdTe(1 1 1) onto planar and vicinal arsenic-passivated Si(111) surfaces. The films were characterized by in situ RHEED, X-ray diffraction, Raman spetroscopy, photoluminescence, secondary electron microscopy, transmission electron microscopy and atomic force microscopy. Rocking curves had peaks narrower than 100 arcsec at a layer thickness of only 1-2 mu m. BeTe buffer layers did not show a dominant effect, whereas the twin content decreased drastically when misoriented substrates were used. Efficient twin suppression can be obtained by realizing an interface step alignment between substrate and epitaxial CdTe film.