We report the characterization of thin and thick Ge layers grown by molecular beam epitaxy on Si(2 1 1) substrates with and without As deposition prior to Ge growth. The role of the As surfactant, as well as the dependence of the overall layer quality on the Ge growth rates and growth temperatures has been studied. The Ge layer growth was monitored in situ by reflection high-energy electron diffraction, and the Ge/Si heterostructures were characterized ex situ by Raman spectroscopy. x-ray diffraction, and cross-sectional transmission electron microscopy. The results indicate that the growth mode is altered significantly by saturating the Si surface with a monolayer of As prior to initiation of Ge growth. Although Ge-Si interdiffusion and alloy formation on the Si(2 1 1) surface are dramatically reduced by nucleating Ge on Si with the aid of a surfactant, they are not completely suppressed. A structural model for initiation of the surfactant-mediated growth is briefly discussed.