The molecular beam epitaxy is a powerful technology for integrating optoelectronic devices in standard Si microelectronics. The MBE growth of high speed germanium detectors is discussed. The necessary lattice accommodation between Si and Ge is realized by an ultra thin virtual substrate. Contact layers with very high doping concentration and very sharp transitions are grown with special doping strategies. As special growth method the differential epitaxy allows the growth of epitaxial layers in oxide windows. (C) 2008 Elsevier B. V. All rights reserved.