We have conducted the first studies of dopant incorporation (gallium, boron, and antimony) in MBE germanium grown on Ge(100) substrates. Excellent germanium films have been grown on Ge substrates with little demarcation of the substrate-epi interface. A first order kinetic incorporation model has been used to describe the behavior of gallium in germanium. Gallium doping of germanium takes place through an adlayer at the growth front and between growth temperatures of 450 and 550°C successful p-doping of germanium by gallium can be accomplished. Boron is an excellent p-dopant in germanium with good activation at high concentrations and sharp transition profiles. The incorporation of antimony in germanium at growth temperatures ≥ 450°C is poor and needs further investigation. © 1991.