A new method of ionized antimony doping of silicon molecular beam epitaxial films has been investigated. Si films were grown on Si (111) substrates by evaporation of Si from ane‐gun evaporator in ultrahigh vacuum. Sb ions were generated with an electron impact ion source. Carrier concentration of doped layers, grown at a substrate temperature of 860 °C, can be accurately controlled over the range 1016–1020cm−3. Doping efficiency of Sb ions is 100%. Doping with ions in the range 130–1000 eV kinetic energy does not degrade the crystallographic or electrical quality of the films. For example, abrupt changes in the doping level of a composite film with three doped layers are given. The in‐depth Sb dopant profile of this film corresponds closely to the Sb ion doping schedule, which indicates that the surface segregation of Sb does not occur attendant ion doping.