We report on the properties ofp‐type delta‐doped layers prepared in molecular beam epitaxy‐Si by growth interruption and evaporation of elemental B. Secondary‐ion mass spectrometry measurements at several primary ion energies have been used to show that the full width at half maximum is ∼2 nm. Hall measurements confirm that the layers are completely activated at 300 K with a mobility of 30±5 cm2/V s for a carrier density of (9±2)×1012cm−2. At temperatures below 70 K nonmetallic behavior is observed which we have attributed to conduction between impurity states. It is concluded that the critical acceptor separation for the Mott metal‐insulator transition in this system is significantly less than the value found in uniformly doped Si:B.