We have developed a dual-step encapsulation process for phosphorus in germanium delta-layers with initial low-temperature encapsulation to suppress dopant redistribution, followed by a higher temperature overgrowth to improve crystalline quality and electrical transport properties. Structural and electrical characterization shows that encapsulation of the delta-layer with a 2-nm-thick Ge layer deposited at 350 degrees C followed by Ge growth at 530 degrees C confines P donors into an atomically flat layer with limited dopant segregation, high carrier concentration and low resistivity. This doping method is promising for the fabrication of ultra-shallow junctions. (C) 2010 Elsevier B.V. All rights reserved.