Dual-temperature encapsulation of phosphorus in germanium δ‐layers toward ultra-shallow junctions

We have developed a dual-step encapsulation process for phosphorus in germanium δ-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 δ-layer with a 2-nm-thick Ge layer deposited at 350 °C followed by Ge growth at 530 °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.