Minimisation of P surface segregation during epitaxial silicon growth for the fabrication of a silicon-based quantum computer

To optimise the fabrication process for a silicon based quantum computer the surface segregation/diffusion of phosphorus atoms in silicon is investigated on an atomic scale using scanning tunnelling microscopy (STM) after epitaxial silicon growth at 255 °C and room temperature, respectively. The phosphorus atom in the Si(001) surface forms a silicon-phosphorus heterodimer identified as a bright zigzag feature in filled state STM images. Sample annealing, used to reduce the surface roughness and the defect density after silicon growth is shown to increase the density of phosphorus atoms at the surface. However, the density of phosphorus atoms can be limited to a few percent of the initial density if the phosphorus atoms are encapsulated in silicon at room temperature.