Encapsulation of phosphorus dopants in silicon for the fabrication of a quantum computer

The incorporation of phosphorus in silicon is studied by analyzing phosphorus delta-doped layers using a combination of scanning tunneling microscopy, secondary ion mass spectrometry, and Hall effect measurements. The samples are prepared by phosphine saturation dosing of a Si(100) surface at room temperature, a critical annealing step to incorporate phosphorus atoms, and subsequent epitaxial silicon overgrowth. We observe minimal dopant segregation (similar to5 nm), complete electrical activation at a silicon growth temperature of 250 degreesC and a high two-dimensional electron mobility of similar to10(2) cm(2)/V s at a temperature of 4.2 K. These results, along with preliminary studies aimed at further minimizing dopant diffusion, bode well for the fabrication of atomically precise dopant arrays in silicon such as those found in recent solid-state quantum computer architectures. (C) 2002 American Institute of Physics.