Suppressing Segregation in Highly Phosphorus Doped Silicon Monolayers

Sharply defined dopant profiles and low resistivity are highly desired qualities in the microelectronic industry, and more recently, in the development of an all epitaxial Si:P based quantum computer. In this work, we use thin (monolayers thick) room temperature grown silicon layers, so-called locking layers, to limit dopant segregation in highly phosphorus doped silicon monolayers. We present secondary ion mass spectroscopy and atom probe tomography measurements that demonstrate the effectiveness of locking layers in suppressing P segregation. Scanning tunneling micrographs of the surface of the locking layer show that the growth is epitaxial, despite the low growth temperature, while magnetotransport measurements reveal a 50% decrease in the active carrier density. We show that applying a finely tuned rapid thermal anneal can restore the active carrier density to 3.4 × 1014 cm-2 while maintaining ultra sharp dopant profiles. In particular, 75% of the initial deposited P is confined in a layer with a full width at half-maximum thickness of 1.0 nm and a peak P concentration of 1.2 × 1021 cm-3 (2.5 atom %).