Structural properties of ultrathin arsenic-doped layers in silicon

We have grown δ-doped layers in Si by low-energy As-ion implantation during molecular beam epitaxy. The layers were investigated using cross-sectional transmission electron microscopy, secondary-ion mass spectrometry, Rutherford backscattering, and electrical measurements. The δ-doped layers were between 3.5 and 5.5 nm thick, and showed perfect epitaxy with 50–80% of the incorporated As on substitutional sites. Layers doped at concentrations from 1×1013 cm−2 to 8×1013 cm−2 had bulk-like mobilities and spanned the metal to insulator transition.