High concentration Bi delta-doping layers on Si(001)
Medium energy ion scattering, X-ray standing waves and measurements of crystal truncation rods were used to show that it is possible to prepare spatially well confined Bi doping layers (δ-doping layers) on Si(001) with a Bi doping level of 3 × 1021 cm−3 by a combination of Bi molecular beam epitaxy and low temperature deposition of a Si top layer with subsequent annealing (solid phase epitaxy). The Bi concentration exceeds the equilibrium Bi solubility by more than three orders of magnitude. The Bi atoms are incorporated into the Si host lattice on substitutional sites. The Bi doping profile exponentially decays into the top Si layer with an attenuation length ranging from 40 to 6 Å and a fraction of Bi atoms in substitutional lattice sites of up to 96%, depending on the annealing conditions.
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