Fig 1 shows the HRXRD of the three different samples with different dopant concentrations. The HRXRD shows the Si and Si:P [004] peaks very clearly. The Si:P peak is at a slightly higher 2θ angle, indicating the difference in lattice constant along the out-of-plane direction. The higher fringe frequency is due to the difference of the thickness of the three recipes. The actual data was fit using the simulation to obtain the thickness and substitutional dopant concentration of the Si:P layers. The results obtained from the simulation are shown in Table . The SIMS profile also shows a gradient in the dopant concentration as we go from the epitaxial layer into the Si/B-substrate. This gradient last for ~ 8 nm at the interface between Si:P and the substrate. The good match between D-SIMS and HRXRD, for thickness and doping, indicates that the overall effects of the artifacts in D-SIMS is likely low . The overall P concentration in Si:P layer and substrate are flat. The dopant gradient, at the interface, can be approximated as: