The good correlation between the HRXRD and D-SIMS also indicates that most of the dopants are substitutional, resulting in some form of tensile lattice strain of the epitaxial layer. This strained epitxial film indicates that there is very minimal interfacial disclocations arising from the discontinuity at the Si:P+/Si:B-interface. In order to confirm the lattice strain we performed lattice strain measurement via electron diffraction (Fig ). The XX direction refers to the lattice strain along the in-plane direction and the YY direction is along the outof-plane direction to the wafer surface. The lattice constant is unchanged along the XX direction. However, along the YY direction, we see a difference in lattice constant between Si:P and substrate. The amount of strain magnitude increases progressively with the dopant concentration, which lines up very well with our expectation, as higher substitutional dopant concentration will lead to bigger lattice mismatch, thereby resulting in higher strain.