We investigated the misfit dislocation nucleation in lightly boron-doped silicon epitaxial layers deposited by vapor-phase epitaxy at 1080°C–1150°C on heavily boron-doped substrates. The substrate resistivity was 4 mΩ cm which produced a misfit of 1.5×10 −4 and the layer thickness was 10 μm. An orthogonal array of 〈1 1 0〉-type dislocations was observed at the interface, as determined by g· b contrast criteria using Lang transmission X-ray topography. The misfit dislocations were observed only around the wafer periphery and the misfit dislocation length was shorter in regions where both orthogonal 〈1 1 0〉 segments existed. The density of the misfit segments was determined at the interface by defect-etching. In regions where the misfits were observed, triple-axis X-ray diffraction measurements determined that the layers were measurably relaxed. The distribution of defects indicates that the wafer periphery possesses heterogeneous nucleation sites for misfit dislocation nucleation.