Transmission electron microscopy has been combined with time‐resolved reflectivity and ion channeling to study the effects of carbon doping on solid‐phase epitaxial regrowth (SPER) of strained 2000 Å, Si0.88Ge0.12Si alloy layers grown by molecular‐beam epitaxy (MBE). Relative to the undoped layers, carbon incorporation in the MBE grown SiGe layers prior to regrowth at moderate temperatures (500–700 °C) has three main effects on SPER. These include a reduction in SPER rate, a delay in the onset of strain‐relieving defect formation, and a sharpening of the amorphous/crystalline (a/c) interface, i.e., promotion of a two‐dimensional (planar) growth front. These results suggest that C incorporated during SPER reduces the lattice‐mismatch strain. © 1996 American Institute of Physics.