In situLEED studies of the homoepitaxial growth of Si(111) films by uhv sublimation, indicate a strong correlation between the type of surface structure generated and the metallic impurity content of the silicon substrates as estimated from minority carrier lifetimes. The development of the familiarSi(4111)−7×7structure is favored by the presence of lifetime-killing impurities in the substrate. Experiments where Fe is introduced on high lifetime substrates prior to annealing and film growth, suggest that this impurity species plays a role in the generation of the7×7surface structure. Electron microscopy reveals that homoepitaxial Si(111) layers are generally faulted, the number density of which increases progressively as the growth temperature is lowered. Films deposited on high-lifetime silicon contain substantially fewer stacking faults than those grown on low-lifetime substrates. These results suggest that the faults originate at microprecipitates at the substrate surface consisting of fast-diffusing, low-solubility impurity species.