SimGenstrained layer superlattice (SLS) structures were grown by molecular beam epitaxy on GexSi1−xbuffer layers on ⟨100⟩ Si substrates to determine the effects of buffer layer composition, SLS thickness ratio, and superlattice periodicity, on the overall quality of these structures. X‐ray diffraction methods were used to determine how closely actual periodicities and compositions met targeted values, and to evaluate the quality of these samples. In most instances the as‐grown structures matched the targeted values to within 10%, though in some instances deviations of 20–25% in either the period or composition were observed. The quality of the SLS structures was greatly dependent on the composition of the buffer layer on which it was grown. SimGenSLS structures grown on Si‐ and Ge‐rich buffer layers were of much higher quality than SimGemSLSs grown on Ge0.50Si0.50layers, but the x‐ray rocking curves of the SimGensamples indicated that they were far from perfect and contained moderate levels of defects. These results were confirmed by cross sectional transmission electron microscopy, which showed that the SimGemstructures contained significant numbers of dislocations and that the layers were nonuniform in thickness and wavy in appearance. SimGenstructures, however, displayed fewer defects but some dislocations and nonparallelism of layers were still observed.