High quality, strained Si/Si1−xGex layered structures have been grown at temperatures in the range 400–625 °C, using a solid‐source molecular‐beam epitaxy (MBE) system with a mass‐spectrometry‐based loop‐control to improve the accuracy and stability of the evaporation rates. Good control of the growth parameters has been achieved as verified by, e.g., high‐resolution x‐ray diffraction. Very high intensities and extremely small peak widths, down to 2.7 meV for the XNP transition at low excitation levels of photoluminescence spectra, indicate high crystalline quality of the layers. It is shown that some previously reported defect‐related luminescence from MBE‐grown SiGe layers is not intrinsic to the MBE process. © 1994 American Institue of Physics.