Epitaxial growth mode and silicon/silicon-germanium heterointerfaces

Silicon-germanium/silicon (Si1-xGex/Si, x<0.50) multiple quantum wells (MQWs) have been grown on (001) Si substrates by gas source molecular beam epitaxy (GSMBE) using disilane (Si2H6) and germane (GeH4) as source gases. Their structural properties have been evaluated by X-ray diffraction (XRD), rocking curve techniques and transmission electron microscopy (TEM). For the substrate temperatures used in this work (450 °C to 520 °C) the Si growth rate is limited by hydrogen desorption kinetics, whereas the growth of SiGe is limited primarily by the arrival rate of the source gases onto the Si substrates. XRD analysis of the structures indicates a significant well plus barrier period variation of approximately 5-10%, attributed to fluctuations in the substrate temperature during growth, since these cause significant variations in the growth rate of the Si barriers. For x