SiGe/Si heterostructure with abrupt interface was formed by molecular-beam epitaxy combined with solid-phase epitaxy. We find that nucleation during the solid-phase epitaxy is a thermally activation-type phenomenon. The activation energy of the nucleation decreases from 4.3 eV to 2.2 eV with increasing Ge concentration (x = 0 → 0.3), while the activation energy of crystal growth decreases from 3.1 eV to 2.1 eV. A phase diagram of crystallinity of SiGe layer was obtained. We found that the crystallinity depends on trade-off between the nucleation- and the growth-rates. Transmission electron microscopy confirmed that the solid-phase epitaxial growth completely suppressed Ge segregation between the Si channel and the SiGe layer. Electron mobility of 1500 cm2/Vs at room temperature was obtained.
