High Electron Mobility in Ge Films Grown on Si (001) by an 8-Inch Molecular Beam Epitaxy System.

Silicon-based germanium films are promising for the fabrication of low-power, high-performance electronic and optoelectronic devices. In this work, we report an effective approach for directly growing Ge films with ultrahigh carrier mobility on Si (001) substrates using molecular beam epitaxy (MBE). Strain relaxation of the germanium films is realized through the formation of partial dislocations and 90° misfit dislocations at the Ge/Si interface. The Ge film exhibits a smooth surface with a root-mean-square roughness of 0.187 nm and a low threading dislocation density of only 1.2 × 10 cm. Hall effect measurements reveal a high room-temperature mobility of up to 1916 cmVs along with a carrier concentration of 1.425 × 10 cm. These findings demonstrate that MBE-grown Ge films, possessing exceptionally high carrier mobility, hold great promise for integration into advanced electronic and optoelectronic devices.