Cyclic thermal annealing on Ge/Si(100) epitaxial films grown by magnetron sputtering

In this work, epitaxial growth of Ge on Si is achieved using magnetron sputtering which is a low-cost and safe method suitable for large-scale production. Smooth surface with RMS roughness of 0.48 nm is obtained at a low deposition temperature of 300 °C. Cyclic thermal annealing is applied to the Ge film reducing the threading dislocation density (TDD) by two orders of magnitude. The in-plane strain in the Ge film changes from compressive to tensile after annealing due to the mismatch in thermal expansion coefficients between Si and Ge. The mechanism of the TDD reduction is investigated revealing formation of dislocation loops and dissociation of dislocations into planar defects at the interface. The Ge epitaxy film on Si may be suitable for use as virtual substrate for the fabrication of III-V high efficiency solar cells.