Formation of Ge(111) on Insulator by Ge epitaxy on Si(111) and layer transfer

We demonstrate the (111)-oriented Ge-on-Insulator (GOI) formed by Ge epitaxial growth on a Si(111) and the layer transfer technique. The two-step growth manner, involving low-temperature growth of a thin Ge layer and subsequent high-temperature growth of a thick Ge layer, enables us to obtain high-quality tensile-strained epitaxial Ge(111) on Si(111). It is found that the strain amount straongly depends on the growth temperatures and we find an optimal growth temperature. We also developed a chemical mechanical polishing (CMP) method modified for Ge, offering the ultra-smooth Ge(111) surface. The polished epitaxial Ge is bonded on a SiO2/Si, followed by the selective etching of Si and the final CMP of Ge. As a result, we achieve the high-quality 200-nm-thick tensile-strained Ge(111)-OI with an ultra-smooth surface, on which, furthermore, we demonstrate the growth of an epitaxial metallic silicide for the metal source/drain in spintronic devices as well as advanced Ge channel devices.