Growth and characterization of epitaxial layers of Ge on Si substrates

Thin single crystalline layers of Ge with atomically sharp boundaries have been formed epitaxially on (100) Si substrates. This was done by 74Ge ion implantation into Si followed by steam oxidation. Using both Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM), we have found that a Ge layer forms as a result of Ge segregated at the moving SiO2 interface during steam oxidation. For a SiO2 layer that has swept through the implanted region, essentially all of the Ge is snow-ploughed and no Ge is lost to the oxide layer. The Ge layers and its two bounding interfaces, i.e., Ge/SiO2 and Ge/Si, have been characterized as a function of the implantation dose and energy. The thickness of the Ge layer formed is dependent on the implantation dose. Thicknesses from a fraction of a monolayer to greater than 50 monolayers of Ge can be formed on Si by this mechanism. Initially the Ge layer forms a coherent interface with the underlying Si with no misfit dislocations, and misfit dislocations only appear as the thickness of the film is increased