Thin germanium-rich layers have been formed by the implantation of Ge into Si substrates, followed by a wet oxidation process. We have measured the germanium concentration profile of layers formed by this method for samples initially implanted to a dose of 1 x 1017cm-2. Structural, optical, and electronic probes have been used, all of which yield similar results. The results from Ruth-erford backscattering (RBS), Auger spectroscopy (AES), Raman spectroscopy, and electroreflectance (ER) show that the germanium-rich layer is about 300A thick, and contains an average germanium concentration of 65%. The SiGe/Si interface is not sharp but diffuse, with a decreasing germanium concentration. In addition, the data suggest a thin layer of Si13Ge87 near the Si02/SiGe interface.