Hetero-structures of GeSi layers on Si have been produced by high dose Ge implantation into p-type (100) Si wafers at 150 or 300 keV at various doses. From spreading resistance profiling measurements, it is found that for samples implanted at 300 keV at a sufficiently high dose, there is an unexpected resistivity type conversion due to the Ge implantation. The depths of the n-p junction formed as-implanted can be larger than 1.5 /xm, far beyond the Ge projected range. Upon annealing, the junction position moves toward the surface and eventually stops at a depth corresponding to the thickness of the GeSi layer. However, no such n-p junction formation was observed in the spreading resistance profiles of the 150 keV implanted samples. These spreading resistance results are discussed in conjunction with results from RBS and SIMS experiments.