Boron diffusion in high-dose germanium-implanted silicon

We report the boron diffusion characteristics in Ge/sup +/-implanted Si with a peak Ge fraction of 12% and a B dose of 10/sup 12/ cm/sup -2/, annealed at 900/spl deg/C for 80 mins in a N/sub 2/ ambient. The boron diffusivity is four times lower than that in Si implanted with the same dose of B and annealed under identical conditions. TEM studies and SIMS results confirm the presence of extended defects in the surface region, end-of-range (EOR) defective region beyond the amorphous/crystalline interface (X/sub a/c/), and threading dislocations in between. The retardation is partially due to the trapping of B atoms and/or self-interstitials by extended defects remaining after the solid phase epitaxy. Future work is required if the dominant cause is to be determined.