Anomalous Sb redistribution during the preparation of delta-doping layers in silicon

We have studied Sb segregation at the moving crystal-amorphous Si(001) interface during preparation of Sb delta-doping layers. X-ray reflectivity measurements reveal a broadening of the delta-doping profile as a result of segregation during amorphous Si crystallization. From ion backscattering measurements, in conjunction with channeling and blocking, it is inferred that bulk diffusion constants are too low to account for the observed segregation behavior. The observed broadening is ascribed to enhanced diffusion at the c-Si/a-Si interface. This interfacial diffusion coefficient is determined to be at least two orders of magnitude larger than the diffusion coefficient in bulk a-Si. Possible causes of this enhancement are discussed.