Accurate modelling of average phosphorus diffusivities in germanium after long thermal anneals: evidence of implant damage enhanced diffusivities

Average phosphorous diffusivities after implantation in < 100 > germanium have been measured for long anneals (i.e., 3-10 h) at temperatures from 600 to 800 degrees C. Considerable dose loss after annealing is also observed and quantified for temperatures below 800 degrees C. A diffusion model using an extrinsic diffusivity coefficient combined with a segregation component between the germanium and the oxide, to account for dopant loss, is found to be sufficient to completely explain the observed diffusion profiles. The best-fit diffusivity and segregation coefficients are reported for this model and the diffusivities are found to be over an order of magnitude slower than those measured after rapid thermal annealing (i.e., short anneals of only a few seconds). It is proposed that this disagreement of diffusivities between short and long anneals is due to implant damage perhaps similar to well-known transient enhanced diffusion effects observed in silicon.