Diffusion behavior of ion-implanted n-type dopants in silicon germanium

The diffusion behavior of ion implanted arsenic and phosphorus in relaxed-Si0.8Ge0.2 is investigated. Both dopants exhibit enhanced diffusivities in SiGe compared to those in Si under equilibrium conditions. The ratio of the effective diffusivity in SiGe relative to that in Si is found to be approximately seven for arsenic, and roughly two for phosphorus at high concentrations. Under transient diffusion conditions, arsenic diffusion in SiGe is retarded while arsenic diffusion in Si is enhanced by the ion implant damage. The transient retardation of arsenic diffusion in SiGe is observed at temperatures ranging from 900 to 1050degreesC. These results suggest that using arsenic, it is possible to form n(+)/p junctions in relaxed-Si0.8Ge0.2 as shallow as those in Si, by optimizing the implant annealing conditions.