Comparison of arsenic and phosphorus diffusion behavior in silicon-germanium alloys

The diffusion behavior of ion-implanted arsenic and phosphorus in relaxed Si0.8Ge0.2 has been investigated. Under equilibrium, extrinsic conditions, both dopants are observed to diffuse faster in SiGe than in Si. Simulations of the measured profiles suggest that the ratio of the effective diffusivity in Si0.8Ge0.2 compared to that in Si is roughly seven for arsenic, and roughly two for phosphorus. Under transient diffusion conditions, the arsenic diffusivity in SiGe is retarded, and the magnitude of the diffusion is roughly the same as that in Si. This result suggests that it is possible to optimize the diffusion conditions to achieve n(+) source/drain junctions that are as shallow in SiGe as in Si. (C) 2002 American Institute of Physics.