Diffusion of Sb in Si1-xGex-Alloy Layers

The diffusion in Si1-xGex alloy lasers, and the change in diffusivity due to chemical effects and secondly strain effects was investigated. All structures were grown by MBE (molecular beam epitaxy) in a VG-80 system on n+-type (100)-oriented Si substrates. The relaxed Si layer was formed by deposition of δ1m of Si with a thin Sb doped layer 200 nm below the surface. The strained Si(SiGe) layer was grown on a relaxed Si.92Ge.08 (Si) layer as a top cap. The diffusivity of Sb was found to be concentration and time independent and described within a diffusion model in which the as-grown profile is allowed to broaden with time according to the concentration gradient and the overall diffusion coefficient. The chemical peak concentration of Sb in the as-grown layers is comparable to the intrinsic carrier concentration, thus the concentration effect is expected to be negligible.