Boron Diffusion in Si_1−x Ge_x Strained Layers

Boron diffusion in Sia7 Gea3 strained layers has been studied as a function of annealing temperature and is compared to boron diffusion in unstrained Si epitaxial layers. A lower diffusivity was observed in Sia7 Gea3 strained layers as compared to the Si control samples. Using the well-accepted model for boron diffusion via charged point defects in Si, the intrinsic diffusivities of the boron atoms in the Sia7 Gea3 layers were derived and an activation energy of 4.4 eV was estimated for the diffusion process.A new approach to describe the diffusion process is also presented here. In this model, we relate the lower diffusivity to a corresponding change in the charged point defect equilibrium concentration caused by a change in band-gap due to the strain and the existence of foreign atoms in a Si matrix.