Experimental study of diffusion and segregation in a Si-(GexSi1−x) heterostructure

Experimental results have been obtained on the segregation coefficients of boron, phosphorus, and arsenic in the Si-(${\mathrm{Ge}}_{\mathit{x}}$ ${\mathrm{Si}}_{1\mathrm{-}\mathit{x}}$) heterostructure. It is found that boron tends to segregate into the ${\mathrm{Ge}}_{\mathit{x}}$ ${\mathrm{Si}}_{1\mathrm{-}\mathit{x}}$ layer, while phosphorus and arsenic tend to segregate away from it. The results are discussed within the framework of Hu’s recent theory. The important factor is the ‘‘ideal work function’’ difference between two regions of the heterostructure; this difference can be estimated from the band-gap change and the band offsets. The effect of pseudomorphic strain energy is found to be appreciable for boron. Within experimental error, the diffusivities have not been appreciably affected.