The diffusion of P was studied in relaxed Si1–xGex samples (x = 0.11 and 0.19) and strained Si/Si1–xGex/Si heterostructures (x = 0.08, 0.13 and 0.18). The diffusivity of P was found to increase with increasing Ge content (figure 21), while the influence of compressive strain resulted in a decrease in diffusivity as compared to that in relaxed material. The effect of strain was found to be equivalent to an apparent activation energy of –13eV per unit strain, where the negative sign indicated that diffusion was mediated by interstitials in Si1–xGex (x < 0.20). This conclusion was also supported by the injection of Si self-interstitials, which resulted in an enhanced P diffusion in strained Si1–xGex.

Diffusion of Phosphorus in Relaxed Si1–xGex Films and Strained Si/Si1–xGex Heterostructures. J.S.Christensen, H.H.Radamson, A.Y.Kuznetsov, B.G.Svensson: Journal of Applied Physics, 2003, 94[10], 6533-40

Figure 21

Diffusivity of P in Si1-xGex

Figure 22

Diffusivity of P in Si0.8Ge0.2

(Open circles: P in SiGe; filled circles: P in Si)