Diffusion of phosphorus in relaxed Si1-xGex films and strained Si/Si1-xGex heterostructures

Phosphorus diffusion has been 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 is found to increase with increasing Ge content, while the influence of compressive strain results in a decrease in diffusivity as compared to that in relaxed material. The effect of strain is found to be equivalent to an apparent activation energy of -13 eV per unit strain, where the negative sign indicates that the P diffusion is mediated by interstitials in Si1-xGex (x<0.20). This conclusion is also supported by an experiment utilizing injection of Si self-interstitials, which results in an enhanced P diffusion in strained Si1-xGex. Further, P is found to segregate into Si across Si/Si1-xGex interfaces and the segregation coefficient increases with increasing Ge concentration. (C) 2003 American Institute of Physics.