Diffusion of beryllium in Ge and Si-Ge alloys

Diffusion of implanted Be-7 in Si1-xGex (x=0.20,0.65,1.00) systems has been studied under intrinsic conditions in the temperature range of 460-720 degrees C by the modified radiotracer technique. Arrhenius-type behavior with activation enthalpies of 2.0 eV for Ge and 2.5 eV for the Si-Ge alloys was noted. Unexpectedly, the diffusivity of beryllium is higher in the Si0.80Ge0.20 material than in Si0.35Ge0.65 which is discussed in terms of possible prevailing diffusion mechanisms. It is proposed that Be diffusion in Si1-xGex systems is dissociative mechanism dominated for germanium rich materials and the kick-out (or interstitialcy) mechanism dominates in silicon rich materials. (C) 2008 American Institute of Physics.