Diffusion of Boron in Germanium and Si1-xGex (x>50%) alloys

Boron diffusion in germanium and relaxed Si1-xGex alloys with Ge content x>50% is reported. Relaxed SiGe layers were grown by LEPECVD and boron was introduced using ion implantation. Samples were given equal thermal budgets using furnace annealing. Diffusivity values of boron have been extracted. The results confirm that diffusion of boron in germanium is indeed slower than that reported in literature. The diffusivity of boron was found to increase gradually for x>50% at 900°C but the increase is not substantial. We found that pairing model is not sufficient to explain boron diffusivity behavior in SiGe alloys over the entire range of germanium content. The results suggest that an interstitial mediation of boron diffusion in germanium should be considered.