The charge state of mobile vacancy-impurity complexes in Ge was studied via the effect of p-type (Ga) doping upon Ga and Sn diffusion (figures 4 and 5). Significant Sn diffusion retardation as a function of doping concentration suggested that diffusion was dominated by negatively-charged vacancy-Sn complexes. The Ga diffusion was essentially unaffected by doping; suggesting that diffusion was dominated by vacancy-Ga complexes having the same charge state as isolated negatively-charged Ga ions. A clear 2 orders of magnitude higher diffusivity of group-V elements in Ge, as compared to that of group-III and IV elements, could be well explained by the present findings.

Vacancy-Impurity Complexes and Diffusion of Ga and Sn in Intrinsic and P-Doped Germanium. I.Riihimäki, A.Virtanen, S.Rinta-Anttila, P.Pusa, J.Räisänen, Isolde: Applied Physics Letters, 2007, 91[9], 091922