The diffusion of B was studied at 800 to 900C by using implantation doping and B-doped epitaxial Ge layers. The concentration profiles, before and after furnace annealing, were obtained by using high-resolution secondary ion mass spectroscopy. The diffusion coefficients were calculated by fitting the annealed profiles. Diffusivity values were obtained which were at least 2 orders of magnitude lower than any values previously reported. By using these values, an activation energy of 4.65eV was calculated (figure 13). These results suggested that an interstitial-mediated mechanism could be considered for B-diffusion in Ge; in accord with recent theoretical calculations. The annealed secondary ion mass spectrometry profiles also suggested that the B solid solubility in Ge was about 2 x 1018/cm3 at 875C; again in agreement with published values.

S.Uppal, A.F.W.Willoughby, J.M.Bonar, N.E.B.Cowern, T.Grasby, R.J.H.Morris, M.G.Dowsett: Journal of Applied Physics, 2004, 96[3], 1376-80

Table 67

Diffusion of Ga in Ge