Ab initio calculations were performed in order to study P diffusion in Ge via vacancy and interstitial-mediated mechanisms as well as a correlated exchange mechanism without interaction with a mediating defect. It was found that the most favorable diffusion mechanism was sensitive to the position of the Fermi level within the band gap. For material with a mid-gap Fermi level, the neutral or singly positive P interstitial was the dominant diffusing species, while in n-type material, it was the doubly negative P-vacancy complex. For a Fermi level position of Ev+0.5eV, a barrier for P diffusion via the doubly negative P-vacancy defect of ~2.5eV was calculated, which was roughly 1eV below the equivalent process in Si.

Ab Initio Investigation of Phosphorus Diffusion Paths in Germanium. C.Janke, R.Jones, S.Öberg, P.R.Briddon: Physical Review B, 2008, 77[19], 195210 (7pp)

Table 5

Diffusivity of Be in Ge0.65Si0.35

Table 6

Diffusivity of Be in Ge0.20Si0.80

Figure 2

Diffusivity of Co, Cr and Fe in Ge

(Squares: Co, circles; Fe; triangles, Cr)