Self- and dopant diffusion in germanium under thermal equilibrium and irradiation conditions was reviewed; including the underlying mechanisms of diffusion and the point defects involved. Diffusion in Ge under thermal equilibrium conditions was controlled mainly by vacancies. However, Ge interstitials mediated the diffusion under concurrent annealing and irradiation. This was verified by the diffusion behavior of self-atoms, boron, phosphorus and arsenic under proton irradiation. The diffusion under irradiation was explained with the property of the Ge surface that was proposed to be an insufficient sink for Ge interstitials. As a consequence, a supersaturation of self-interstitials was established during irradiation, whereas the vacancy concentration was kept at thermal equilibrium. This explains that under irradiation the diffusion of self- and dopant atoms via self-interstitials became visible that was otherwise negligible under conventional annealing conditions. The findings indicated ways of switching between vacancy and self-interstitial mediated diffusion and revealed new strategies in the diffusion doping of Ge for technological applications.

Diffusion and Doping Issues in Germanium. H.Bracht, S.Schneider, R.Kube: Microelectronic Engineering, 2011, 88[4], 452-7