It was pointed out that the introduction of high-permittivity gate dielectric materials into complementary metal oxide semiconductor technology had renewed interest in Ge as a channel material. But since HfO2 and ZrO2 were two of the most promising dielectric candidates, it was important to investigate whether Hf and Zr could diffuse into the Ge channel. Using ab initio density functional theory calculations, a study was made of substitutional and interstitial Hf and Zr impurities in c-Ge, with the object of looking for neutral defects. It was found that substitutional Zr and Hf defects were energetically more favourable than were interstitial defects, that under oxygen-rich conditions neither Zr nor Hf migration towards the channel was likely to occur, and that under either Hf- or Zr-rich conditions it was very likely (particularly for Zr) that defects would be incorporated in the channel.

Theoretical Investigation of Hf and Zr Defects in c-Ge. W.L.Scopel, A.Fazzio, A.J.R.da Silva: Journal of Physics - Condensed Matter, 2009, 21[1], 012206