Comment on “Diffusion of n-type dopants in germanium” [Appl. Phys. Rev. 1, 011301 (2014)]

The authors of the above paper call into question recent evidence on the properties of self-interstitials, I, in Ge [Cowern et al., Phys. Rev. Lett. 110, 155501 (2013)]. We show that this judgment stems from invalid model assumptions during analysis of data on B marker-layer diffusion during proton irradiation, and that a corrected analysis fully supports the reported evidence. As previously stated, I-mediated self-diffusion in Ge exhibits two distinct regimes of temperature, T: high-T, dominated by amorphous-like mono-interstitial clusters - i-morphs - with self-diffusion entropy30k, and low-T, where transport is dominated by simple self-interstitials. In a transitional range centered on 475°C both mechanisms contribute. The experimental I migration energy of 1.84±0.26 eV reported by the Münster group based on measurements of self-diffusion during irradiation at 550°C<T<680°C further establishes our proposed i-morph mechanism.