Response to "Comment on 'Diffusion of n-type dopants in germanium' " [Appl. Phys. Rev. 2, 036101 (2015)]

Abstract

In this reply to the comment of Cowern et al., we demonstrate on the basis of full numerical simulations of radiation enhanced dopant diffusion via the kick-out mechanism that the g/λ analysis fails to consistently describe boron (B) diffusion in germanium (Ge) under irradiation. Cowern et al. missed to perform a consistency check with results for the diffusivity DI of Ge interstitials (I) determined from Ge self-diffusion under irradiation. Data deduced for DI from the exponential B profile reported by Cowern et al. deviate several orders of magnitude from the self-diffusion study. This clearly disproves the validity of the kick-out mechanism to control radiation enhanced B diffusion in Ge. Exponential B profiles like those established in Ge under irradiation are also reported for silicon by Venezia et al. [Phys. Rev. B 69, 125215 (2004)]. The characteristic shape is not described by the kick-out mechanism but rather explained qualitatively by the complex formation and dissolution of defect clusters. Modeling of B diffusion in Ge under irradiation performed by Schneider et al. [Phys. Rev. B 87, 115202 (2013)] is fully consistent with self-diffusion under irradiation. This constraint led us to conclude that the characteristic B profiles are additionally affected by the formation of immobile B clusters. Although a direct microscopic proof of B cluster formation is still lacking, the report of Venezia et al. on B clustering in Si during irradiation with similar exponential B profiles also supports our interpretation of B diffusion in Ge under irradiation.