Correlation and morphology of dopant decomposition in Mn and Co codoped Ge epitaxial films

Atom probe tomography (APT) was used to quantify inhomogeneities in the distribution of Mn and Co in doped epitaxial Ge thin films for which X-ray diffraction (XRD) studies indicate single phase material. The segregation of dopants into Co and Mn-rich regions with characteristic sizes was evident upon visual inspection of the APT reconstruction and a frequency distribution analysis of the concentration of Co, Mn, and Ge atoms verified that the composition fluctuations exceeded those of a random alloy. Isoconcentration surfaces were generated to establish the connectedness of regions enriched in Mn that have been proposed to enhance the Curie temperature in dilute magnetic semiconductors. The analysis demonstrates important contributions that APT can make to the understanding of magnetism in these materials.