Radiogenic Sn Impurity Defects in Germanium

Sn impurity defect structures in germanium have been investigated by Mössbauer emission spectroscopy on the 24 keV γ-radiation of 119 Sn. The defects have been created by ion implantation of radioactive 119 In + and 119 Sb + which both populate the Mössbauer level of 119 Sn in their decays. From the Mössbauer parameters (hyperfine structure and Debye-Waller factor) determined, the Sn atoms are concluded to be incorporated in a number of different defect structures. For both implantations of 119 In and 119 Sb, large substitutional fractions are found. An interstitial fraction, which is attributed to non-bonding interstitial sites of the Sn atoms, is identified. Three further defect structures, each found for either 119 In or 119 Sb implantations only, are attributed to different Sn-vacancy complexes. For 119 In implantations, one complex is proposed to be a (substitutional) Sn-vacancy pair characterized by a dangling bond at the Sn atom. For 119 Sb implantations, more than one vacancy is associated to the impurity atoms, which is proposed to result in a structurally different defect. A third impurity-vacancy defect type found for 119 In implantations is modelled to consist of interstitial Sn atoms in the center of a divacancy. The three vacancy complexes anneal at different annealing temperatures.