American Institute of Physics, Applied Physics Letters, 26(101), p. 261904
DOI: 10.1063/1.4773185
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We present an experimental lattice location study of Ga atoms in Ge after ion implantation at elevated temperature (250 degrees C). Using extended x-ray absorption fine structure (EXAFS) experiments and a dedicated sample preparation method, we have studied the lattice location of Ga atoms in Ge with a concentration ranging from 0.5 at. % down to 0.005 at. %. At Ga concentrations <= 0.05 at:%, all Ga dopants are substitutional directly after ion implantation, without the need for post-implantation thermal annealing. At higher Ga concentrations, a reduction in the EXAFS amplitude is observed, indicating that a fraction of the Ga atoms is located in a defective environment. The local strain induced by the Ga atoms in the Ge matrix is independent of the Ga concentration and extends only to the first nearest neighbor Ge shell, where a 1% contraction in bond length has been measured, in agreement with density functional theory calculations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773185]