Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 63: Group IV elements and compounds
HL 63.5: Vortrag
Donnerstag, 19. März 2015, 10:30–10:45, EW 015
Iron segregation at dislocations in silicon: a combined first-principles and kinetic Monte Carlo study — •Benedikt Ziebarth1,2, Matous Mrovec2, Christian Elsässer2, and Peter Gumbsch1,2 — 1Karlsruher Institute of Technology, Karlsruhe, Germany — 2Fraunhofer IWM, Freiburg, Germany
The efficiency of silicon based solar-cells is strongly affected by internal defects and impurities. Metallic impurities, in particular interstitial iron, result in a large loss of electric power production as they act as recombination centers for photo-induced charge carriers. It is known that metallic impurities like iron atoms are influenced by stress fields inside the silicon crystal. Here, we present a systematic study on how iron impurities are influenced by stress fields of dislocations in silicon using first-principles methods based on density functional theory. In a first step, the formation energies of iron impurities in bulk silicon has been investigated for hydrostatic, uniaxial and shear strain. Surprisingly, the most stable configuration of interstitial iron – the tetrahedral site – seems to be unaffected by any deformation of the crystal. Other configurations, however, are affected by deformations which results in a different diffusivity of Fe. The first-principles results from the formation energies are carried over to a kinetic Monte Carlo simulation in order to understand the effect on diffusion by a stress field induced by a screw dislocation or a 60∘ mixed dislocation. The kinetic Monte Carlo simulations reveal an effective segregation of iron atoms to the compressive-strain region of the mixed dislocation.