(460c) A Comparative Computational Study of Point Defect Aggregation in Germanium and Silicon

Point defect aggregation is an important factor to consider in the processing of bulk electronic materials such as silicon and germanium. While point defects are generally harmless and unavoidable, defect clusters can significantly reduce device yield and alter dopant distributions. Defect thermodynamic and transport properties have been extensively studied in crystalline silicon, but there exists a much more limited literature for germanium. On the other hand, germanium has recently received renewed interest for both electronic device fabrication as well as a substrate for multijunction photovoltaic devices.

In this talk, we present a computational study of point defects and their clusters in germanium, with direct comparisons to their counterparts in silicon. We consider both vacancy aggregates (voids) and self-interstitial clusters that can assume a multitude of morphologies ranging from three-dimensional disordered structures to several different types of planar configurations. We employ large-scale molecular dynamics simulations to perform direct simulations of the aggregation process, and interpret the results using a recently developed technique based on sampling the energy landscape associated with particular defects [1]. Both of these simulation frameworks are based on empirical interatomic potentials for silicon and germanium. In particular, results using the Tersoff [2], Modified Embedded-Atom Method (MEAM) [3], and Stillinger-Weber (SW) [4] interaction models are compared and contrasted for both materials.

[1] S. S. Kapur, M. Prasad, J. C. Crocker, and T. Sinno, Phys. Rev. B 72, 014119 (2005). [2] J. Tersoff, Phys. Rev. B 39 (1989) 5566. [3] E.H. Kim, Y.H. Shin, and B.J. Lee, Comp. Coupling Phase Diag. Therm. 32 (2007) 34. [4] S.J. Cook, P. Clancy, Phys. Rev. B 47 (1993) 7686.