Rabie M.A., Haddara Y.M.*McMaster University, CA*

Keywords: diffusivity, empirical model, germanium diffusivity, germanium self diffusivity, modeling, physics based modeling, self diffusivity, SiGe, silicon-germanium

We propose a physics-based model for the Ge diffusivity in SiGe and empirically fit the model to previously reported experimental results. The self-diffusivity of Ge can be given by: DGe=D0*exp(Sx)*exp(-E/kT) where x is the Ge concentration, E is the activation energy given by 3.85 eV, S is a measure of the vacancy disorder entropy given by 11.56, D0 is the pre-exponential factor given by 0.137 cm2/sec, k is the Boltzmann constant and T is the temperature. The given values offer the best match with the published experimental data. It has been well-established in the literature that self-diffusion in pure Ge is mediated only by vacancies. It has been also shown that Ge diffusion is dominated by a vacancy mechanism at low temperatures. Since the published data on Ge diffusivity are in most cases for experiments done at temperatures lower than 1050 ºC, therefore; the only dominant mechanism for the self-diffusion of Ge is the vacancy exchange mechanism. The new term modifying the regular diffusivity equation to relate the diffusivity to the change in Ge concentration is a consequence of the change in the point defects disorder entropy as a result of adding more Ge atoms to the SiGe system.

Journal: TechConnect Briefs

Volume: 3, Nanotechnology 2008: Microsystems, Photonics, Sensors, Fluidics, Modeling, and Simulation – Technical Proceedings of the 2008 NSTI Nanotechnology Conference and Trade Show, Volume 3

Published: June 1, 2008

Pages: 583 - 585

Industry sectors: Advanced Materials & Manufacturing | Sensors, MEMS, Electronics

Topic: Informatics, Modeling & Simulation

ISBN: 978-1-4200-8505-1