Regensburg 2013 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 50: Computational Materials Modelling - Defects & Interfaces I

MM 50.2: Talk

Thursday, March 14, 2013, 10:30–10:45, H24

Stability and Mobility of Point Defects in Silicon Studied with Hybrid Density-Functional Theory Including van der Waals Interactions — •Wang Gao and Alexandre Tkatchenko — Fritz-Haber-Institut der MPG, Berlin, Germany

The intrinsic point defects often significantly affect the electronic and optical properties of semiconductors; therefore their study is important from both fundamental and technological points of view. However, our understanding of self-diffusion in Si remains incomplete and full of controversies, despite decades of seminal work on the subject. Here we present a study of the stability and mobility of point defects in Si and heavier semiconductors using hybrid density-functional theory including screened long-range van der Waals (vdW) interactions [1,2]. The reduction in crystal symmetry around defect sites results in pronounced polarization, which strongly depends on the effective dimensionality of the defect. Furthermore, the screened vdW interactions promote the diffusion of interstitials by decreasing the activation energy by as much as 0.5 eV and suppress the formation of vacancies, supporting the self-diffusion mechanism proposed from P mobility experiments [3]. Notably, our calculations explain a series of experimental observations for the diffusion of interstitials, vacancies, and foreign atoms in Si. For heavier and more polarizable semiconductors, such as Ge, GaAs, and InAs, vdW interactions are found to play an increasingly important role on the stability of point defects, increasing the formation energy by as much as 0.27 eV (11.2%). [1] G. X. Zhang, et al., PRL (2011). [2] A. Tkatchenko, et al., PRL (2012). [3] A. Ural, et al., PRL (1999).