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Atomistically Informed Electrostatic Model of an Edge Dislocation in a Complex Crystalline Material

Department of Mechanical Science & Engineering, University of Illinois at Urbana-Champaign, USA

Jun-Qiang Lu

Department of Mechanical Science & Engineering, University of Illinois at Urbana-Champaign, USA

H.T. Johnson

Department of Mechanical Science & Engineering, University of Illinois at Urbana-Champaign, USA

Dislocations are not only mechanical features of crystalline materials, but also complex electrostatic features; this has important implications for understanding electrical and optical properties of real semiconductor materials. An edge dislocation in a semiconductor material becomes electrically charged when free electrons migrate to the dangling bonds along the core; the line charge along the core is then partially screened by the background free carrier concentration. In this work we consider the atomistic structure of an edge dislocation in a technologically important compound semiconductor material, GaN, and develop a complete continuum model of the electrostatic structure of the dislocation. The atomistic analysis is used to determine the maximum charged state of the dislocation core according to first principles electronic structure analysis; the maximum charged state is then expressed as a continuum electrostatic potential. By formulating an energy balance model as a function of the incremental filling of electron acceptor sites, the equilibrium electrostatic state of the dislocation is then determined. This electrostatic state can then be used as the basis for predictive models of electrical scattering or optical absorption.

Key Words: GaN • dislocation • filling fraction • charge distribution • atomistic structure

Mathematics and Mechanics of Solids, Vol. 13, No. 3-4, 267-291 (2008)
DOI: 10.1177/1081286507086902


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