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Impact ionization in GaAs: a screened exchange density functional approach

S. Picozzi·R. Asahi·C. B. Geller·A. Continenza·A. J. Freeman
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Abstract

Results are presented of a fully ab-initio calculation of impact ionization rates in GaAs within the density functional theory framework, using a screened-exchange formalism and the highly precise all-electron full-potential linearized augmented plane wave (FLAPW) method. The calculated impact ionization rates show a marked orientation dependence in {\bf k} space, indicating the strong restrictions imposed by the conservation of energy and momentum. This anisotropy diminishes as the impacting electron energy increases. A Keldysh type fit performed on the energy-dependent rate shows a rather soft edge and a threshold energy greater than the direct band gap. The consistency with available Monte Carlo and empirical pseudopotential calculations shows the reliability of our approach and paves the way to ab-initio calculations of pair production rates in new and more complex materials.

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S. Picozzi, R. Asahi, C. B. Geller, A. Continenza, A. J. Freeman. 2001-08-24. Impact ionization in GaAs: a screened exchange density functional approach. https://doi.org/10.1103/physrevb.65.113206

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