Impact ionization in GaAs a screened exchange density functional approach.pdfVIP

1 Impact ionization in GaAs: a screened exchange density 0 0 2 functional approach g u A S. Picozzi∗ 4 2 INFM - Dip. Fisica, Univ. L’Aquila, 67010 Coppito (L’Aquila), Italy ] i c s - R.Asahi l r t m Toyota Central R D Labs., Inc., Nagakute, Japan . t a m C.B.Geller - d n Bettis Atomic Power Laboratory, West Mifflin, PA 15122, USA o c [ A.Continenza 1 v 0 INFM - Dip. Fisica, Univ. L’Aquila, 67010 Coppito (L’Aquila), Italy 0 4 8 0 A. J. Freeman 1 0 Department of Physics and Astronomy and Materials Research Center / t a m Northwestern University, Evanston, IL 60208 (U.S.A.) - d n o c Abstract : v i X r Results are presented of a fully ab-initio calculation of impact ionization rates a 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 k space, indicating the strong restrictions imposed by the conservation of energy and momentum. This ∗Corresponding author: silvia.picozzi@aquila.infn.it 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