**Simulation and modeling of the electronic structure of GaAs damage
clusters**

JE Moussa and SM Foiles and PA Schultz, JOURNAL OF APPLIED PHYSICS, 113, 093706 (2013).

DOI: 10.1063/1.4794164

In an effort to build a stronger microscopic foundation for radiation
damage models in gallium arsenide (GaAs), the electronic properties of
radiation-induced damage clusters are studied with atomistic
simulations. Molecular dynamics simulations are used to access the time
and length scales required for direct simulation of a collision cascade,
and density functional theory simulations are used to calculate the
electronic properties of isolated damaged clusters that are extracted
from these cascades. To study the physical properties of clusters, we
analyze the statistics of a randomly generated ensemble of damage
clusters because no single cluster adequately represents this class of
defects. The electronic properties of damage clusters are accurately
described by a classical model of the electrical charging of a
semiconducting sphere embedded in a uniform dielectric. The effective
band gap of the cluster depends on the degree of internal structural
damage, and the gap closes to form a metal in the high-damage limit. We
estimate the Fermi level of this metallic state, which corresponds to
high-energy amorphous GaAs, to be 0.46+/-0.07 eV above the valence band
edge of crystalline GaAs. (C) 2013 American Institute of Physics.
**http://dx.doi.org/10.1063/1.4794164**

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