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Comparative Study of Defect Properties in GaN: Ab Initio and Empirical Potential Calculations

Published online by Cambridge University Press:  01 February 2011

Fei Gao ,
Eric J. Bylaska ,
Anter El-Azab  and
William J. Weber
Fei Gao
Affiliation:
Pacific Northwest National Laboratory, MS K8–93, P. O. Box 999, Richland, WA 99352, USA
Eric J. Bylaska
Affiliation:
Pacific Northwest National Laboratory, MS K8–93, P. O. Box 999, Richland, WA 99352, USA
Anter El-Azab
Affiliation:
Pacific Northwest National Laboratory, MS K8–93, P. O. Box 999, Richland, WA 99352, USA
William J. Weber
Affiliation:
Pacific Northwest National Laboratory, MS K8–93, P. O. Box 999, Richland, WA 99352, USA
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Abstract

Density functional theory (DFT) is used to study the formation, properties and atomic configurations of monovacancies, antisite defects and possible interstitials in GaN. The relaxation around a vacancy is generally small, but the relaxation around antisite defects is large, particularly for a Ga antisite defect, which is not stable and converts to an N-N<0001> split interstitial. All N interstitials, starting from any possible site, eventually transfer into the N-N split interstitials, forming N2 molecules with one N-N bond, but also some covalent bonds to the surrounding atoms. In the case of Ga interstitials, the most favorable configuration is the Ga octahedral interstitial. However, it is found that the Ga-Ga<1120> split interstitial can bridge the gap between non-bonded Ga atoms along the <1120> direction, which leads to the formation of Ga atomic wires in GaN, with bond distance (2.3Å) close to those noted in bulk Ga. In addition, two representative potentials, namely Stillinger-Weber and Tersoff-Brenner potentials, have been employed to determine the formation of defects using molecular dynamics (MD) method in GaN. The MD results are discussed and compared to DFT calculations. The present DFT and MD results provide guidelines for evaluating the quality and fit of empirical potentials for large-scale simulations of ion-solid interaction and thermal annealing of defects in GaN.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 792: Symposium R – Radiation Effects and Ion Beam Processing of Materials , 2003 , R6.7
Copyright
Copyright © Materials Research Society 2004

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