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Structural and Electronic Properties of a-Gaas: A Tight-Binding–Molecular-Dynamics–Art Simulation

Published online by Cambridge University Press:  10 February 2011

Laurent J. Lewis
Affiliation:
Département de physique et GCM, Université de Montréal, C.P. 6128, Suce. Centre-Ville, Montréal, Québec, Canada H3C 3J7
Normand Mousseau
Affiliation:
Computational Physics — Faculty of Applied Physics, Technische Universiteit Delft, Lorentzweg 1, 2628 C J Delft, The Netherlands
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Abstract

By combining tight-binding (TB) molecular dynamics (MD) with the recently-proposed activation-relaxation technique (ART), we have constructed structural models of a-GaAs and a-Si of an unprecedented level of quality: the models are almost perfectly four-fold coordinated and, in the case of a-GaAs, exhibit a remarkably low density of homopolar bonds. In particular, the models are superior to structures obtained using melt-and-quench TB-MD or quantum MD. We find that a-Si is best described by a Polk-type model, while a-GaAs resembles closely the mechanical model proposed by Connell and Temkin, which is free of wrong bonds. In this paper, the structural, electronic, and dynamical properties of a-GaAs based on this approach will be reviewed, and compared to experiment and other structural models. Our study provides much-needed information on the intermediate-range topology of amorphous tetrahedral semiconductors; in particular, we will see that the differences between the Polk and Connell-Temkin models, while real, are difficult to extract from experiment, thus emphasising the need for realistic computer models.

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