A comparative DFT study of the structural and electronic properties of nonpolar GaN surfaces (original) (raw)

Applied Surface Science, 2014

Abstract

ABSTRACT A comparative analysis of the geometry and the electronic characteristics of nonpolar GaN surfaceswas carried out using density-functional theory (DFT) with different approximations for the exchange-correlation energy (LDA, PBE, PBEsol, RPBE, TPSS, revTPSS, and HSE). The obtained data show that theGaN(1 0¯1 0) (m-plane) is more energetically stable than the GaN(1 1¯2 0) (a-plane) surface. However,these surfaces have similar surface relaxation geometry, with a Ga-N surface bond-length contraction ofaround 6–7% and a Ga-N surface rotational angle in the range of 6–9◦. Our results show that the use ofdifferent exchange-correlation functionals does not significantly change the surface energy and surfacegeometry. In addition, we found the presence of surface intra-gap states that reduce the band gap of thenonpolar GaN surface with respect to the bulk value, in agreement with recent photoelectron and surfaceoptical spectroscopy experiments.

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