Reconstructions and electronic structure of (11(2)over-bar2) and (11(2)over-bar(2)over-bar) semipolar AlN surfaces

The energetics, atomic geometry, and electronic structure of semipolar (11 (2) over bar2) and (11 (2) over bar(2) over bar) AlN surfaces are investigated employing first principles calculations. For metal-rich growth conditions, metallic reconstructions are favoured on both polarity surfaces. For N rich to moderate Al rich conditions, the (11 (2) over bar2) planes promote semiconducting reconstructions having 2 x 2 or c(2 x 2) periodicity. In contrast, under the particular range of the Al chemical potential the (11 (2) over bar(2) over bar) surfaces stabilize reconstructions with excess metal and it is only at the extreme N rich limit that the semiconducting c(2 x 2) N adatom structure prevails. The present study reveals that the reconstructed (11 (2) over bar2) surfaces do not contain steps in contrast to (11 (2) over bar(2) over bar) where surface steps are inherent for N rich to moderate metal rich growth conditions and may result in intrinsic step-flow growth and/or growth of parasitic semipolar orientations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4743007]