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   Reconstructions and electronic structure of (11-22) and (11-2-2) semipolar AlN surfacesKalesaki, Efterpi  ; ; et alin Journal of Applied Physics (2012), 112 The energetics, atomic geometry, and electronic structure of semipolar (11-22) and (11-2-2) AlN surfaces are investigated employing first principles calculations. For metal-rich growth conditions ... [more ▼] The energetics, atomic geometry, and electronic structure of semipolar (11-22) and (11-2-2) 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 (11-22) planes promote semiconducting reconstructions having 2 × 2 or c(2 × 2) periodicity. In contrast, under the particular range of the Al chemical potential the (11-2-2) surfaces stabilize reconstructions with excess metal and it is only at the extreme N rich limit that the semiconducting c(2 × 2) N adatom structure prevails. The present study reveals that the reconstructed (11-22) surfaces do not contain steps in contrast to (11-2-2) 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. [less ▲] Detailed reference viewed: 228 (2 UL)Electronic structure of 1/6⟨20-23⟩ partial dislocations in wurtzite GaN; Kalesaki, Efterpi ; et alin Journal of Applied Physics (2011), 109 The I1 intrinsic basal stacking faults (BSFs) are acknowledged as the principal defects observed on {11-20} (a-plane) and {1-100} (m-plane) grown GaN. Their importance is established by recent ... [more ▼] The I1 intrinsic basal stacking faults (BSFs) are acknowledged as the principal defects observed on {11-20} (a-plane) and {1-100} (m-plane) grown GaN. Their importance is established by recent experimental results, which correlate the partial dislocations (PDs) bounding I1 BSFs to the luminescence characteristics of GaN. PDs are also found to play a critical role in the alleviation of misfit strain in hetero-epitaxially grown nonpolar and semipolar films. In the present study, the energetics and the electronic structure of twelve edge and mixed 1/6⟨20-23⟩ PD configurations are investigated by first principles calculations. The specific PD cores of the dislocation loop bounding the I1 BSF are identified for III-rich and N-rich growth conditions. The core structures of PDs induce multiple shallow and deep states, attributed to the low coordinated core atoms, indicating that the cores are electrically active. In contrast to edge type threading dislocations no strain induced states are found. [less ▲] Detailed reference viewed: 426 (0 UL) |
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