First-principles calculations of gap bowing in In x Ga 1 − x N and<mml:…
2002; American Physical Society; Volume: 65; Issue: 7 Linguagem: Inglês
10.1103/physrevb.65.075213
ISSN1095-3795
Autores Tópico(s)Advanced Chemical Physics Studies
ResumoFirst-principles pseudopotential plane-wave calculations are used to investigate the electronic, structural, and thermodynamic properties of cubic nitride alloys ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ and ${\mathrm{In}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{N}.$ The alloys are described within a cluster-expansion method considering configurations in large 64-atom supercells. We find a strong composition-dependent gap bowing for both InGaN and InAlN alloys. The strongest contribution to the gap bowing is due to a structural effect, i.e., the composition-induced disorder in the bond lengths. Charge transfer is found to be important only for InAlN alloys. A small deviation from Vegard's law is found for the lattice parameter variation in InGaN and InAlN alloys. The calculated first- and second-nearest-neighbor distances in ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ alloys are in good agreement with the experimental data. The investigation of the thermodynamic stability of InGaN and InAlN alloys shows a significant tendency for spinodal decomposition.
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