Atomic structures and electronic properties of III-nitride alloy nanowires: A first-principle study

Abstract

On the basis of first-principle calculations, wurtzite Ga1−xAlxN, Al1−yInyN, In1−zGazN (x/y/z=0, 0.167, 0.333, 0.500, 0.667, 0.833) nanowires along the [001] growth direction are investigated. Atomic structures and electronic properties, including formation energy, atomic structures, bond lengths, E-Mulliken distributions, band structures and density of states of these ternary III-nitride nanowires are discussed. Results suggest that Al atoms can enhance the stability of alloys, oppositely, In atoms reduce the stability. After optimization, Ga, Al and In atoms tend to move outwards while N atoms slightly move inwards. For all alloy nanowires, the bond lengths from long to short all abide by an order as: In-N, Ga-N, Al-N, and the lengths vary slightly with different alloy composition. Ga-N shows the strongest covalence, followed by In-N, and the covalence of Al-N is the weakest. All the nanowires are indirect bandgap semiconductors with wide band gaps and thus are suitable for applications in flexible pulse wave sensors, light-emitting diodes and ultraviolet light detecting. With increasing Al constituent, In constituent and Ga constituent in Ga1−xAlxN, Al1−yInyN, In1−zGazN nanowires, the band gaps increase, decrease and increase, respectively. With the changes of the alloy compositions, the variation trend for the bowing parameters of the band gaps is similar to bulk phase Ga1−xAlxN, Al1−yInyN, In1−zGazN. The band gaps of III-nitride alloy nanowires depend on the hybridization of s and p states of Ga, Al and In with N 2s and 2p states, additionally, the Ga 3d and In 4d states only contribute to the lower valence band.