Giant growth-plane optical anisotropy in wurtzite InN/GaN disk-in-wire structures

• Published in: Superlattices and microstructures 2012-11, Vol.52 (5), p.949-961
• Main Authors: Merrill, Ky, Yalavarthi, Krishna, Ahmed, Shaikh
• Format: Article
• Language: English
• Subjects: Anisotropy; Disks; Gallium nitrides; III-nitride LEDs; Molecular structure; Optical polarization; Piezoelectricity; Spontaneous polarization; Strain; Symmetry; Tight-binding; Wavefunctions; Wurtzite
• ISSN: 0749-6036; 1096-3677
• DOI: 10.1016/j.spmi.2012.08.001

► Simulations consider millions of atom within 20-band tight-binding formalism. ► Internal fields are long-ranged and significantly lower the crystal symmetry. ► Strong suppressions of the interband optical transitions. ► Growth-plane optical polarization ratio is significantly large. ► Transition rates and anisotropy are strong function of InN disk thickness. Using a combination of valence force-field molecular mechanics, 20-band sp3d5s∗ atomistic tight-binding approach, and appropriate post-processing tools, we have studied the origin and nature of optical polarization anisotropy in semiconducting GaN/InN/GaN disk-in-wire structures having wurtzite crystal symmetry and varying InN disk thicknesses. True atomistic symmetry due to the presence of strong internal fields, coupled with quantum mechanical size quantization effects, results in unconventional characteristics in the electronic structure related to non-degeneracy in the excited P states and rotation (symmetry lowering) in the wavefunctions. The optical polarization ratio projected on the XY (growth) plane and, in particular, the transition rates have been shown to be strongly dependent on the crystal internal fields and the thickness of the InN disk.