Radius-dependent polarization anisotropy in semiconductor nanowires

Polarization anisotropy in semiconductor nanowires is studied using the standard eight-band k·p theory. We show that the anisotropy ratio ranges from giant (∼90%) to moderate (∼60%) for the nanowire radius between 3 and 10 nm. Our result resolves an apparent contradiction between a recent tight-binding study [M. P. Persson and H. Q. Xu, Phys. Rev. B 70, 161310(R) (2004)], which predicts 100% anisotropy, and an earlier k·p study [P. C. Sercel and K. J. Vahala, Phys. Rev. B 44, 5681 (1991)], which predicts 60% anisotropy independent of radius. We show that with proper inclusion of band mixing, the k·p theory agrees well with the tight-binding study on anisotropy.