Influence of InAiN Nanospiral Structures on the Behavior of Reflected Light Polarization

The influence of structural configurations of indium aluminum nitride (InA1N) nanospirals, grown by reactive magnetron sputter epitaxy, on the transformation of light polarization are investigated in terms of varying structural chirality, growth temperatures, titanium nitride (TiN) seed (buffer) layer thickness, nanospiral thickness, and pitch. The handedness of reflected circularly polarized light in the ultraviolet-visible region corresponding to the chirality of nanospirals is demonstrated. A high degree of circular polarization (P-c) value of 0.75 is obtained from a sample consisting of 1.2 mu m InA1N nanospirals grown at 650 degrees C. A film-like structure is formed at temperatures lower than 450 degrees C. At growth temperatures higher than 750 degrees C, less than 0.1 In-content is incorporated into the InA1N nanospirals. Both cases reveal very low P-c-A red shift of wavelength at P-c peak is found with increasing nanospiral pitch in the range of 200-300 nm. The P-c decreases to 0.37 for two-turn nanospirals with total length of 0.7 mu m, attributed to insufficient constructive interference. A branch-like structure appears on the surface when the nanospirals are grown longer than 1.2 mu m, which yields a low P-c around 0.5, caused by the excessive scattering of incident light.