Antireflection structure of self-organized GaN nanotips

Self-organized GaN nanotips, which were nanoscale tip-shaped pillar structure, were fabricated by reactive ion etching using chlorine plasma. It has been found that the structure has a two-dimensional isotropic distribution with broadband periodicity of subwavelength from the ultraviolet (UV) to the visible (VIS) region by Fourier transform analysis. The nanotips exhibited a diameter of approximately 20 nm, a most frequent periodicity of 96 nm and a height of approximately 200 nm on the GaN surface. The reflectance of the nanotip surface was significantly suppressed to less than 0.01 compared with 0.3 of the smooth surface in UV region. The transmittance was also improved approximately 12% at longer wavelength than the band edge (∼365 nm). We have found that the nanotip surface provides antireflection and enhanced transmission effects from the UV to the VIS region (300 nm to 900 nm). These excellent antireflective-properties of the self-organized GaN nanotips are expected to improve the performances of light-emitting and photo-detective devices.