Multi-color broadband visible light source via GaN hexagonal annular structure.

Multi-color and broadband visible emission was realized thorough the hexagonal annular structure of GaN. The annular structure fabricated by selective-area growth emitted purple, blue and green color-emission from the multi-facets. The hexagonal annular structure provided various sidewalls of {101} and {112} semi-polar facets, and (0001) polar facet. From the cathodoluminescence study, the (0001) plane had the longest wavelength of 525 nm, and the {101} facet of 440 nm peak wavelength had longer wavelength emission than the {112} of 412 nm peak wavelength. The origin of longer wavelength emission of {101} was mostly due to high In-composition, as well as slightly larger well thickness, which means that {101} facet has higher In-incorporation efficiency. Various In-composition of each facet provided multi-color and broadband emission with the international commission on illumination (CIE) of (0.22, 0.45) and high emission efficiency. The hexagonal annular structure becomes building blocks for highly efficient broadband visible lighting sources.