Crystal structure and optical properties of a high-density InGaN nanoumbrella array as a white light source without phosphors

摘要

High-density arrays of nanocrystals with peculiar, umbrella-like shapes can act as low-cost white light sources that require no phosphors. The bright optical emissions of gallium nitride based semiconductors are enhanced under nanoscale confinement into shapes such as wires or disks. Turning nitride nanocrystals into photonic devices typically requires complex fabrication, but Tetsuya Kouno from Japan’s Shizuoka University and co-workers have uncovered a simpler route using a special nitrogen-polarized template. Exposing this substrate to gallium and nitrogen gas beams produced arrays of self-assembled nanocolumns. Then, a quick plasma treatment with additional indium gas caused spherical plates to grow on top of the columns. Because each nanoumbrella structure is a ‘whispering gallery mode’ photonic cavity with slightly varying shape, they potentially respond to laser stimulations with a range of optical emissions broad enough for white-light applications.