Directional radiation beam from yellow-emitting InGaN-based nanocolumn LEDs with ordered bottom-up nanocolumn array

Yellow-emitting (572 nm) InGaN-based nanocolumn LEDs, consisting of orderly arranged bottom-up nanocolumns in a triangular lattice, were fabricated. We observed a spectral linewidth of 37.3 nm at 226 A/cm 2 , which was exceptionally narrow for yellow emission. The periodic arrangement of nanocolumns leads to the photonic crystal effect. We measured the angular dependence of the emission spectrum, using which the photonic band diagram was experimentally traced, evincing that the yellow light was diffracted at the photonic band edge. As a result, a highly directional radiation beam with a radiation angle of ±20° suitable for display applications was successfully demonstrated.