Multicolor Emission from Ultraviolet GaN-Based Photonic Quasicrystal Nanopyramid Structure with Semipolar InxGa1-xN/GaN Multiple Quantum Wells.

In this study, we demonstrated large-area high-quality multi-color emission from the 12-fold symmetric GaN photonic quasicrystal nanorod device which was fabricated using the nanoimprint lithography technology and multiple quantum wells regrowth procedure. High-efficiency blue and green color emission wavelengths of 460 and 520 nm from the regrown InxGa1-xN/GaN multiple quantum wells were observed under optical pumping conditions. To confirm the strong coupling between the quantum well emissions and the photonic crystal band-edge resonant modes, the finite-element method was applied to perform a simulation of the 12-fold symmetry photonic quasicrystal lattices.

Significantly improved luminescence properties of nitrogen-polar (0001Ì ) InGaN multiple quantum wells grown by pulsed metalorganic chemical vapor deposition.

We have demonstrated nitrogen-polar (0001̅) (N-polar) InGaN multiple quantum wells (MQWs) with significantly improved luminescence properties prepared by pulsed metalorganic chemical vapor deposition. During the growth of InGaN quantum wells, Ga and N sources are alternately injected into the reactor to alter the surface stoichiometry. The influence of flow duration in pulsed growth mode on the luminescence properties has been studied. We find that use of pulsed-mode creates a high density of hexagonal mounds with an increased InGaN growth rate and enhanced In composition around screw-type dislocations, resulting in remarkably improved luminescence properties. The mechanism of enhanced luminescence caused by the hexagonal mounds is discussed. Luminescence properties of N-polar InGaN MQWs grown with short pulse durations have been significantly improved in comparison with a sample grown by a conventional continuous growth method.

Electrically driven green, olivine, and amber color nanopyramid light emitting diodes.

We report the fabrication and studies of electrically driven green, olivine, and amber color nanopyramid GaN light emitting diodes (LEDs). InGaN/GaN multiple quantum wells (MQWs) were grown on the nanopyramid semipolar facets. Compared with the commonly used (0001) c-plane MQWs, the semipolar facet has lower piezoelectric field, resulting in much faster radiative recombination efficiency. This is important for high In content MQWs. The measured internal quantum efficiencies for green, olivine, and amber color LED are 30%, 25%, and 21%, respectively. The radiative and non-radiative lifetime of the semipolar MQWs are also investigated.

Lasing action in gallium nitride quasicrystal nanorod arrays.

We report the observation of lasing action from an optically pumped gallium nitride quasicrystal nanorod arrays. The nanorods were fabricated from a GaN substrate by patterned etching, followed by epitaxial regrowth. The nanorods were arranged in a 12-fold symmetric quasicrystal pattern. The regrowth grew hexagonal crystalline facets and core-shell multiple quantum wells (MQWs) on nanorods. Under optical pumping, multiple lasing peaks resembling random lasing were observed. The lasing was identified to be from the emission of MQWs on the nanorod sidewalls. The resonant spectrum and mode field of the 12-fold symmetric photonic quasicrystal nanorod arrays is discussed.