We report the observation of lasing action from optically pumped gallium nitride nanorod arrays in a quasicrystal
pattern. The nanorods were fabricated from a GaN substrate by nanoimprint patterned etching, followed by epitaxial
regrowth to form crystalline facets. The imprint was a 12-fold symmetric quasicrystal pattern. The regrowth grew a
multiple quantum well core-shell structure on nanorods. The cathodoluminescent emission of quantum wells red shifts
from the bottom to top region of nanorod. Under optical pumping, multiple lasing peaks were observed. The lasing
modes formed by 12-fold symmetric photonic quasicrystal nanorod arrays are discussed.
An electrically driven nanopyramid green light emitting diode (LED) was demonstrated. The nanopyramid arrays were
fabricated from a GaN substrate by patterned nanopillar etch, pillar side wall passivation, and epitaxial regrowth.
Multiple quantum wells were selectively grown on the facets of the nanopyramids. The fabricated LED emits green
wavelength under electrical injection. The emission exhibits a less carrier density dependent wavelength shift and higher
internal quantum efficiency as compared with a reference c-plane sample at the same wavelength. It shows a promising
potential for using nanopyramid in high In content LED applications.
We report the efficiency droop behaviors of InGaN/GaN blue LEDs with different thickness of GaN quantum barriers
(QBs). The droop percentage from efficiency peak to 70 A/cm2 is only about 10% as reducing the thickness of GaN QBs
from 104 Å to 33 Å. A less carrier localization has been observed from wavelength dependent time resoled
photoluminescence measurement as reducing the thickness of GaN QBs. The alleviation of droop percentage may due to
more uniform distribution of electron and hole carrier in the active region, which resulted from super-lattice (SL) like
active structure. The crystalline quality does not become worse from the results of v-pits density even thickness of GaN
QBs is as low as 33 Å. The SL like active structure could be a potential structure to alleviate the efficiency droop for the
application of solid state general lighting.