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We integrated into GaN LEDs both two-dimensional photonic crystal patterns and angled sidewall deflectors. The resultant devices exhibited about three-fold enhancement in vertical emission intensity when compared with the planar reference LED device.
We demonstrated CW laser operation of GaN-based VCSELs under current injection at 77 K. CW laser action was achieved at a threshold current of 1.4 mA, emitting at 462 nm with a narrow linewidth of about 0.15 nm.
We report on the study of incorporation of organic thin film semiconductors with GaN to explore new types of photodetector or solar cell application. Photovoltaic effect and photoconductivity gain have been demonstrated using GaN/CuPc and GaN/alpha -NPD hybrid device structure, which offer new opportunities in design of versatile optoelectronic devices.
We have observed resonance-enhanced Stokes and anti-Stokes Raman scattering of coherent picosecond pulses by one as well as two longitudinal-optical phonons in GaN film grown on Si (111) substrate.
A high emitting efficiency GaN-based white LED with 2D PQC on surface and PSS were successfully fabricated. After packaging, 21% enhancement in emitting luminous flux was achieved under the driving current 20 mA.
Angular and spectral reflectivities of GaN nano-pillar structures are investigated for heights of 350 nm, 550 nm and 720 nm. Calculations based on rigorous coupled-wave analysis show excellent agreement with the measured reflectivities for s- and p-polarizations.
The authors report on the spectroscopy and laser results of diode pumped Pr-doped fluorides. We obtained efficient laser emission in the visible range with LiYF4, LiLuF4 and LiGdF4 crystals.
We report the lasing behaviors of a GaN defect photonic crystal membrane structure. The high Q factor and low threshold condition show the effective photon confinement with the full photonic band gap structure.
The azimuthal anisotropy of GaN photonic crystal light-emitting diode is investigated using an annular structure. The extracted light distribution has P/S ratio of 5.5 for light propagating in GammaX direction and 2.1 for GammaM direction.
We report on a first successful operation of current-driven GaN photonic-crystal surface-emitting laser, which can operate in blue-violet wavelength regions at room temperature.
We report fabrication of GaN-based two-dimensional surface emitting photonic-crystal lasers and successful demonstration of lasing action at room temperature with the emission wavelength at 424.3 nm and a low threshold pumping energy density of 3.5 mJ/cm2.
The physical origin of efficiency droop in GaN-based light-emitting diodes when driven with high current is systematically investigated. Based on our simulations and experimental results, a polarization-matched active region is proposed as the solution.
We observe polarized terahertz emission from nonpolar gallium nitride due to an in-plane polarization terminated by stacking faults. A measured flip of the THz waveform polarity agrees with carrier transport in an in-plane electric field.
Ultrafast wavelength-tunable optical measurements on semiconductor nanowires allow us to independently probe the dynamics of electrons, holes, and defect states. These investigations reveal the influence of two-dimensional confinement on carrier dynamics in these nanosystems.
We demonstrated nanostructured semipolar III-nitride light emitters on low cost c-plane GaN templates using one-step epitaxy. The total light emission efficiency is improved by a factor of 2.6 compared to polar emitters at room temperature.
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