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We demonstrate ultrafast self- and cross-absorption saturation and self-phase modulation based on near-infrared intersubband transitions in GaN/AlN quantum-well waveguides designed to minimize the nonlinear switching energy.
An InGaN/GaN thin-film light-emitting diode with the photonic crystal (PhC) on the surface and a TiO2/SiO2 omnidirectional reflector on the bottom was fabricated and found the line-width emission spectrum of 5 nm by the PhC.
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 present time-resolved photoluminescence on InGaN/GaN multiple-quantum well LEDs grown on nonpolar and semipolar bulk GaN substrates and investigate increasing indium concentrations toward higher power, longer wavelength light emitters.
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.
We demonstrate the high light-extraction efficiency by using the photoelectrochemical etching technique for forming photonic crystal structures on an InGaN/GaN quantum-well light-emitting diode through phase-mask interference. More than 90% increase of output power is observed.
Optimization studies of InGaN quantum wells light emitting diodes employing SiO2/polystyrene microlens arrays are conducted. The use of microlens arrays leads to increase in light extraction efficiency by 2.7-times, in agreement with simulation.
InGaN micro-hole-array LEDs (mu-LEDs) with and without oxide-film on it were fabricated. Compared with conventional LED, output power of mu-LEDs without and with oxide film have enhancement of 38% and 82% at 20 mA, respectively.
We have studied the crystal orientation effect on optical anisotropy in InGaN/GaN quantum-well light-emitting diodes. The absolute value of the anisotropy is found to increase rapidly with increasing crystal angle.
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.
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.
Three-pair AlGaN/GaN multiple quantum well structure with superlattice was grown using metal-organic chemical vapor deposition system. The AlGaN barrier and GaN well of the MQW were grown by atomic layer deposition and conventional growth, respectively.
Self-consistent optical gain analysis of strain-compensated InGaN-AlGaN quantum wells (QWs) using 6-band kldrp formalism shows 28% improvement, which is suitable for laser active regions. MOCVD-grown strain-compensated InGaN QW exhibited 62.7% improvement in integrated luminescence intensity.
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.
We have evidenced hot and cold longitudinal-optical (LO) phonons induced by electric field and resonant Raman scattering in GaN/AlN triangular quantum well, probed by first-order and second-order resonant Raman scattering of 3-ps light pulses.
Patterning the dicing streets technology was used to define the high extraction efficiency region of InGaN-GaN multiple-quantum-well light-emitting diodes (LEDs). The external quantum efficiency (EQE) of the LEDs at 20 mA increased by 12.9% because of the roughening of the passive region which enhanced the escape cone.
In this paper, we have studied the band structure of InGaN based quantum dot devices. The valence force field model and k middot p method have been applied to study the band structures in InGaN quantum dot devices including the piezoelectric polarization effects. A comparison with InGaN quantum wells shows that InGaN quantum dots can provide better e-h overlap and reduce the radiative lifetime. The...
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.
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