Browsing by Author "Yeh, W. Y."

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Anisotropy light extraction with high polarization ratio from photonic crystal fight-emitting diodes
(2008)
Lai, Chun-Feng
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Kuo, Hao-Chung
;
Lu, Tien-Chang
;
Wang, Shing-Chang
;
Chao, C. H.
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 fight propagating in Gamma X direction and 2.1 for Gamma M direction. @2007 Optical Society of America
Anisotropy of light extraction from two-dimensional photonic crystal light-emitting diodes
(2007-09-17)
Lai, Chun-Feng
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Kuo, H. C.
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Chao, C. H.
;
Hsueh, H. T.
;
Wang, J.-F. T.
Anisotropic light extraction of photonic crystal (PhC) light-emitting diodes in the azimuthal direction has been investigated with an annular structure of triangular PhC lattice. The optical images of the photoluminescence light extraction are obtained with laser excitation. For increasing lattice constant, sixfold symmetric patterns with varying numbers of petals in multiples of six are observed and analyzed. A map of the anisotropy for various lattice constants and numerical apertures is constructed. Several features of light propagations associated with the PhC are observed including the focusing and collimating behaviors.(c) 2007 American Institute of Physics.
Azimuthal anisotropy of light extraction from photonic crystal light-emitting diodes
(2008)
Lai, Chun-Feng
;
Kuo, H. C.
;
Chao, C. H.
;
Hsueh, H. T.
;
Wang, J. -F. T.
Photonic crystal (PhC) light-emitting diodes (LEDs) exhibiting anisotropic light extraction have been investigated experimentally and theoretically. It is found that the anisotropic light extraction strongly depends on the lattice constant and orientation. Optical images of the anisotropy in the azimuthal direction are obtained using annular structure with triangular lattice. 6-fold symmetric light extraction patterns with varying number of petals are observed. More petals in multiple of 6 appear in the observed image with lattice constant increasing. This anisotropic behavior suggests a new means to optimize the PhC design of GaN LED for light extraction.
Azimuthal anisotropy of light extraction from photonic crystal light-emitting diodes
(2007)
Hsuch, H. T.
;
Wang, J. -F. T.
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Chao, C. H.
;
Yeh, W. Y.
;
Chi, J. Y.
Photonic crystal light-emitting diodes exhibiting anisotropic light extraction efficiency have been investigated experimentally and theoretically. Images of the anisotropy in the azimuthal direction are obtained using annular structures with triangular lattice. Depending on the lattice constants, 6-fold symmetric patterns with varying number of petals are obtained.
Hole shape effect of photonic crystals on the guided resonance modes in GaN-based ultra-thin film-transferred light-emitting diodes
(2010)
Lai, C. F.
;
Chao, C. H.
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Kuo, H. C.
;
Yu, P.
;
Yeh, W. Y.
The guided resonance mode affected the different hole shapes of photonic crystals in GaN ultra-thin film-transferred light-emitting diodes. The ellipse-hole PhC extracted a fewer modes than the regular PhC due to the lattice symmetry break. @2010 Optical Society of America
Improvement of GaN-based LED with SiO2 photonic crystal on an ITO film by holographic lithography
(2008)
Yen, H. H.
;
Kuo, H. C.
;
Yeh, W. Y.
;
光電工程學系
;
Department of Photonics
GaN-based light-emitting diode (LED) with SiO2 photonie crystals (PCs) structure made by holographic lithography on an indium-tin-oxide (ITO) film was fabricated. The PCs made on SiO2 but an ITO film both improves the light extraction efficiency of the GaN-based LED and prevents the sheet resistance increasing of the ITO film from the dry etching damage. It was found that the forward voltage at 20 mA of the GaN-based LED with SiO2 PCs on an ITO film was 1.9% higher than the GaN-based LED with a planar ITO film only. The output power of GaN-based LED with SiO2 PCs on an ITO film at 20mA was 17.1%, 26.5% and 125.3% higher than that of the GaN-based LEDs with the planar SiO2/ITO, planar ITO or Ni/Au surface layers, respectively.
Micro-Photoluminescence from a Single InGaN-based Nano-Pillar Fabricated by Focused Ion Beam Milling
(2008)
Yen, H. H.
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Chiu, C. H.
;
Yu, Peichen
;
Kao, C. C.
;
Lin, C.
Micro-photoluminescence from GaN/InGAN multiple quantum wells embedded in a nano-pillar structure with a diameter of 300nm is characterized. The emission spectrum shows a blue shift of 68.3 meV in energy due to strain relaxation. (c) 2008 Optical Society of America
Strain relaxation induced microphotoluminescence characteristics of a single InGaN-based nanopillar fabricated by focused ion beam milling
(2008-08-25)
Yu, Peichen
;
Chiu, C. H.
;
Wu, Yuh-Renn
;
Yen, H. H.
;
Chen, J. R.
A freestanding nanopillar with a diameter of 300 nm and a height of 2 mu m is demonstrated by focused ion beam milling. The measured microphotoluminescence (mu-PL) from the embedded InGaN/GaN multiple quantum wells shows a blueshift of 68 meV in energy with a broadened full width at half maximum, similar to 200 meV. Calculations based on the valence force field method suggest that the spatial variation of the strain tensors in the nanopillar results in the observed energy shift and spectrum broadening. Moreover, the power-dependent mu-PL measurement suggests that the strain-relaxed emission region exhibits a higher radiative recombination rate than that of the strained region, indicating potential for realizing high-efficiency nanodevices in the UV/blue wavelength range. (C) 2008 American Institute of Physics.