-
Yang Kuo,
Shao-Ying Ting,
Che-Hao Liao,
Jeng-Jie Huang,
Chih-Yen Chen,
Chieh Hsieh,
Yen-Cheng Lu,
Cheng-Yen Chen,
Kun-Ching Shen,
Chih-Feng Lu, Dong-Ming Yeh,
Jyh-Yang Wang,
Wen-Hung Chuang,
Yean-Woei Kiang,
C C Yang
[show abstract]
[hide abstract]
ABSTRACT: The experimental demonstrations of light-emitting diode (LED) fabrication with surface plasmon (SP) coupling with the radiating dipoles in its quantum wells are first reviewed. The SP coupling with a radiating dipole can create an alternative emission channel through SP radiation for enhancing the effective internal quantum efficiency when the intrinsic non-radiative recombination rate is high, reducing the external quantum efficiency droop effect at high current injection levels, and producing partially polarized LED output by inducing polarization-sensitive SP for coupling. Then, we report the theoretical and numerical study results of SP-dipole coupling based on a simple coupling model between a radiating dipole and the SP induced on a nearby Ag nanoparticle (NP). To include the dipole strength variation effect caused by the field distribution built in the coupling system (the feedback effect), the radiating dipole is represented by a saturable two-level system. The spectral and dipole-NP distance dependencies of dipole strength variation and total radiated power enhancement of the coupling system are demonstrated and interpreted. The results show that the dipole-SP coupling can enhance the total radiated power. The enhancement is particularly effective when the feedback effect is included and hence the dipole strength is increased.
Optics Express 07/2011; 19 Suppl 4:A914-29. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The implementation of a series of optically pumped GaN photonic crystal (PhC) membrane lasers is demonstrated at room temperature. The photonic crystal is composed of a scalene-triangular arrangement of circular holes in GaN. Three defect structures are fabricated for comparing their lasing characteristics with those of perfect PhC. It is observed that all the lasing defect modes have lasing wavelengths very close to the band-edge modes in the perfect PhC structure. Although those lasing modes, including band-edge and defect modes, have different optical pump thresholds, different lasing spectral widths, different quality factors (Q factors), and different polarization ratios, all their polarization distributions show maxima in the directions around one of the hole arrangement axes. The similar lasing characteristics between the band-edge and defect modes are attributed to the existence of extremely narrow partial band gaps for forming the defect modes. Also, the oriented polarization properties are due to the scalene-triangle PhC structure. In one of the defect lasing modes, the lasing threshold is as low as 0.82 mJ cm(-2), the cavity Q factor is as large as 1743, and the polarization ratio is as large as 25.4. Such output parameters represent generally superior lasing behaviors when compared with previously reported implementations of similar laser structures.
Nanotechnology 01/2011; 22(2):025201. · 3.98 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The enhancement of light extraction by fabricating a surface grating structure around the mesa of a light-emitting diode (LED) with an approach combining photoelectrochemical (PEC) wet etching and phase mask interferometry is demonstrated. The PEC etching rate is controlled by the intensity of illuminating UV light, which is spatially modulated by the fringe pattern of phase mask interferometry, for forming the grating structure. Without affecting the resistance characteristics of the device, the diffraction of such a grating structure leads to LED output enhancement by > 43% on either the top or bottom side.
IEEE Photonics Technology Letters 06/2010; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Surface plasmon polariton and localized surface plasmon couplings with InGaN/GaN quantum wells in bluegreen light-emitting diodes are used for enhancing their emission efficiencies by 25–200 % depending on the used quantum well crystal quality.
Nano-Optoelectronics Workshop, 2008. i-NOW 2008. International; 09/2008
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
Nano-Optoelectronics Workshop, 2008. i-NOW 2008. International; 09/2008
-
[show abstract]
[hide abstract]
ABSTRACT: The output enhancement of a green InGaN/GaN quantum-well (QW) light-emitting diode (LED) through the coupling of a QW with localized surface plasmons (LSPs), which are generated on Ag nanostructures on the top of the device, is demonstrated. The suitable Ag nanostructures for generating LSPs of resonance energies around the LED wavelength are formed by controlling the Ag deposition thickness and the post-thermal-annealing condition. With a 20 mA current injected onto the LED, enhancements of up to 150% in electroluminescence peak intensity and of 120% in integrated intensity are observed. By comparing this with a similar result for a blue LED previously published, it is confirmed that surface plasmon coupling for emission enhancement can be more effective for an InGaN/GaN QW of lower crystal quality, which normally corresponds to the emission of a longer wavelength.
Nanotechnology 08/2008; 19(34):345201. · 3.98 Impact Factor
-
Min Yann Hsieh,
Cheng Yin Wang,
Liang Yi Chen,
Tzu Pu Lin,
Min Yung Ke,
Yun Wei Cheng,
Yi Cheng Yu,
Cheng Pin Chen, Dong Ming Yeh,
Chih Feng Lu,
Chi Feng Huang,
C.C. Yang,
Jian Jang Huang
[show abstract]
[hide abstract]
ABSTRACT: A practical approach to fabricate textured GaN-based light-emitting diodes (LEDs) by nanosphere lithography is presented. By spin coating a monolayer of SiO<sub>2</sub> nanoparticles as the mask, textured LEDs can be fabricated. Both textured p-GaN and textured indium tin oxide LEDs show significant improvement over conventional LEDs without damaging the electrical characteristics. The results show that the method is promising for manufacturing low-cost high-efficient GaN-based LEDs.
IEEE Electron Device Letters 08/2008; · 2.85 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The authors demonstrate the implementation of a white-light device by spin-coating CdSe/ZnS nanocrystals (NCs) on the top of a blue/green two-color InGaN/GaN quantum-well light-emitting diode for converting blue and green emissions into red light through the absorption/reemission process. Meanwhile, Au nanoparticles are mixed with CdSe/ZnS NCs for generating localized surface plasmon (LSP) modes to couple with the CdSe/ZnS NCs. The LSP modes can absorb green emission and effectively transfer the energy into the CdSe/ZnS NCs through the coupling process for enhancing red emission. With the LSP coupling process, the conversion efficiency from the blue/green range into red light can be increased by around 30%. The conversion quantum efficiency can reach 52.8%.
Applied Physics Letters 03/2008; 92(9):091112-091112-3. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Two approaches for fabricating white-light light-emitting diodes are discussed, including the stacking of various InGaN/GaN quantum wells for mixing into white light and the use of ll-VI nano-crystals for converting short-wavelength photons into long-wavelength light.
Optical Fiber Communication and Optoelectronics Conference, 2007 Asia; 11/2007
-
[show abstract]
[hide abstract]
ABSTRACT: The authors demonstrate the coupling effects between the quantum well (QW) and surface plasmon (SP) generated nearby on the p-type side in an InGaN/GaN single-QW light-emitting diode (LED). The QW-SP coupling leads to the enhancement of the electroluminescence (EL) intensity in the LED sample designed for QW-SP coupling and reduced SP energy leakage, when compared to a LED sample of weak QW-SP coupling or significant SP energy loss. In the LED samples of significant QW-SP coupling, the blueshifts of the photoluminescence and EL emission spectra are observed, indicating one of the important features of such a coupling process. The device performance can be improved by using the n-type side for SP generation such that the device resistance can be reduced and the QW-SP coupling effect can be enhanced (by further decreasing the distance between the QW and metal) because of the higher carrier concentration in the n-type layer.
Applied Physics Letters 10/2007; 91(17):171103-171103-3. · 3.84 Impact Factor
-
Applied Physics Letters. 10/2007; 91:183107--3.
-
[show abstract]
[hide abstract]
ABSTRACT: We demonstrate the variations of the photoluminescence (PL) spectral peak position and intensity through the surface plasmon (SP) coupling with an InGaN/GaN quantum well (QW) by forming Ag nanostructures of different scale sizes on the QW structure with thermal annealing. By transferring an Ag thin film into a nanoisland structure, we can not only enhance the PL intensity, but also adjust the SP dispersion relation and hence red-shift the effective QW emission wavelength. Such an emission spectrum control can be realized by initially coating Ag films of different thicknesses. Although the screening process of the quantum-confined Stark effect, which can result in PL spectrum blue-shift and intensity enhancement, also contributes to the variations of the emission behaviour, it is found that the SP-QW coupling process dominates in the observed phenomena.
Nanotechnology 07/2007; 18(26):265402. · 3.98 Impact Factor
-
C.C. Yang,
Chi-Feng Huang, Dong-Ming Yeh,
Cheng-Yen Chen,
Chih-Feng Lu,
Tsung-Yi Tang,
Jeng-Jie Huang,
Yen-Cheng Lu,
Yung-Shen Chen,
Wen-Yu Shiao,
Kun-Ching Shen,
Yun-Li Li,
J.J. Huang
[show abstract]
[hide abstract]
ABSTRACT: We report some recent developments in all-semiconductor multi-color and white-light light-emitting diodes. The potential of the development of phosphor-free all-InGaN/GaN quantum-well white-light light-emitting diode will be evaluated.
Lasers and Electro-Optics, 2007. CLEO 2007. Conference on; 06/2007
-
Applied Physics Letters. 05/2007; 90:193103--3.
-
Applied Physics Letters. 04/2007; 90:183114--3.
-
[show abstract]
[hide abstract]
ABSTRACT: The authors demonstrate the metallic-structure dependent surface plasmon (SP) coupling behaviors with a blue-emitting In Ga N / Ga N quantum well (QW), which is 10 nm away from the metallic structures. The SP-QW coupling behaviors in the areas of semiconductor surface coated with silver thin film and silver nanoparticles are compared. It is found that both the suppression of photoluminescence (PL) intensity and the reduction of time-resolved PL (TRPL) decay time strongly depend on the metallic morphology. A phenomenological model of carrier relaxation in the SP-QW coupling process is built to fit the TRPL decay profiles for calibrating the reasonable decay time constants of carrier and SP.
Applied Physics Letters 12/2006; · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We grew and processed a blue/green two-wavelength light-emitting diode (LED) based on the mixture of two kinds of quantum wells (QW) in epitaxial growth. The X-ray diffraction and photoluminescence measurements indicated that the crystalline structure and the basic optical property of individual kinds of QW are not significantly changed in the mixed growth. The relative electroluminescence (EL) intensity of the two colors depends on the injection current level, which controls the hole concentration distribution among the QWs. At low injection levels, the top green-emitting QW dominates in EL. As the injection current increases, the blue-emitting QWs beneath become dominating. We also coated CdSe-ZnS nanocrystals on the top of the two-wavelength LED for converting blue photons into red light. With the coating of such nanocrystals, the device emits blue, green, and red lights for white light generation
IEEE Photonics Technology Letters 08/2006; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We investigate the contribution of sidewall illumination in InGaN-GaN quantum-well-based light-emitting diode (LED) arrays with various cell radii. The intensity contribution from the array sidewall decreases with the increase of radius as the perimeter/area ratio is reduced. We then compare the effects of current spreading in the LED arrays of different sizes and conclude that the effect of current spreading needs to be given full consideration when the cell size in a microarray becomes larger. This letter provides a novel approach to calculate the intensity contributions of sidewall illumination and current spreading to GaN-based LED arrays.
IEEE Photonics Technology Letters 05/2006; · 2.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nanoposts of 10–40 nm top diameter on an InGaN/GaN quantum well structure were fabricated using electron-beam lithography and inductively coupled plasma reactive ion etching. Significant blue shifts up to 130 meV in the photoluminescence (PL) spectrum were observed. The blue-shift range increases with decreasing post diameter. For nanoposts with significant strain relaxation, the PL spectral peak position becomes less sensitive to carrier screening. On the basis of the temperature-dependent PL and time-resolved PL measurements and a numerical calculation of the effect of quantum confinement, we conclude that the optical behaviours of the nanoposts are mainly controlled by the combined effect of 3D quantum confinement and strain relaxation.
Nanotechnology 02/2006; 17(5):1454. · 3.98 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Blue-red polychromatic light-emitting devices are fabricated by attaching red-emitting CdSe-ZnS nano-crystals on a blue-emitting InGaN-GaN multiple-quantum-well (MQW) structure. To improve the red/blue intensity contrast, holes of different diameters are fabricated for increasing the direct contact area between the MQW active regions and CdSe-ZnS nano-crystals. By comparing the devices of 10-, 50-, 60-, and 70-mum hole diameters, and a reference device of no hole, it is found that the hole diameter of 60 mum represents an optimized condition from the viewpoint of maintaining high quantum efficiency. However, the device of 10-mum holes has the highest red/blue intensity ratio, which corresponds to a 36% increase. This result is attributed to its largest side-wall area in the holes among various samples
IEEE Photonics Technology Letters 02/2006; · 2.19 Impact Factor
