Browsing by Author "Huang, H. W."

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Efficiency Improvement of GaN-Based LEDs With a SiO(2) Nanorod Array and a Patterned Sapphire Substrate
(2010-06-01)
Huang, H. W.
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Huang, J. K.
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Lin, C. H.
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Lee, K. Y.
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Hsu, H. W.
The enhancement of light extraction from GaN-based light-emitting diodes (LEDs) with a patterned sapphire substrate (PSS) and a SiO(2) 12-fold photonic quasi-crystal (PQC) structure using nanoimprint lithography is presented. At a driving current of 20 mA on transistor-outline-can package, the light output powers of LED with a PSS and LED with a PSS and a SiO(2) PQC structure are enhanced by 35% and 48%, compared with the conventional LED. In addition, the higher output power of the LED with a PSS and a SiO(2) PQC structure is due to better reflectance on PSS and higher epitaxial quality on an n-GaN using a SiO(2) 12-fold PQC structure pattern. These results provide promising potential to increase output powers of commercial light-emitting devices.
Efficiency Improvement of GaN-Based LEDs With a SiO2 Nanorod Array and a Patterned Sapphire Substrate
(2010-06-01)
Huang, H. W.
;
Huang, J. K.
;
Lin, C. H.
;
Lee, K. Y.
;
Hsu, H. W.
The enhancement of light extraction from GaN-based light-emitting diodes (LEDs) with a patterned sapphire substrate (PSS) and a SiO2 12-fold photonic quasi-crystal (PQC) structure using nanoimprint lithography is presented. At a driving current of 20 mA on transistor-outline-can package, the light output powers of LED with a PSS and LED with a PSS and a SiO2 PQC structure are enhanced by 35% and 48%, compared with the conventional LED. In addition, the higher output power of the LED with a PSS and a SiO2 PQC structure is due to better reflectance on PSS and higher epitaxial quality on an n-GaN using a SiO2 12-fold PQC structure pattern. These results provide promising potential to increase output powers of commercial light-emitting devices.
Enhanced light output from a nitride-based power chip of green light-emitting diodes with nano-rough surface using nanoimprint lithography
(2008-05-07)
Huang, H. W.
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Lin, C. H.
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Yu, C. C.
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Chiu, C. H.
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Lai, C. F.
Enhanced light extraction from a GaN-based power chip (PC) of green light-emitting diodes (LEDs) with a rough p-GaN surface using nanoimprint lithography is presented. At a driving current of 350 mA and with a chip size of 1 mm x 1 mm packaged on transistor outline (TO)-cans, the light output power of the green PC LEDs with nano-rough p-GaN surface is enhanced by 48% when compared with the same device without a rough p-GaN surface. In addition, by examining the radiation patterns, the green PC LED with nano-rough p-GaN surface shows stronger light extraction with a wider view angle. These results offer promising potential to enhance the light output powers of commercial light-emitting devices by using the technique of nanoimprint lithography under suitable nanopattern design.
Enhanced light output power of GaN-based vertical-injection light-emitting diodes with a 12-fold photonic quasi-crystal by nano-imprint lithography
(2009-08-12)
Huang, H. W.
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Lin, C. H.
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Lee, K. Y.
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Yu, C. C.
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Huang, J. K.
GaN-based thin-film vertical-injection light-emitting diodes (VLEDs) with a 12-fold photonic quasi-crystal (PQC) by nano-imprint lithography (NIL) are fabricated and presented. At a driving current of 20 mA and with a chip size of 350 mu m x 350 mu m, the light output power of our thin-film LED with a 12-fold PQC structure reaches 41 mW. This result is an enhancement of 78% when compared with the output power of a VLED without a PQC structure. In addition, the corresponding light radiation pattern shows a narrower beam shape due to the strong guided light extraction effect by the formed PQC structure in the vertical direction.
Enhanced vertical extraction efficiency from a thin-film InGaN-GaN light-emitting diode using a 2-D photonic crystal and an omnidirectional reflector
(2008-05-01)
Lin, C. H.
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Yen, H. H.
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Lai, C. F.
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Huang, H. W.
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Chao, C. H.
An InGaN-GaN thin-film vertical-type light-emitting diode with a two-dimensional photonic crystal (PC) on the emitting surface and a TiO2-SiO2 onmidirectional reflector on the bottom was fabricated. The device was investigated by performing a series of experiments and numerical computations. Electroluminescence measurement revealed a strong extraction enhancement in the vertical direction at 433-nm wavelength. The emission spectrum of the light was found to be strongly modified by the PC to have a significantly narrow linewidth of 5 nm. Our experimental results were in accord with those obtained from our numerical findings.
Enhanced vertical extraction efficiency from a thin-film InGaN/GaN photonic crystal light-emitting diodes
(2008)
Lai, Chun-Feng
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Huang, H. W.
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Lin, C. H.
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Kno, H. C.
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Lu, T. C.
An InGaN/GaN thin-film light-emitting diode with the photonic crystal (PhC) on the surface and a TiO(2)/SiO(2) omnidirectional reflector on the bottom was fabricated and found the line-width emission spectrum of 5 nm by the PhC. (C) 2007 Optical Society of America
Enhancement of InGaN-GaN indium-tin-oxide flip-chip light-emitting diodes with TiO2-SiO2 multilayer stack omnidirectional reflector
(2006-09-01)
Lin, C. H.
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Lai, C. F.
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Ko, T. S.
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Huang, H. W.
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Kuo, H. C.
Enhancement of light extraction of GaN-based flip-chip indium-tin-oxide light-emitting diodes (FC ITO LEDs) with an onmidirectional reflector (ODR) is presented. The ODR consisting of alternating layers of TiO2 and SiO2 is designed to possess a complete photonic bandgap within the blue region of interest, and it is fabricated by E-beam deposition. At a driving current of 300 mA and a chip size of 1 mm x 1 mm, the light output power of the FC ITO LEDs with the ODR reaches 156 mW. This is an enhancement of 31% when compared with the same device with an Al mirror instead. Furthermore, by examining the radiation patterns, the FC ITO LED with the ODR shows stronger enhancement around the vertical direction. Our work offers promising potential for enhancing output powers of commercial light-emitting devices.
Enhancement of InGaN/GaN flip-chip ITO LEDs with incline sidewalls coated with TiO2/SiO2 omnidirectional reflector
(2007)
Chiu, C. H.
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Kuo, H. C.
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Lai, C. F.
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Huang, H. W.
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Wang, W. C.
The light extraction enhancement of GaN-based flip-chip indium-tin oxide light-emitting diodes (FC ITO LEDs) with an inclined sidewall coated with TiO2/SiO2 omnidirectional reflectors (ODRs) is presented. At a driving current of 350 mA and a chip size of 1x1 mm, the light output power and the light extraction enhancement of the FC ITO LEDs coated TiO2/SiO2 ODRs with inclined sidewall reached 183 mW and 15% when compared with the results from the same device, FC ITO LEDs coated TiO2/SiO2 ODRs with vertical sidewall. Furthermore, by examining the radiation patterns of the FC ITO LEDs, the increased optical power within 150 degrees cone contributed to the stronger enhancement around the vertical direction of an inclined sidewall ODR within blue regime. Our work offers promising potential for enhancing output powers of commercial light-emitting devices. (c) 2007 The Electrochemical Society.
Enhancement of light output intensity by integrating ZnO nanorod arrays on GaN-based LLO vertical LEDs
(2008)
Chiu, C. H.
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Lee, C. E.
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Chao, C. L.
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Cheng, B. S.
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Huang, H. W.
Enhancement of light output intensity for GaN-based vertical light-emitting diodes (LEDs), combining wafer bonding and the laser lift-off (LLO) process, employing an omnidirectional extraction surface with synthesized single-crystal ZnO nanorod arrays in aqueous solution at room temperature is presented. The light output intensity and wall-plug efficiency of the GaN-based LLO vertical LED with the omnidirectional extraction surface by ZnO nanorod arrays shows 38.9 and 41.2% increases, respectively, at 200 mA current injections compared to that of a vertical LED without ZnO nanorod arrays. The ZnO nanorod arrays not only support a current spreading layer but enhance the probability of photon escape through the omnidirectional extraction surface. (C) 2008 The Electrochemical Society.
Enhancement of light output power of GaN-based light-emitting diodes using a SiO(2) nano-scale structure on a p-GaN surface
(2010-06-01)
Huang, H. W.
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Lai, F. I.
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Huang, J. K.
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Lin, C. H.
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Lee, K. Y.
GaN (gallium nitride)-based light-emitting diodes (LEDs) with a nano-scale SiO(2) structure between a transparent indium-tin oxide (ITO) layer and p-GaN were fabricated. The forward voltage at 20 mA for a GaN-based LED with a SiO(2) nano-scale structure was slightly higher than that of a conventional GaN-based LED because the total area of the p-type metal contact between the transparent ITO layer and p-GaN was smaller. However, the light output power for the GaN-based LED with a nano-scale structured SiO(2) at 20 mA was 24% higher than that for a conventional GaN-based LED structure. This increase in the light output power is mostly attributed to the scattering of light from the SiO(2) photonic quasi-crystal (PQC) layer.
Enhancement of light output power of GaN-based light-emitting diodes using a SiO2 nano-scale structure on a p-GaN surface
(2010-06-01)
Huang, H. W.
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Lai, F. I.
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Huang, J. K.
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Lin, C. H.
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Lee, K. Y.
GaN (gallium nitride)-based light-emitting diodes (LEDs) with a nano-scale SiO2 structure between a transparent indium-tin oxide (ITO) layer and p-GaN were fabricated. The forward voltage at 20 mA for a GaN-based LED with a SiO2 nano-scale structure was slightly higher than that of a conventional GaN-based LED because the total area of the p-type metal contact between the transparent ITO layer and p-GaN was smaller. However, the light output power for the GaN-based LED with a nano-scale structured SiO2 at 20 mA was 24% higher than that for a conventional GaN-based LED structure. This increase in the light output power is mostly attributed to the scattering of light from the SiO2 photonic quasi-crystal (PQC) layer.
Fabrication and characteristics of thin-film InGaN-GaN light-emitting diodes with TiO2/SiO2 omnidirectional reflectors
(2007-07-01)
Chiu, C. H.
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Kuo, H. C.
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Lee, C. E.
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Lin, C. H.
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Cheng, P. C.
In this paper, a novel GaN-based thin-film vertical injection light-emitting diode (LED) structure with a TiO2 and SiO2 omnidirectional reflector (ODR) and an n-GaN rough surface is designed and fabricated. The designed ODR, consisting of alternating TiO2 and SiO2, layers possesses a complete photonic band gap within the blue region of interest. The arrays of the conducting channels are integrated into the TiO2/SiO2 ODR structure for vertically spreading the current. Assisted by the laser lift-off and photo-enhanced chemically etched surface roughening process, the light output power and the external quantum efficiency of our thin-film LED with a TiO2/SiO2 ODR (at a driving current of 350 mA and with chip size of 1 mm x 1 mm) reached 330 mW and 26.7%, increased by 18% and 16%, respectively, compared with the results from the thin-film LED with an Al mirror. By examining the radiation patterns of the LEDs, the optical output power mainly increased within the 120 deg cone due to the higher reflectance of the TiO2/SiO2 ODR within the blue regime.
Fabrication and photoluminescence of InGaN-based nanorods fabricated by plasma etching with nanoscale nickel metal islands
(2006-07-01)
Huang, H. W.
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Chu, J. T.
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Hsueh, T. H.
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Ou-Yang, M. C.
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Kuo, H. C.
InGaN-based nanorods with a rod density of similar to 3.0 x 10(10) cm(-2) were fabricated from a light-emitting diode structure by an inductively coupled plasma dry-etching with nanoscale nickel metal islands. The nanoscale nickel metal islands were formed from a Ni film by a rapid thermal annealing at 850 degrees C for 1 min. The influence of thicknesses of Ni metal film on the diameter and density of nanorods was also investigated. Structural and optical properties of the InGaN-based nanorods were studied with field-emission scanning electron microscopy, transmission electron microscopy, and photoluminescence. The diameters and heights of nanorods were estimated to be 60-100 nm and more than 0.28 mu m, respectively. The emission-peak wavelength of nanorods showed a blueshift of 5.1 nm from that of the bulk structure. An enhancement by a factor of five times in photoluminescence intensity of nanorods compared to that of the bulk structure was also observed in this work. The blueshift is attributed to the strain relaxation in the well, quantum-confinement effect, or a combination of the two, which result in the enhancement in emission intensity. (c) 2006 American Vacuum Society.
Fabrication of InGaN/GaN nanorod light-emitting diodes with self-assembled Ni metal islands
(2007-11-07)
Chiu, C. H.
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Lu, T. C.
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Huang, H. W.
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Lai, C. F.
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Kao, C. C.
We report the fabrication of InGaN/GaN nanorod light-emitting diodes (LEDs) using inductively coupled plasma reactive-ion etching (ICP-RIE) and a photo-enhanced chemical (PEC) wet oxidation process via self-assembled Ni nanomasks. An enhancement by a factor of six times in photoluminescence (PL) intensities of nanorods made with the PEC process was achieved in comparison to that of the as-grown structure. The peak wavelength observed from PL measurement showed a blue shift of 3.8 nm for the nanorods made without the PEC oxidation process and 8.6 nm for the nanorods made with the PEC oxidation process from that of the as-grown LED sample. In addition, we have demonstrated electrically pumped nanorod LEDs with the electroluminescence spectrum showing more efficiency and a 10.5 nm blue-shifted peak with respect to the as-grown LED sample.
High Efficiency White LEDs with 2D Photonic Quasi-Crystal and Patterned Sapphire Substrate
(2008)
Chiu, C. H.
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Cheng, B. S.
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Kuo, H. C.
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Lu, T. C.
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Wang, S. C.
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. (C) 2008 Optical Society of America
High-performance GaN-based vertical-injection light-emitting diodes with TiO2-SiO2 omnidirectional reflector and n-GaN roughness
(2007-03-01)
Huang, H. W.
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Kuo, H. C.
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Lai, C. F.
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Lee, C. E.
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Chiu, C. W.
We have designed and fabricated a new type of GaN-based thin-film vertical-injection light-emitting diode (LED) with TiO2-SiO2 onmidirectional reflector (ODR) and n-GaN roughness. The associated ODR designed for LED operation wavelength at 455 nm vias integrated with patterned conducting channels for the purpose of vertical current spreading. With the help of laser lift-off and. photo-electrochemical etching technologies, at a driving current of 350 mA and with chip size of 1 mm x 1 mm, the light-output power and the external quantum efficiency of our thin-film LED with TiO2-SiO2 ODR reached 330 mW and 26.7%. The result demonstrated 18% power enhancement when compared with the results from the thin-film LED with Al reflector replace.
Highly Efficient InGaN-Based Light Emitting Devices grown on Nanoscale Patterned Substrates by MOCVD
(2011)
Lin, Chien-Chung
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Chiu, Ching-Hsueh
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Huang, H. W.
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Chang, Shih-Pang
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Kuo, Hao-Chung
Highly efficient InGaN-base light emitting diodes are crucial for next generation solid state lighting. However, drawbacks in substrate materials such as lattice and thermal expansion coefficient mismatches hold back the lamination efficiency improvement. In the past, patterned sapphire sustrate (PSS) has been proven to be effect to enhance the LED's performance. In this work, we reviewed several promising nano-scale technologies which successfully increase the output of LED through better material quality and light extraction. First, we presented a study of high-performance blue emission GaN LEDs using GaN nanopillars (NPs). It exhibits smaller blue shift in electroluminescent peak wavelength and great enhancement of the light output (70% at 20 mA) compared with the conventional LEDs. Secondly, GaN based LEDs with nano-hole patterned sapphire (NHPSS) by nano-imprint lithography are fabricated structure grown on sapphire substrate. At an injection current of 20mA, the LED with NHPSS increased the light output power of LEDs by 1.33 times, and the wall-plug efficiency is 30% higher at 20mA indicating that it had larger light extraction efficiency (LEE). Finally, we fabricated the high performance electrical pumping GaN-based semipolar {10-11} nano-pyramid LEDs on c-plane sapphire substrate by selective area epitaxy (SAE). The emission wavelength only blue-shifted about 5nm as we increased the forward current from 40 to 200mA, and the quantum confine stark effect (QCSE) had been remarkably suppressed on semipolar surface at long emission wavelength region. These results manifest the promising role of novel nanotechnology in the future III-nitride light emitters.
Highly Efficient InGaN-Based Light Emitting Devices grown on Nanoscale Patterned Substrates by MOCVD
(2012)
Lin, Chien-Chung
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Chiu, Ching-Hsueh
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Huang, H. W.
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Chang, Shih-Pang
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Kuo, Hao-Chung
Highly efficient InGaN-base light emitting diodes are crucial for next generation solid state lighting. However, drawbacks in substrate materials such as lattice and thermal expansion coefficient mismatches hold back the lamination efficiency improvement. In the past, patterned sapphire sustrate (PSS) has been proven to be effect to enhance the LED\'s performance. In this work, we reviewed several promising nano-scale technologies which successfully increase the output of LED through better material quality and light extraction. First, we presented a study of high-performance blue emission GaN LEDs using GaN nanopillars (NPs). It exhibits smaller blue shift in electroluminescent peak wavelength and great enhancement of the light output (70% at 20 mA) compared with the conventional LEDs. Secondly, GaN based LEDs with nano-hole patterned sapphire (NHPSS) by nano-imprint lithography are fabricated structure grown on sapphire substrate. At an injection current of 20mA, the LED with NHPSS increased the light output power of LEDs by 1.33 times, and the wall-plug efficiency is 30% higher at 20mA indicating that it had larger light extraction efficiency (LEE). Finally, we fabricated the high performance electrical pumping GaN-based semipolar {10-11} nano-pyramid LEDs on c-plane sapphire substrate by selective area epitaxy (SAE). The emission wavelength only blue-shifted about Snm as we increased the forward current from 40 to 200mA, and the quantum confine stark effect (QCSE) had been remarkably suppressed on semipolar surface at long emission wavelength region. These results manifest the promising role of novel nanotechnology in the future III-nitride light emitters.
Improvement of light output in GaN-based power chip light-emitting diodes with a nano-rough surface by nanoimprint lithography
(2008-04-01)
Huang, H. W.
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Lin, C. H.
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Yu, C. C.
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Lee, B. D.
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Chiu, C. H.
The enhancement of light extraction of gallium nitride (GaN)-based power chip (PC) light-emitting diodes (LEDs) with a p-GaN rough surface by nanoimprint lithography (NIL) is presented. At a driving current of 350 mA and a chip size of 1 mm x 1 mm, the light output power of the PC LEDs with a p-GaN rough surface (etching depth from 130 to 150 nm) showed an enhancement of 24% on wafer when compared with the same device without NIL. Current-voltage results indicated an ohmic contact by the increase in the contact area of the nano-roughened surface at 200 mA. This paper offers a promising potential for enhancing the output powers of commercial LEDs.
InGaN/GaN MQW Nanorods LED Fabricated by ICP-RIE and PEC Oxidation Processes
(2007-01-01)
Lai, Fang-, I
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Huang, H. W.
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Chiu, Ching-Hua
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Lai, C. F.
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Lu, T. C.
The InGaN/GaN nanorods LED was successfully fabricated by ICP-RIE and PEC processes. Compared with as-grown sample, the PL and EL peak-wavelengths of the nanorods with PEC show 8.6 and 10.5 nm blue-shift, respectively. (c) 2007 Optical Society of America