Browsing by Author "Lee, Kang-Yuan"

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Double Photonic Quasi-Crystal Structure Effect on GaN-Based Vertical-Injection Light-Emitting Diodes
(2010)
Huang, Hung-Wen
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Lin, Chung-Hsiang
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Huang, Zhi-Kai
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Lee, Kang-Yuan
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Yu, Chang-Chin
GaN-based thin-film vertical-injection light-emitting diodes (VLEDs) with a double 12-fold photonic quasi-crystal (PQC) structure formed using nanoimprint lithography (NIL) and inductively coupled plasma reactive-ion etching (ICP-RIE) are fabricated and presented. At a driving current of 20 mA and with a chip size of 350 x 350 mu m(2), our thin-film LED with a double-12-fold-PQC structure gave a light output power of 40.5 mW, which is an increase of 77% when compared with the output power of a VLED without a PQC structure at a peak wavelength of 460 nm. In addition, the corresponding light radiation patterns show a narrow beam shape due to the strong guided light extraction on the n-GaN surface and the reflected light effect of the PQC structure formed in the vertical direction on the p-GaN surface. (C) 2010 The Japan Society of Applied Physics
Efficiency Improvement of Blue LEDs Using a GaN Burried Air Void Photonic Crystal With High Air Filling Fraction
(2014-05-01)
Liu, Jia-Zhe
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Charlton, Martin D. B.
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Lin, Chung-Hsiang
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Lee, Kang-Yuan
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Krishnan, Chirenjeevi
In this paper, we investigate the efficiency enhancement of blue InGaN/GaN light-emitting diodes (LEDs) by incorporating a burried air void photonic crystal (BAVPC) layer within the epitaxial structure. As compared with the conventional patterned sapphire substrate (C-PSS) LEDs and flat sapphire substrate LEDs with BAVPC, the fabricated patterned sapphire substrate (PSS) LEDs with BAVPC exhibit the lowest full-width at half-maximum of (002) and (102) diffraction peaks, the highest light output power of 20.6 mW, and the highest external quantum efficiency of 37.4%. Remarkable performance improvement in the PSS LED with BAVPC is attributed to the better epitaxial quality with threading dislocations terminated by the BAVPC and the higher scattering at interface between GaN and air-void. By positioning the BAVPC directly below the multiple quantum wells (MQWs), it would cause the reduction in the number of trapped optical modes. The methodology optically isolates the MQWs from the underlying substrate and increases the optical output power. Moreover, threading dislocations are significantly suppressed using the BAVPC with high air filling fraction of similar to 50%. It is well proposed that this methodology provides a promising alternative to C-PSS LEDs.
Enhanced Light Output Power and Growth Mechanism of GaN-Based Light-Emitting Diodes Grown on Cone-Shaped SiO2 Patterned Template
(2013-04-01)
Lin, Da-Wei
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Huang, Jhih-Kai
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Lee, Chia-Yu
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Chang, Ruey-Wen
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Lan, Yu-Pin
In this study, we successfully transferred the patterns of a cone-shaped patterned sapphire substrate (CPSS) into SiO2 layer to fabricate a cone-shaped SiO2 patterned template by using nanoimprint lithography (NIL). The GaN-based light-emitting diodes (LEDs) were grown on this template by metal-organic chemical vapor deposition (MOCVD). The transmission electron microscopy (TEM) images suggest that the stacking faults formed near the cone-shaped SiO2 patterns during the epitaxial lateral overgrowth (ELOG) can effectively suppress the threading dislocations, which results in an enhancement of internal quantum efficiency. The Monte Carlo ray-tracing simulation reveals that the light extraction efficiency of the LED grown on cone-shaped SiO2 patterned template can be enhanced as compared with the LED grown on CPSS. As a result, the light output power of the LED grown on cone-shaped SiO2 patterned template outperformed the LED grown on CPSS.
High extraction efficiency GaN-based light-emitting diodes on embedded SiO(2) nanorod array and nanoscale patterned sapphire substrate
(2010-06-28)
Huang, Hung-Wen
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Huang, Jhi-Kai
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Kuo, Shou-Yi
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Lee, Kang-Yuan
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Kuo, Hao-Chung
In this paper, GaN-based LEDs with a nanoscale patterned sapphire substrate (NPSS) and a SiO(2) photonic quasicrystal (PQC) structure on an n-GaN layer using nanoimprint lithography are fabricated and investigated. The light output power of LED with a NPSS and a SiO(2) PQC structure on an n-GaN layer was 48% greater than that of conventional LED. Strong enhancement in output power is attributed to better epitaxial quality and higher reflectance resulted from NPSS and PQC structures. Transmission electron microscopy images reveal that threading dislocations are blocked or bended in the vicinities of NPSS layer. These results provide promising potential to increase output power for commercial light emitting devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456385]
High extraction efficiency GaN-based light-emitting diodes on embedded SiO2 nanorod array and nanoscale patterned sapphire substrate
(2010-06-28)
Huang, Hung-Wen
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Huang, Jhi-Kai
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Kuo, Shou-Yi
;
Lee, Kang-Yuan
;
Kuo, Hao-Chung
In this paper, GaN-based LEDs with a nanoscale patterned sapphire substrate (NPSS) and a SiO2 photonic quasicrystal (PQC) structure on an n-GaN layer using nanoimprint lithography are fabricated and investigated. The light output power of LED with a NPSS and a SiO2 PQC structure on an n-GaN layer was 48% greater than that of conventional LED. Strong enhancement in output power is attributed to better epitaxial quality and higher reflectance resulted from NPSS and PQC structures. Transmission electron microscopy images reveal that threading dislocations are blocked or bended in the vicinities of NPSS layer. These results provide promising potential to increase output power for commercial light emitting devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456385]
Improved Light Output Power of GaN-Based Light-Emitting Diodes Using Double Photonic Quasi-Crystal Patterns
(2009-11-01)
Huang, Hung-Wen
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Lin, Chung-Hsiang
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Huang, Zhi-Kai
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Lee, Kang-Yuan
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Yu, Chang-Chin
The enhancement of light extraction from GaN-based light-emitting diodes (LEDs) with a double 12-fold photonic quasi-crystal (PQC) structure using nanoimprint lithography is presented. At a driving current of 20 mA on a transistor-outline-can package, the light output power of an LED with a nanohole patterned sapphire substrate (NHPSS) and an LED with a double PQC structure are enhanced by 34% and 61%, compared with the conventional LED. In addition, the higher output power of the LED with the double PQC structure is due to better reflectance on NHPSS and higher scattering effect on p-GaN surface using a 12-fold PQC structure pattern. These results provide promising potential to increase the output powers of commercial light-emitting devices.
Investigation and Comparison of the GaN-Based Light-Emitting Diodes Grown on High Aspect Ratio Nano-Cone and General Micro-Cone Patterned Sapphire Substrate
(2013-12-01)
Huang, Jhih-Kai
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Lin, Da-Wei
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Shih, Min-Hsiung
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Lee, Kang-Yuan
;
Chen, Jyun-Rong
In this paper, we demonstrated the high performance GaN-based LEDs by using a high aspect ratio cone-shape nano-patterned sapphire substrate (HAR-NPSS). We utilized nano-imprint lithography (NIL) and dry-etching system to fabricate a high depth HAR-NPSS. The micro-scale patterned sapphire substrate (PSS) was also used for comparison. A great enhancement of light output was observed when GaN-based LEDs were grown on a HAR-NPSS or a PSS. The light output power of LEDs with a HAR-NPSS and LEDs with a PSS were enhanced of 49 and 38% compared to LEDs with a unpatterned sapphire substrate. The high output power of the LED with a HAR-NPSS indicated that the technology of NAR-NPSS not only can improve the crystalline quality of GaN-based LEDs but also a promising development to a NPSS.
Performance Enhancement of Ultraviolet Light-Emitting Diodes by Incorporating a Thin Al(In)GaN Interlayer in Multiquantum-Well Region
(2015-07-01)
Liu, Jia-Zhe
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Lin, Chung-Hsiang
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Lee, Kang-Yuan
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Wang, Yu-Li
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Liao, Chien-Lan
In this paper, the performance improvement of 380-nm InGaN/AlGaN ultraviolet light-emitting diodes (UV-LEDs) is investigated by incorporating an undoped Al(In)GaN thin interlayer between the InGaN well and AlGaN barrier in multiquantum-well (MQW) active region. By inserting the graded-composition AlGaN and AlInGaN thin interlayers, the light output powers of UV-LEDs are significantly increased by 70% and 105% at 20 mA, respectively, as compared with the LED without the interlayer. Remarkable efficiency enhancement in the UV-LEDs with graded-composition AlGaN and AlInGaN interlayers is mainly attributed to the further improvement of the electron confinement and hole injection with more uniform distribution in the MQW active region. Besides, photoluminescence and atomic force microscope analyses indicate that the MQW quality can be enhanced by incorporating a graded-composition AlInGaN thin interlayer in the MQW active region of UV-LEDs.