Browsing by Author "Cheng, B. S."

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Enhanced light extraction of InGaN-based green LEDs by nano-imprinted 2D photonic crystal pattern
(2008-05-01)
Cheng, B. S.
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Chiu, C. H.
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Huang, K. J.
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Lai, C. F.
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Kuo, H. C.
In this paper, we propose a simple, low cost and mass producible nanoimprint lithography (NIL) method to texture the surface of GaN-based light emitting diodes (LEDs) with a two-dimensional photonic crystal (2DPC). Such a 2DPC structure not only enhanced the light output power but also changed the far-field pattern simultaneously. Also, a TiO(2)/SiO(2) omnidirectional reflector (ODR) was deposited on the backside of the LEDs to further increase the light output power. Under 350 mA current injection, it was found that forward voltages were 3.35, 3.34 and 3.75 V while the light output powers of the LEDs were 59.5, 92.5 and 112.1 mW for the conventional LED, the PCLED with 20 nm depth, and the PCLED with 120 nm depth all with chip size of 1 mm x 1 mm, respectively. A 88.4% enhancement in light output power of PCLED with a 120 nm depth and ODR on the backside could be achieved when compared to the conventional LED under the driving current of 350 mA. From the measurement results, it was also found that the NIL process does not degrade the electrical properties of the fabricated LEDs.
Enhancement of flip-chip light-emitting diodes with omni-directional reflector and textured micropillar arrays
(2007-07-01)
Lee, Chia-En
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Lee, Yi-Jiun
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Kuo, Hao-Chung
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Tsai, Meng-Ru
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Cheng, B. S.
The flip-chip light-emitting diodes (FC-LEDs) with a conductive omni-directional reflector and textured micropillar arrays were investigated. The micropillar arrays structure was formed on the bottom side of sapphire substrate by dry etching process to increase the light-extraction efficiency. The light output power of the FC-LED was increased by 65% for a 3.2-mu m textured micropillar on the bottom side of the sapphire substrate. Our work offers promising potential for enhancing output powers of commercial light-emitting devices.
Enhancement of flip-chip light-emitting diodes with omni-directional reflector and textured micropillar arrays (vol 19, pg 18, 2007)
(2007-09-01)
Lee, Chia-En
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Lee, Yea-Chen
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Kuo, Hao-Chung
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Tsai, Meng-Ru
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Cheng, B. S.
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.
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
Output Power Enhancement of Vertical-Injection Ultraviolet Light-Emitting Diodes by GaN-Free and Surface Roughness Structures
(2009)
Lee, C. E.
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Cheng, B. S.
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Lee, Y. C.
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Kuo, H. C.
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Lu, T. C.
Nitride-based UV, vertical-injection light-emitting diodes (VLEDs) with GaN-free and surface roughness structures operating at 365 nm were proposed and demonstrated by a combination of wafer bonding and laser lift-off processes. The GaN-free structure offers a promising potential for enhancing the light output of UV-VLEDs. The 3.2x light output enhancement was performed by removing the GaN. With the help of adopting a roughened surface, the light-output power of the UV-VLEDs could be further enhanced by a factor of 2.3 as compared with that of UV-VLED without a roughened surface. The total enhancement of surface-roughened GaN-free UV-VLEDs was increased by a factor of 7.8 compared to that of conventional UV-LEDs at a driving current injection of 250 mA.