Browsing by Author "Lee, C. E."

Now showing 1 - 7 of 7

Enhancement of light output intensity by integrating ZnO nanorod arrays on GaN-based LLO vertical LEDs
(2008)
Chiu, C. H.
;
Lee, C. E.
;
Chao, C. L.
;
Cheng, B. S.
;
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.
Fabrication and characteristics of thin-film InGaN-GaN light-emitting diodes with TiO2/SiO2 omnidirectional reflectors
(2007-07-01)
Chiu, C. H.
;
Kuo, H. C.
;
Lee, C. E.
;
Lin, C. H.
;
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.
High brightness GaN-based flip-chip light-emitting diodes by adopting geometric sapphire shaping structure
(2008-02-01)
Lee, C. E.
;
Lee, Y. C.
;
Kuo, H. C.
;
Tsai, M. R.
;
Lu, T. C.
GaN-based flip-chip LEDs (FC-LEDs) with geometric sapphire shaping structure were fabricated. The sapphire shaping structure was formed on the bottom side of the sapphire substrate by the chemical wet etching technique for the purpose of light extraction. The crystallography-etched facets were `(1 0 1 0) M-plane, (1 1 0 2) R-plane and (1 1 2 0) A-plane against the (0 0 0 1) c-axis with the angles range between similar to 29 degrees and similar to 60 degrees. It is demonstrated that the geometrical shape of the sapphire windows layer improves the light extraction efficiency. Compared to the conventional FC-LED, the sapphire-shaped FC-LED significantly enhanced the output power. The light output power of sapphire-shaped FC-LEDs was increased by 55% (at 350 mA current injection) compared to that of conventional FC-LEDs.
High-performance GaN-based vertical-injection light-emitting diodes with TiO2-SiO2 omnidirectional reflector and n-GaN roughness
(2007-03-01)
Huang, H. W.
;
Kuo, H. C.
;
Lai, C. F.
;
Lee, C. E.
;
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.
Luminance enhancement of flip-chip light-emitting diodes by geometric sapphire shaping structure
(2008-01-01)
Lee, C. E.
;
Kuo, H. C.
;
Lee, Y. C.
;
Tsai, M. R.
;
Lu, T. C.
The flip-chip light-emitting diodes (FC-LEDs) with geometric sapphire shaping structure were investigated. The sapphire shaping structure was formed on the. bottom side of the sapphire substrate by a chemical wet etching technique for light extraction purpose. The crystallography-etched facets were (1010) M-plane, (1102) R-plane, and (1120) A-plane against the (0001) c-axis with the angles range between 29 degrees similar to 60 degrees. These large slope oblique sidewalls are useful for light extraction efficiency enhancement. The light-output power of sapphire shaping FC-LEDs was increased 55% (at 350-mA current injection) compared to that of conventional FC-LEDs.
Output Power Enhancement of Vertical-Injection Ultraviolet Light-Emitting Diodes by GaN-Free and Surface Roughness Structures
(2009)
Lee, C. E.
;
Cheng, B. S.
;
Lee, Y. C.
;
Kuo, H. C.
;
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.
Small GaN-based light-emitting diodes with a single electrode pad fabricated on a sapphire substrate
(2008-04-01)
Lee, Y. C.
;
Lee, C. E.
;
Lu, T. C.
;
Kuo, H. C.
;
Wang, S. C.
Small-scale GaN-based LEDs with a single electrode pad enjoying such properties as low cost, low series resistance, high efficiency and high yield were fabricated on a sapphire substrate by a novel and simple method. The devices present not only lower series resistance but higher light output power due to a specific n-contact design and better current spreading properties. Furthermore, higher ESD resistance (> -800 V at machine-mode operation) was demonstrated. The single-pad electrode of small-scale GaN-based LEDs has a chip size of 180 x 180 mu m(2), and showed a lower forward voltage of 3.15 V and 53.4% output power enhancement at 20 mA.