Browsing by Author "Tsai, R. J."

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Efficiency enhancement of GaN-based power-chip LEDs with sidewall roughness by natural lithography
(2007)
Huang, Hung-Wen
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Lai, C. F.
;
Wang, W. C.
;
Lu, T. C.
;
Kuo, H. C.
This study reports the development of GaN-based power-chip light-emitting diodes (LEDs) with sidewall roughness using natural lithography with polystyrene spheres as the etching mask. At an injection current of 350 mA, the LED with sidewall roughness increased the light output intensity of the InGaN/GaN multiple quantum well LEDs by a factor of 1.26, indicating that the LED with sidewall roughness had larger light extraction efficiency. The wall-plug efficiency of GaN-based LED was increased by 26.5% with sidewall roughness. After 1000 h life test, it was found that normalized output power of power-chip LED with sidewall roughness did not show any significant degradation. (c) 2006 The Electrochemical Society.
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.
;
Lai, C. F.
;
Ko, T. S.
;
Huang, H. W.
;
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.