Browsing by Author "Chiang, Yen-Chih"

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Efficiency and Droop Improvement in GaN-Based High-Voltage Flip Chip LEDs
(2014-01-01)
Chiang, Yen-Chih
;
Lin, Bing-Cheng
;
Chen, Kuo-Ju
;
Chiu, Sheng-Huan
;
Lin, Chien-Chung
The GaN-based high-voltage flip chip light-emitting diode (HVFC-LED) is designed and developed for the purpose of efficiency enhancement. In our design, the distributed Bragg reflector (DBR) is deposited at the bonded substrate to increase the light extraction. After the flip chip process, the general current-voltage characteristics between the flip chip sample and the traditional sample are essentially the same. With the help of great thermal conductive silicon substrate and the bottom DBR, the HVFC-LED is able to enhance the power by 37.1% when compared to the traditional high-voltage LEDs. The wall-plug efficiencies of the HVFC-LED also show good droop reduction as high as 9.9% compared to the traditional devices.
Efficiency and Droop Improvement in GaN-Based High-Voltage Flip Chip LEDs
(2014-01-01)
Chiang, Yen-Chih
;
Lin, Bing-Cheng
;
Chen, Kuo-Ju
;
Chiu, Sheng-Huan
;
Lin, Chien-Chung
The GaN-based high-voltage flip chip light-emitting diode (HVFC-LED) is designed and developed for the purpose of efficiency enhancement. In our design, the distributed Bragg reflector (DBR) is deposited at the bonded substrate to increase the light extraction. After the flip chip process, the general current-voltage characteristics between the flip chip sample and the traditional sample are essentially the same. With the help of great thermal conductive silicon substrate and the bottom DBR, the HVFC-LED is able to enhance the power by 37.1% when compared to the traditional high-voltage LEDs. The wall-plug efficiencies of the HVFC-LED also show good droop reduction as high as 9.9% compared to the traditional devices.
Efficiency and Droop Improvement in Hybrid Warm White LEDs Using InGaN and AlGaInP High-Voltage LEDs
(2013-04-01)
Chen, Kuo-Ju
;
Kuo, Hsuan-Ting
;
Chiang, Yen-Chih
;
Chen, Hsin-Chu
;
Wang, Chao-Hsun
This study investigates the optical and electrical characteristics in hybrid warm white high-voltage light-emitting diodes (HV-LEDs). The luminous efficiency of the hybrid warm white LED in this study improved by 11% and 51%, compared to conventional cool and warm LEDs, respectively, solving the warm white gap in white LEDs. The efficiency droop of the hybrid warm white LED was reduced to 21.8% from 26.8% for the conventional cool white LED, and from 26.3% in the conventional warm white LED at 40 mA (35 A/cm(2)) the operated current. Furthermore, the color rendering index (CRI) and angular correlated color temperature (CCT) were analyzed, indicating a significant improvement in hybrid warm white HV-LEDs.
Innovative Fabrication of Wafer-Level InGaN-Based Thin-Film Flip-Chip Light-Emitting Diodes
(2015-07-01)
Chiang, Yen-Chih
;
Lin, Bing-Cheng
;
Chen, Kuo-Ju
;
Lin, Chien-Chung
;
Lee, Po-Tsung
In this letter, an innovative fabrication method for InGaN-based light-emitting diode (LED) was proposed, and the produced optical device was called the wafer-level InGaN-based thin-film flip-chip LEDs (wTFFC-LEDs). Packaging technologies, such as wafer-to-wafer bonding, laser lift-off, textured surface, and interconnection techniques, were applied to complete the device. Through this architecture, the absorption caused by electrodes in traditional vertical injection LEDs (V-LEDs) can be minimized, as well as the light extraction efficiency can be improved. Light-output power of wTFFC-LEDs (350 mA) was increased by 36.5% and 17.2% compared with the V-LEDs and flip-chip LEDs. Furthermore, the external quantum efficiency was also relatively enhanced by 36.3% and 15.5% higher than those of reference devices.