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International Journal of Photoenergy
Volume 2014, Article ID 385257, 7 pages
Research Article

Efficiency and Droop Improvement in GaN-Based High-Voltage Flip Chip LEDs

1Institute of Lighting and Energy Photonics, National Chiao Tung University, Tainan 71550, Taiwan
2Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
3Institute of Photonics System, National Chiao Tung University, Tainan 71550, Taiwan
4Research Center for Applied Sciences, Academia Sinica, 128 Academia Road, Sec. 2 Nankang, Taipei 115, Taiwan

Received 13 February 2014; Accepted 2 June 2014; Published 30 June 2014

Academic Editor: Nelson Tansu

Copyright © 2014 Yen-Chih Chiang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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.