Browsing by Author "Hung, Cheng-Wei"

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Output Power Enhancement of Light Emitting Diodes with Defect Passivation layer
(2010)
Lo, Ming-Hua
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Tu, Po-Min
;
Cheng, Yuh-Jen
;
Wang, Chao-Hsun
;
Hung, Cheng-Wei
We demonstrate high efficiency blue light emitting diodes with defect passivation layers. The defect passivation layers were formed by defect selective wet etching, SiO(2) deposition, and chemical mechanical polishing process. The process does not require photolithography patterning. The threading dislocation density of grown sample was reduced down to similar to 4x10(7) cm(-2). The defect passivated epi-wafer is used to grow light emitting diode (LED) and the output power of the fabricated chip is enhanced by 45% at 20 mA compared to a reference one without using defect passivation.
Patterned structure of REMOTE PHOSPHOR for phosphor-converted white LEDs
(2011-07-04)
Kuo, Hao-Chung
;
Hung, Cheng-Wei
;
Chen, Hsin-Chu
;
Chen, Kuo-Ju
;
Wang, Chao-Hsun
High efficiency white light-emitting diodes with superior color-mixing have been investigated. It is suggested that the patterned remote phosphor structure could improve the uniformity of angular-dependent correlated color temperature (CCT) and achieve high chromatic stability in wider operating current range, as compared to the conventional remote phosphor coating structure. In this experiment, we employed a pulse spray coating method to place the patterned phosphor on the package and to leave a window region. The window area, a clear space without coating of the phosphor not only increases the extraction efficiency of blue rays at large angle, but also improves the stability of angular-dependent CCT. Moreover, the CCT deviation could be reduced from 1320 K to 266 K by this patterned remote phosphor method, and the stray blue/yellow light within the package can be effectively reduced and controlled. The design was verified both experimentally and theoretically. (C) 2011 Optical Society of America