Browsing by Author "Huang, Sheng-Bang"

Now showing 1 - 3 of 3

Assessment of ESD Robustness in High Power Light-Emitting Diodes
(2010)
Yang, Shih-Chun
;
Lin, Pang
;
Fu, Han-Kuei
;
Wang, Chien-Ping
;
Chen, Tzung-Te
The capability of high-power nitride-based light-emitting diodes (HPLED) to withstand electrostatic discharge (ESD) is very important key index due to the horizontal structure of the insulating property of the sapphire substrate. However, it is difficult to real-time monitor the damage caused by the ESD stress because it occurred in a very short period. Current-voltage (I-V) curves and electroluminescence (EL) spectrum were applied to study the change during the series ESD stress. Time-resolved optical beam induced current (TR-OBIC) was used to analyze the characteristics of the delay time between normal region and the defect point caused by ESD stress. Transmission electron microscopy (TEM) was used to compare to the difference in the distribution of damage region and investigate the failure modes. During the series ESD stresses, V-shaped pits suffered from the high electrical field and the distance from multi-quantum well (MQW). The bottom of V-shaped defect would be one of index to assess the ESD endurance of LED chips.
Synthesis and luminescence properties of intensely red-emitting M5Eu(WO4)(4-x)(MoO4)(x) (M = Li, Na, K) phosphors
(2008)
Chiu, Chuang-Hung
;
Liu, Chih-Hsuan
;
Huang, Sheng-Bang
;
Chen, Teng-Ming
;
應用化學系
We have investigated the luminescence of a series of M5Eu(WO4)(4-x)(MoO4)(x) (M = Li, Na, K) phosphors and discovered that Na5Eu(WO4)(4-x)(MoO4)(x) (0 <= x <= 4.0) exhibit the most intense red emission among the three investigated. Powder X-ray diffraction investigations show that a complete solid solution can be formed in the indicated composition range. The effect of chemical compositions on the luminescence properties of Na5Eu(WO4)(4-x)(MoO4)(x) has been investigated and discussed. The Commission International de l'Eclairage chromaticity coordinates were found to be (0.66,0.33) for Na5Eu(WO4)(4-x)(MoO4)(x), which reaches the same level as that of the Y2O2S:Eu3+ commodity. The color-rendering index (Ra) of a typical white-light-light emitting diode (WL-LED) based on Na5Eu(WO4)(2)(MoO4)(2) was found to be 82.3, higher than that (i.e., Ra similar to 70.8) obtained for the WL-LED fabricated using the commodity of La2O2S:Eu3+ when the WL-LEDs were operated at a forward-bias current (I-f) of 20 mA at room temperature. Na5Eu(WO4)(4-x)(MoO4)(x) is therefore suggested to be a potential red-emitting phosphor for WL-LED. (c) 2008 The Electrochemical Society.
White-light-emitting diodes using red-emitting LiEu(WO4)(2-x)(MoO4)(x) phosphors
(2007)
Chiu, Chuang-Hung
;
Liu, Chih-Hsuan
;
Huang, Sheng-Bang
;
Chen, Teng-Ming
;
應用化學系
The fundamental luminescence and chromaticity properties of a class of red-emitting phosphors LiEu(WO4)(2-x)(MoO4)(x) under near-UV excitation have been investigated. The photoluminescence (PL) and photoluminescence excitation (PLE) spectra reveal that the absorption is mainly attributed to O -> Mo(W) charge transfer at 300 nm and the Eu3+ transitions in near-UV and visible regions, and red emissions are assigned to intraconfigurational 4f-4f transitions of Eu3+. Both PL and PLE intensity were found to increase with increasing doped Mo content. The intensity of the D-5(0) -> F-7(2) emission of Eu3+ activated at 394 nm was found to reach a maximum when the relative ratio of Mo/W was 2:0. The CIE chromaticity coordinates were found to be (0.66, 0.33) for LiEu(MoO4)(2) and it reached the same level as the commodity phosphor Y2O2S:Eu3+. A white-light-emitting diode fabricated using the composition-optimized LiEu(MoO4)(2) and the matching green- and blue-emitting phosphors shows that the quality of red color reproduction based on LiEu(MoO4)(2) was found to be much higher and improved than that using La2O2S:Eu3+. (C) 2007 The Electrochemical Society.