Abstract
AbstractThe high‐power white light emitting diode (LED) is packaged by GaN‐based blue LED chip with the size of 1 × 1 mm2, YAG:Ce yellow fluorescer, epoxy and an effective heat sinking. The wavelength of the LED chip emission blue‐shifts from 482 to 475 nm, while that of the fluorescer emission does not change in electroluminescence (EL) spectrum when the injection current increases from 5 to 200 mA. And the correlated color temperature decreases from 5300 to 4800 K. When the injection current increases to 200 mA, the luminous power (Pe) increases to 13.8 mW, which is about 10 times of those of the normal size (0.3 × 0.3 mm2) diodes fabricated with the same wafer and same injection density. Pe and forward bias (Vf) at 200 mA are measured for the aging high‐power white LED. At the beginning, Pe decreases dramatically 20% and Vf decreases about 0.2 V in 2 days. And then Pe and Vf decrease slowly in the remaining 79 days aging. The contact metals electro migration along the channels induced by the threading dislocations may be the dominant aging mechanism. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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