Improved thermal management of GaN/sapphire light-emitting diodes embedded in reflective heat spreaders

Horng, R. H.; Chiang, C. C.; Hsiao, H. Y.; Zheng, X.; Wuu, D. S.; Lin, H. I.
September 2008
Applied Physics Letters;9/15/2008, Vol. 93 Issue 11, p111907
Academic Journal
Using maskless lithography and electroforming techniques, we have demonstrated an enhanced performance of GaN/sapphire light-emitting diode (LED) embedded in a reflective copper heat spreader. The chip size and dominant wavelength of the blue emitter used in this research is 1×1 mm2 and 455 nm, respectively. The cup-shaped LED heat sink is electroformed on sapphire directly using the spin-coated photoresist coated with the Au/Cr/Ag mirror as a mold and dicing into the embedded LED with a Cu base dimension of 3×3 mm2, which effectively enhances the heat dissipation down to the metal frame and reaps the light flux generated from the side emission. With the aid of a reflective heat spreader, the encapsulated LED sample driven at 1 A yields the light output power of 700 mW and around 2.7-times increase in the wall-plug efficiency compared to that of the conventional GaN/sapphire LED. Infrared thermal images confirm the GaN/sapphire LED with more efficient heat extraction and better temperature uniformity. These results exhibit an alternative solution to thermal management of high power LED-on-sapphire samples besides the laser lift-off technique.


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