Browsing by Author "Hwang, JM"

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Enhancing the output power of GaN-based LEDs grown on wet-etched patterned sapphire substrates
(2006-05-01)
Lee, YJ
;
Hwang, JM
;
Hsu, TC
;
Hsieh, MH
;
Jou, MJ
GaN-based light-emitting diodes (LEDs) with emitting wavelength of 450 nm were grown on patterned sapphire substrates (PSSs) fabricated by chemical wet etching. The crystallography-etched facet was {1-102} R-plane with a 57 degrees against {001} C-axis and had superior capability for enhancing light extraction efficiency. The light output power of the PSS LED was 1.15 times higher than that of the conventional LED at an injection current of 20 mA. The output power and external quantum efficiency were estimated to be 9 mW and 16.4%, respectively. The improvement was attributed not only to geometrical shapes of {1-102} crystallography-etched facets that efficiently scatter the guided light to find escape cones, but also to dislocation density reduction by adopting the PSS growth scheme.
GaN-based LEDs with Al-deposited V-shaped sapphire facet mirror
(2006-03-01)
Lee, YJ
;
Hwang, JM
;
Hsu, TC
;
Hsieh, MH
;
Jou, MJ
A GaN-based light-emitting diodes (LEDs) with V-shaped sapphire facet reflector was fabricated using the double transferred scheme and sapphire chemical wet etching. The {1-102} R-plane V-shaped facet reflector with a 57 degrees against {0001} C-axis has the superior capability for enhancing the light extraction efficiency. The light output power of the V-shaped sapphire facet reflector LED was 1.4 times higher than that of a flat reflector LED at an injection current of 20 mA. The significant improvement is attributable to the geometrical shape of sapphire facet reflector that efficiently redirects the guided light inside the chip toward to the top escape-cone of the LED surface.