Abstract
A new volcano-shaped patterned sapphire substrate (VPSS), which enhances the light extraction efficiency (LEE) of GaN-based light emitting diodes (LEDs), was presented. The Monte Carlo ray-tracing method shows that the VPSS with a crater slope angle of about 50° has the highest LEE. To compare the optical characteristics, 380 nm ultraviolet LEDs were grown on an optimized VPSS, hemispherical PSS (HPSS), and planar sapphire substrate by metal-organic chemical vapor deposition (MOCVD). As a result, the extraction efficiency of the LED grown on the optimized VPSS was estimated to be almost 2.8 times larger than that of the planar sapphire substrate and was enhanced 1.6 times compared with that of the LED grown on the HPSS.
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