We fabricated ultra high power ultraviolet (UV) light emitting diodes (LEDs), whose emission wavelength is 365 nm. We found that, in order to improve the external quantum efficiency (ηex) of UV-LEDs, it is very important to reduce the optical self-absorption and the threading dislocation density (TDD) of epi-layers. Therefore, at first, UV-LEDs epi-layers were grown on high-quality GaN templates (TDD=1x108/cm2) with sapphire substrates, and then the GaN templates and the sapphire substrates were removed by using laser-induced lift-off and polishing techniques. Moreover, in order to enhance the extraction efficiency, a higher reflectance Ag p-type electrode and patterned surface were used for this LED chip. As a result, we obtained the low self-absorption and low TDD UV-LEDs with practical high power and high quantum efficiency.
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