Ultra High Power 365 nm Ultraviolet Light Emitting Diodes

Abstract

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 (η_ex) 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.