High-voltage thin-film GaN LEDs fabricated on ceramic substrates: The alleviated droop effect at 670 W/cm²

High-voltage thin-film GaN LEDs with the emission wavelength of 455 nm were fabricated on ceramic substrates (230 W/m·K). The high-voltage operation was achieved by three cascaded sub-LEDs with dielectric passivation and metal bridges conformally deposited on the side walls. Under the driving power of 670 W/cm2, the high-voltage LEDs exhibit much alleviated efficiency droop and the operative temperature below 80°C. The excellent performances were attributed to the improved current spreading within each sub-LED and the superior heat sinking of the ceramic substrate.