High-output-power deep ultraviolet light-emitting diode assembly using direct bonding

We fabricated high-output-power 255 and 280 nm light-emitting diodes (LEDs) using direct bonding. The LED chips were bonded to sapphire lenses at room temperature using either atomic diffusion bonding or surface-activated bonding. The LEDs with lenses had a higher light extraction efficiency than conventionally structured LEDs. As a result, at a forward current of 350 mA, the output power of the 255 nm LED increased by a factor of 2.8, reaching 73.6 mW, while that of the 280 nm LED increased by a factor of 2.3, reaching 153 mW.