Surface-plasmon-enhanced deep-UV light emitting diodes based on AlGaN multi-quantum wells.

We report the development of complete structural AlGaN-based deep-ultraviolet light-emitting diodes with an aluminum thin layer for increasing light extraction efficiency. A 217% enhancement in peak photoluminescence intensity at 294 nm is observed. Cathodoluminescence measurement demonstrates that the internal quantum efficiency of the deep-UV LEDs coated with Al layer is not enhanced. The emission enhancement of deep-UV LEDs is attributed to the higher LEE by the surface plasmon-transverse magnetic wave coupling. When the proportion of the TM wave to the Al layer increases with the Al content in the Al(x)Ga(1-x)N multiple quantum wells, i.e., the band edge emission energy, the enhancement ratio of the Al-coated deep-UV LEDs increases.