National Research Program of China [2012CB619301, 2011CB301905, 2011CB925600]; National Natural Science Foundation of China [61108064, 61227009, 90921002]; Fundamental Research Funds for the Central Universities [2011120143]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 nmis 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 AlxGa1-xN multiple quantum wells, i.e., the band edge emission energy, the enhancement ratio of the Al-coated deep-UV LEDs increases
