The III-nitride based ultraviolet light-emitting diodes (UV LEDs) have tunable emission wavelengths covering a range from 210nm to 400nm, making them suited to be applied in many fields, such as industrial, environmental, medical and biochemical detection fields. Rapid great technical breakthroughs have been made to improve the performance of the AlGaN UV LEDs over the past few years. However, there is still much room for the improvement of the external quantum efficiency and the wall plug efficiency of the deep-UV LEDs due to the intrinsic properties of the Al-rich AlGaN materials. This paper reviews the recent development of the AlGaN UV LEDs, as well as the key challenges to the efficiency improvement, including the epitaxy quality, the doping efficiency, the quantum structure, the light extraction and the reliability, and the effective solutions. It is estimated that by the year 2025, the single-chip light output power of the deep-UV LED will exceed the watt level, the wall plug efficiency is expected to be increased to over 20%, and the lifetime will reach a level of 10⁴ hours.

ultraviolet light-emitting diodes  /  AlGaN  /  doping  /  light extraction