High‐Power III‐Nitride Deep‐Ultraviolet Light Emitters With Record 21% Wall‐Plug Efficiency

ABSTRACT The complete replacement of toxic mercury lamps requires III‐nitride deep‐ultraviolet (DUV) light emitters with high wall‐plug efficiency (WPE at least 20%) under high‐current operation, but their WPE is seriously limited by difficult forward light emission and low light extraction. Herein, a high‐power DUV light emitter with a record 21.2% WPE is proposed by a cooperative photon‐redirection strategy. The DUV chip architecture synergistically integrates an in situ nano‐porous AlN scattering layer with an optimized reflective mesa and a double‐sided patterned sapphire substrate. This strategy efficiently redirects laterally propagating photons into the escape cone through coupled reflection and multi‐stage scattering, thereby increasing the TM‐mode light extraction efficiency by 252.1%. Consequently, the fabricated DUV light emitter achieves a record‐high WPE of 21.2% at an injected current of 70 mA, maintaining a WPE exceeding 16% over a wide current range from 10 to 350 mA. Furthermore, a DUV light emitter array module with a high irradiance of 1.33 W/cm 2 is integrated in a large‐flow water‐treatment system, making >99.999% inactivation of bacteria under an ultra‐high water flow rate of 20 m 3 /h. This work will definitely accelerate the large‐scale commercialization of the new‐generation solid‐state DUV source.