Arrays of Truncated\nCone AlGaN Deep-Ultraviolet Light-Emitting\nDiodes Facilitating Efficient Outcoupling of in-Plane Emission

Despite a rapidly\ngrowing demand for efficient man-made deep-ultraviolet\n(DUV) light sources, widespread adoption of AlGaN-based DUV light-emitting\ndiodes (LEDs) is currently obstructed by extremely poor extraction\nof DUV photons due to the intrinsic material properties of the AlGaN\nactive region. Here, we present 280 nm AlGaN DUV LEDs having arrays\nof truncated cone (TC)-shaped active mesas coated with MgF₂/Al reflectors on the inclined sidewalls of the cone to effectively\nextract the intrinsically strong transverse-magnetic-polarized emission.\nRay tracing simulations reveal that the TC DUV LEDs show an isotropic\nemission pattern and much enhanced light-output power in comparison\nwith stripe-type DUV LEDs with the same MgF₂/Al reflectors.\nConsistent with the ray tracing simulation results, the TC DUV LEDs\nshow an isotropic emission pattern with much higher light-output power\nas well as lower operating voltage than the stripe-type DUV LEDs.\nOn the basis of our results, strategies for designing high-performance\nDUV LEDs to further enhance the optical and electrical performances\nsimultaneously are suggested.