Arrays of Truncated Cone AlGaN Deep-Ultraviolet Light-Emitting Diodes Facilitating Efficient Outcoupling of in-Plane Emission

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