Physics of Visible and UV LED Devices

Large performance gap between the performance visible and deep ultraviolet light emitting diodes (DUV LEDs) is primarily attributed to material properties of high aluminum content group III-nitride semiconductor alloys used for DUV LEDs. For current state of art DUV LED devices the external quantum efficiencies (EQE) -ranges from 2% to 10%. A lower DUV LED efficiency is also due to poor transparency of semiconductor layers to UV light, poor UV light reflectivity of n- and p- contacts, low conductivity of semiconductor heterostructure, and high contact-to-semiconductor layer resistance. In this paper we discuss and compare physics of DUV LEDs and discuss the design of the next generation of DUV LEDs.