Deep Ultraviolet Light Sources for Water Purification and Surface Sterilization

This proposal is related to the development of high efficiency ultraviolet (UV) light emitting devices (LEDs) operating at 265 nm and 219 nm, which have the potential to replace conventional mercury lamps for many applications including dinsinfection and water purification. To date, the wall-plug efficiency of commercial LEDs operating at 265 nm is in the range of 2-3%, which has been limited by the presence of large densities of dislocations, poor p-type conduction and inefficient light extraction of conventional AlGaN quantum well structures. In this project, we aim to address these critical challenges by utilizing dislocation-free AlGaN nanostructures. We will investigate the design, epitaxy, fabrication and characterization of AlGaN nanowire ultraviolet LEDs that can operate relatively efficiently at 265 nm and 219 nm. The light extraction efficiency will be significantly enhanced by exploiting the coupling of photon modes through the nanowires in the light transmission regime of nanowire photonic crystal structures, and efficient p-type conduction will be realized through the formation of Mg impurity band in dislocation-free AlGaN nanostructures. Through these studies, we aim to demonstrate AlGaN LEDs with efficiency >5%, and to further identify the technical feasibility for achieving a wall-plug efficiency >15% for LEDs operating at ~265 nm.