AlGaN-based Ultraviolet Light Emitting Diodes(<Special Issue> Where are the Materials for Ultraviolet Devices and Where are These Going ?)

Abstract

The fabrication and evaluation of AlGaN-based ultraviolet light emitting diodes (UV-LEDs) are described. First, the formation of an atomically flat GaN surface and the control of GaN/AlGaN heterointerfaces is confirmed. From the photoluminescence measurement of GaN/AlGaN quantum well structures achieved by this heterointerface control, we found a clear quantum confinement effect and extremely large internal polarization field of nitride heterostructures. In consideration of the importance of this internal polarization field, the superiority of the active layer consisting of AlGaN quantum wells, and of the cladding layers consisting of short-period alloy super lattice (SPASL) are discussed. Finally, a highly efficient UVLED grown on a high quality bulk GaN substrate and its application are demonstrated.