Polarization Effect in AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
The polarization effect in AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) is investigated, which is critical for the development of DUV LEDs, because the basal material, epitaxial structure, and polarization characteristics are very distinct to those of the well-developed (In)GaN-based near-ultraviolet and visible light emitters. In this paper, the influence of the polarization effect in multi-quantum well active region and p-type layers on the characteristics of DUV LEDs with Ga-face or N-face polarization is explored. Simulation results show that the severe band bending of the p-type layers induced by the polarization field markedly affects the optical and electrical performance. A band-engineered DUV LED structure with compositional grading electron-blocking layer and p-interlayer is proposed to enhance the electron confinement and hole injection with the mitigation of polarization effect. The device performance of the proposed LED structure with Ga-face or N-face polarization is comparable with that of the DUV LED without polarization.