Efficient Structure for Deep-Ultraviolet Light-Emitting Diodes with High Emission Efficiency: A First-Principles Study of AlN/GaN Superlattice

Abstract

We investigate an efficient structure for the near-band-edge C-plane emission of a deep-ultraviolet light-emitting diode using first-principles calculations based on density functional theory. We find that a negative crystal-field splitting in the AlN bulk is converted to a positive one in the AlN/GaN superlattice with more than one GaN monolayer. The quantum-confinement Stark effect is minimized by decreasing the GaN thickness down to 1–2 monolayers. The optical matrix element of such superlattices is 57% relative to the GaN bulk, and its C-plane component accounts for the majority of the total; the emission wavelength is found to be 224 nm. The reverse of the negative ΔCR in the AlN/GaN superlattice is ascribed mainly to two factors: quantum confinement effects and the internal parameter u. Our calculations demonstrate that using the AlN/GaN superlattices with one or two GaN monolayers significantly improves the near-band-edge C-plane emission of deep-UV light-emitting diodes.