Ultraviolet electroluminescence from ZnO/NiO-based heterojunction light-emitting diodes

Abstract

Ultraviolet light-emitting diodes based on ZnO/NiO heterojunctions were fabricated on commercially available n+-GaN/sapphire substrates using a radio frequency magnetron sputtering system. Near band edge emission of ZnO peaking at ∼370 nm with a full-width at half maximum of ∼7 nm was achieved at room temperature when the devices were under sufficient forward bias. With the help of an electron blocking i-Mg1−xZnxO(0<x<1) layer inserted between the ZnO and NiO layers, the emission intensity has been much enhanced and the threshold current drops down to ∼23 from ∼70 mA. The results were discussed in terms of the band diagrams of the heterojunctions.