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

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 similar to 370 nm with a full-width at half maximum of similar to 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 similar to 23 from similar to 70 mA. The results were discussed in terms of the band diagrams of the heterojunctions. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3176440]