Enhancement of ultraviolet electroluminescence based on n-ZnO/n-GaN isotype heterojunction with low threshold voltage

Abstract

Ultraviolet light-emitting diodes based on simple n-ZnO/n-GaN isotype heterojunction have been fabricated using a radio frequency magnetron sputtering system. Ultraviolet emission peaking around ∼368 nm with a full-width at half maximum of ∼7 nm was observed at room temperature when the devices were under sufficient forward bias. With the presence of an i-MgO layer inserted between the ZnO and GaN layers, the ultraviolet emission intensity and output power have been much enhanced, while the threshold voltage drops down to 2.5 V. The electroluminescence mechanisms in these devices were discussed in terms of the band diagrams of the heterojunctions.