Ultraviolet electroluminescence from n-ZnO/NiO/p-GaN light-emitting diode fabricated by MOCVD

Ultraviolet light-emitting diodes (LED) based on n-ZnO/NiO/p-GaN were realized by metal-organic chemical vapor deposition (MOCVD). The devices exhibited diode-like rectifying current-voltage characteristics and had a turn-on voltage of 7.5 V. High quality NiO film as an electron blocking layer inserted between the ZnO and GaN films showed high resistance state with preferred [1 1 1] orientation, which produced a larger ZnO/NiO conduction band offset of 2.93 eV than that of ZnO/GaN (0.15 eV). The electroluminescence spectra of the n-ZnO/i-NiO/p-GaN heterostructure demonstrated that electrons were effectively confined in the ZnO active region, and thus leading to the enhancement of the excitonic emission from the ZnO side.