Ultraviolet electroluminescence from Au/MgO/MgxZn1−xO heterojunction diodes and the observation of Zn-rich cluster emission

In this work, ultraviolet (UV) electroluminescence (EL) is achieved from Au/MgO/MgxZn1−xO heterojunction diodes. The EL mechanism and laser forming process are discussed based on the energy band diagram, impact-ionization process and disordered optical structure. For ZnO and low Mg-content MgZnO devices, their EL spectra show single near-band-edge (NBE) emission. While in high Mg-content MgZnO devices, the emission from self-formed Zn-rich MgZnO clusters is observed and also contribute to the UV EL band. These Zn-rich clusters can act as thermally-stable luminescence centers, suggesting a promising route for developing MgZnO-based UV light-emitting devices.