Defect-Related White-Light Emission from ZnO in an n -Mg 0.2 Zn 0.8 O/ n -ZnO/SiO x Heterostructure on n -Si

An n -Mg 0.2 Zn 0.8 O/ n -ZnO/SiO x ( x < 2) heterostructure has been fabricated on n -Si by sputtering and electron-beam evaporation. The device showed nonrectifying behavior, and emitted strong white light under reverse bias with positive voltages applied to n -Si. The white-light electroluminescence (EL) is believed to result from electron–hole recombination at defect levels of ZnO. The EL mechanism has been tentatively explained in terms of the energy band structure of the device under forward and reverse bias.