Light-emitting diodes (LEDs) based on p-GaN/ZnO heterojunction were fabricated. ZnO thin film deposited by electron-beam deposition and ZnO nanorods grown by electrodeposition were used as n-type materials. Devices with and without ~ 10 nm thick MgO interlayer between p-GaN and ZnO were prepared. The existence of MgO interlayer significantly affected LED performance compared to LEDs without MgO interlayer. In the photoluminescence measurements, p-GaN/MgO/ZnO nanorods exhibited stimulated emission under pulsed optical excitation, while no stimulated emission was observed in the absence of MgO. The effect of MgO interlayer on ZnO growth, optical and electrical properties, as well as the emission spectra of LEDs is discussed in detail. ; Department of Applied Biology and Chemical Technology ; Department of Electronic and Information Engineering