Resonant tunneling action in a ZnO/Zn0.8Mg0.2O double barrier device is reported. The device structures consist of a single ZnO quantum well, with thickness of 6, 8, or 50 nm, placed between two Zn0.8Mg0.2O barriers, with a thickness of 7 nm. The structures were grown by pulsed laser deposition on (0 0 0 1) c-cut sapphire substrates. Negative differential resistance peaks were observed at room temperature and at 200 K. The optical transitions in the quantum wells were evaluated from pulsed photoluminescence spectroscopy measurements, and found to be at 3.588 eV for the 6 nm and 3.56 eV for the 8 nm quantum well. The FWHM of the photoluminescence peaks were found to be 5.3 and 5.6 meV at 77 K, for the 6 and 8 nm wells respectively, indicating high quality heterointerfaces. (C) 2002 Elsevier Science Ltd. All rights reserved.