Studies of oxide/ZnO near-interfacial defects by photoluminescence and deep level transient spectroscopy

The evolution of near-interfacial defects from Al2O3∕ZnO and MgO∕ZnO upon thermal annealing has been studied by photoluminescence, deep level transient spectroscopy, and secondary ion mass spectroscopy. We find that all the results are strongly connected and that they point to the direction that Zn outdiffuses from ZnO to the oxide layer during annealing and creates deep level defects near the interfacial region. These defects reduce the band-edge emission and increase the deep level emission at 2.37eV. Our study shows that the oxide/ZnO interface is relatively fragile and caution must be taken for making metal-oxide-ZnO based transistors and light emitting diodes.