The interface structure of high performance ZnO Schottky diodes

Oxidized iridium (IrOx) anodes fabricated on n-type ZnO single crystal wafers using reactive pulsed laser deposition are known to produce high quality Schottky barriers with ideality factors approaching the image-force-controlled limit for laterally homogeneous interfaces. These high performance IrOx/ZnO Schottky contacts were cross-sectioned and analyzed using transmission electron microscopy, revealing an amorphous interfacial layer of 2-3 nm thickness. Electron energy loss spectroscopy, used to study the composition of the interface region, showed evidence of significant zinc diffusion across the interface into the IrOx film, which leads to the creation of Zn vacancies (acceptors), in the ZnO sub-interface region. There is also evidence for oxygen passivation near the interface resulting from the use of an active oxygen ambient during the IrOx deposition. Both these factors may explain the outstanding electrical performance of these Schottky devices. (C) 2011 Elsevier B.V. All rights reserved.