Improved Pt∕Au and W∕Pt∕Au Schottky contacts on n-type ZnO using ozone cleaning

Abstract

UV-ozone cleaning prior to metal deposition of either e-beam Pt contacts or sputtered W contacts on n-type single-crystal ZnO is found to significantly improve their rectifying characteristics. Pt contacts deposited directly on the as-received ZnO surface are Ohmic but show rectifying behavior with ozone cleaning. The Schottky barrier height of these Pt contacts was 0.70eV, with ideality factor of 1.5 and a saturation current density of 6.2×10−6Acm−2. In contrast, the as-deposited W contacts are Ohmic, independent of the use of ozone cleaning. Postdeposition annealing at 700°C produces rectifying behavior with Schottky barrier heights of 0.45eV for control samples and 0.49eV for those cleaned with ozone exposure. The improvement in rectifying properties of both the Pt and W contacts is related to removal of surface carbon contamination from the ZnO.