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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 0.70 eV, with ideality factor of 1.5 and a saturation current density of 6.2×10-6 A cm-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 0.45 eV for control samples and 0.49 eV 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. [ABSTRACT FROM AUTHOR]

Sc[sub 2]O[sub 3] thin-film layers deposited by rf plasma-assisted molecular-beam epitaxy were found to significantly reduce the concentration of prominent surface traps with activation energies of 1 and 0.9 eV on AlGaN/GaN high electron mobility transistors (HEMTs). The surface passivation is accompanied by effective mitigation of the current collapse observed under rf conditions in HEMTs without Sc[sub 2]O[sub 3]. The passivation is stable to post-deposition annealing temperatures of 400 °C and device degradation at higher temperatures is due to reaction of the gate metal with the AlGaN. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]