Electrical Characterisation of NiO/ZnO Structures

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Nickel oxide/zinc oxide structures were formed by evaporating Ni onto ZnO and annealing in oxygen. The electrical properties of this nickel oxide layer were investigated by four-point probe measurements and those of the nickel oxide/zinc oxide junction by variable temperature current-voltage (I-V) measurements. NiO layers had a maximum room temperature resistivity of approximately 100 Ω.cm after oxidation and a bandgap of 3.5–3.6 eV. Upon cooling to 75 K the resitivity increased by six orders of magnitude. IV measurements showed that the rectification of these structures is sufficient for DLTS. Finally, we demonstrate the usefulness of this structure for DLTS measurements of defects in ZnO in the temperature range 20 K–390 K. We report the properties of one new shallow level, possibly the H-donor, and one new radiation induced deep level defect that could be the O-vacancy. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)