Using a DC and RF magnetron sputtering system, we fabricated an ultraviolet (UV) reactive hetero-structured diode with n-type ZnO, p-type NiO and a Ni electrode with an indistinct interface between the NiO layer and the Ni electrode. To decrease the contact resistance and the number of process steps, we fabricated the hetero-structured diode via a one-step process, which could deposit the ZnO, NiO and Ni electrode sequentially in one chamber without heat treatment or vacuum break. We compared the I-V characteristics of the hetero-structured diodes with various metal electrodes (Al, Ni and Ni with an indistinct interface) to investigate the decrease in the contact resistance between the NiO layer and the Ni electrode. In the I-V measurements, the hetero-structured diode with the indistinct interface between the NiO layer and the Ni electrode exhibited distinct rectifying current-voltage (I-V) characteristics. The threshold voltage decreased 0.57 V with the hetero-structured diode fabricated by using a sputtering system. The current increased 0.9 mA at a forward voltage of 2.5 eV. The indistinct interface between the NiO and the Ni was analyzed using scanning electron microscopy. UV light with a wavelength of 325 nm reacted on a hetero-structured diode. Based on these results, we demonstrated that the hetero-structured diode with an indistinct interface between the NiO layer and the Ni electrode is a good UV photodetector.
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