Electrical characterization of Cr Schottky contacts on undoped and Ni-doped p-ZnO films grown by pulsed laser deposition on Si (100) substrates

摘要

Wide band gap semiconducting layers of undoped and Ni-doped p-type ZnO thin films were developed on (100) silicon substrates by pulsed laser deposition (PLD) at a constant oxygen partial pressure of 1.0×10~(-4) Torr and at constant temperature of 250 ℃. The electrical properties of the films were studied by resistivity and Hall coefficient measurements at room temperature. P-type conductivity was found to be dominant in these films at room temperature although the incorporation of Ni dopants caused a reduction in the p-character of ZnO films. The surface morphology of the films was evaluated by contact mode atomic force microscopy (AFM) in air. Cr-Schottky contacts were deposited on these p-type ZnO films, and the rectifying properties of the contacts were evaluated. The current-voltage (I-V) characteristics of the Cr/ZnO Schottky diodes were measured at room temperature. Due to series resistance, the Cheung and Cheung functions were used to determine the barrier height and ideality factor of the diodes while Norde function was used to determine barrier height. Ideality factors of 1.07 and 1.22 were obtained for the Cr/undoped ZnO and Cr/Ni-doped ZnO diodes, respectively, while the barrier height was 0.59 eV by the Norde model, and in good agreement with 0.62 eV of the Cheung-Cheung model, for both undoped and Ni-doped samples.