Schottky Diodes Prepared with Ag, Au, or Pd Contacts on a MgZnO/ZnO Heterostructure

We successfully fabricated lateral Schottky diodes with a thin MgZnO layer inserted between the ZnO and Schottky contact metal layers. The MgZnO/ZnO heterostructure was deposited onto a $c$-sapphire substrate by pulsed laser deposition using Mg 0.3 Zn 0.7 O and ZnO targets. Ti/Au was used to achieve ohmic contact with the Mg 0.3 Zn 0.7 O thin film layer, whereas Schottky contacts were prepared using silver (Ag), gold (Au), and palladium (Pd). The Ag Schottky diode devices exhibited rectification ratios as high as ${\sim}10^{3}$ at a bias voltage of $\pm 1$ V, with an ideality factor of 2.37 and a work function of 0.73 eV. The possibility of preparing Schottky contacts with a high carrier concentration on the ZnO layer is discussed as a function of the presence or absence of a MgZnO thin layer and in terms of the measured current--voltage properties.