Fabrication and characterization of rare earth (Ce, Gd, and Y) doped ZrO_2 based metal-insulator-semiconductor (MIS) type Schottky barrier diodes

摘要

The 8 wt% rare earth (RE = Ce, Gd, and Y) doped zirconium dioxide (ZrO_2) thin films were prepared on glass substrates by spin-coating technique and annealed at 600 C. Also, the RE:ZrO_2 based metal-insulator-semiconductor (MIS) type Schottky barrier diodes were fabricated. X-ray diffraction (XRD) patterns revealed the mixed phase of monoclinic and tetragonal ZrO_2 for the RE: ZrO_ films, and the pure monoclinic phase for the undoped ZrO_2 film. Because of the doping with RE ions, the crystallite size reduced with the increase of oxygen vacancies. The scanning electron microscopic (SEM) images exhibited the rod-shaped and square-shaped grains for the undoped ZrO_2 and Gd:ZrO_2 thin films, respectively. Elemental compositions were confirmed by the energy dispersive X-ray (EDX) analysis. The UV-vis analysis showed the lower transmittance for the RE: ZrO_2 films with a reduced band gap (E_g). The dc electrical conductivity (σ_(dc)) was increased with the decrease of activation energy (E_a) due to the RE doping. When compared to the A1/undoped ZrO_2/p-Si Schottky barrier diode, the Al/RE:ZrO_2/p-Si showed an improvement in the values of barrier height (Φ_B), ideality factor (n), and series resistance (R_s).