Co-doping Effect of Ca and N on the Structure and Properties of CuAlO[sub 2] Thin Film

Ca-doped CuAlO 2 films were prepared by the radio-frequency magnetron sputtering technique. As shown by X-ray diffraction measurements, single-phase hexagonal CuAl 1 − x Ca x O 2 is formed for Ca concentrations up to 1.5 atom %. Hall measurements confirm the p-type conduction for all films. The introduction of Ca leads to a sharp improvement in electrical conductivity due to the increase in carrier concentration. With increasing doping concentrations, the bandgaps of CuAl 1 − x Ca x O 2 thin films increase. We attribute this to Burstein–Moss shift from increased carrier concentrations. A nitrogen plasma treatment results in further enhancement of the electrical conductivity due to introducing N as an acceptor into CuAl 0.985 Ca 0.015 O 2 thin film.