Influence of barium doping on structural and magnetic properties of c-ZnO epitaxial layers grown on c-GaN/sapphire templates

Abstract

Ba doped ZnO epitaxial layers (Ba:ZnO) with different Ba concentrations are grown on c-GaN/sapphire templates by chemical vapor deposition technique, where mixture of Ba and Zn powders is used as the source for these metals. Concentration of Ba in these layers is determined by secondary ion mass spectrometry and Rutherford backscattering techniques. X-ray diffraction studies demonstrates high epitaxial quality of these c-axis oriented films. c-lattice constant of these layers is found to increase with the Ba concentration, while a-lattice constant does not vary much. This suggests the strain developed in the film is uniaxial in nature. The width of the rocking curves taken at (0006) reflection is also found to increase with Ba concentration indicating the enhancement in the structural defects. This is also supported by the photoconductivity measurements. Thermally stimulated current spectroscopy reveals certain trap states with the activation energy of ∼ 192 meV in Ba doped layers. These layers also show ferromagnetic like behavior and the saturation magnetization is found to increase with the Ba-concentration, which may indicate the involvement of the generated defects in ferromagnetic ordering.