Investigation of band offsets and direct current leakage properties of nitrogen doped epitaxial Gd2O3 thin films on Si

Abstract

Dielectric properties of epitaxial Gd2O3 thin films grown on Si have been found to improve significantly by incorporation of suitable dopants. However, in order to achieve optimum electrical properties from such doped oxides, it is important to understand the correlation between doping and the electronic structure of the material. In the present article, we report about the effect of nitrogen doping on the electronic structure and room temperature dc leakage properties of epitaxial Gd2O3 thin films. Epitaxial Gd2O3:N thin films were grown on p-type Si (111) substrates by solid source molecular beam epitaxy technique using molecular N2O as the nitridation agent. First investigations confirmed the presence of substitutional N in the Gd2O3:N layers. Incorporation of nitrogen did not affect the structural quality of the oxide layers. X ray photoelectron spectroscopy investigations revealed band gap narrowing in epitaxial Gd2O3 due to nitrogen doping, which leads to reduction in the valence band offset of the Gd2O3:N layers with Si. DC leakage current measured at room temperature revealed that despite reduction in the band gap and valence band offsets due to N doping, the Gd2O3:N layers remain sufficiently insulating. A significant reduction of the leakage current densities in the Gd2O3:N layers with increasing nitrogen content suggests that doping of epitaxial Gd2O3 thin films with nitrogen can be an effective route to eliminate the adverse effects of the oxygen vacancy induced defects in the oxide layers.