Origin of high solubility of silicon in La2 O3: A first-principles study

Abstract

The solubility of silicon in high-permittivity (high- κ) oxides significantly affects the performance of field-effect transistors. Our comparative study of silicon impurities in La2 O3 and HfO2 reveals that the stability of silicon at substitutional sites strongly depends on its coordination number. When substituted for lanthanum, a silicon atom fits comfortably in La2 O3, thanks to the formation of a SiO4 tetrahedral structure. In addition, the substitutional silicon acts as a donor impurity in La2 O3, increasing oxygen content in the oxide. This contributes to absorbing silicon and oxygen from the interface region, leading to the formation of lanthanum silicate at the La2O3/silicon interface. © 2010 American Institute of Physics.