Thermal evolution and electrical correlation of defect states in Hf-based high-k dielectrics on n-type Ge (100): Local atomic bonding symmetry

The crystal field splittings and Jahn-Teller (J-T) distortions in Hf-based high-k dielectric oxides on n-type Ge (100) substrates were investigated through the examination of O K-1 edge spectra, obtained via x-ray absorption spectroscopy. Second derivative analysis of these O K-1 edge spectra provided unambiguous evidence of J-T d-state degeneracy removal, resulting from the symmetry of the local atomic bonding environment. Additionally, two distinct defect states were found below the conduction band edge. The conduction band's molecular orbital energy structure, including defect states, was determined based on the results of these investigations. Moreover, the thermal evolution of the defect states was found to be dependent on both postdeposition annealing temperature and Hf-based high-k dielectric oxides. These subband-edge defect states were determined to be electrically active, and their density and the local atomic bonding symmetry were found to be correlated with the effective electron charge trapping measured in related device structures. (C) 2009 American Institute of Physics. [doi:10.1063/1.3236679]