Electronic properties at the oxide interface with silicon and germanium through x-ray induced oxide charging

A dependence of the binding energy of the Hf 4f and O 1s photoemission lines on the thickness of the HfO2 film is identified in HfO 2/Si heterojunctions and associated with differential charging phenomena. No shifts of Hf 4f and O 1s binding energies are observed in HfO 2/Ge heterojunctions, irrespective of the HfO2 film thickness. The time evolution of Hf 4f and Ge 3d signals correlates with a large number of electrically active traps, which are close to the Ge valence bands and determine a negative charge builds-up at the interface, causing the commonly observed p-type surface inversion in n-Ge. © 2012 American Institute of Physics.