Band offsets of HfO2/GeON/Ge stacks measured by ultraviolet and soft x-ray photoelectron spectroscopies

Electronic properties of the HfO2/GeON/Ge stacks were studied using ultraviolet and synchrotron radiation photoelectron spectroscopies. The valence band offset of HfO2 with Ge is equal to 2.9 +/- 0.1 eV. Intermediate electronic states were observed in the GeON band gap related to structural defects, oxygen vacancies, and N 2p states. As a consequence, the GeON valence band offset with Ge is reduced by 2.4 +/- 0.1 eV to reach 1.2 +/- 0.1 eV. This value is lower than the previous reported results with a GeOx interfacial layer, but still compatible with the semiconductor technology.