Electron states at the (1 0 0)Ge/HfO 2 Interface

Abstract

The energy distribution of extended and localized electron states at the Ge/HfO 2 interface is determined by combining the internal photoemission of electrons and holes from Ge into the Hf oxide and AC capacitance/conductance measurements. The inferred offsets of the conduction and valence band at the interface, i.e., 2.0 ± 0.1 and 3.0 ± 0.1 eV, respectively, suggest the possibility to apply the deposited HfO 2 layer as a suitable insulator on Ge. The post-deposition annealing of the Ge/HfO 2 structures in oxygen results in ∼1 eV reduction of the valence band offset, which is attributed to the growth of a GeO 2 interlayer. However, this treatment enables one to substantially reduce the density of Ge/HfO 2 interface traps, approaching ≈1×10 12 cm −2 eV −1 near the Ge midgap.