Electron states at the (100)Ge/HfO2 interface

The energy distribution of extended and localized electron states at the Ge/HfO2 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 HfO2 layer as a suitable insulator on Ge. The post-deposition annealing of the Ge/HfO2 structures in oxygen results in similar to1 eV reduction of the valence band offset, which is attributed to the growth of a GeO2 interlayer. However, this treatment enables one to substantially reduce the density of Ge/HfO2 interface traps, approaching approximate to1 x 10(12)cm(-2)eV(-1) near the Ge midgap. (C) 2004 Elsevier Ltd. All rights reserved.