Energy band alignment at the (100)Ge/HfO2 interface

Abstract

The ${\mathrm{Ge/HfO}}_2$ interface band diagram was directly determined using internal photoemission of electrons and holes from Ge into the Hf oxide. The inferred offsets of the conduction and valence band at the interface, $\text{2.0±0.1}$ and $\text{3.0±0.1\hspace{0.5em}}\mathrm{eV},$ respectively, suggest the possibility to apply the deposited ${\mathrm{HfO}}_2$ as an insulator on Ge. The post-deposition annealing of the ${\mathrm{Ge/HfO}}_2$ structures in oxygen results in ∼1 eV reduction of the valence band offset attributed to the growth of ${\mathrm{GeO}}_2$ interlayer.