Band Alignment of atomic layer deposited HfO2 on clean and N passivated Germanium surfaces

Hard x-ray photoelectron spectroscopy (HAXPES) has been used to study the band alignment between atomic layer deposited (ALD) HfO2 on clean Ge (100) and nitrogen treated Ge (100) surfaces. The position of the valence-band maximum was determined by convolving theoretically calculated density of states from first-principles calculations and comparing with experimental valence-band data. The valence-band offset was found to be 3.2 $\pm $ 0.1 and 3.3 $\pm $ 0.1 eV for the samples grown on clean and N passivated Ge, respectively. The oxide charge however shows a significant increase between the two samples. The small change in the band offset between the two systems strongly indicates negligible contribution of the interface to the conduction/valence-band barrier and the band alignment of the heterojunctions.