Morphology and defect properties of the Ge–GeO2 interface

Ge-based devices, currently being pursued as replacement of their Si counterparts, typically contain a germanium oxide layer next to the substrate. Here we show using first-principles calculations that, in contrast to Si technology, hydrogenation and fluorination are not effective ways of passivating Ge–GeO2 interfacial Pb centers with a Ge dangling bond (DB). Moreover, we identify DB geometries that differ from the Pb structures and we find that the Ge–GeO2 boundary has a higher atomic-scale roughness than the Si–SiO2 interface. These key differences in interface morphology and defect properties are consistent with experimental data.