Identifying a suitable passivation route for Ge interfaces

We compare the usefulness of HfO2, LaGeOx, HfGeOy, GeNx, and Al2O3 as passivating gate dielectrics for Ge substrates. We argue that a key role is to block O vacancy diffusion through the GeO2, inhibiting defect creation at the Ge-oxide interface. Al2O3 is shown to be preferred for this role, being a diffusion barrier and having large band offsets. HfGeOx can phase-separate, leaving HfO2 through which O vacancies and Ge could diffuse. LaGeOx can cause flat-band shifts of undesired polarity, whereas GeNx has a rather small valence band offset and band tail states.

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