Energetics of hydrogen in GeO2, Ge, and their interfaces

The energetics of interstitial hydrogen in GeO2, Ge, and their interfaces are calculated using a hybrid density functional. We find that interstitial atomic hydrogen unexpectedly behaves as a donor in GeO2, like H in ZnO but unlike H in SiO2. At Ge:GeO2 interfaces, the donor electron can transfer to the lower lying Ge conduction band, which stabilises the O-H bond/donor complex. This reduces the probability of passivating Ge dangling bond (Pb) centers at Ge:GeO2 interfaces.