Remote Plasma Enhanced Chemical Deposition of Non-Crystalline GeO₂ on Ge and Si Substrates

Non-crystalline GeO₂ films remote were plasma deposited at 300 °C onto Ge substrates after a final rinse in NH₄OH. The reactant precursors gas were: (i) down-stream injected 2% GeH₄ in He as the Ge precursor, and (ii) up-stream, plasma excited O₂–He mixtures as the O precursor. Films annealed at 400 °C displayed no evidence for loss of O resulting in Ge sub-oxide formation, and for a 5–6 eV mid-gap absorption associated with formation of GeO _x suboxide bonding, x < 2. These films were stable in normal laboratory ambients with no evidence for reaction with atmospheric water. Films deposited on Ge and annealed at 600 °C and 700 °C display spectra indicative of loss of O-atoms, accompanied with a 5.5 eV absorption. X-ray absorption spectroscopy and many-electron theory are combined to describe symmetries and degeneracies for O-vacancy bonding defects. These include comparisons with remote plasma-deposited non-crystalline SiO₂ on Si substrates with SiON interfacial layers. Three different properties of remote plasma GeO₂ films are addressed comparisons between (i) conduction band and band edge states of GeO₂ and SiO₂, and (ii) electronic structure of O-atom vacancy defects in GeO₂ and SiO₂, and differences between (iii) annealing of GeO₂ films on Ge substrates, and Si substrates passivated with SiON interfacial transition regions important for device applications.