Native point defects and dangling bonds in α-Al2O3

摘要

We performed hybrid functional calculations of native point defects and dangling bonds (DBs) in α-Al₂O₃ to aid in the identification of charge-trap and fixed-charge centers in Al₂O₃/III-V metal-oxide-semiconductor structures. We find that Al vacancies (V _{face='roman'>Al}) are deep acceptors with transition levels less than 2.6 eV above the valence band, whereas Al interstitials (Al_i) are deep donors with transition levels within ∼2 eV of the conduction band. Oxygen vacancies (V _{face='roman'>O}) introduce donor levels near midgap and an acceptor level at ∼1 eV below the conduction band, while oxygen interstitials (O_i) are deep acceptors, with a transition level near the mid gap. Taking into account the band offset between α-Al₂O₃ and III-V semiconductors, our results indicate that V _{face='roman'>O} and Al DBs act as charge traps (possibly causing carrier leakage), while V _{face='roman'>Al}, Al_i, O_i, and O DBs act as fixed-charge centers in α-Al₂O₃/III-V metal-oxide-semiconductor structures.