Native point defects and dangling bonds in α-Al2O3

Abstract

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 (VAl) are deep acceptors with transition levels less than 2.6 eV above the valence band, whereas Al interstitials (Ali) are deep donors with transition levels within ∼2 eV of the conduction band. Oxygen vacancies (VO) introduce donor levels near midgap and an acceptor level at ∼1 eV below the conduction band, while oxygen interstitials (Oi) 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 VO and Al DBs act as charge traps (possibly causing carrier leakage), while VAl, Ali, Oi, and O DBs act as fixed-charge centers in α-Al2O3/III-V metal-oxide-semiconductor structures.

Structural and electronic properties of Σ7 grain boundaries in α-Al2O3

“…If only one k-point was used, we chose the point at the fractional coordinates [28,29]. In 310 order to avoid spurious distortions due to the different bulk lattice parameters, we rescaled candidate structures generated using the empirical potential in order to be fully consistent with the PBE lattice parameters.…”

Kinetic Monte Carlo of transport processes in Al/AlOx/Au-layers: Impact of defects

“…43 Similarly, for α-Al 2 O 3 , they reported most interestingly in our terms, that V O and Al i are the dominant defect types located at ∼ 4.1 eV and ∼ 1.9 eV below CBM, respectively, and also transition levels due to Al dangling bonds at ∼ 2.8 eV below CBM. 44 45 However, the latter value also suffered from an underestimation of the bandgap being only 6.2 eV. As we expect to get primarily amorphous alumina from our plasma oxidation process, this latter value is the most important reference here.…”

“…So electrons tend to be injected from Al into AlO x defect levels and are transported via small-polaron hopping confirming ab initio predictions on AlO x . 44 Hence, we suggest an optimization of the work function by minimizing interface defects to guarantee E B,Al/AlOx > 2.7 eV and good control of bulk defects so that E D > 2.8 eV and n D 4 × 10 18 cm −3 , especially for d ox ∼ 4 nm or operating voltages V ox 4 V.…”

“…Hence, growth techniques providing good crystallinity and stoichiometry of AlO x are required to guarantee its applicability as gate dielectrics. O-rich conditions, for example, induce a Fermi-level within Al-AlO x -Au-contacts that causes less rather shallow V O s and Al int s, but more deep V Al s. 44 Thirdly, we encountered that DT/FN dominates over the trap-related processes, like TAT and PF. Also when shifting the trap energies between 2.3 to 3.2 eV at 1.2 V bias, cf.…”

Электронно-Лучевая Зарядка Диэлектриков, Предварительно Облученных Ионами И Электронами Средних Энергий

“…Глубокие ловушки -уровни, лежащие по-середине запрещенной зоны, -связаны с примесными атомами в кристалле или со связью Si-Si в кристаллах, обогащенных кремнием. В кристалле Al 2 O 3 [28] с вакан-сией алюминия (V Al ) связан глубокий акцепторный уро-вень, расположенный на 2.6 eV выше потолка валентной зоны. Энергетический уровень междоузельного атома алюминия (Al i ) лежит примерно на 2 eV ниже зоны проводимости и является глубоким донорным уровнем.…”