Local bonding effect on the defect states of oxygen vacancy in amorphous HfSiO_4

摘要

We perform first-principles calculations to investigate the defect properties of O vacancies in amorphous HfSiO_4. For atomic models generated from molecular dynamics simulations, we find that O vacancies, which have only Hf atoms or a mixture of Hf and Si in the neighborhood, behave as charge trap centers, similar to those in HfO_2. On the other hand, O vacancies surrounded by only Si atoms are energetically most favorable and have very high trap energies for both electron and hole carriers. Thus, these defects are suggested to be responsible for the reduction of threshold voltage instability.