Oxygen vacancies and carrier mobility at the a-ZrO2/Si(001) interface

Based on density-functional theory combined with molecular dynamics simulations, we systematically investigate the effects of oxygen vacancy defects on the electronic structure, interfacial charge transfer, and carrier transport properties of the amorphous ZrO2/Si (a-ZrO2/Si) interface. The band edges are dominated by the Si side, yielding band offsets exceeding 1 eV. Among six representative oxygen vacancies (three single and three double vacancies), double vacancies induce substantially stronger bandgap perturbations, with VO2 and VO12 introducing quasi-flat defect bands. While oxygen vacancies do not alter the overall direction of interfacial charge transfer, VO12 markedly enhances electron accumulation on the a-ZrO2 side. Notably, under both n-type and p-type conditions, the carrier mobility of the perfect interface is primarily limited by polar optical phonon scattering. Oxygen vacancies significantly degrade the mobility, whereas hydrogen passivation suppresses defect states and partially restores the mobility. In particular, at 300 K under n-type doping, the total mobility of VO2 and VO12 is below 8.5 cm2 V−1 s−1 and increases to 20.3–23.4 cm2 V−1 s−1 after passivation. These findings elucidate the microscopic mechanisms of oxygen vacancy and hydrogen passivation in regulating a-ZrO2/Si interface and provide atomic scale insights for high-k interface defect modulation.