Atomic Level Insight into the Variation and Tunability of Band Alignment between Si and Amorphous SiO₂/HfO₂

The band alignment between silicon and high-k dielectrics, which is a key factor in device operation and reliability, still suffers from uncontrolled fluctuations and ambiguous understanding. In this study, by conducting atomic-level ab initio calculations on realistic Si/SiO₂/HfO₂ stacks, we reveal the physical origin of band alignment fluctuations, i.e., the oxygen density-dependent interface and surface dipoles, and demonstrate that band offsets can be tuned without introducing other materials. This is instructive for reducing the gate tunneling current, alleviating device-to-device variation, and tuning the threshold voltage. Additionally, this study indicates that significant attention should be focused on model construction in emerging atomistic studies on semiconductor devices.