First Principles Calculation of Band Offsets and Defect Energy Levels in Al₂O₃/β-Ga₂O₃ Interface Structures with Point Defects

Abstract

The β -Ga₂O₃ (beta-gallium oxide) is one of the most promising candidate materials for the future power and RF (radio frequency) devices. The Al₂O₃ (aluminum oxide) is widely adopted as the gate dielectric layer, which is mandatory for developing the Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) based on Ga₂O₃. Therefore, the theoretical investigation on the properties of the Al₂O₃/ β -Ga O interface is required. We have generated several atomistic models for the Al₂O₃ / β -Ga₂O₃ interface, whose structural parameters are consistent with the experimental findings. From the electronic band structure based on the density-functional theory (DFT) calculation, it is confirmed that the generated interface structures are physically stable. The band offsets between the Ga₂O₃ channel and the Al₂O₃ dielectric layer are calculated for various interface structures. For both the conduction band and the valence band, the Al₂O₃ / β -Ga₂O₃ interface provides sufficiently large band offsets, which makes it attractive for the MOSFET application. The point defects in the interface structure play a critical role in determining the device characteristics. The formation energies and transition levels of various point defects are calculated by using the DFT. It is found that the Ga-, O-, and Al- vacancies have the energy levels close to the conduction band minimum. It is expected that those vacancy defects act as the electron traps at the interface.