First Principles Calculation of Band Offsets and Defect Energy Levels in Al2O3/beta-Ga2O3 Interface Structures with Point Defects
J Park and SM Hong, JOURNAL OF SEMICONDUCTOR TECHNOLOGY AND SCIENCE, 19, 413-425 (2019).
The beta-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 /beta-Ga2O3 interface is required. We have generated several atomistic models for the Al2O3/beta-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/beta-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.
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