Microstructures and electronic characters of β-Ga 2 O 3 on different substrates: exploring the role of surface chemistry and structures.

Unveiling the microstructural and electronic properties of β-Ga ₂ O ₃ on different substrates is vital to realize the high quality and performance of β-Ga ₂ O ₃ . Here, the microstructure disorder, defect characters and orbital structures of β-Ga ₂ O ₃ on the Al ₂ O ₃ , MgO, and SiC substrates with different terminations are studied. Although several growth mechanisms for β-Ga ₂ O ₃ are observed on the same substrate, β-Ga ₂ O ₃ prefers to deposit the octahedral Ga atom firstly on the Al ₂ O ₃ and MgO substrates, and the latter can restrain the oxygen-vacancy formation and migration. The structural disorder, band offsets and gap states can be improved upon depositing β-Ga ₂ O ₃ on a substrate with metal terminations under the oxygen-poor conditions. Compared to the Al ₂ O ₃ substrate, β-Ga ₂ O ₃ on the SiC substrate shows a smaller structure disorder and a higher defect formation energy, in particular under the oxygen-rich conditions, since β-Ga ₂ O ₃ prefers to deposit the tetrahedral Ga atom firstly on the SiC substrate to form a SiC-Ga ₂ O ₃ interface with less dangling bonds. The type-II band alignment of the SiC-Ga ₂ O ₃ interface can be changed into the type-I character with larger band offsets when β-Ga ₂ O ₃ is deposited under the oxygen-rich conditions, irrespective of the termination of the SiC substrate. These results provide a useful understanding of the effect of substrates on the quality and performance of β-Ga ₂ O ₃ and a scientific basis for the application of substrate-Ga ₂ O ₃ interfaces.