First-principles study of planar defects in β-Ga₂O₃

β-Ga₂O₃ is a wide-bandgap semiconductor which is promising for high-power electronic device applications. Planar defects such as stacking faults and twin boundaries have been observed in β-Ga₂O₃. We use density functional theory to explore the energetics and electronic structure of these defects. We find that twin boundaries can form on the (001)A, (001)B, (100)A, (100)B and (102) planes. The (100)A twin boundary has the lowest formation energy, indicating that it is more likely to find twin-boundary structures during the (100)-oriented growth. Scanning transmission electron microscopy (STEM) studies show that a stacking fault forms at a (010) plane in samples in which the growth direction switches from [010] to [001] [APL Mater. 8, 031104 (2020)]. We explain the origin of this stacking fault and describe its structure and energetics.