A range of alloying candidates have been identified for beta gallium oxide ($\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$) as a means of tuning its electronic properties, primarily the band gap. Scandium has been recognized as a promising alloying candidate, but its effect on $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$'s electronic, structural, and defect behavior must be better understood to enable further development. Here, Czochralski-grown (100) $\beta \text{−}{\left({\mathrm{Sc}}_{0.06}{\mathrm{Ga}}_{0.94}\right)}_2{\mathrm{O}}_3$ crystals were investigated using atomic-resolution scanning transmission electron microscopy, monochromated electron energy loss spectroscopy, and first-principles simulations. These results show that Sc preferentially occupies octahedral Ga sites and increases the material's band gap from 4.8 eV to 4.92 eV when alloyed with 10 mol% Sc. It is also demonstrated that the alloying of Sc can result in unique extended defect formation in both intrinsic and mechanically deformed $\beta \text{−}{\left({\mathrm{Sc}}_{0.06}{\mathrm{Ga}}_{0.94}\right)}_2{\mathrm{O}}_3$. The structure of a unique planar defect in the as-grown crystal was determined to be a set of closely spaced, (100)-oriented stacking faults resulting in a unique atomic projection. Mechanical deformation of the crystal, performed to help understand intrinsic defect structure, resulted in the identification of an atomic configuration within a stacking fault heavily influenced by local strain, which we term a “strained stacking fault”. No widespread formation of point defects or dislocations was observed in the as-grown crystal. These results reveal the ability of unique extended defects, such as multiple stacking faults in close proximity, to form in $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ systems when alloyed. These findings provide insight into the potential of $\beta \text{−}{\left({\mathrm{Sc}}_{\mathrm{x}}{\mathrm{Ga}}_{1-x}\right)}_2{\mathrm{O}}_3$ alloys to produce substrates with a range of electronic and structural properties, enabling further development of $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ for next-generation power semiconductor applications.

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• Defects
• Alloys
• Semiconductors
• Wide band gap systems
• Electron energy loss spectroscopy
• First-principles calculations