Structural and electronic properties of Ti- and Ca-doped hexagonal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>TbInO</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:math>

Hexagonal ${\mathrm{TbInO}}_{3}$ exhibits spin liquid behavior at low temperatures and improper ferroelectricity at room temperature, and as such may host novel electronic and magnetic states upon carrier doping. This paper presents density functional theory (DFT) calculations of the electronic, dielectric, and defect properties of ${\mathrm{TbInO}}_{3}$. We study ${\mathrm{Ti}}^{4+}$ and ${\mathrm{Ca}}^{2+}$ as substitutional dopants replacing ${\mathrm{In}}^{3+}$ and ${\mathrm{Tb}}^{3+}$ to introduce electron- and hole-doping, respectively. Point defect calculations reveal that ${\mathrm{Ti}}^{4+}$ dopants introduce shallow defect states near the conduction band minimum, suggesting the possibility of $n$-type conductivity, whereas ${\mathrm{Ca}}^{2+}$ dopants result in deep in-gap states. We also analyze changes to structural properties with relatively large (8%--16%) Ca and Ti concentrations. We utilize molecular beam epitaxy (MBE) to synthesize epitaxial thin films of ${\mathrm{TbInO}}_{3}$ doped with ${\mathrm{Ti}}^{4+}$ and ${\mathrm{Ca}}^{2+}$, and use scanning transmission electron microscopy (STEM) imaging to show that the experimental films corroborate the doping-induced structural changes found with DFT. However, all samples remain electrically insulating, which we attribute to the localization of added carriers on the Tb cation. Finally, we propose charge-transfer doping as an alternative strategy to induce conductivity in ${\mathrm{TbInO}}_{3}$, and identify several possible substrates to achieve this.