Band offsets at the interfaces between β−Ga2O3 and Al2O3

The band offsets at the interfaces between ($\overline{2}01$) $\ensuremath{\beta}\ensuremath{-}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ polymorphs are calculated through hybrid functional calculations. For alumina, we consider four representative phases, i.e., $\ensuremath{\alpha}, \ensuremath{\kappa}, \ensuremath{\theta}$, and $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$. We generate realistic slab models for the interfaces, which satisfy electron counting rules. The O atoms bridge the $\ensuremath{\beta}\ensuremath{-}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and the ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ slabs and the dangling bonds at the interfaces are saturated. The band offsets are obtained through an alignment scheme, which requires separate bulk and interface calculations. The calculated band offsets are useful for the design of devices based on the $\ensuremath{\beta}\ensuremath{-}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}/{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ heterojunctions, particularly $\ensuremath{\beta}\ensuremath{-}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ metal-oxide semiconductor field effect transistors.