Band offsets and electronic structure at ${\alpha}$/${\beta}$-Ga$_2$O$_3$ and ${\kappa}$/${\beta}$-Ga$_2$O$_3$ phase heterojunctions

Abstract

Ga$_2$O$_3$ phase heterojunction materials are emerging as promising candidates for deep-ultraviolet optoelectronics. Here, the band offsets at the ${\alpha}$/${\beta}$-Ga$_2$O$_3$ and ${\kappa}$/${\beta}$-Ga$_2$O$_3$ phase heterojunctions are investigated through hybrid functional calculations. Explicit, realistic slab models that satisfy electron counting rules are constructed for the heterojunctions. Our calculations demonstrate that a type-II staggered band alignment forms at the ${\alpha}$/${\beta}$-Ga$_2$O$_3$ and ${\kappa}$/${\beta}$-Ga$_2$O$_3$ phase heterojunctions, where both the valence and conduction band edges of ${\alpha}$-Ga$_2$O$_3$ and ${\kappa}$-Ga$_2$O$_3$ are higher than those of ${\beta}$-Ga$_2$O$_3$. Strain effects on the band alignment are also discussed. Spatially resolved local density of states maps are presented, clearly revealing the interfacial electronic structures. These results provide valuable insights into the physical properties of Ga$_2$O$_3$ phase heterojunctions, offering guidance for future device design efforts.