The electronic structure of β-Ga2O3

$\beta {\text{-Ga}}_2{\text{O}}_3$ has the widest energy gap of the transparent conducting oxides. The interest in its electronic properties has recently increased because of its applications in various optoelectronic devices, semiconductor lasers, and ultrasensitive gas detecting systems. In contrast, information on the electronic structure of $\beta {\text{-Ga}}_2{\text{O}}_3$ is very scarce. Here, we present the experimental valence-band structure of $\beta {\text{-Ga}}_2{\text{O}}_3$ single crystals determined by high-resolution angle-resolved photoelectron spectroscopy utilizing synchrotron radiation. We find good matching of the experimental band structure with the advanced density functional theory calculations employing hybrid functionals and projector augmented wave potentials.