  Gallium oxide (Ga2O3) is a wide-band-gap semiconductor promising for UV
sensors and high power transistor applications, with Baliga's figure of merit
that far exceeds those of GaN and SiC, second only to diamond. Engineering its
band structure through alloying will broaden its range of applications. Using
hybrid density functional calculations we study the effects on adding Bi to
Ga2O3. While in III-V semiconductors, such as GaAs and InAs, Bi tend to
substitute on the pnictide site, we find that in Ga2O3, Bi prefers to
substitute on the Ga site, resulting in dilute (Ga_{1-x}Bi_{x})2O3 alloys with
unique electronic structure properties. Adding a few percent of Bi reduces the
band gap of Ga2O3 by introducing an intermediate valence band that is
significantly higher in energy than the valence band of the host material. This
intermediate valence band is composed mainly of Bi 6s and O 2p orbitals, and it
is sufficiently high in energy to provide opportunity for p-type doping.
