Phase diagram and polarization of stable phases of (Ga1− x In x )2O3

The full phase diagram of (Ga1%xInx)2O3 is obtained theoretically. The phases competing for the ground state are monoclinic β (low x), hexagonal (x > 0.5), and bixbyite (large x). Three disconnected mixing regions interlace with two distinct phase-separation regions, and at x > 0.5, the coexistence of hexagonal and β alloys with phase-separated binary components is expected. We also explore the permanent polarization of the phases, but none of them are polar. On the other hand, we find that ε-Ga2O3, which was stabilized in recent experiments, is pyroelectric with a large polarization and piezoelectric coupling, and could be used to produce high-density electron gases at interfaces.