Gallium(III) oxide

Gallium(III) oxide is an inorganic compound with the formula Ga₂O₃. A ultra-wide-bandgap semiconductor, it has been studied for applications in power electronics, phosphors, and gas sensing. The compound has several polymorphs, of which the monoclinic β-phase is the most stable.

Hydrated gallium trioxide precipitated upon neutralization of acidic or basic solution of gallium salt. Also, it is formed on heating gallium in air or by thermally decomposing gallium nitrate at 200–250 °C.

Crystalline Ga₂O₃ occur in five polymorphs, α, β, γ, δ, and ε. Of these polymorphs β-Ga₂O₃ is the most thermodynamically stable phase at standard temperature and pressure while α-Ga₂O₃ is the most stable polymorph under high pressures.

Bulk substrates of β-Ga₂O₃ can be produced, which is one of the major advantages of this material system. Bulk substrates can be produced in multiple orientations and by multiple techniques.

Gallium(III) trioxide is amphoteric. It reacts with alkali metal oxides at high temperature to form, e.g., NaGaO₂, and with Mg, Zn, Co, Ni, Cu oxides to form spinels, e.g., MgGa₂O₄. It dissolves in strong alkali to form a solution of the gallate ion, Ga(OH)⁻
₄.

With HCl, it forms gallium trichloride GaCl₃.

It can be reduced to gallium suboxide (gallium(I) oxide) Ga₂O by H₂. or by reaction with gallium metal:

β-Ga₂O₃, with a melting point of 1900 °C, is the most stable crystalline modification. The oxide ions are in a distorted cubic closest packing arrangement, and the gallium (III) ions occupy distorted tetrahedral and octahedral sites, with Ga–O bond distances of 1.83 and 2.00 Å respectively.