Electronic Properties of Ga 2 O 3 Polymorphs

Abstract

Ga2O3 is an ultra-wide-band-gap semiconductor especially promising for power electronic applications. One advantage of this material is its ability to exist in different phases, which may add flexibility to device design, namely through polarization engineering of two-dimensional electron gases. Although much is known about monoclinic β-Ga2O3, much less is known about many basic electronic properties of other phases. In this work, four of the most common phases of Ga2O3 (α, β, κ, and ) are investigated with first-principles calculations based on hybrid density functional theory. The structural and electronic properties of each phase are compared, and band offsets between the phases and other common wide-band-gap semiconductors are determined. All four phases of Ga2O3 are found to exhibit self-trapping holes, large Mg acceptor ionization energies, deep oxygen vacancy donor levels, and low-lying valence-band maxima. In addition, all phases have large valence-band offsets but small or modest conduction-band offsets with GaN, SiC, and Si. With AlN and diamond, all Ga2O3 phases have large conduction-band and valence-band offsets.