Materials issues and devices of α- and β-Ga₂O₃

Ga2O3 is an ultrawide bandgap semiconductor with a bandgap energy of 4.5–5.3 eV (depending on its crystal structure), which is much greater than those of conventional wide bandgap semiconductors such as SiC and GaN (3.3 eV and 3.4 eV, respectively). Therefore, Ga2O3 is promising for future power device applications, and further high-performance is expected compared to those of SiC or GaN power devices, which are currently in the development stage for commercial use. Ga2O3 crystallizes into various structures. Among them, promising results have already been reported for the most stable β-Ga2O3, and for α-Ga2O3, which has the largest bandgap energy of 5.3 eV. In this article, we overview state-of-the-art technologies of β-Ga2O3 and α-Ga2O3 for future power device applications. We will give a perspective on the advantages and disadvantages of these two phases in the context of comparing the two most promising polymorphs, concerning material properties, bulk crystal growth, epitaxial growth, device fabrication, and resulting device performance.