*Review* **Ga2O<sup>3</sup> and Related Ultra-Wide Bandgap Power Semiconductor Oxides: New Energy Electronics Solutions for CO<sup>2</sup> Emission Mitigation**

**Zeyu Chi 1,† , Jacob J. Asher 2,†, Michael R. Jennings <sup>2</sup> , Ekaterine Chikoidze <sup>1</sup> and Amador Pérez-Tomás 3,\***


**Abstract:** Currently, a significant portion (~50%) of global warming emissions, such as CO<sup>2</sup> , are related to energy production and transportation. As most energy usage will be electrical (as well as transportation), the efficient management of electrical power is thus central to achieve the XXI century climatic goals. Ultra-wide bandgap (UWBG) semiconductors are at the very frontier of electronics for energy management or energy electronics. A new generation of UWBG semiconductors will open new territories for higher power rated power electronics and solar-blind deeper ultraviolet optoelectronics. Gallium oxide—Ga2O<sup>3</sup> (4.5–4.9 eV), has recently emerged pushing the limits set by more conventional WBG (~3 eV) materials, such as SiC and GaN, as well as for transparent conducting oxides (TCO), such asIn2O<sup>3</sup> , ZnO and SnO<sup>2</sup> , to name a few. Indeed, Ga2O<sup>3</sup> as the first oxide used as a semiconductor for power electronics, has sparked an interest in oxide semiconductors to be investigated (oxides represent the largest family of UWBG). Among these new power electronic materials, AlxGa1-xO<sup>3</sup> may provide high-power heterostructure electronic and photonic devices at bandgaps far beyond all materials available today (~8 eV) or ZnGa2O<sup>4</sup> (~5 eV), enabling spinel bipolar energy electronics for the first time ever. Here, we review the state-of-the-art and prospects of some ultra-wide bandgap oxide semiconductor arising technologies as promising innovative material solutions towards a sustainable zero emission society.

**Keywords:** energy electronics; ultra-wide bandgap; power electronics; diodes; transistors; gallium oxide; Ga2O<sup>3</sup> ; spinel; ZnGa2O<sup>4</sup>
