Ultrawide bandgap (UWBG) gallium oxide (Ga₂O₃) represents an emerging semiconductor material with excellent chemical and thermal stability. It has a band gap of 4.5-4.9 eV, much wider than that of the GaN (3.4 eV) and 4H-SiC (3.2 eV). The monoclinic β-phase Ga₂O₃ represents the thermodynamically stable crystal among the known five known phases (α, β, γ, d, ε/κ). The breakdown field of β-Ga₂O₃ is predicted to be 6-8 MV/cm, which is much larger than that of the 4H-SiC and GaN. These unique properties make β-Ga₂O₃ a promising candidate for high power electronic device and solar blind photodetector applications. Single crystal β-Ga₂O₃ substrates can be synthesized by scalable and low cost melting based growth techniques. Metalorganic chemical vapor deposition (MOCVD) growth technique was demonstrated to produce high quality β-Ga₂O₃ thin films and its ternary (Al_xGa_1-x)₂O₃ alloys. Control of background and n-type doping in β-Ga₂O₃ will be discussed. Record carrier mobilities of 194 cm²/V·s at room temperature and ~10,000 cm²/V·s at low temperature were measured for MOCVD β-Ga₂O₃ thin films. Growth and fundamental understanding of β-(Al_xGa_1-x)₂O₃ are still limited. The incorporation of Al in beta-phase Ga₂O₃ has not been well understood, although it was predicted up to 60% of Al composition could be incorporated into β-Ga₂O₃. MOCVD growth of β-AlGaO targeting for Al composition of > 40% will be discussed. N-type doping capability as a function of Al composition in (Al_xGa_1-x)₂O₃ is another important fundamental question. Charge carrier transport properties in (Al_xGa_1-x)₂O₃ will be discussed. In addition, MOCVD growth of different phases of Ga₂O₃ and AlGaO will be presented.

Acknowledgement: The authors acknowledge the funding support from the Air Force Office of Scientific Research FA9550-18-1-0479 (AFOSR, Dr. Ali Sayir) and the National Science Foundation (1810041, 2019753, 1755479).