Tutorial: Microscopic properties of O-H centers in -Ga₂O₃ revealed by infrared spectroscopy and theory

beta-Ga2O3 is an ultrawide bandgap semiconductor that is attracting much attention for applications in next-generation high-power, deep UV, and extreme-environment devices. Hydrogen impurities have been found to have a strong effect on the electrical properties of beta-Ga2O3. This Tutorial is a survey of what has been learned about O-H centers in beta-Ga2O3 from their vibrational properties. More than a dozen, O-H centers have been discovered by infrared absorption spectroscopy. Theory predicts defect structures with H trapped at split configurations of a Ga(1) vacancy that are consistent with the isotope and polarization dependence of the O-H vibrational spectra that have been measured by experiment. Furthermore, O-H centers in beta-Ga2O3 have been found to evolve upon thermal annealing, giving defect reactions that modify conductivity. While much progress has been made toward understanding the microscopic properties and reactions of O-H centers in beta-Ga2O3, many questions are discussed that remain unanswered. A goal of this Tutorial is to inspire future research that might solve these puzzles.