Deep-level defects in gallium oxide

As an ultrawide bandgap semiconductor, gallium oxide (Ga2O3) has superior physical properties and has been an emerging candidate in the applications of power electronics and deep-ultraviolet optoelectronics. Despite numerous efforts made in the aspect of material epitaxy and power devices based on β-Ga2O3 with rapid progresses, the fundamental understanding of defect chemistry in Ga2O3, in particular, acceptor dopants and carrier compensation effects, remains a key challenge. In this focused review, we revisited the principles of popular approaches for characterizing defects in semiconductors and summarized recent advances in the fundamental investigation of defect properties, carrier dynamics and optical transitions in Ga2O3. Theoretical and experimental investigations revealed the microstructures and possible origins of defects in β-Ga2O3 bulk single crystals, epitaxial films and metastable-phased α-Ga2O3 epilayers by the combined means of first-principle calculation, deep level transient spectroscopy and cathodoluminescence. In particular, defects induced by high-energy irradiation have been reviewed, which is essential for the identification of defect sources and the evaluation of device reliability operated in space and other harsh environments. This topic review may provide insight into the fundamental properties of defects in Ga2O3 to fully realize its promising potential in practical applications.