【Member Papers】First-principles calculations of screw dislocations in β-Ga₂O₃

      Researchers from the Wuhan University have published a paper titled " First-principles calculations of screw dislocations in β-Ga₂O₃" in Journal of Physics D: Applied Physics.

Project Support

      This work was funded by the Major Program (JD) of Hubei Province, the National Natural Science Foundation of China, the Shenzhen Science and Technology Program, the State Key Laboratory of Micro-nano Engineering Science, and the Open Fund of Hubei Key Laboratory of Electronic Manufacturing and Packaging Integration (Wuhan University).

Background

      Gallium oxide (Ga₂O₃) is becoming a promising candidate for certain classes of power electronic devices due to its excellent electrical properties, such as an ultra-wide bandgap and ultra-high breakdown voltage. Ga₂O₃ has at least five polymorphs: α, β, γ, δ, and ε (κ), with the β-polymorph being the stable form under normal conditions. Many high-quality growth methods for β-Ga₂O₃ have been developed, including edge-defined film-fed growth method (EFG), Czochralski growth method (Cz), hydride vapor phase epitaxy method (HVPE), molecular beam epitaxy method (MBE), and metalorganic chemical vapor deposition method (MOCVD). However, regardless of the growth method used, various defects are inevitably formed during the growth process. These defects may include point defects, line defects, or surface defects. Currently, there is a wealth of reports on the experimental observation and study of various defects in β-Ga₂O₃. At the same time, theoretical studies of β-Ga₂O₃ defects are also essential, as they provide insights into their microstructure, formation mechanisms, effects on material properties, and potential control strategies. In recent years, there have been a number of studies on the theoretical calculations of defects in Ga₂O₃. However, these reports mainly focus on point defects and surface defects, with very few reports addressing line defects. Dislocations are the predominant form of line defects and significantly influence the mechanical and electrical properties of materials.

Abstract

      Gallium oxide (Ga₂O₃) is an ultra-wide bandgap semiconductor with excellent potential for high-power device applications. Some defects will inevitably occur during the growth of Ga₂O₃. Dislocations, as one of the main defects, have a significant impact on the mechanical and electrical properties of materials. In this work, dislocations in β-Ga₂O₃ are systematically studied via first principles calculations, with a primary focus on the screw dislocation occurring on the (-201) plane with b = <010>. The concept of Ga_tetra-Ga_octa-dislocation is proposed. The three dislocation core structures, Ga_octa-O_Ⅰ-Ga_tetra-near-dislocation, Ga_octa-O_Ⅰ-Ga_tetra-far-dislocation, and Ga_octa-O_Ⅲ-Ga_octa-far-dislocation have been verified. The study find that the introduction of dislocations leads to a narrowing of the bandgap. This suggests that the presence of dislocations may reduce the breakdown voltage, radiation resistance, and other related properties of β-Ga₂O₃. This study provides a new perspective for the theoretical investigation of dislocations in β-Ga₂O₃, with significant guiding implications. It also reveals the impact of dislocations on the electrical properties of β-Ga₂O₃, laying a foundation for further research.

Conclusion

      In this work, dislocations in β-Ga₂O₃ are systematically studied using first-principles calculations, with a primary focus on the screw dislocation characterized by a Burgers vector of b =<010>. The concept of a Ga_tetra-Ga_octa-dislocation on the (-201) plane is further proposed. This concept suggests that the core structure of the screw dislocation occurring on the (-201) plane with b =<010> should not consist solely of Ga_octa and O atoms, but rather should be composed of Ga_tetra, Ga_octa, and O atoms. Furthermore, based on this concept, three initial dislocation core structures are constructed. After sufficient relaxation, three stable dislocation core structures are obtained: Ga_octa-O_I-Ga_tetra-near-dislocation, Ga_octa-O_I-Ga_tetra-far-dislocation, and Ga_octa-O_III-Ga_octa-far-dislocation. This also validates the correctness of the proposed concept. Finally, the influence of these dislocations on the electrical properties of β-Ga₂O₃ is analyzed by DOS, and it is found that the introduction of dislocations leads to a narrowing of the bandgap. This implies that the presence of dislocations may degrade the breakdown voltage, radiation resistance, and other related properties of β-Ga₂O₃. Furthermore, ELF is employed to analyze the charge distribution at the dislocation core structure. It is found that the dislocation core structure leads to a decrease in ELF values for certain atoms at the core region. The decrease in ELF value may be the primary reason for the reduction in bandgap caused by dislocations. This study proposed a different approach for the theoretical investigation of β-Ga₂O₃ dislocations, offering important guiding significance and laying a foundation for further research.