라만 산란법을 이용한 β-Ga2O3 단결정의 면방위별 결정학적 특성 연구 = Crystallographic orientation-dependent properties of β-Ga2O3 single crystals investigated by raman scattering

다국어 초록 (Multilingual Abstract)

β-Ga₂O₃, with an ultrawide bandgap of ~4.9 eV, a high critical electric field, and excellent stability, has emerged as a promising candidate material for next-generation power and optoelectronic devices. Wafer technology has rapidly advanced through large-diameter bulk growth using the EFG (Edge-defined Film-Fed Growth) and VB (Vertical Bridgman) methods; however, exploiting the strong anisotropy inherent to its monoclinic crystal structure remains a critical challenge. The electrical and optical properties vary significantly with crystallographic orientation, both out-of-plane and in-plane of β-Ga₂O₃. In particular, the (100) surface has been widely employed for device fabrication but has attracted attention due to its low surface energy and tendency to form twin boundaries. In this study, unintentionally doped (UID) β-Ga₂O₃ single crystals grown by the EFG method were processed into a (100) oriented sample, and its orientation was identified using high-resolution X-ray diffraction (HR-XRD) and Raman spectroscopy. Raman analysis revealed that phonon mode intensities varied markedly among the orientations depending on lattice symmetry. Angle-resolved Raman measurements on the (100) surface further showed that Ag and Bg modes exhibited 2-fold, 4-fold, or complete symmetry, indicating a strong dependence on the interaction between the incident light polarization and the crystallographic orientation of β-Ga₂O₃. These results demonstrate that Raman spectroscopy is an effective, non-destructive technique for probing crystallographic orientation and anisotropy in β-Ga₂O₃ single crystals, providing fundamental insights for device design, optimization of wafer fabrication process, and the evaluation of stress and defects in β-Ga₂O₃ based technologies