Growth and characterization of a 2-inch (02) plane β-Ga2O3 crystal via the edge-defined film-fed growth method

Abstract

β-Ga₂O₃, with its exceptional performance, is highly favored in the application of vertical structure power devices. However, its low symmetry and anisotropy present a series of challenges during the wet etching process for device fabrication. In this work, a 2-inch (02) plane β-Ga₂O₃ crystal was successfully grown via the edge-defined film-fed growth (EFG) method, and its comprehensive characterization analysis was performed. High-resolution XRD results revealed that the FWHM of the rocking curve was 57.672 arcsec; after surface etching, the dislocation density of the crystal was estimated to be 5.69 × 10³ cm⁻², indicating a high-quality crystal. Additionally, no nanopipes perpendicular to the crystal plane were observed on the (02) plane, which helped in preventing device leakage. SEM results of the (02) plane after wet etching revealed that the β-Ga₂O₃ (02) plane remained perpendicular to the (100) plane of the sidewall, a characteristic that effectively enhanced the device's voltage withstanding capability and prevented premature breakdown. Furthermore, the (02) plane exhibits a thermal conductivity of 15.8 W (m⁻¹ K⁻¹) at room temperature, superior to that of the (100) plane. The polarized Raman results showed that all the A_g-mode peaks of the (02) plane could be measured; however, B_g(1) and B_g(3) peaks were not detected, and anisotropy was observed within the (02) plane. XPS analysis was also conducted to assess the surface chemical composition and defects of the (02) plane. Most importantly, the bandgap of the (02) plane was calculated to be 4.70 eV using transmittance spectroscopy, and the valence band maximum of the (02) plane was measured to be 3.70 eV using XPS. Notably, the surface barrier of the (02) plane was calculated to be only 1.00 eV, which is the lowest value among all the known β-Ga₂O₃ planes, indicating that the (02) plane is more likely to form high-quality ohmic contacts in power devices. In summary, the (02) plane demonstrated excellent comprehensive performance in the preparation of vertical structure power devices, suggesting its significant application potential in the field of β-Ga₂O₃ device fabrication.