Dopant Segregation at the Solid–Liquid Interface in the Single Crystal Growth of β-Ga₂O₃ by an Edge-Defined Film-Fed Growth Method

The dopant distribution on the cross section of the crystal grown by the edge-defined film-fed growth (EFG) method is usually inhomogeneous due to the segregation. The inhomogeneous distribution of intentional dopant will decrease the yield and performance of the semiconductor devices. In this work, it was found that the appearance of the solidification sequence at the interface determined the doping concentration; therefore, the shape of the solid–liquid growth interface has an important effect on the distribution of the dopants. At low electron concentrations, the interface is typically convex, leading to the aggregation of dopant ions toward the center of the crystal cross section. Conversely, at high electron concentrations, the interface is typically concave, causing the dopant ions in the cross section to aggregate toward the edges. The shape of the interface was effectively controlled to be flat by controlling the axial temperature gradient at the interface, and the high homogeneous Sn-doped 2-in. β-Ga2O3 single crystals were successfully grown with high electron concentration by controlling the solid–liquid growth interface. The electron concentration of Sn-doped β-Ga2O3 single crystal was 6.93 × 1018 cm–3 with a deviation of about 15%. Furthermore, the crystalline quality of the heavily Sn-doped β-Ga2O3 single crystal was characterized by high-resolution X-ray diffraction, and the binding energy and atomic composition were measured by X-ray photoelectron spectroscopy (XPS). Therefore, through the solid–liquid growth interface optimization technology in this study, the heavy doping concentration and distribution uniformity in the Sn-doped β-Ga2O3 single crystal were greatly improved.