Silicon carbide (SiC) as a third-generation semiconductor material with stable chemical properties is currently the most widely used wide-band material. Moreover, SiC has significant advantages such as a high device limit temperature, a high critical breakdown field strength, and a high thermal conductivity. SiC single crystals with high-quality, large-size, low-cost can be used in large-scale SiC applications. The high-temperature solution growth method (HTSG) for growing SiC offers some advantages such as reduced crystal dislocations, ease of operation, feasibility of P-type doping, and low cost. These advantages can compensate for the drawbacks of high energy consumption, poor crystal quality, and high costs associated with the crystal growth process of the physical vapor transport (PVT) method. Nevertheless, the selection of solvents in the HTSG method is a key factor in improving the crystal growth efficiency and growth quality. The existing mainstream systems of the HTSG method are Si–Cr binary system and Si–Cr–Al ternary system. 4H–SiC has a hexagonal lattice point and a cubic lattice point, and the diatomic layers are connected in the form of ABCB–ABCB. Therefore, a regular atomic arrangement is needed to avoid the entrapment of other solvent atoms. For a deeper understanding of advances in solvents for the growth of 4H–SiC single crystals by HTSG technique, this review firstly summarized the research history of the solvent, analyzed the influence of the solvent system on the crystal growth from different perspectives of thermodynamics, and gave different methods used for solvent research. Finally, this review represented the crucial points and difficulties in the research of solvents in the growth of 4H–SiC single crystals by high-temperature solution growth method. Summary and prospects Recent research on co solutions for the growth of SiC single crystals by HTSG method through various methods is represented. The research scope of solvents involves thermal physical performance parameters, C dissolution, thermochemical properties, thermodynamic properties, and other aspects. However, the existing research has not yet identified the optimal solubilizing system from a theoretical perspective, as well as the substantial impact of element ratios in various solution systems on crystal growth. There are still several difficulties in the research of solutions as follows: 1) It is difficult to test the mixed solution due to the high experimental temperature of the HTSG method. At present, it is possible to roughly predict the thermal and physical performance parameters of solutions through theoretical calculations, but equipment for the related experiments is unavailable and the cost is also high. Effectively improving the accuracy of simulation and conducing accurate predictions for experiments can be achieved via in-depth research on the changes in thermal and physical performance parameters of solutions. 2) The concentration of C in the solution is a key factor affecting the quality of crystal growth. The concentration of C is investigated both theoretically and experimentally under ideal conditions of thermal equilibrium. The seed crystals can experience melt-through during the remelting process of crystal growth, if the concentration of C in the solution is too low. On the contrary, if the concentration of C in the solution is too high, it is likely that crystallization can occur before the impurities on the surface of the seed crystal are completely melted. The situations above could seriously affect the quality of the crystal growth. It plays an important role in improving crystal quality via in-situ detecting the changes in C concentration inside the crucible. 3) The existing HTSG method usually uses graphite crucibles as a C source for crystal growth. As the temperature inside the crucible increases, graphite crucible is continuously corroded by the solution, presenting different shapes. Different shaped crucibles can seriously affect the stability of the flow field inside the crucible, and even change the trajectory of the flow field. In-depth research on the corrosion process of graphite crucibles by auxiliary solutions can effectively avoid negative effects caused by changes in flow field and temperature field in the later stage of growth. Although there are still some difficulties to overcome in the study of solvents for the growth of SiC single crystals by the HTSG method with the continuous efforts of numerous research teams, some key issues are constantly proposed and solved. The research on solvents can also accelerate the pace of HTSG method for growing SiC single crystals, opening a door to low-cost and low-energy SiC single crystal growth. © 2024 Chinese Ceramic Society. All rights reserved.
