Macrostep Flow Behavior in 4H-SiC Solution Growth with Different Solvent Compositions and Its Correlation with the Conversion Efficiency of Threading Screw Dislocations

The influence of solvent additives on macrostep flow behavior during SiC solution growth was investigated with a particular emphasis on interactions between macrosteps and threading screw dislocations (TSDs). Using Si, Si–5 mol % Al, and Si–5 mol % Ti solvents, we found that the Si–Ti solvent showed a remarkable enhancement of lateral macrostep flow, with a flow distance per unit growth thickness approximately 1 order of magnitude larger than those for the other solvents. Morphological analyses revealed that macrosteps formed with the Si–Ti solvent exhibit smaller slope angles, which kinetically favor lateral macrostep flow under identical solute diffusion conditions. Ti addition also reduced the nanometer-scale step density on macroterraces by nearly 2 orders of magnitude compared with Al addition, thereby suppressing vertical growth on terraces. This reduced step density on macroterraces shifts solute consumption preferentially toward macrosteps, further enhancing their lateral growth. This increases the interaction frequency between the macrosteps and TSDs, thus improving the TSD conversion efficiency. These findings demonstrate that the TSD conversion efficiency is governed not by static macrostep geometry alone, but by the dynamic lateral macrostep flow behavior. This kinetic insight provides useful guidance for achieving effective dislocation reduction during SiC solution growth.