Mechanism for the influence of surface micro-defects on step-flow growth in 4H-SiC epitaxy: A thermodynamic Monte Carlo investigation

Silicon carbide (SiC) epitaxial growth on vicinal substrates, crucial for high-power device performance, is highly sensitive to surface micro-defects which disrupt the preferred step-flow growth mode, leading to defects like step-bunching. While thermodynamic Monte Carlo (MC) simulations are invaluable for studying such atomic-scale surface kinetics, the specific mechanism by which micro-defects modulate step-flow dynamics in SiC remains inadequately understood. In this study, a thermodynamic MC framework was employed to systematically investigate how the distribution and density of initial pit defect affect the step-flow growth characteristics of 4° off-axis 4H-SiC substrate. Crucially, the distribution and density of defects on the step surface are identified as key regulatory factors, exhibiting significant orientation-dependent effects. Defects at the step center inhibit growth in both orientations, though [1-100] steps show weaker sensitivity to increasing density. Defects near the lower step edge induce morphological instability. Most strikingly, defects near the upper step edge produce opposing effects: they promote [1-100] step propagation while inhibiting [11-20] step front advancement. This location-specific influence is dramatically amplified as defect density increases. These findings provide fundamental insights into the complex role of micro-defects in governing step-flow kinetics, offering guidance for defect engineering strategies to achieve high-quality, defect-tolerant SiC epitaxy.