Investigation of Spoke Pattern of Stacking Faults in 4H-SiC Wafers Grown by Physical Vapor Transport Method

Synchrotron monochromatic beam X-ray topography (SMBXT), synchrotron white beam X-ray topography (SWBXT) and high-resolution X-ray topography (HRXRT) were used to characterize a series of wafers sliced from two PVT-grown 4H-SiC boules under similar growth conditions. A unique spoke-shaped distribution of the threading screw/mixed dislocations (TSDs/TMDs) density map can be observed from wafers sliced from later stages of growth of both boules. Systematic sequential analysis of the SMBXT grazing incidence images and HRXRT reflection images of the wafers reveals the spoke patterns are formed due to continuous deflection process of TSDs/TMDs by thin layer of polytypes that propagate along step flow direction and expand vertically, leading to TSD density difference across the wafer. Regions with high TSD densities have higher growth rate, resulting in a ridge and valley structure. Generation of macrosteps in the valley regions due to regular step structure deflect more TSDs/TMDs that then form mixed type (Shockley+Frank) stacking faults.