Characterization of the Defect Evolution in Thick Heavily Al-Doped 4H-SiC Epilayers

Abstract

The defect evolution on 90 μm-thick heavily Al-doped 4H-SiC epilayers with Al doping level higher than 1020 cm-3 was studied by tracing back to initial growth stage to monitor major dislocations and their propagations in each growth stage. Results from X-ray topography and KOH etching demonstrate that all existing dislocations on the surface of 90 μm-thick epilayer can be identified as the defects originating from substrate. In other words, there seems no new dislocation generated after a long-term growth. Nevertheless, a high density of misfit dislocation was found appearing near the substrate/epilayer interface for epilayer with Al doping level of 3.5×1020 cm-3, while misfit dislocation cannot be seen on epilayer with Al doping level of 1.5×1020 cm-3.