Site Specific TEM Specimen Preparation for Characterization of Extended Defects in 4H-SiC Epilayers

Silicon carbide (SiC) is an important semiconductor for high temperature, high voltage and high power electronic applications. Unfortunately, SiC still has not reached its potential in these applications due to the presence of extended defects in epilayers, which degrade the performance of SiC-based devices. In this work, focused ion beam (FIB) is employed to prepare site-specific cross-sectional transmission electron microscopy (TEM) specimens allowing direct characterization of unwanted in-grown stacking faults (IGSFs) and basal plane dislocations (BPDs). IGSFs are known to decrease breakdown voltages and increase leakage currents in SiC diodes [1]; however, their nucleation mechanism is currently not established. BPDs can form recombination-induced stacking faults, which lead to device performance degradation over time [2]. Recently, KOH etching of the substrate was reported to cause conversion of BPDs to electrically benign threading edge dislocations (TEDs) in the epilayer. However, for some BPDs this conversion was also associated with a shift in the locations of etch pits [3]. In this study, FIB and TEM are used to explain the nucleation mechanism of IGSFs and the previously observed shift in the locations of BPDs.