Structure of Carrot Defects in 4H-SiC Epilayers
Structure of the “carrot” defects in 4H-SiC homoepitaxial layers deposited by CVD has been investigated by plan-view and cross-sectional transmission x-ray topography, cross-sectional transmission electron microscopy, atomic force microscopy, and KOH etching. The carrot defects nucleate at the substrate/epilayer interface at the emergence points of threading screw dislocations propagating from the substrate. The typical defect consists of two stacking faults: one in the prismatic plane with second one in the basal plane. The faults are connected by a stair-rod dislocation with Burgers vector 1/n[10-10] with n>3 at the cross-over. The basal plane fault is of Frank-type. Carrot defects are electrically active as evidenced by contrast in EBIC images indicating enhanced carrier recombination rate. Presence of carrot defects in the p-i-n diodes results in higher pre-breakdown reverse leakage current and approximately 50% lower breakdown voltage compared to the nominal value.
Robert P. Devaty, David J. Larkin and Stephen E. Saddow
X. Zhang et al., "Structure of Carrot Defects in 4H-SiC Epilayers", Materials Science Forum, Vols. 527-529, pp. 327-332, 2006