Structural investigation of triangular defects in 4H-SiC epitaxial layers as nucleation source for bar shaped stacking faults (BSSFs)

Abstract

The formation of recombination-induced bar shaped stacking faults (BSSFs) during forward voltage operation of SiC devices, can lead to increased voltage drop and enhanced device degradation. In this study, a triangular epitaxial defect is identified as a nucleation source for the growth of BSSF in forward-biased 4H-SiC p-n diode test structures. We performed low and high voltage current emission microscopy measurements in order to detect the position of BSSFs in the active area of the device and in-depth structural analysis to locate their nucleation source. It was found that basal plane dislocations that converted into threading screw dislocations, close to the surface of the epitaxial layer and included in the triangular defect, act as nucleation source for the BSSFs. Those BSSFs expand from the top towards the bottom of the epitaxial layer, which is a newly reported expansion mechanism compared to the already reported BSSFs growing from the substrate/epitaxial layer interface towards the epitaxial layer surface.