No abstract

Wide-bandgap semiconductors such as silicon carbide, gallium nitride, and diamond are inherently suitable for high power electronics for example in renewable energy applications and electric vehicles. Despite the high interest, the theoretical limit regarding device performance has not yet been reached for these materials. This is often due to charge trapping in defects at the semiconductor-insulator interface. Here we report a one-to-one correlation between electrically stimulated photon emission and the threshold voltage shift obtained from a fully processed commercial 4H-SiC metal-oxide-semiconductor field-effect power transistor. Based on this observation, we demonstrate that the emission spectrum contains valuable information on the energetic position of the charge transition levels of the responsible interface defects. We etch back the transistor from the reverse side in order to obtain optical access to the interface and record the emitted light. Our method opens up point defect characterization in fully processed transistors after device passivation and processing. This will lead to better understanding and improved processes and techniques, which will ultimately push the performance of these devices closer to the theoretical limit.

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 (BPDs) that converted into threading screw dislocations (TEDs), close to the surface of the epitaxial layer and included in the triangular defect, act as nucleation source of the BSSFs. Those BSSFs expand from the top towards the bottom of the epitaxial layer and is a newly reported expansion mechanism to the already reported BSSFs growing from the substrate/epitaxial layer interface towards the epitaxial layer surface.