Estimation of threshold hole density in single Shockley stacking fault expansion and its suppression through proton implantation in 4H-SiC PiN Diodes
Abstract
One critical issue in the long-term reliability of 4H-SiC power MOSFETs is its body diode's VF (forward voltage drop) increase from the unique phenomenon of bipolar degradation. This is caused by the expansion of stacking faults (SFs) which originate from basal plane dislocations (BPDs) in the sublimation grown SiC substrate. Inserting a buffer layer with a short carrier lifetime is currently the standard method in preventing electron-hole recombination from triggering SFs growth. However, at higher current densities, the hole concentration can be substantial and reach the buffer/substrate interface where BPD-TED (threading edge dislocation) conversion points are present (Fig. 1). We have estimated this critical concentration of holes through electroluminescence (EL) analysis and TCAD simulation of fabricated 4H-SiC PiN diodes. Then proton irradiation was applied to the buffer layer to suppress SF expansion.
