Degradation of 4H-SiC IGBT threshold characteristics due to SiC/SiO2 interface defects

• SiC/SiO2 interface defect density is incorporated in 4H-SiC IGBT device simulation.
• Deep traps shift the threshold voltage to higher voltages while shallow traps cause current reduction.
• SiC is prone to degradation due to its wide bandgap and high interface defect density.

Previously reported measurements of the interface state density at the 4H-SiC/SiO2 interface and carrier recombination in the SiC substrate are incorporated into the device simulation of a 4H-SiC IGBT trench-type device structure. Cross-sectional simulation results show two important degradation characteristics on the conduction current; shift of the threshold voltage toward higher gate voltages due to the deep traps and reduction of the current magnitude due to the shallow traps. The wide bandgap of SiC and the high interface defect density magnitude distributed widely within the bandgap due to conventional SiC/SiO2 process technology make SiC-based devices prone to degradation, which are observed not only as a subthreshold-slope degradation but also causes variations of the threshold voltage. Conventional Si process technology usually results in a dominating homogeneous shallow-type trap which only results in a degradation of the subthreshold-slope.