Theoretical study of strain-induced modulation of the bandgap in SiC

The low electron mobility of 4H-SiC MOSFETs at the (0001) interface is a problem for high-performance power devices, and some experiments have shown higher electron mobilities by using other interfaces. We studied bandgap modulation induced by strain and showed that different bandgap modulations occur in different SiC polytypes. Moreover, we found that biaxial strain causes a larger modulation than hydrostatic strain, and that biaxial strain in the o1 (1100) thorn and (1120) thorn planes causes a larger modulation than that in the (0001) plane for 4H-SiC. The modulated bandgap acts as electron traps and degrades the electron mobility of 4H-SiC MOSFETs. However, the effects of bandgap modulation appear strongly and the number of electronic states increases in 4H-SiC MOSFETs on the (0001) interface when considering the intrinsic nature of 4H-SiC. Therefore, appropriate interface orientations must be used for high-electron-mobility 4H-SiC MOSFETs. (C) 2018 The Japan Society of Applied Physics.