Effect of shallow n-doping on field effect mobility in p-doped channels of 4H-SiC MOS field effect transistors

A high inversion channel mobility is a key parameter of normally off Silicon-Carbide MOS field effect power transistors. The mobility is limited by scattering centers at the interface between the semiconductor and the gate-oxide. In this work we investigate the mobility of lateral normally-off MOSFETs with different p-doping concentrations in the channel. Additionally the effect of a shallow counter n-doping at the interface on the mobility was determined and, finally, the properties of interface traps with the charge pumping method were examined. A lower p-doping in the cannel reduces the threshold voltage and increases the mobility simultaneously. A shallow counter n-doping shows a similar effect, but differences in the behavior of the charge pumping current can be observed, indicating that the nitrogen has a significant effect on the electrical properties of the interface, too.