A New Anisotropic Driving Force Model for SiC Device Simulations

We present a new anisotropic driving force model to compute the anisotropy of the mobility and impact ionization rate in TCAD simulations of silicon carbide (SiC) devices. We derive the model from the relationship between mobility, driving force, and carrier heating. The obtained driving force along the
${c}$
-axis and that perpendicular to the
${c}$
-axis depend on the gradient of the quasi-Fermi potential and the mobility anisotropy factor. Since mobility also depends on the driving force, we solve for the mobility anisotropy factor to determine the anisotropic mobility and driving force together. We also propose a new interpolation scheme to consider the anisotropy of the impact ionization rate using the derived anisotropic driving force. We perform the simulation of a 4H-SiC vertical power MOSFET device and compare the present model with the existing models in the commercial simulator.