3.4 Dielectric and Thermal Properties

The dielectric permittivity ( $\varepsilon$) of a material is the ratio of the electric displacement to the electric field strength, $D/E$. In an isotropic material, $D$ and $E$ are parallel and $\varepsilon$ is a scalar, but in anisotropic materials $\varepsilon$ is a rank-2 tensor. It can also be defined as a dimensionless relative permittivity, or dielectric constant, normalized to the absolute vacuum permittivity $\varepsilon_0$. However, at high frequencies, it is no longer constant, and decreases with increasing frequency.

Thermal conductivity ($\kappa$) is a property of materials that expresses the heat flux through the material if a certain temperature gradient exists over the material. The thermal conductivity in $\alpha$-SiC has also anisotropic properties. The high thermal conductivity of SiC allows high power densities in a device.
T. Ayalew: SiC Semiconductor Devices Technology, Modeling, and Simulation