Experimental and Theoretical Study on Anisotropic Electron Mobility in 4H‐SiC

Abstract

Electron mobility parallel to the c‐axis in 4H‐SiC is experimentally determined by Hall effect measurements over wide donor density and temperature ranges (6 × 1014–3 × 1018 cm−3 and 140–600 K), and it is compared with that perpendicular to the c‐axis obtained for the same conditions. Empirical equations for the mobility along both directions are determined as functions of donor density and temperature, which contribute to the simulation and designing of SiC devices. The origin of the mobility anisotropy is discussed, focusing on the electron effective mass anisotropy. For a precise analysis, taking into account the effect of electrons at a higher energy region than the conduction band bottom, an average electron effective mass considering the energy distribution is theoretically calculated from the band structure of SiC. As a result, it is clarified that the electron mobility anisotropy including its temperature dependence is explained by the average electron effective mass anisotropy.