Group velocity of electrons in 4H-SiC from Density Functional Theory simulations

Silicon carbide (SiC) power MOSFETs actually represent the heart of power electronic converters due to the superior properties of SiC. However, they are affected by reliability issues which can lead to a reduction of the converter ruggedness. For this reason, it is fundamental to predict the long-term stability of the device performance in terms of threshold voltage and on-resistance drifts. In this perspective, TCAD simulations can be a very useful tool for the understanding of the phenomena that dominate such degradation mechanisms. The models actually available in the TCAD deck for the degradation analysis require the knowledge of the density of states and group velocity of the semiconductor under investigation as they are based on the direct solution of the Boltzmann equation. Despite several works are available in literature on the electronic properties of 4H-SiC, the group velocity has never been reported. In this work, it has been calculated by using the Density Functional Theory (DFT).