Measurement of electron and hole impact ionization coefficients for SiC

Silicon carbide has received increasing attention for power switching, microwave and high temperature applications due to its high breakdown electric field, thermal conductivity and electron saturation drift velocity. One of the most important parameters of a SiC power device is its breakdown voltage. In order to obtain a clear understanding of its breakdown characteristics, it is important to have an exact knowledge of the impact ionization coefficients for SiC. However, there is very little information available in literature for 6H-SiC and none for 4H-SiC. In this work, measured impact ionization coefficient data for 4H and 6H-SiC are provided as a function of temperature. It is demonstrated that that the data obtained from these measurements allows a more accurate simulation of reverse breakdown voltage characteristics than that obtained using previously published data. These results have widespread utility for SiC device analysis and design.