Comparative Study on Silicon Carbide (SiC) Polytypes in High Voltage Devices

Silicon Carbide (SiC) devices have been increasingly adopted in many applications owing to their many advantages when compared their silicon (Si) counterparts. On a material level, the crystal structure, commonly known as polytype, dictates many features of the SiC device at the device level. Hence, in-depth understanding of the different polytypes of SiC is imperative for the proper selection of the SiC polytype, depending on the desired operational envelope of the device. In this paper, the crystallography of the major polytypes as well as their electrical properties are reviewed. A material physical model is also presented. Based on the available literature, a comparison of the different polytypes is made at the device level, using Schottky barrier diodes (SBDs) and MOSFETs. Based on the surveyed studies, it can be generalized that the hexagonal polytypes (i.e. 4H and 6H) are the polytype of choice for SiC devices with breakdown voltages above 2.5 kV, owing to their high electron mobility and low conduction losses. On the other hand, the cubic (3C) polytype can yield lower conduction losses for SiC devices with lower breakdown voltages.