High Speed Switching Devices in 4H-SiC - Performance and Reliability

Silicon carbide (SiC) is a very attractive material for high temperature semiconductor devices because of its very wide bandgap (3.26 eV). Due to the wide bandgap, thermal carrier generation is very low in SiC, resulting in negligible junction leakage currents for temperatures up to 500 degC. Other advantage of SiC is high breakdown strength (10times that of silicon) and high thermal conductivity. This allows the drift layers in SiC power devices to be 10times thinner with 100times the doping concentration, compared to a silicon device for a given blocking voltage. Thus, high voltage majority carrier power devices with reasonably low on-resistances are possible in SiC (Ryu et al., 2004). Due to lack of excess minority carriers, these devices can operate at much higher switching frequencies with acceptable switching losses. The ability to operate at higher frequencies reduces the passive components in a power system. In addition, higher temperature capability of SiC devices can translate into more relaxed heat sinking requirements. This means that smaller heat sinks and/or passive cooling can be used for SiC power devices. It is expected that the size and weight of power electronics utilizing SiC switching devices and diodes will be significantly reduced by means of passive cooling, and smaller and lighter passive components