The high temperature operation and power handling capabilities make silicon carbide (SiC), a wide band gap (WBG) semiconductor, the material of choice for the production of power switching devices.  For a long time the defense industry has been interested in the use of SiC technology for high power applications such as  the all electric ship, high power weapon systems, the hybrid electric vehicle, and  highly electric aircraft.  Power electronics converter systems with SiC-based power semiconductor switching devices are more compact, lighter, and more efficient, so they are ideal for high-voltage power electronic applications.  These desirable device improvements will also substantially trim the power loss in electric motor drive power conversion applications.  In addition, SiC high temperature electronic sensors such as Schottky Diodes, PIN diodes, IGBTs, and  JFETs are used in automative, under the hood applications.  These are similar to the high reliability requirements of many military applications.  Such high power, high frequency and high temperature applications are the ideal uses for these SiC devices. The development of Gallium Nitride (GaN) Schottky diodes has recently been reported with comparable performance to SiC diodes.

One of the largest potential commercial applications for SiC Schottky rectifiers in the near future is in the continuous conduction mode (CCM) power factor correction (PFC) circuit.  The performance improvements include higher switching speed and lower switching loss.  For example, in a test case power converter, replacing the best available
600 V Si diodes with a 1500 V SiC diode, results in an increase of power supply efficiency from 82% to 88% for switching at 186 kHz, and a reduction in EMI emissions .  SiC Schottky diodes have been considered as replacements for silicon PIN diodes in many high-frequency motor drive applications.  Just about any consumer or industrial electric motor in the world requires a power electronic drive — a drive that can be made smaller and more efficient with the use of WBG devices.  However, WBG technology must become less expensive and more readily available, perhaps in the next five years, before it can compete in the commercial industry of motors and motor drivers.

For DoD applications, adopting advanced technologies for shipboard power electronic systems has become the focal point in the planning, designing, and manufacturing of next generation all electric vessels such as DDG1000 for  the US Navy. 
DDG1000 requires power control, distribution and Integrated Power System (IPS) power conversion at multi-MW levels.  IPS combines the power generation for propulsion and for shipboard services into a single unified electrical system, which provides a flexible architecture that makes propulsion power available to the other users such as the weapon systems and radar systems on the ship.  The power conversion modules (PCM-1, 2, and 4) for use in the Integrated Fight Through Power (IFTP) of the IPS certainly would benefit from WBG technology.  Figure 1-1 shows one of building blocks in IFTP system.  A PCM-4 consists of a transformer and rectifier to convert 3-phase, 60 Hz AC power from the propulsion bus to DC power.  The Ship Service Conversion Modules (SSCMs) in PCM-1 convert a higher DC input to a lower DC voltage output. PCM-2 contains DC-AC inverters (Ship Service Inverter Modules “SSIMs”) with a required rating in the megawatts range.  Si IGBT modules with a 100 kw power rating are currently used. 

A recent EMPF study using P-Spice modeling software compared the performance of a Si IGBT module and a SiC VJFET.  In a test circuit similar to a power conversion module PCM sub-system, the saturation current and voltage, transient time, and power dissipation were compared.  The modeling results reveal a great improvement in most cases when SiC devices replace Si devices.  For example, use of a SiC VJFET instead of a Si IGBT in this test circuit has improved the power dissipation by a factor of 25x.  The SiC VJFET switches much faster than Si IGBT because the transient time for SiC VJFET is over 200 times shorter than the transient time for the Si IGBT.   In this study, the parameters of Si IGBT are based on a Eupec product and the parameters of SiC VJFET are obtained from SiCED, A Siemens Company.  Figure 1-2 is an image of a SiC VJFET device. It consists of more than 2000 individual transistor cells on a SiC chip.   

Overall, the implementation of SiC devices in high power systems is expected to significantly improve the system performance, reduce the system size, and reduce the power loss which can potentially lower the overall system cost.   The challenges of implementing SiC device technology are lack of high quality of materials and lack of suitable high temperature packages.  The wide band gap semiconductor industry has been working aggressively to improve the quality of the materials. Over the past decade, device fabrication processes and device reliability have made impressive advances.  The US government has also made sizable investments to advance WBG technology.  Presently, SiC Schottky diodes are commercially available from a few companies, and SiC MOSFETs and JFETs have been demonstrated and are expected to advance even further in the next few years.