One of the limiting components of high current, high voltage systems is the switch.  The switch is required to block high voltage, conduct high current, operate at high frequency and survive under extreme conditions such as high dv/dt, di/dt and high action.  Applications such as High Power Microwaves, High Energy Lasers, EM guns, EM armor, Biological and Environmental, accelerators and radars are just some of the systems that require high voltage and high current switches. The two main areas of switching are continuous applications such as in high voltage power supplies, and power conditioning in power electronics applications.  The next application for power switches are in the area of pulsed switching where the frequency of operation may be lower, but the peak current and voltage can be significantly higher.  Semiconductor power switches have matured over the years and are being integrated into pulsed power systems.  Bipolar type switches such as thyristors and GTOs are ideal for high current pulsed applications. Unipolar devices such as MOSFETS and JFETS are ideal for continuous operation.  The most popular device for continuous operation is the IGBT.  The IGBT is a bipolar device that can handle high current and block high voltage, but the switching frequency is much lower than the MOSFETs.  In order to reach the high voltage and current requirement for pulsed power applications, individual devices are stacked in series and parallel.  This leads to other challenges such as packing, thermal management and gate driver design.

Silicon (Si) power semiconductors were the devices of choice for pulsed power and continuous power applications.  The Si material is reaching its limit for high voltage, high current and high temperature operation. New wide bandgap materials such as Silicon Carbide (SiC) and Gallium Nitride (GaN) are being investigated for high pulsed power and continuous applications.  SiC is more mature that GaN and some low power devices are being introduced to the market place.  Research of SiC devices have demonstrated very high voltage and temperature operation.

This presentation will focus on power semiconductors for pulsed and continuous operations.  An overview of semiconductor physics will be given with a focus on the basic parameters such as bandgap, avalanche, mobility, and lifetime.  A review of the operation of power devices such as IGBTs, Thyristors, GTOs, and Power diodes such as P-I-N and JBS will be given.  Thermal and electrical performance will be covered in addition to failure analysis and limitations of the devices.  A discussion of SiC power devices, results, and updates on the state-of-the-art of the devices will be covered.  Modules for high voltage and high current applications will be discussed, along with how to select the appropriate devices for the right applications.  Silvaco simulation results will be provided to determine the high electric field across the devices under high blocking voltage.  Simulation results will also be provided to show the high current density and high temperature areas within the devices.