Coordinating research in energy networks

Power Electronics

Silicon carbide power devices for the electricity grid

The role of power devices

The conversion and control of electrical power can be performed using power electronics. One of the most important applications of power electronics is in high voltage power transmission systems. Semiconductor switching devices, typically various types of diode and transistor, are used in the conversion of electrical power (AC to DC and visa versa). The efficiency of a power electronic system is ultimately limited by the efficiency of these devices. Therefore improving the efficiency of power electronic devices is key to making future transmission systems more efficient, as HVDC plays an increasingly significant role in power systems.

Why Silicon Carbide?

Currently, the majority of power devices are made from silicon. However, as the grid is up-scaled to handle higher voltages, silicon power devices will be too inefficient. Silicon carbide (SiC) is a much more efficient material for converting power as its band-gap is three times larger than silicon. This permits smaller devices with a lower on-resistance per unit area that are able to operate at higher temperatures. Furthermore it has a higher thermal conductivity which enhances heat dissipation alleviating the need for bulky heat sinks or cooling technology.

Device challenges

For high voltage applications, the most sought after SiC devices are the MOS (metal-oxide-semiconductor) transistor and PiN diode. Despite the significant material advantages, numerous technological issues have hampered the production of SiC power devices, including:

  • The on-resistance of SiC MOS transistors is much higher than the theoretical value predicted from SiC?s physical properties, due to the formation of a poor interface between the oxide and SiC.
  • SiC PiN diodes are hindered by ineffective electric field termination, high resistance ohmic contacts and forward voltage instability.

These are the challenges that the HubNet Power Electronics theme is seeking to address.

Power Electronics research

Research is underway to fabricate and test SiC MOS transistors and PiN diodes for high voltage (>10kV) applications. The University of Warwick is home to a state of the art cleanroom laboratory dedicated to research into the materials physics and device fabrication technology of SiC.

The images above show the cleanroom laboratory at the University of Warwick. Operational since 2010, the specialised laboratory contains a suite of processing equipment dedicated to the research and fabrication of SiC devices.