An Introduction to Silicon Carbide
Silicon carbide is a semiconductor material that is disrupting the power electronics market. Find out how this material is today maximising the range of electric vehicles; discover its potential to revolutionise the power grid, ensuring less renewable energy is wasted on route to your home.
Silicon Carbide, a wide bandgap semiconductor
A wide bandgap semiconductor, SiC has an ideal set of material properties for the development of power electronic devices. Compared to silicon, SiC has...
Critical Electric Field
Higher Voltage, Lower Resistance
The huge critical field of SiC means that we can design power devices that can withstand 10x greater voltage rating than legacy silicon devices, or we can design for the same voltage and have 100x lower resistance. Low resistance equals high efficiency!
Faster Switching = Smaller Power Systems
SiC power devices are today being adopted by the automotive industry to make small, light and ultra-efficient DC-AC power converters for electric vehicles. This is possible because legacy slow-switching Si power devices (known as IGBTs) are being replaced with these new fast-switching SiC power devices (MOSFETs). Faster switching speeds allow the designer to shrink down the large and heavy passive components (inductors, capacitors) within their power conversion solutions. An all SiC automotive inverter will be up to 43% smaller than a Si solution.
A Complex, Unique Supply Chain
The SiC supply chain is unique. The starting material, the SiC substrates, are produced and supplied by a small number of companies, and dictate the quality of the devices to be developed. Substrates are today 150mm diameter, with 200mm on the horizon. 'Epitaxy' is the process by which a thin layer of SiC is grown on the substrate surface. This is a critical layer responsible for supporting the voltage of the final device (e.g. 1200 V). A growing number of SiC chip manufacturers carry out the device fabrication, and the packaging, resulting in the final 'discrete' diodes or MOSFET transistors, or a module with a number of packaged devices. In the automotive industry, a tier 1 supplier will integrate these devices into the final DC-AC inverter.
The SiC story is only at its beginning
Today, SiC devices are available at voltage ratings from 600-1700 V, which is perfect for the booming EV industry. Yet at PGC, we are looking to the future, to when a range of SiC devices matching those available in Si today will be available at voltages beyond 50,000 V. These devices have the potential to revolutionise the electrical power grid.
Silicon Carbide Applications
SiC power devices were first adopted by Tesla in their 2018 Model 3, resulting in a DC/AC inverter that weighed less than half that of a 2019 Nissan Leaf Inverter using Si IGBT technology. The secret now out, numerous OEMs including McLaren and VW, and tier 1 suppliers such as BorgWarner are developing SiC inverter products. Furthermore as more manufacturers like Porsche step up their system voltage from 400 V to 800 V, the advantage for SiC becomes more pronounced, with 1200 V rated SiC MOSFETs having even greater gains over IGBTs than at 650 or 900 V.
Solar inverters convert the DC electricity generated from one or more solar arrays into AC for connection with the grid. With a trend towards higher voltage operation (1500 Vdc), to reduce cable losses, the high voltage rating of SiC devices, combined with their fast switching and high temperature operation make them ideal for future solar inverters. Two highly efficient 250 kW solar inverters have recently been demonstrated by Sungrow and Fraunhofer ISE.
Clean renewable energy often has to travel a long distance to get to our homes, going through numerous power conversion stages. Getting offshore wind energy to land, for instance, requires long high voltage DC connections with MW (or even GW!) power conversion stages. HVDC/AC conversion is carried out with Si technology today, but as the voltage range of SiC extends beyond Si, there will be major efficiency savings to be had by moving to all-SiC solutions.