Today most semiconductors are made from a silicon (Si) base material, but within recent years a relatively new semiconductor base material is making headlines. That material is silicon carbide, also known as SiC. Today, MOSFETs and Schottky diodes are the main semiconductor technologies utilizing SiC.
What are the advantages of SiC over Si?
At the foundation, silicon carbide (SiC) is considered a wide-bandgap semiconductor which has its inherent advantages over conventional Si semiconductors. These material properties of SiC result in higher:
- Breakdown field
- Electron drift velocity
- Thermal conductivity
Breakdown field
The higher breakdown field allows the device to withstand higher voltages for a given area. This gives device designers the ability to increase the area devoted to current flow for the same die size which lowers the devices resistance for a given area, Rsp. The devices resistance is directly correlated to the conduction power losses, so a smaller Rsp will result in lower losses, yielding higher efficiency.
Electron drift velocity
Electron drift velocity is how fast the electrons travel in a material due to an electric field. In the case of SiC semiconductors, the electron drift velocity is two times higher than that of Si based semiconductors. The faster the electrons move, the faster the device can switch on and off. A system designer gets two benefits from this faster switching. First, lower power losses during the transition time from on and off. Second, higher switching frequencies allow for the use of smaller magnetics and capacitors.
Thermal conductivity
The thermal conductivity of SiC is roughly three times better than Si and ties all the benefits from the other properties together. Thermal conductivity translates to how fast the heat is transferred from the semiconductor junction to the outside environment. This means that SiC devices can operate up to 200°C compared to the typical 150°C limit of Si.
Combining these three advantages allows for the system designer to design a more efficient product all while making it smaller, lighter, and ultimately at a lower cost. It is known that SiC devices are more expensive compared to their Si equivalents, but when adding the cost reductions from using smaller passive components and less thermal management, the overall system cost can decrease by 20%. Silicon carbide’s material properties make it highly advantageous for high power applications where high voltage, high current, high temperatures, and high thermal conductivity with less overall weight are required. MOSFETs and Schottky diodes (in both discrete and power module packaging) are the main technologies utilizing SiC.
Practical applications of silicon carbide advantages
Silicon carbide is being adopted across a variety of existing applications such as electric vehicles, solar inverters, energy storage systems, and EV charging stations. It provides multiple benefits to system designers and manufacturers to drive this change, but how do these translate to benefits for the consumer of these end-products?
To start, let’s take a look at electric vehicles (EV). The main reason limiting widespread adoption is range anxiety. With the use of SiC, the range of an EV can be extended by over 7%. This has a dramatic impact on range by simply switching from an IGBT based inverter to a SiC inverter. The benefits do not stop there. The use of SiC for EVs also addresses the EV adoption challenge: cost. The batteries used in EVs are the costliest part of the EV. If using SiC gives the EV an extended range of 7%, it can also allow the battery size to decrease by 7% while keeping the range equivalent to the non-SiC baseline. A smaller battery pack will directly result in a lower overall cost of the EV. This is why SiC adoption in EVs is so strong and is what is driving the large revenue forecasts for SiC manufacturers.
Associated with EVs, are EV charging stations and the build out of this charging infrastructure. In the case of EV charging stations, one of the primary considerations is power density. This is where SiC contributes, enabling system designers to get more power delivered in the same volume or keep the power the same and reduce the volume by 300%. Getting more power out in the same volume is the primary driving force behind using SiC for EV charging stations. The goal is to be able to charge an EV in the same amount of time a person spends at a gas station. This can only be done by increasing the amount of power delivered to the EV by the charging station.
Silicon carbide is also helping the renewable energy market by making smaller and lighter solar inverters. Using a faster switching frequency enabled by SiC, solar inverters can use smaller and lighter magnetics. Depending on the power level this can make the solar inverter less than fifty pounds. Fifty pounds is the max limit for an individual to lift, set by the Occupational Safety and Health Administration, OSHA. Lifting equipment that exceeds fifty pounds requires two or more people or a lifting device. By creating a lighter solar inverter, an organization needs only one person for installation. This lowers the installation cost, making it desirable for installers and consumers. This advantage also applies to wallbox EV chargers. There are of course other practical benefits to using SiC in solar inverters, such as an overall efficiency gain and overall system cost reductions.
Industrial motor drives also benefit by switching to SiC. SiC provides motor inverters with efficiency improvements, smaller sizes, and increased heat dissipation, which allows the motor drive to be placed locally or on the motor itself. This reduces the need of multiple long cables running back to the power cabinet for a solution using Si IGBTs. Instead, SiC solutions only need 2 cables running to the power cabinet. This eliminates hundreds of feet of expensive and complex cabling needed for this example of a seven-motor articulating robotic arm in Image 2. You can find more information on this topic here: SiC MOSFET vs. Si IGBT: SiC MOSFET advantages
The previous application examples all benefit from SiC’s robust durability and reliability which is a crucial differentiator when designers are considering using other Wide Bandgap semiconductors such as Gallium Nitride (GaN).
Read more about the differences between GaN vs SiC.
Moving the world towards decarbonization with silicon carbide
A common thread of the applications described above is that they all enable the movement towards decarbonization. However, they do so in different ways.
Electric vehicles contribute towards decarbonization by directly reducing the number of pounds of CO2 that are emitted due to transportation. They have zero tailpipe emissions; however, they consume electricity that is produced by CO2 emitting sources. Including these emissions, the U.S. DoE averages the annual emissions of an EV to be 2,817 pounds of CO2 versus 12,594 pounds of CO2 from a vehicle that uses gasoline. That is a 78% reduction in the amount of CO2 emitted into the atmosphere.
EV charging stations do not have a direct impact on decarbonization, but without a robust infrastructure of DC fast charging stations, the adoption of EVs will be limited. Range anxiety remains a large contributor to the lack of EV adoption. Ninety percent of U.S. households that own an EV own another vehicle that is likely not an electric vehicle. These stats highlight that consumers do not have confidence that their EV can satisfy all their needs, specifically, long-distance trips.
Since 2009, the cost of photovoltaics (PV) solar energy generation has dropped nearly ninety percent, making it the lowest cost source of energy generation at $37/MWh as of 2020. Compare this to coal at $112/MWh and natural gas at $59/MWh. Solar is allowing the world to generate energy with zero emissions of CO2 all while doing it at the lowest cost of other energy sources. SiC cannot take credit for this cost reduction in its entirety, but it is a contributing reason to solar energy generation decreasing in cost.
The world is moving towards using more electric energy, so it is important to keep improving the efficiency of equipment that consumes this electric energy. Electric motors account for 40-50% of the world’s electricity consumption. It is critical to make these electric motors highly efficient as a small efficiency gain is amplified by the vast amount of these motors in the world.
Not only is SiC helping accelerate decarbonization in existing applications, but it is enabling applications that have not been feasible before. One example of this is electric vertical take-off and landing, eVTOL, aircraft. Just as SiC allows for extended range in EVs, it provides that extended range for eVTOLs as well, making them more practical.
SiC semiconductors help accelerate the adoption of these end-systems by making them more efficient, reliable, robust, smaller, lighter, and with an overall lower cost.
Let Arrow Electronics be your SiC guide
As with any new technology, there are going to be rapid changes and difficulties to overcome. Arrow Electronics has worked with its leading portfolio of SiC suppliers to develop expertise and tools to successfully and quickly make this transition to SiC. These SiC suppliers include Infineon Technologies, Microchip Technology, onsemi, ST Microelectronics, and Wolfspeed.
To get all the benefits from SiC, it is necessary to reevaluate the complete design, requiring system designers to select new gate drivers, current sensors, capacitors, magnetics, connectors, and even the controller. In recognition of this, Wolfspeed and Arrow Electronics worked jointly to develop the Wolfspeed SpeedVal Kit™ that is a modular evaluation platform for SiC. It allows a system designer to quickly evaluate different SiC devices in combination with various gate drivers and controllers in a plug-and-play environment.
SiC has clear advantages over Si technologies that enable the world to accelerate towards decarbonization. Arrow Electronics is uniquely positioned to help accelerate SiC adoption and the movement towards decarbonization with its dedicated high-power expertise and leading portfolio of suppliers.
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