What Is a SiC (Silicon Carbide) Power Semiconductor? Why Tesla Used It in Its Inverter, Explained From the Differences With Silicon

A SiC (silicon carbide) power semiconductor is a high-power switching semiconductor made of a compound of silicon and carbon. Compared with silicon it has about 3x the bandgap (3.26 eV vs 1.12 eV), withstands about 10x the electric field before breaking down, and conducts heat about 3x as well. So the part that blocks a given voltage can be made thinner, resistance when on and losses when switching are smaller, and it can run hotter. Oak Ridge National Laboratory describes Tesla's Model 3 (deliveries began in 2017) as the first production car to use SiC in its traction inverter.

An electric car's battery stores direct current. But the motor that drives the car runs on alternating current. The part that reshapes the electricity in between is the inverter, and its heart is the power semiconductor, an "electric switch." For the material of that switch, Tesla used SiC (silicon carbide) instead of ordinary silicon. In this article we look at what SiC is and why it suits electric cars, checking the numbers as we go.

Background: four basics for reading this article

1. Direct current and alternating current

Direct current (DC) is electricity that keeps flowing in one direction at a steady strength. Dry cells, smartphone batteries and electric car batteries are DC. Alternating current (AC) is electricity whose direction flips back and forth dozens of times per second. Household outlets are AC: 60 times a second in North America, 50 in much of Europe. Many of Tesla's motors are AC motors (Tesla's motor types). So a part that converts the battery's DC into AC for the motor is unavoidable. The U.S. Department of Energy (DOE) also explains that an inverter is needed "to convert the DC energy from a battery to AC power to drive the motor."

2. Voltage, current and power

Think of a water pipe. Voltage (volts, V) is the "pressure" pushing the water, and current (amperes, A) is the "amount of water" flowing. Power (watts, W) is the two multiplied together: the amount of work delivered per second. For example, 400 V at 250 A is 400 × 250 = 100,000 W, or 100 kW. That is roughly 100 household microwave ovens (about 1 kW each). An electric car's inverter handles this much power continuously.

3. Making AC by switching very fast

The inverter uses no magic to turn DC into AC. It turns its switches on and off thousands to tens of thousands of times per second. By making the "on" time longer or shorter, it builds, on average, a wave that smoothly rises and falls, close to AC. It is similar to flickering a room light faster than the eye can see and changing the brightness by the share of time it is on. The number of switching events per second is the switching frequency, measured in hertz (Hz). Ten thousand per second is 10 kHz.

4. Every loss becomes heat

Switches are not perfect. They lose a little energy while conducting and at every on/off moment, and that energy becomes heat. If a device handling 100 kW is 97% efficient, 3 kW (about three hair dryers) becomes heat. At 99%, only 1 kW does. The difference looks like "just 2%," but the heat drops to one-third. The heat is energy that left the battery without turning the wheels, and it also needs cooling equipment to remove. Cutting losses helps both range and cooling.

The conclusion: SiC is a switch material that withstands high voltage, switches fast and runs hot

SiC is a crystal of silicon (Si) bonded with carbon (C), called silicon carbide. Power semiconductors made from it beat silicon ones on three points (from the table in a technical article by Toshiba Electronic Devices & Storage).

"4H" names one of the crystal arrangements of SiC, the one mainly used in power semiconductors. The DOE report (QTR 2015) calls materials with a bandgap above 3 eV wide bandgap semiconductors, gives SiC (3.3 eV) and gallium nitride (GaN, 3.4 eV) as examples, and says they "can enable device operation at higher frequencies, temperatures, and voltages."

How it works 1: the bandgap is "the height of a step"

Electrons in a semiconductor are normally tied to atoms and cannot move freely. To carry electricity, an electron has to jump over a "step" of a certain height. That height is the bandgap. Its unit, the eV (electron volt), expresses the energy of a single electron.

If the step is low, a rise in temperature alone lets heat kick electrons over it, and electricity "leaks even when the switch is off." Silicon's step is 1.12 eV and SiC's is 3.26 eV, about three times higher. That is why SiC leaks less when switched off, even at high temperature. DOE's vehicle technologies office also says wide bandgap semiconductors "are more efficient and can withstand higher temperatures than silicon components."

How it works 2: a 10x breakdown field means a thinner layer

When the switch is off, a special layer inside the semiconductor (the drift layer) "holds back" the battery's high voltage, like a dam. The voltage it can hold back is roughly "the field strength it withstands × the layer thickness." The electric field is how many volts are applied per centimeter: the strength of electricity's push.

Let's do a simple calculation. The idealized minimum thickness to hold back 1,200 V is:

• Silicon: 1,200 V ÷ 300,000 V/cm = 0.004 cm = about 40 micrometers
• SiC: 1,200 V ÷ 2,800,000 V/cm ≈ 0.00043 cm = about 4 micrometers

(Real parts are made thicker than this, with margin.) The blocking layer can be about one-tenth as thick. And when the switch is on, this same layer becomes the "corridor" electricity passes through. The shorter the corridor, the lower the resistance and the smaller the loss while conducting (conduction loss). Toshiba's article also explains that SiC withstands high voltage even when heavily doped (made easier to conduct), so the chip can be thinner, which lowers losses. In silicon, "conducting easily" and "withstanding high voltage" pull against each other. SiC loosens that tug-of-war a great deal.

How it works 3: losses at the switching moment, and frequency

For an instant during each on/off transition, both voltage and current are non-zero. Since power is voltage × current, heat is produced in that instant. This is switching loss. Each event is small, but it repeats tens of thousands of times per second, so it adds up.

The DOE report gives a figure for 1,200 V SiC MOSFETs (a type of transistor switched by voltage): the energy lost per switching event fell 28%, from 0.78 millijoules to 0.56 millijoules, between 2011 and 2013. If it switches 10,000 times per second, 0.56 mJ × 10,000 = 5.6 joules per second, or 5.6 W per transistor turned into heat by switching alone. The smaller this number, the faster you can switch without overheating.

Why is fast switching useful? The same report says that a 10x increase in frequency produces a 10x decrease in the required inductance and capacitance. Coils (inductors) and capacitors are bulky parts that smooth the electrical wave. Being able to switch fast leads to a smaller, lighter device overall.

As a concrete example, the report describes a drive for a 30-horsepower motor (six transistors rated 1,200 V, 50 A). With SiC, the heat sink could shrink to one-third of its size, and the motor could deliver 30 hp at any frequency from 8 kHz to 16 kHz. With silicon, losses prevented 30 hp at 12.5 kHz or above, and at 16 kHz output was limited to 20 hp.

Why SiC for electric cars: working backward from first principles

Let's work backward using first principles, thinking from basic physics (what is first-principles thinking).

1. All of an electric car's energy comes from the battery. Batteries are heavy and expensive.
2. Losses on the way from battery to inverter to motor become heat and cannot be used for driving (how an electric car moves).
3. Removing that heat takes coolant pumps and plumbing (battery coolant, the Octovalve).
4. So cutting inverter losses lets the same battery go farther, and lets the cooling be smaller.

The inverter carries electricity not only when accelerating but also in the opposite direction during regenerative braking, when it returns energy to the battery. It is a checkpoint passed both ways, so its losses matter the whole time the car is moving.

The DOE report cites a simulation of a 2004 Prius with an all-SiC inverter, in which fuel consumption improved from 3.94 L to 3.36 L per 100 km, a 14.7% improvement. This is a hybrid-car calculation that also includes the effects of lighter weight and smaller size.

SiC has drawbacks, though. According to the same report, in 2015 a 1,200 V, 20 A SiC MOSFET cost about $0.54 per amp, about five times the price of silicon devices. SiC also takes more than 2.5x as much energy per cm² in materials and manufacturing. Even so, the report concludes that the energy saved while the vehicle is in use exceeds that manufacturing difference by two orders of magnitude (about 100x). The part is expensive, but the car as a whole comes out ahead: that is the idea behind SiC.

In real cars: the Model 3, and what comes next

Oak Ridge National Laboratory (ORNL) describes Tesla's Model 3 (deliveries began in 2017) as the first production car to use SiC in its traction inverter. ORNL also describes research in which replacing only the diodes (parts that pass current in one direction) of a 55 kW inverter with SiC cut losses and thermal requirements by 33%.

On what's inside the Model 3 inverter, a report by teardown firm System Plus Consulting (announced in August 2018) says there are 24 power modules, each with two SiC MOSFETs. Multiplied out, that is 48 SiC transistors. It also says a pin-fin heat sink (a plate lined with thin posts) was used to remove heat.

Meanwhile, at its investor event on March 1, 2023, Tesla announced that its next powertrain would use 75% less silicon carbide, "without compromising performance or efficiency of the vehicle" (as reported by TechCrunch). Aehr Test Systems, a company that makes equipment for SiC, said Tesla clarified to it that the 75% cut applies to next-generation lower-cost drive units, not to the current Model S/X/3/Y ones. The direction is not to abandon SiC but to use an expensive material in smaller amounts. Tesla has not published how it achieves the 75% reduction.

Common misconceptions, and numbers worth remembering

• Misconception 1: "SiC is a new battery material." No. SiC is a material for electrical switches such as those in inverters, not for batteries. Battery materials are covered in the 4680 cell article.
• Misconception 2: "Cutting it by 75% means SiC was a failure." No. Tesla's announcement was about using less while keeping performance and efficiency. Cutting an expensive part is a cost measure.
• Misconception 3: "A few percent of efficiency doesn't matter." At 100 kW, the difference between 97% and 99% is 3 kW of heat versus 1 kW. Heat drops to one-third, and cooling can shrink.

The numbers to tell a friend: "a 3x higher step, 10x the strength, 3x the heat flow." Those three lead to "made thin, switched fast, works hot."

Frequently asked questions

Summary

• A SiC (silicon carbide) power semiconductor is a switch that turns large currents on and off quickly. Versus silicon: about 3x the bandgap, about 10x the breakdown field, about 3x the thermal conductivity.
• A thinner layer means smaller conduction loss; faster switching means smaller switching loss. Higher frequency allows smaller coils and capacitors (10x the frequency, one-tenth the size).
• The parts are expensive (in 2015, about 5x silicon per amp), but savings during use far exceed the extra manufacturing energy (DOE).
• Tesla's Model 3 was the first production car with SiC in its traction inverter (ORNL). In 2023 Tesla announced its next powertrain would use 75% less SiC.

A question to continue: With the AC the inverter makes, how does the motor actually produce turning force? And what differs between motors that use magnets and those that don't?

Read next: What Are Tesla's Motors? Why Induction and Permanent Magnet Motors Are Used Side by Side

Sources (checked 2026-10-27)

• U.S. Department of Energy, "Quadrennial Technology Review 2015, Chapter 6, Technology Assessment 6N: Wide Bandgap Semiconductors for Power Electronics" (2015): https://www.energy.gov/sites/prod/files/2016/02/f29/QTR2015-6N-Wide-Bandgap-Semiconductors-for-Power-Electronics.pdf
• U.S. Department of Energy, Vehicle Technologies, "Power Electronics Research and Development": https://www.energy.gov/cmei/vehicles/power-electronics-research-and-development
• Toshiba Electronic Devices & Storage, "High withstand voltage (reverse voltage) characteristics of SiC SBDs": https://toshiba.semicon-storage.com/kr/semiconductor/product/diodes/sic-schottky-barrier-diodes/articles/high-withstand-voltage-reverse-voltage-characteristics-of-sic-sbds.html
• Oak Ridge National Laboratory, "Powering a clean, electrified future: Burak Ozpineci" (checked 2026-10-20): https://www.ornl.gov/news/powering-clean-electrified-future-burak-ozpineci
• Warren, J. et al., "Energy Impact of Widespread Adoption of Silicon Carbide (SiC) Power Electronics," Environmental Science & Technology 49(17), 2015 (OSTI 1414278): https://www.osti.gov/biblio/1414278
• GlobeNewswire (August 17, 2018; announcement of a System Plus Consulting report), "Tesla Model 3 Inverter with SiC Power Module from STMicroelectronics" (checked 2026-10-20)
• TechCrunch (March 1, 2023), "Everything Elon Musk and execs shared and skipped at Tesla Investor Day": https://techcrunch.com/2023/03/01/everything-elon-musk-and-execs-shared-and-skipped-at-tesla-investor-day/
• Aehr Test Systems (March 2023), "Aehr Comments on Recent Tesla Statements on Silicon Carbide": https://www.aehr.com/2023/03/aehr-comments-on-recent-tesla-statements-on-silicon-carbide-and-reiterates-its-annual-guidance/

This article is for learning about science and technology and is not investment advice. Facts and the author's interpretations are kept separate.