SiC vs GaN Power Devices: Key Differences

Silicon carbide (SiC) and gallium nitride (GaN) are both wide-bandgap semiconductors that beat silicon in power conversion: they withstand higher fields, switch faster and lose less energy. The practical split is voltage. SiC is the choice for high-voltage, high-power systems such as electric-vehicle inverters, while GaN excels at lower voltages and very high switching frequencies, such as compact fast chargers.

AspectSiCGaN
Band gapAbout 3.3 eV (4H-SiC), compared with 1.12 eV for siliconAbout 3.4 eV
Critical electric fieldAbout ten times that of siliconAbout ten times that of silicon
Thermal conductivityHigh, roughly three times silicon, which makes cooling easierSimilar to silicon, lower than SiC
Typical deviceVertical MOSFETs and Schottky diodesLateral HEMTs that use a two-dimensional electron gas as the channel
Typical voltage rangeAround 650 V to 3.3 kV, and higherMostly up to about 650 V
Switching frequencyHigh (tens to hundreds of kHz)Very high (hundreds of kHz up to MHz)
Substrate and wafersSiC wafers are expensive and difficult to growUsually grown on silicon wafers (GaN-on-Si), which is cheaper and works in silicon fabs; GaN-on-SiC is used for RF
Design challengesGate oxide reliability and the need for higher gate drive voltageNormally-on behavior must be avoided, and the gate tolerates only a small voltage swing
Typical usesEV traction inverters, on-board chargers, solar inverters, industrial motor drives, railwaysCompact fast chargers and adapters, data-center power supplies, 5G RF amplifiers

Figures are typical orders of magnitude and vary by process generation and product.

When to use which

SiC
When voltage and power are high and efficiency and heat matter: vehicle inverters, solar and industrial power systems.
GaN
When voltage is moderate and you want small, light, very efficient converters at high switching frequency: chargers, adapters, server power.
Either
Both need care at high switching speed, because fast edges cause ringing and noise. Layout and gate driving matter as much as the device.

FAQ

Which is better, SiC or GaN?

Neither is better overall. SiC suits high voltage and power, such as electric-vehicle inverters, while GaN suits lower voltage and very high switching frequency, such as compact chargers.

Why are SiC and GaN better than silicon for power devices?

Both have a wider band gap and about ten times the critical electric field of silicon, so they withstand higher voltages, switch faster and lose less energy.

Why is GaN-on-silicon cheaper than SiC?

GaN power devices are usually grown on silicon wafers, which are cheap and fit existing silicon fabs. SiC wafers are expensive and hard to grow.

Which handles heat better, SiC or GaN?

SiC. Its thermal conductivity is roughly three times that of silicon, while GaN is similar to silicon.

Check your understanding

What is the main reason SiC (silicon carbide) is advantageous over Si for high-voltage power devices?

  1. AIts breakdown electric field is about 10 times that of Si
  2. BIts band gap is smaller than that of Si
  3. CIts wafers are cheaper than Si and easier to make in large diameters
Show answer and explanation

Answer: A. Its breakdown electric field is about 10 times that of Si

SiC has a wide band gap of about 3.3 eV and a breakdown field about ten times silicon's (about 3 MV/cm). For the same voltage rating the drift layer can be about one tenth as thick and about 100 times more heavily doped, cutting its resistance theoretically by a factor of several hundred. Its thermal conductivity is about three times silicon's, so it handles heat well, and it is spreading in EV inverters. SiC wafers remain costlier, and the move to 8-inch is still under way.

What is the general term for semiconductors with a larger band gap than silicon, such as SiC and GaN?

  1. AWide-band-gap semiconductors
  2. BNarrow-gap semiconductors
  3. CAmorphous semiconductors
Show answer and explanation

Answer: A. Wide-band-gap semiconductors

Semiconductors with bandgaps of roughly 3 eV or more are called wide-bandgap semiconductors; SiC (about 3.3 eV) and GaN (about 3.4 eV) are the main examples. High breakdown fields and few intrinsic carriers let them operate at high temperature, suiting high-voltage, low-loss power and RF devices. Even wider-gap Ga2O3 (about 4.8 eV) and diamond (about 5.5 eV) are called ultra-wide-bandgap semiconductors.

What is the main advantage of using SiC power devices in electric vehicle inverters?

  1. AThey are always cheaper than silicon
  2. BLower losses lead to longer driving range and smaller cooling systems
  3. CThe motor becomes unnecessary
Show answer and explanation

Answer: B. Lower losses lead to longer driving range and smaller cooling systems

SiC devices have low on-resistance and switching losses and tolerate heat, reducing EV inverter losses. That can extend range on the same battery by several percent to about 10% and shrink cooling systems and inverters. Adoption accelerated after the 2018 Tesla Model 3, and the benefit is greatest with 800 V battery systems. The main drawback is higher cost than silicon IGBTs.

  1. When SiC or GaN power devices switch at high speed, which problem particularly needs countermeasures?
  2. Why is GaN well suited to high-frequency, high-power transistors?
  3. What structure do most of today's widely used GaN power devices adopt?

Practice Power semiconductors questions

Key terms explained

SiC (silicon carbide)
A wide-band-gap semiconductor with a band gap of about 3.3 eV. Its high breakdown field makes it suitable for high-voltage, low-loss power devices.
GaN (gallium nitride)
A III-V compound semiconductor with a band gap of about 3.4 eV. Used in blue LEDs and in high-frequency and power devices.
Wide-bandgap semiconductor
Semiconductors with a larger band gap than silicon, such as SiC and GaN. Their high breakdown field makes them strong for high-voltage, high-temperature operation.
Power MOSFET
A MOSFET built to handle large currents and voltages. It switches quickly and is widely used in power supply circuits and the like.

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