Power Solutions—GaN, SiC, and Si—What You Should Know

by Carolyn Mathas

A large variety of power solutions exist between silicon (Si) to wide bandgap (SiC and GaN), enabling design criteria to meet performance, efficiency, reliability, and cost. GaN is becoming the technology of choice. Compared with legacy silicon solutions, it enables lighter, smaller, and more efficient onboard chargers and inverters. In the data center, GaN power semiconductors in power supplies increase profits and substantially reduce CO2 emissions. Electric vehicles’ rapid charging and dynamic performance drive more car manufacturers to use SiC technology in main inverters.

However, when considering what wide bandgap GaN and SiC deliver, where does that leave silicon? Here’s what you need to know.

GaN (Gallium Nitride)

Given its proven reliability and performance superiority over silicon, GaN is rapidly becoming the technology of choice for power conversion in automotive power electronics. Its performance over legacy silicon solutions fosters the design of lighter, smaller, and significantly more efficient onboard chargers and inverters.

Recent GaN-based motor drives, for example, target such applications as warehouse autonomous robots, eMobility, and drones, reducing size and weight, extending range, and increasing reliability.

Highlights of GaN include:

  • GaN-based USB-C fast chargers are up to 40% smaller and charge 2.5x faster than silicon-based chargers
  • GaN can charge devices faster while using up to 50% less energy in the process
  • Given their small size, multiple devices can charge simultaneously
  • GaN power supplies will allow data centers to increase server density by approximately 56% and reduce CO2 emissions
  • Warranties for GaNFast technology are now reaching 10x longer than silicon, SiC, and discrete GaN power semiconductors—a necessity for GaN use in several industries

GaN transistors are an essential part of EVs. Used in onboard chargers and traction inverters, GaN can increase driving range by 6%–a significant consideration for EV adoption.

 Silicon Carbide (SiC)

Silicon carbide (SiC) is a growing alternative to silicon-based electronics in wide bandgap applications. It features a unique combination of greater power efficiency, smaller size, lighter weight, and lower overall cost.

Silicon carbide (SiC) delivers a strong physical bond for high mechanical, chemical, and thermal stability. SiC devices can work at junction temperatures over 200°C. Its main advantage in power applications is its low drift region resistance, which is crucial for high-voltage power devices.

The combination of silicon with carbon provides:

  • high thermal conductivity
  • low thermal expansion
  • excellent thermal shock resistance
  • low power and switching losses
  • high energy efficiency
  • high operating frequency and temperature
  • small die size
  • excellent thermal management, which reduces cooling operations

There are still challenges for SiC production, given its hardness. It requires higher temperatures, more energy, and more time for crystal growth and processing. The most used crystalline structure (4H-SiC) features high transparency and a high refractive index, so it is difficult to inspect the material for surface defects/

SiC represents a breakthrough for industrial power applications targeting components with blocking voltages > 100 V and power ratings to several hundreds of kilowatts. SiC applications include Schottky diodes and FET/MOSFET transistors, converters, inverters, power supplies, battery chargers, and motor control systems.

Silicon (Si)

So, what’s with silicon and its future? Silicon has limitations, especially in high-power applications. If the bandgap is high, its electronics can be smaller, faster, and more reliable. It can also operate at higher temperatures, voltages, and frequencies. Silicon has a bandgap of around 1.12eV; silicon carbide has a nearly three times greater value of around 3.26eV. Thermal conductivity is an index of how the semiconductor can dissipate the heat it generates. If heat dissipation is not adequate, it affects the maximum operating voltage and temperature that the device withstands. The thermal conductivity of silicon carbide is 1490 W/m-K, vs. 150 W/m-K offered by silicon.

Silicon is not going away anytime soon—it still dominates the industry. Silicon is reliable, rugged, inexpensive, and can handle high current. GaN and SiC have comparatively high production costs, defects, and expensive manufacturing processes compared to silicon.

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