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BASIC KNOWLEDGE - SiC The role of silicon carbide in power electronics

From Luke James

Silicon carbide has been hailed as the potential replacement for silicon due to its unique properties. Here’s a look at the properties that make the material so extraordinary, and its use in power electronics.

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SiC technology is widely recognized as a reliable alternative and replacement to silicon.
SiC technology is widely recognized as a reliable alternative and replacement to silicon.
(Source: missisya - stock.adobe.com)

Silicon carbide (SiC) may seem like a recent innovation, however, it has been used in practical applications since the 19th century. Its earliest use was as an abrasive material until its utilization in a wide range of industries, including the manufacturing of semiconductors, was realized.
Although SiC has been around for a long time, the material’s use in semiconductors is a relatively recent innovation. This is mostly down to the availability of large, high-quality wafers.

What is silicon carbide?

Despite silicon being the most widely used semiconductor in electronics, it’s starting to show some limitations, especially in high-power applications. This is where SiC comes in as a potential replacement for silicon.

SiC Definition

SiC is a semiconductor compound made up of silicon (Si) and carbon (C). It belongs to the wide bandgap family of materials and has a very strong physical bond, which gives the material high mechanical, chemical, and thermal stability.

Indeed, it is the material’s wide bandgap (or energy gap) that enables SiC devices to endure temperatures much higher than regular silicon can, even those in excess of 200 °C, thus making it suitable in high-power applications. When a material’s bandgap is high, electronics can be smaller, run faster, and are more reliable. A wide bandgap also enables applications to operate at higher temperatures, voltages, and frequencies than other semiconductors. These properties have led to a radical transformation of power electronics in recent years as new SiC-based power devices have been developed.

Silicon carbide properties

The wide-ranging uses of SiC, also known as ‘carborundum’, is a consequence of the material’s extraordinary physical properties. SiC is a combination of silicon and carbon in a crystalline structure, and there are roughly 250 different crystalline forms that SiC can take.

Individual grains of SiC, for example, can be sintered together to build strong ceramics while SiC fibers can be used together with polymer to form a composite material. Meanwhile, large, individual crystals of SiC can be grown for use in semiconductor applications.

Some of SiC’s extraordinary properties in the context of power electronics include:

  • High thermal conductivity
  • Low thermal expansion
  • High thermal shock resistance
  • High energy efficiency
  • High operating temperature
  • Low power and switching losses
  • A small die size
  • High durability for long-life applications

SiC’s application in electric vehicles

Designers of power electronics systems are using the material to innovate and to take full advantage of SiC devices, and SiC is being used at a rapid pace in many exciting applications to meet the energy and cost challenges in developing high-efficiency, high-power devices that will help to drive the 21st century.

One area where SiC has been found to be a particular boon to innovation is in e-mobility – think any vehicle that is fully or partially powered by electricity, such as e-bikes and electric vehicles (EVs).

Electric vehicles use new components and frequency converters to power engines, on-board battery chargers and induction chargers, and inverters for auxiliary loads such as power steering. These systems require high-voltage batteries, and this represented one of the major obstacles to the early adoption of EVs. With SiC, however, it’s possible to shrink the size of EV batteries while reducing the total cost to the consumer, thus lowering barriers to adoption.
In addition, SiC’s thermal performance also enables automakers to reduce the cost of cooling powertrain components. This delivers further benefits by reducing the weight and cost of EVs.

The future belongs to SiC

SiC technology is widely recognized as a reliable alternative and replacement to silicon. The wide bandgap material offers unprecedented energy efficiency by reducing switching and conduction losses under specific loads while also offering drastic improvements in thermal management.

SiC devices also require fewer external components, have more reliable system layouts, and have lower production costs. The higher efficiency, smaller form factor, and lower weight of SiC also enable smarter designs with reduced cooling requirements, which has created huge potential for innovation — and manufacturers are quickly finding new ways to tap into this.

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